CN112071453A - Design scheme of direct-current countercurrent pore channel type heat exchanger/evaporator - Google Patents

Abstract

A design scheme of a direct-current countercurrent pore channel type heat exchanger/evaporator utilizes a special circular, elliptical or oblong pore channel arranged in a heat exchange unit to perform direct-current countercurrent heat exchange. The heat exchange among the pore passages of the small holes or the micropores which mainly take the heat conduction and convection of the multilayer metal is high in heat transfer coefficient, good in heat transfer efficiency, small in thermal stress and small in heat transfer temperature difference; the heat can be safely and stably transferred among the pore canals under the condition of ultrahigh temperature superposition and ultrahigh pressure, and the method is efficient, simple, safe and reliable; the accident of pipe breaking and water loss of the shell-and-tube heat exchanger under the working condition of ultrahigh temperature and ultrahigh pressure can be avoided. Compared with a shell-and-tube heat exchanger with the same heat transfer capacity, the volume, the weight and the manufacturing cost of the direct-current countercurrent pore channel type heat exchanger are reduced by more than one third, and the direct-current countercurrent pore channel type heat exchanger supports heat transfer under the severe conditions of extreme high temperature not exceeding 1000 ℃ or extreme high pressure not exceeding 1000 kilograms. A direct current countercurrent pore channel type heat exchanger belongs to the technical field of heat transfer equipment and is mainly applied to the fields of nuclear power thermal power, petrochemical industry, chemical industry and medicine, metallurgical hydrogen production and the like.

Description

Design scheme of direct-current countercurrent pore channel type heat exchanger/evaporator

The technical field is as follows:

the invention relates to a design scheme of a novel heat exchanger/evaporator suitable for extremely high temperature or extremely high pressure, which utilizes a direct-current countercurrent special pore channel arranged in a heat exchange unit module to exchange heat and is called as a direct-current countercurrent pore channel type heat exchanger/evaporator. The heat exchange between the pore canals of the direct current counter-flow small holes or the micropores which mainly takes heat conduction and heat convection of a heat transfer material is high in heat transfer coefficient, small in heat transfer temperature difference and small in thermal stress, the heat can be safely and stably transferred between the pore canals under the conditions of extreme high temperature, extreme high pressure or ultra-high temperature superposition ultrahigh pressure, the heat exchange device has the characteristics of high efficiency, simplicity, safety and reliability, belongs to the technical field of heat transfer equipment, and the main application fields are nuclear thermoelectricity, petrochemical industry, chemical industry and medicine, metallurgical energy, food electronics and the like.

(II) background technology:

a nuclear power steam generator (steam generator) is a heat exchange device for generating steam required by a steam turbine, in a nuclear reactor, heat generated by nuclear fission is taken out by a coolant, and is transferred to a two-loop working medium through the steam generator, so that the steam generator generates steam with a certain temperature, a certain pressure and a certain dryness. The steam enters a steam turbine to do work and is converted into electric energy or mechanical energy. In this energy conversion process, the steam generator is a primary and a secondary loop device, and is therefore called a primary and secondary loop hub. The nuclear power steam generator is also one of the most critical main devices of the nuclear power station, is connected with a reactor pressure vessel, not only directly influences the power and the efficiency of a power station, but also plays a role in blocking radioactive heat-carrying agents when heat exchange is carried out, and is of great importance to the safety of the nuclear power station. Therefore, steam generators perform quality requirements of safety class one, class I anti-seismic class one, class one specification class and class one quality assurance class one, with high technical content of materials and manufacturing being the most important for contemporary manufacturing.

The nuclear power steam generator is used as a primary loop device of a nuclear island, and has the main functions of: transferring the heat of the coolant of the primary loop to feed water of the secondary loop through a heat transfer pipe, heating the feed water to boiling, and generating dry saturated steam for driving a steam turbine after steam-water separation; the first safety barrier is used as a first loop pressure boundary, bears the first loop pressure, and forms a third safety barrier for preventing the radioactive fission product from overflowing together with other first loop pressure boundaries; and the reliable operation of the reactor device is ensured under the expected operation event, the design benchmark accident condition and the transition condition. Practical operation experience shows that whether the steam generator can safely and reliably operate has very important influence on the economy, safety and reliability of the whole nuclear power plant.

Pressurized water reactor nuclear power plants typically employ vertical, natural circulation, U-tubes, and shell and tube steam generators. The U-shaped tube type heat exchanger is a tube-shell type heat exchanger with a tube bundle composed of U-shaped tubes with different bend pipe radiuses and two ends of each tube fixed on the same tube plate. Because each U-shaped pipe can freely stretch out and draw back, the temperature difference stress can not be produced between the tube bundle and the shell. A baffle plate, a longitudinal baffle plate and the like are arranged in the shell pass. The baffle plate is fixed by a pull rod. The longitudinal partition is a rectangular flat plate and is arranged in a direction parallel to the heat transfer pipe to increase the flow velocity of the shell-side medium. The structure is more complex than that of a fixed tube-plate heat exchanger and is simpler than that of a floating head heat exchanger.

The U-shaped tube shell and tube steam generator for the pressurized water reactor nuclear power station has the working principle that: the coolant flowing out of the reactor enters the water chamber through the heat pipe section of the primary loop and is close to the inlet of the lower end socket of the steam generator, then flows in the inverted U-shaped pipe bundle, the outer surface of the inverted U-shaped pipe is in contact with the feed water of the secondary loop, and transfers the heat to the water of the secondary loop to vaporize the water, thereby completing the heat exchange between the primary loop and the secondary loop. After the heat carried by the coolant in the primary circuit is transferred to the secondary circuit, the temperature is reduced, and the heat flows through the outlet water chamber and the outlet connecting pipe of the lower end socket, flows to the transition pipeline of the primary circuit and then enters the suction inlet of the main pump. The water supply of the two loops enters a water supply ring pipe from a water supply connecting pipe of the steam generator, enters an annular space (namely a descending channel) between the lower barrel and the pipe bundle sleeve through a group of inverted J-shaped pipes on the ring pipe, flows downwards after being mixed with the water separated by the steam-water separator until reaching a bottom pipe plate, then turns, flows upwards along the outside of the pipe (namely an ascending channel) of the inverted U-shaped pipe bundle, is heated by a primary loop coolant flowing in the heat transfer pipe, and part of the water is evaporated into steam. The steam-water mixture leaves the top of the inverted U-shaped pipe bundle and continuously rises, and then sequentially enters the rotary vane type steam-water separator and the dryer, after steam-water separation, steam flows to the steam turbine from the top outlet of the steam generator to do work, and separated water is downwards mixed with feed water to be recycled. Steam generator secondary loop side fluid flow is typically driven by natural circulation; the tube bundle sleeve divides the water on the secondary side into an ascending channel and a descending channel; the mixture of low-temperature water and saturated water separated by the steam-water separator flows in the descending channel and belongs to single-phase water (supercooled water), the mixture of steam and water flows in the ascending channel, the density of the single-phase water is higher than that of the mixture of steam and water under the same pressure, the difference in density between the single-phase water and the mixture of steam and water causes pressure difference on two sides of the tube bundle sleeve, the water in the descending channel is driven to continuously flow to the ascending channel, and natural circulation is established.

According to the statistics of accidents of a pressurized water reactor nuclear power plant, the steam generator is in the leading position in the accidents of the nuclear power plant. The reliability of some steam generators is relatively low and evaporator tube breakage has a significant impact on the safety, reliability and economic benefits of nuclear power plants. Therefore, research and improvement of the steam generator are taken as important links for perfecting the technology of the pressurized water reactor nuclear power plant in all countries, and a huge scientific research plan is made, which mainly comprises thermal hydraulic analysis of the steam generator; corrosion theory and heat transfer tube material development; nondestructive inspection technology; vibration, abrasion and fatigue research; the structural design is improved, and the concentration of corrosive chemicals is reduced; improved water quality control, etc.

The high-temperature gas cooled reactor nuclear power plant selects a spiral coil type evaporator. The steam generator is a core heat exchange device for connecting and isolating the primary loop and the secondary loop, and executes a safety first-level grade, an anti-seismic I grade and a quality assurance QA1 grade. The primary function is to transmit the heat generated by the reactor core of the nuclear reactor from the primary loop to the secondary loop, generate superheated steam to drive a steam turbine to do work and generate electricity through a generator. The high-temperature gas cooled reactor evaporator adopts a vertical direct-current countercurrent component type design structure, is arranged side by side with a reactor pressure vessel, and is placed in an evaporator pressure-bearing shell together with a main helium fan. The evaporator heat exchange unit is positioned at the lower part of the pressure-bearing shell and mainly comprises a heat exchange assembly, a main steam connecting tube bundle, a main water supply connecting tube bundle, a tube box, a heat preservation layer, a bearing plate, a positioning plate, an internal component bearing cylinder, a heat compensation assembly, a cold helium gas ascending tube, a connecting flange, other internal components and the like. The single evaporator is composed of 19 heat exchange components to form a heat exchange unit, each heat exchange component is provided with 35 heat exchange tubes, and the heat exchange tubes are arranged in an annular space between the outer sleeve and the central tube. The heat exchange tube adopts a spiral coil tube structure, each heat exchange assembly is provided with 5 layers of spiral coil tube type heat exchange tubes, and the number of the heat exchange tubes on each layer is 5, 6, 7, 8 and 9 in sequence from inside to outside. The winding directions of two adjacent layers of spiral coils are opposite, the heat transfer pipe bundle of each layer is fixed through three groups of supporting structures, and the fixing pieces are uniformly distributed along the axial direction. In order to improve the economy of equipment, materials of the heat exchange tube are selected in sections; mature and cheap T22 pipes are adopted in the preheating section, the evaporation section and a small part of the overheating section of the heat exchange tube, and high-temperature alloy pipes are adopted in the high-temperature overheating section of the heat exchange tube. In order to improve the compactness of the evaporator and reduce the heat exchange area and the volume of the evaporator, a counter-flow arrangement mode is selected on the flow modes of the primary side and the secondary side. In order to meet the requirements of the stability of gas-liquid two-phase flow in the heat exchange tubes and the flow distribution among the heat exchange tubes, a throttling resistance piece is additionally arranged at the inlet of each heat exchange tube of the evaporator.

The spiral coil type heat exchanger/evaporator is made by arranging one or more groups of pipes wound into a spiral shape in a shell; the spiral wound tube type heat exchanger is manufactured by manufacturing a plurality of heat exchange tubes into a coil pipe, and then stacking the coil pipe on a central circular tube; the heat exchange tubes in the tube coil are spirally wound from inside to outside. In the heat exchange process, high-pressure working medium water and water vapor pass through the spiral tube pass from bottom to top, low-pressure working medium helium passes through the shell pass from top to bottom, and the two working media flow reversely in the axial direction. During heat exchange, high-pressure fluid flows through the inner pipe, and low-pressure fluid reversely passes through the gap between the outer pipes. Although the structure ensures that the fluid is subjected to countercurrent heat exchange, the heat exchange effect is influenced due to the existence of more airflow dead zones in the two flows, so that the total heat transfer efficiency is low. The design features of the spiral coil evaporator are compact structure, larger heat transfer area than straight pipe, small temperature difference stress, difficult cleaning in pipe, and can be used for heating or cooling fluid with higher viscosity.

The high-temperature gas cooled reactor has the inherent safety characteristic, the working medium parameter of the primary loop is higher, the helium outlet temperature reaches 750 ℃, and the high-efficiency power generation of the supercritical parameter of the secondary loop is completely supported, so that the economic efficiency of a commercial engineering project is improved. Besides the difficulty in selecting high-temperature alloy materials, the high-temperature gas cooled reactor ultra-supercritical parameter power generation has the main restriction factor that the pressure bearing reliability of a working medium of a secondary loop of a spiral coil pipe steam generator is insufficient within the working pressure of 25 MPa-35 MPa and the working temperature range of 600-700 ℃, and the pipe breakage accident is easy to happen after long-term operation. The reason is that the high-temperature endurance strength and the high-temperature creep property of the high-temperature alloy material which can resist the working temperature of 750 ℃ are usually not high (for example, the high-temperature endurance strength of the high-temperature alloy material at 760 ℃ is about 100 MPa), and the high-temperature endurance strength and the high-temperature creep property of the high-temperature alloy material which can resist the working temperature of 750 ℃ are superposed on the high-temperature endurance strength and the high-temperature creep property to require the heat transfer pipe to bear ultrahigh pressure, the wall thickness of the heat transfer pipe is increased in multiples, the heat transfer coefficient is reduced in multiples, the manufacturing cost of the evaporator equipment is increased in multiples along with the high-temperature endurance strength, the pressure-.

In the future, the parameters of the primary loop working medium of the ultra-high temperature gas cooled reactor for hydrogen production and hydrogen smelting are increased to 950 ℃, and heat needs to be transferred to a 900 ℃ intermediate helium loop through a helium intermediate heat exchanger, so that the harsh extreme high temperature provides more serious challenges for the design and operation of a high temperature gas cooled reactor steam generator.

In the future, pressurized water reactor nuclear power stations also face the market requirement of ultra-supercritical power generation, and U-shaped tube shell-and-tube evaporators cannot technically meet the heat transfer requirement of extremely high temperature or extremely high pressure. Even if the working pressure and the working temperature of the current primary loop are met, the U-shaped tube shell-and-tube evaporator is high in cost in design and manufacture because the heat transfer tube material cannot be used along with the temperature field in a gradient manner, and has the design potential that the cost is reduced by one third.

The method has the following defects: whether the U-shaped tube evaporator of the pressurized water reactor or the spiral coil evaporator of the high-temperature gas-cooled reactor is adopted, the design scheme of the shell-and-tube evaporator exposes the insufficient reliability of equipment under the severe conditions of extreme high temperature or extreme high pressure or the severe conditions of ultra-high temperature and ultra-high pressure (such as ultra-supercritical power generation parameters), the tube breakage of a heat transfer tube is easily caused, and even the soft rib of a large-break accident is generated, thus threatening the safety of a nuclear reactor; and the equipment cost of the traditional design scheme is too expensive, and the economic efficiency of the project is seriously influenced.

Disclosure of the invention

The invention provides a brand new heat exchanger/evaporator design scheme suitable for extreme high temperature, extreme high pressure or ultra high temperature superimposed ultra high pressure, which utilizes a direct current countercurrent pore canal arranged in a heat exchange unit module to exchange heat and is called as a direct current countercurrent pore canal type heat exchanger/evaporator. The heat exchange between the pore passages of the small holes or the micropores which mainly take the heat conduction and the heat convection of the heat transfer material is realized, the heat transfer coefficient is higher, and the thermal stress is smaller; the heat transfer between the pore canals can be safely and stably carried out under the condition of extreme high temperature or extreme high pressure, and the heat transfer device has the characteristics of high efficiency, simplicity, safety and reliability.

The design scheme of the direct-current countercurrent pore channel type heat exchanger/evaporator is shown in the figures 1, 2, 3 and 4, and mainly comprises an upper heat exchange unit (1), a middle heat exchange unit (2), a lower heat exchange unit (3), a primary side pore channel (H1), a secondary side pore channel (H2), a primary side inflow pipeline (4), a primary side inflow header (5), a primary side outflow pipeline (6), a heat exchange unit bearing support (7), a pressure-bearing outer cylinder bearing bracket (8), a pressure-bearing outer cylinder (9), an outer cylinder bottom end socket (10), a primary side outflow header (11), a heat exchange unit heat insulation layer (12), a heat insulation layer cladding plate (13), a secondary side outflow header (14), a secondary side outflow pipeline (15), an outflow pipeline heat insulation layer (16), an outer cylinder top end socket (17), a secondary side inflow header (18), a secondary side inflow pipeline (19), a pressure-bearing outer, The device comprises a hemispherical blind flange (21), a blind flange sealing ring (22), a blind flange fastener (23) and a primary side working medium forced circulation pump or fan (24). The main structure is characterized in that a primary side pore channel (H1) is arranged on two working faces (B1, A2) of an upper heat exchange unit (1) according to calculation of high-temperature and high-pressure bearing strength of a heat exchange unit material and analysis of heat transfer of a thermal fluid, and a secondary side pore channel (H2) is arranged on the two working faces (A1, A2) according to calculation of high-temperature and high-pressure bearing strength of the heat exchange unit material and analysis of heat transfer of the thermal fluid; two working faces (A1, A2) of the middle heat exchange unit (2) are provided with a primary side pore passage (H1) and a secondary side pore passage (H2) according to the calculation of the high-temperature and high-pressure bearing strength of the heat exchange unit material and the heat transfer analysis of the hot working fluid; three working faces (A1, B1 and B2) of the lower heat exchange unit (3) are provided with a primary side pore canal (H1) according to the calculation of the high-temperature and high-pressure bearing strength of the heat exchange unit material and the heat transfer analysis of the thermal fluid, and two working faces (A1 and A2) are provided with a secondary side pore canal (H2) according to the calculation of the high-temperature and high-pressure bearing strength of the heat exchange unit material and the heat transfer analysis of the thermal fluid. The number, the size, the shape, the path, the bending, the flow resistance, the position relation, the form and position tolerance and the surface roughness of the primary side pore canal are determined through design calculation, and the number, the size, the shape, the path, the bending, the flow resistance, the position relation, the form and position tolerance and the surface roughness of the secondary side pore canal are determined through design calculation; the design and manufacture need to ensure that the drift diameters (H1, H2) of the pore channels of the upper heat exchange unit (1), the middle heat exchange unit (2) and the lower heat exchange unit (3), the primary side-hole inter-bridge (T1), the secondary side-hole inter-bridge (T2) and the primary side and secondary side-hole channel bridge (T3) are completely consistent, and the straightness, coaxiality, parallelism, perpendicularity and ellipticity of the pore channels are within the range of requirements on form and position tolerance precision. The working surface (A2) of the upper heat exchange unit (1) and the working surface (A1) of the middle heat exchange unit (2), the working surface (A2) of the middle heat exchange unit (2) and the working surface (A1) of the lower heat exchange unit (3) are welded together through a vacuum heating and pressurizing molecular diffusion welding process to form a primary side direct current countercurrent heat exchange flow channel and a secondary side direct current countercurrent flow channel; the middle heat exchange units (2) can be arranged in series according to the heat transfer calculation requirement; the upper heat exchange unit (1) has the main functions of baffling primary side working medium, isolating the primary side working medium from secondary side working medium, and respectively guiding and connecting the primary side working medium and the secondary side working medium to a primary side inflow header (5) and a secondary side outflow header (14); the structure of the middle heat exchange unit (2) mainly has the function of direct-current countercurrent heat transfer of a primary side working medium and a secondary side working medium; the lower heat exchange unit (3) mainly has the functions of baffling the primary side working medium, isolating the primary side working medium from the secondary side working medium and respectively guiding and connecting the primary side working medium and the secondary side working medium to a primary side outflow header (11) and a secondary side inflow header (18).

As shown in fig. 4, the primary side working medium is introduced into the primary side inflow header (5) from the primary side inflow pipe (4), flows in the primary side pore channel (H1) of the upper heat exchange unit, flows into the primary side pore channel (H1) and the secondary side pore channel (H2) of the middle heat exchange unit (2) after being deflected, flows through direct-current and counter-current heat transfer, then flows into the primary side pore channel of the lower heat exchange unit (3), and flows out after being deflected into the primary side outflow header (11) after heat exchange (heat dissipation) is completed; secondary side working media are led into a secondary side inflow header (18) from a secondary side inflow pipeline (19) and flow in secondary side pore channels (H2) of the lower heat exchange unit (3), the middle heat exchange unit (2) and the upper heat exchange unit (1) in sequence, and after heat exchange is completed (heat absorption), the secondary side working media flow out from a secondary side outflow header (14) and a secondary side outflow pipeline (15); the primary side pore passage and the secondary side pore passage are in direct-current countercurrent but are not communicated with each other, and have certain pressure bearing (pressure difference of working media on the primary side and the secondary side) capacity under certain temperature condition; the counter-flow convection heat transfer function of the primary side working medium and the secondary side working medium with heat convection as the main part and heat conduction and heat radiation as the auxiliary part is realized.

The technical principle of the invention is as follows: the heat exchange unit is internally provided with formed small holes or micropores which are tightly attached to the multilayer metal heat conduction and convection heat transfer, and the heat transfer coefficient is far higher than that of the heat radiation and convection heat transfer of the wall surface of the shell-and-tube heat transfer pipe; the heat exchange among the pore passages of the small holes or the micropores which mainly take the heat conduction of the heat transfer material is realized, so that the heat transfer coefficient is higher, and the thermal stress is smaller; the heat transfer between the pore canals can be safely and stably carried out under the condition of extreme high temperature or extreme high pressure, and the heat transfer device is efficient, simple, safe and reliable. Under the condition of the same size and material, the direct current countercurrent pore channel type heat exchanger can realize the dense and compact arrangement of multilayer pore channels, while the shell-and-tube type heat exchanger cannot compactly arrange a heat transfer pipe due to the strength of pore bridges of tube plates at two ends, and the heat transfer area of the wall surface of the multilayer pore channel is greatly increased compared with that of the heat transfer pipe; under the condition of the same heat exchange capacity, the pore channel type heat exchanger can realize smaller heat exchange temperature difference between the primary side and the secondary side than a shell-and-tube type heat exchanger. The channel type heat exchanger/evaporator has the characteristic of high thermal efficiency, only exchanges heat and does not exchange working media; the heat transfer under the severe working medium condition of extreme high temperature or extreme high pressure can be realized, the heat transfer efficiency is higher than that of the traditional shell-and-tube heat exchanger, and the heat transfer temperature difference between the primary side and the secondary side is small; compared with a shell-and-tube heat exchanger with the same heat transfer capacity, the volume, the weight and the cost of the direct-current countercurrent pore channel type heat exchanger evaporator are reduced by one third or more than one half. Under the conditions of proper heat exchange unit material selection and proper heat transfer pore channel design selection, the heat exchange unit can support heat transfer under the severe heat transfer conditions of extreme high temperature not exceeding 1000 ℃ or extreme high pressure not exceeding 1000 kilograms. Under the conditions of special heat transfer structure design and material selection, a plurality of process flows are supported by the primary side or the secondary side to be combined into one flow passage to realize the heat transfer function.

As shown in figure 2, a plurality of middle heat exchange units (2) are connected in series with an upper heat exchange unit (1) and a lower heat exchange unit (3) through working surfaces (A1 and A2) in an assembling welding or material increase manufacturing mode to form a heat exchange unit group, and the heat exchange unit group is mainly structurally characterized in that large temperature difference heat transfer and temperature shock heat transfer are achieved through cascade continuous heat transfer of the plurality of heat exchange units. The heat exchange unit is provided with a heat exchange unit heat insulation layer (12) and a heat insulation layer cladding plate (13) at the periphery, and the heat exchange unit is mainly structurally characterized in that the heat of high-temperature working media at the primary side and the secondary side hot ends is blocked from being lost to the inner cooling end of the pressure-bearing outer cylinder (9) in a non-heat-transfer mode through heat conduction and heat radiation, and the heat transfer efficiency of a working medium flow channel is improved. The primary side inflow pipeline (4), the primary side inflow header (5), the secondary side outflow header (14), the secondary side outflow pipeline (15) and other high-temperature area components are provided with heat insulation layers in the same way to block heat loss, and each heat insulation layer is fixed by a heat insulation layer cladding plate respectively.

The primary side cold end working medium heat exchange unit is mainly structurally characterized in that a primary side working medium hot end heat exchange unit is surrounded by the pressure-bearing outer cylinder (9) as a primary side working medium cold end, the primary side outflow pipeline (6) as a primary side working medium cold end surrounds the primary side working medium hot end inflow pipeline (4), and the primary side outflow pipeline (6) as a primary side working medium cold end surrounds the primary side working medium hot end primary side inflow pipeline (4) so as to realize the cold-heat-in-package design concept. In principle, working media with lower pressure are usually selected as primary side working media, so that the pressure-bearing outer cylinder only bears low-temperature low-pressure primary side cold end working media after heat exchange, the difficulty of material selection is reduced, and a mature heat-resistant steel pressure-bearing material can be usually selected. Under the condition of extremely high temperature of the primary side and the secondary side, although the heat exchange unit bears higher temperature and the selection surface of the high-temperature alloy material is limited, the heat exchange unit only bears the working pressure difference between the primary side and the secondary side, compared with the heat exchange unit which is only required to bear larger absolute high pressure of the secondary side, the consumption of expensive high-temperature alloy material is greatly reduced, and the equipment cost of a heat exchanger or an evaporator is reduced to a certain extent.

In the heat exchange unit groups connected in series, along with continuous direct-current countercurrent heat transfer of the primary side working medium and the secondary side working medium, the temperature fields of the primary side working medium flow channel (L1) and the secondary side working medium flow channel (L2) are gradually decreased along with the flow field of the working medium; the heat exchange unit group can select a proper heat-resistant pressure-bearing material according to the descending degree and the direction gradient configuration of the temperature field, for example, an expensive high-temperature alloy material is selected in an extreme high-temperature section, a mature heat-resistant pressure-bearing material is selected in a common high-temperature section and a medium-temperature section, and a pressure-bearing material with lower manufacturing cost is selected in a low-temperature section.

A pressure boundary of a primary side cold end working medium pressure-bearing shell is formed by a pressure-bearing outer cylinder (9), an outer cylinder bottom end enclosure (10), an outer cylinder top end enclosure (17) and a pressure-bearing outer cylinder flange (20), and the flange is used for opening a pressure-bearing inner cylinder welding line of the pressure-bearing shell in service inspection, and inspecting, maintaining or blocking a pore channel; a hemispherical blind flange (21), a blind flange seal (22) and a blind flange fastener (23) are arranged at the bottom end socket (21) of the outer cylinder and are used for primary side working medium forced circulation pump or fan (24) maintenance to prevent primary side working medium leakage, and the outer cylinder is particularly suitable for primary side working medium with radioactivity.

The duct for heat transfer is typically specifically designed according to the heat transfer performance of the structural material and the pressure-bearing function of the working medium, and meanwhile, the convenience of the duct processing technology is considered, and sometimes the flow resistance characteristic of the duct is also considered. The cross section of the pore passage can be generally round, oval, long round, semicircular, rectangular, rhombic, triangular, polygonal, irregular and the like, the non-round pore passage is easy to generate stress concentration and microscopic defects in the processing process, and the non-round pore passage is not recommended to be selected under the working condition of high-pressure fluid; circular, elliptical and oblong tunnel cross-sections are preferred. The inner surfaces of the pore channels can be understood as or equal to the inner wall surface of the heat transfer pipe, the functional structures of the pore channels are completely similar, the size and the dimension of the pore channels are determined by combining the heat transfer performance of working fluid and the pressure bearing function of heat exchange materials, and a certain wall thickness (pore channel bridge) is arranged between the primary side pore channel and the secondary side pore channel to prevent a high-pressure end working medium from leaking to a lower pressure medium end; in general, small-sized pores or micropores can bear high pressure or extremely high pressure, and can not cause the breakage and leakage of pore channels, but the flow resistance of the pores or micropores is larger. The heat exchange area of the pore canal is generally the product of the perimeter of the cross section of the pore canal and the length of the path of the pore canal, and the path of the pore canal in the heat exchange unit can be designed and arranged along a straight line or can be designed and arranged in a path bending way; the straight-through hole channel is convenient for processing and forming in various processing modes and controlling the form and position tolerance precision, and the bent hole channel is limited in general processing technology and high in processing cost.

After the size and the cross-sectional shape of the through hole are designed and determined, the technical requirements on the straightness and the surface roughness of the hole are generally set on a design drawing; a plurality of pore channels of a primary side or a secondary side are generally arranged in the heat exchange unit, the technical requirements of position tolerance and parallelism form and position tolerance should be provided between the pore channel of the primary side and the axial lead of the pore channel, and the technical requirements of position tolerance and parallelism form and position tolerance between the pore channel of the secondary side and the pore channel are also provided between the pore channel of the secondary side; the technical requirements of form and position tolerance of position degree and verticality (or space included angle precision) are required to be provided between the primary side pore canal and the secondary side pore canal. The processing precision requirements aim at ensuring the quality level of the pore channels and preventing the wall thickness of the material between the pore channels from being reduced and weakened due to processing deviation in the pore channel processing process so as to generate the accident of broken pipe and pressure loss. According to the size and the cross-sectional shape of the pore canal, the pore canal is generally processed and formed by deep hole drilling, 3D printing additive manufacturing, chemical etching of a multilayer board, vacuum molecular diffusion welding, wire cutting and the like.

(IV) description of the drawings

FIG. 1 is a schematic diagram of a duct structure of a heat exchange unit in the design scheme of the direct-current countercurrent duct type heat exchanger/evaporator.

FIG. 2 is a schematic diagram of a duct structure of a heat exchange unit in the design scheme of the direct-current countercurrent duct type heat exchanger/evaporator.

FIG. 3 is a schematic diagram of the duct structure of the heat exchange unit in the design scheme of the direct-current countercurrent duct type heat exchanger/evaporator.

FIG. 4 is a schematic structural diagram of the application aspect of the direct-current countercurrent pore channel type steam generator/intermediate heat exchanger of the high-temperature gas cooled reactor or the ultra-high-temperature gas cooled reactor.

(V) detailed description of the preferred embodiments

Figure 4 shows an embodiment of the invention in a high temperature gas cooled reactor or ultra high temperature gas cooled reactor steam generator/intermediate heat exchanger application.

The design scheme is very suitable for the design scheme of the steam generator for the ultra-supercritical parameter power generation of the high-temperature gas cooled reactor, the ultra-high temperature superimposed ultra-high pressure technical parameters are the design difficulty and pain point of the design scheme, and the design scheme of the spiral coil type evaporator is not enough in the reliability of a heat transfer pipe under the ultra-high temperature and ultra-high pressure design condition and is easy to cause pipe breaking and water loss accidents. The working medium at the primary side of the high-temperature gas cooled reactor is hot helium with the working pressure of 8MPa and the working temperature of 750 ℃, the hot helium is introduced into a primary side inflow header (5) through a primary side inflow pipeline (4) and then flows in a primary side pore channel (H1) of an upper heat exchange unit, the hot helium after baffling enters a primary side pore channel (H1) and a secondary side pore channel (H2) of a middle heat exchange unit (2) for direct-current countercurrent heat transfer, then enters a primary side pore channel of a lower heat exchange unit (3), after heat exchange (heat dissipation) is completed, the hot helium baffls enter a primary side outflow header (11) and then flows out to a primary side working medium forced circulation fan (24), and the working medium entering the fan is cold helium with the working pressure of slightly. The secondary side is deionized and desalted water with the working pressure of 30MPa and the working temperature of 205 ℃, the deionized and desalted water is introduced into a secondary side inflow header (18) through a secondary side inflow pipeline (19), flows in a secondary side pore passage (H2) of the lower heat exchange unit (3), the middle heat exchange unit (2) and the upper heat exchange unit (1) in sequence, and flows out from a secondary side outflow header (14) and a secondary side outflow pipeline (15) after heat exchange is completed (heat absorption), so that superheated steam with the working pressure of 28MPa and the working temperature of 630-700 ℃ is formed and is used for power generation with the ultra-supercritical parameters. The heat exchange unit material selects martensite heat-resistant stainless steel in the preheating section of water, selects ferrite heat-resistant steel for the steam turbine cylinder body in the heating section and the evaporation section, and selects high-temperature nickel-based alloy as the material of the overheating section.

The embodiment is also very suitable for the design scheme of the intermediate heat exchanger of the ultra-high temperature gas cooled reactor in the field of hydrogen production or hydrogen smelting. The intermediate heat regenerator is a primary loop pressure-bearing boundary of the ultra-high temperature gas cooled reactor, only exchanges heat with a user loop through the intermediate heat regenerator and does not exchange working media, the secondary side pressure is higher than the primary side pressure, the main function is to prevent the radioactive working media of the primary loop from escaping, the extreme high temperature is a design difficulty and a pain point of the intermediate heat exchanger of the ultra-high temperature gas cooled reactor, the shell-and-tube intermediate heat regenerator is complex in structure and high in manufacturing cost, and potential tube breaking risks exist in the operation process. The inflow working medium at the primary side of the ultra-high temperature gas cooled reactor is hot helium with the working pressure of 8MPa and the working temperature of 950 ℃, and the cold helium with the working pressure of slightly lower than 8MPa and the working temperature of 250 ℃ is formed after heat transfer with the secondary side; the secondary side inflow working medium is cold helium with the working temperature of 200 ℃ and the working pressure of 9MPa, and hot helium with the working temperature of 900 is generated after heat transfer with the primary side. The working principle of the device is the same as that of a steam generator for high-temperature gas cooled reactor ultra-supercritical power generation. The material selection logic is similar, and the material is selected according to the temperature field gradient.

The above examples are only for illustrating the present invention and are not to be construed as limiting the present invention. In accordance with the principles of the present invention, one of ordinary skill in the art can design many variations on the design of the direct current counterflow port heat exchanger and evaporator. The scope of the invention is defined by the following claims.

Claims (7)

1. A design scheme of a direct-current and countercurrent pore channel type heat exchanger/evaporator mainly comprises an upper heat exchange unit (1), a middle heat exchange unit (2), a lower heat exchange unit (3), a primary side pore channel (H1), a secondary side pore channel (H2), a primary side inflow pipeline (4), a primary side inflow header (5), a primary side outflow pipeline (6), a heat exchange unit bearing support (7), a pressure-bearing outer cylinder bearing bracket (8), a pressure-bearing outer cylinder (9), an outer cylinder bottom end enclosure (10), a primary side outflow header (11), a heat exchange unit heat insulation layer (12), a cladding heat insulation layer plate (13), a secondary side outflow header (14), a secondary side outflow pipeline (15), an outflow pipeline heat insulation layer (16), an outer cylinder top end enclosure (17), a secondary side inflow header (18), a secondary side inflow pipeline (19), The device comprises a pressure-bearing outer cylinder flange (20), a hemispherical blind flange (21), a blind flange sealing ring (22), a blind flange fastener (23) and a primary side working medium forced circulation pump or fan (24). The main structure is characterized in that a primary side pore channel (H1) is arranged on two working faces (B1, A2) of an upper heat exchange unit (1) according to calculation of high-temperature and high-pressure bearing strength of a heat exchange unit material and analysis of heat transfer of a thermal fluid, and a secondary side pore channel (H2) is arranged on the two working faces (A1, A2) according to calculation of high-temperature and high-pressure bearing strength of the heat exchange unit material and analysis of heat transfer of the thermal fluid; two working faces (A1, A2) of the middle heat exchange unit (2) are provided with a primary side pore passage (H1) and a secondary side pore passage (H2) according to the calculation of the high-temperature and high-pressure bearing strength of the heat exchange unit material and the heat transfer analysis of the hot working fluid; three working faces (A1, B1 and B2) of the lower heat exchange unit (3) are provided with a primary side pore canal (H1) according to the calculation of the high-temperature and high-pressure bearing strength of the heat exchange unit material and the heat transfer analysis of the thermal fluid, and two working faces (A1 and A2) are provided with a secondary side pore canal (H2) according to the calculation of the high-temperature and high-pressure bearing strength of the heat exchange unit material and the heat transfer analysis of the thermal fluid. The number, the size, the shape, the path, the bending, the flow resistance, the position relation, the form and position tolerance and the surface roughness of the primary side pore canal are determined through design calculation, and the number, the size, the shape, the path, the bending, the flow resistance, the position relation, the form and position tolerance and the surface roughness of the secondary side pore canal are determined through design calculation; the design and manufacture need to ensure that the drift diameters (H1, H2) of the pore channels of the upper heat exchange unit (1), the middle heat exchange unit (2) and the lower heat exchange unit (3), the primary side-hole inter-bridge (T1), the secondary side-hole inter-bridge (T2) and the primary side and secondary side-hole channel bridge (T3) are completely consistent, and the straightness, coaxiality, parallelism, perpendicularity and ellipticity of the pore channels are within the range of requirements on form and position tolerance precision. The working surface (A2) of the upper heat exchange unit (1) and the working surface (A1) of the middle heat exchange unit (2), the working surface (A2) of the middle heat exchange unit (2) and the working surface (A1) of the lower heat exchange unit (3) are welded together through a vacuum heating and pressurizing molecular diffusion welding process to form a primary side direct current countercurrent heat exchange flow channel and a secondary side direct current countercurrent flow channel; the middle heat exchange units (2) can be arranged in series according to the heat transfer calculation requirement; the upper heat exchange unit (1) has the main functions of baffling primary side working medium, isolating the primary side working medium from secondary side working medium, and respectively guiding and connecting the primary side working medium and the secondary side working medium to a primary side inflow header (5) and a secondary side outflow header (14); the structure of the middle heat exchange unit (2) mainly has the function of direct-current countercurrent heat transfer of a primary side working medium and a secondary side working medium; the lower heat exchange unit (3) mainly has the functions of baffling the primary side working medium, isolating the primary side working medium from the secondary side working medium and respectively guiding and connecting the primary side working medium and the secondary side working medium to a primary side outflow header (11) and a secondary side inflow header (18).

Primary side working media are led into a primary side inflow header (5) from a primary side inflow pipeline (4) and then flow in a primary side pore passage (H1) of an upper heat exchange unit, enter a primary side pore passage (H1) and a secondary side pore passage (H2) of a middle heat exchange unit (2) after being baffled, are subjected to direct-current countercurrent heat transfer, then enter a primary side pore passage of a lower heat exchange unit (3), and are baffled after heat exchange is finished (heat dissipation) and then flow out after entering a primary side outflow header (11); secondary side working media are led into a secondary side inflow header (18) from a secondary side inflow pipeline (19) and flow in secondary side pore channels (H2) of the lower heat exchange unit (3), the middle heat exchange unit (2) and the upper heat exchange unit (1) in sequence, and after heat exchange is completed (heat absorption), the secondary side working media flow out from a secondary side outflow header (14) and a secondary side outflow pipeline (15); the primary side pore passage and the secondary side pore passage are in direct-current countercurrent but are not communicated with each other, and have certain pressure bearing (pressure difference of working media on the primary side and the secondary side) capacity under certain temperature condition; the counter-flow convection heat transfer function of the primary side working medium and the secondary side working medium with heat convection as the main part and heat conduction and heat radiation as the auxiliary part is realized.

Because the pore channel type heat transfer forms close-fitting type multilayer metal heat conduction heat transfer in the heat exchange unit, the heat transfer coefficient is far higher than that of the heat radiation heat transfer of the wall surface of the shell-and-tube heat transfer pipe; under the condition of the same size and material, the direct current countercurrent pore channel type heat exchanger can realize the dense and compact arrangement of multilayer pore channels, while the shell-and-tube type heat exchanger cannot compactly arrange a heat transfer pipe due to the strength of pore bridges of tube plates at two ends, and the heat transfer area of the wall surface of the multilayer pore channel is greatly increased compared with that of the heat transfer pipe; under the condition of the same heat exchange capacity, the pore channel type heat exchanger can realize smaller heat exchange temperature difference between the primary side and the secondary side than a shell-and-tube type heat exchanger. The channel type heat exchanger/evaporator has the characteristics of high thermal efficiency, is simple, practical, safe and reliable, and only exchanges heat but not exchanges working media; the heat transfer under the severe working medium condition of extreme high temperature or extreme high pressure can be realized, the heat transfer efficiency is higher than that of a shell-and-tube heat exchanger taking heat radiation as a main part and heat conduction and heat convection as an auxiliary part, and the heat transfer temperature difference between the primary side and the secondary side is small; compared with a shell-and-tube heat exchanger with the same heat transfer capacity, the volume and the weight of the direct-current countercurrent pore channel type heat exchanger are reduced by more than one third. Under the conditions of proper heat exchange unit material selection and proper heat transfer pore channel design selection, the heat exchange unit can support heat transfer under the severe heat transfer conditions of extreme high temperature not exceeding 1000 ℃ or extreme high pressure not exceeding 1000 kilograms. Under the conditions of special heat transfer structure design and material selection, a plurality of process flows are supported by the primary side or the secondary side to be combined into one flow passage to realize the heat transfer function.

The heat exchange unit set is characterized in that a plurality of middle heat exchange units (2) are welded with the upper heat exchange unit (1) and the lower heat exchange unit (3) in an assembly mode or manufactured in an additive mode through working faces (A1 and A2) to form a heat exchange unit set in series, and the main structure of the heat exchange unit set is characterized in that large temperature difference heat transfer and temperature shock heat transfer are achieved through cascade continuous heat transfer of the heat exchange units. The multistage through-penetration channel from top to bottom is formed by high-power vacuum electron beam welding, high-power vacuum molecular diffusion welding, high-power laser self-fluxing welding, laser narrow-gap composite cladding welding or TIG narrow-gap welding. The structural design has the advantages that the pore passage can be inspected in service, and is particularly suitable for heat transfer of high-pressure fluid; the design structure that the working face is welded in sequence also saves primary side and secondary side baffling. The heat exchange unit is provided with a heat exchange unit heat insulation layer (12) and a heat insulation layer cladding plate (13) at the periphery, and the heat exchange unit is mainly structurally characterized in that the heat of high-temperature working media at the primary side and the secondary side hot ends is blocked from being lost to the inner cooling end of the pressure-bearing outer cylinder (9) in a non-heat-transfer mode through heat conduction and heat radiation, and the heat transfer efficiency of a working medium flow channel is improved. The primary side inflow pipeline (4), the primary side inflow header (5), the secondary side outflow header (14), the secondary side outflow pipeline (15) and other high-temperature area components are provided with heat insulation layers in the same way to block heat loss, and each heat insulation layer is fixed by a heat insulation layer cladding plate respectively.

The primary side cold end working medium heat exchange unit is mainly structurally characterized in that a primary side working medium hot end heat exchange unit is surrounded by the pressure-bearing outer cylinder (9) as a primary side working medium cold end, the primary side outflow pipeline (6) as a primary side working medium cold end surrounds the primary side working medium hot end inflow pipeline (4), and the primary side outflow pipeline (6) as a primary side working medium cold end surrounds the primary side working medium hot end primary side inflow pipeline (4) so as to realize the cold-heat-in-package design concept. In principle, working media with lower pressure are usually selected as primary side working media, so that the pressure-bearing outer cylinder only bears low-temperature low-pressure primary side cold end working media after heat exchange, the difficulty of material selection is reduced, and a mature heat-resistant steel pressure-bearing material can be usually selected. Under the condition of extremely high temperature of the primary side and the secondary side, although the heat exchange unit bears higher temperature and the selection surface of the high-temperature alloy material is limited, the heat exchange unit only bears the working pressure difference between the primary side and the secondary side, compared with the heat exchange unit which is only required to bear larger absolute high pressure of the secondary side, the consumption of expensive high-temperature alloy material is greatly reduced, and the equipment cost of a heat exchanger or an evaporator is reduced to a certain extent.

In the heat exchange unit groups connected in series, along with continuous direct-current countercurrent heat transfer of the primary side working medium and the secondary side working medium, the temperature fields of the primary side working medium flow channel (L1) and the secondary side working medium flow channel (L2) are gradually decreased along with the flow field of the working medium; the heat exchange unit group can select a proper heat-resistant pressure-bearing material according to the descending degree and the direction gradient configuration of the temperature field, for example, an expensive high-temperature alloy material is selected in an extreme high-temperature section, a mature heat-resistant pressure-bearing material is selected in a common high-temperature section and a medium-temperature section, and a pressure-bearing material with lower manufacturing cost is selected in a low-temperature section. The direct current countercurrent pore canal composed of a plurality of heat exchange units is generally subjected to heat transfer activities such as preheating, heating, evaporation, drying and the like, and the heat exchange units are made of martensitic stainless heat-resistant steel or austenitic stainless steel in a preheating section, a heating section and an evaporation section of a medium, so that the use of high-temperature alloy is avoided, and the equipment cost can be greatly reduced.

A pressure boundary of a primary side cold end working medium pressure-bearing shell is formed by a pressure-bearing outer cylinder (9), an outer cylinder bottom end enclosure (10), an outer cylinder top end enclosure (17) and a pressure-bearing outer cylinder flange (20), and the flange is used for opening a pressure-bearing inner cylinder welding line of the pressure-bearing shell in service inspection, and inspecting, maintaining or blocking a pore channel; a hemispherical blind flange (21), a blind flange seal (22) and a blind flange fastener (23) are arranged at the bottom end socket (21) of the outer cylinder and are used for primary side working medium forced circulation pump or fan (24) maintenance to prevent primary side working medium leakage, and the outer cylinder is particularly suitable for primary side working medium with radioactivity. A hanging basket is arranged at the upper part of the inner wall of the pressure-bearing outer barrel (9) and is parallel to the top end face of the heat exchange tube unit, or a bracket is arranged at the lower part of the inner wall of the pressure-bearing outer barrel and is parallel to the bottom end face of the heat exchange tube unit so as to transmit the weight of the heat exchange unit to an external foundation or support through the outer barrel, and spring dampers (solid springs, hollow springs, disc springs and the like) are embedded in the hanging basket and the bracket so as to absorb thermal expansion generated under the thermal working condition of the.

2. The design scheme of a once-through counterflow porthole heat exchanger/evaporator according to claim 1, as shown in fig. 4, characterized by performing a deformation design on an upper heat exchange unit (1), and its main structural features are that three working faces (B1, B2, a2) of the upper heat exchange unit (1) are provided with a primary porthole (H1) according to the calculation of the high-temperature and high-pressure bearing strength of the heat exchange unit material and the analysis of the heat transfer of the thermal fluid, and two working faces (a1, a2) are provided with a secondary porthole (H2) according to the calculation of the high-temperature and high-pressure bearing strength of the heat exchange unit material and the analysis of the heat transfer of the; working surfaces of upper heat exchange units (1), B1 and B2 are respectively provided with a primary side inflow pipeline (4) and a primary side inflow header (5), a primary side working medium is introduced into the primary side inflow header (5) from the primary side inflow pipeline (4) and then flows in a primary side pore channel (H1) of the upper heat exchange unit, after being baffled, the primary side working medium enters a primary side pore channel (H1) and a secondary side pore channel (H2) of a middle heat exchange unit (2) for direct-current countercurrent heat transfer, then enters a primary side pore channel of a lower heat exchange unit (3), and after heat exchange (heat dissipation) is completed, the working medium is baffled, enters a primary side outflow header (11) and; the secondary side working medium is the same as in claim 1. If the primary side pressure is higher than the secondary side pressure, in order to facilitate the service inspection of the high-pressure side pore passage during the operation, the primary side and the secondary side can exchange flow passages, namely the primary side high-pressure working medium flows through A1 and A2 surface multi-stage direct-current backflow pore passages, and the secondary side low-pressure working medium flows through B1, B2 and A2 baffling pore passages. Such a design is also reasonably feasible.

3. A design scheme of a direct current counterflow tunnel heat exchanger/evaporator according to claim 1 and claim 2, characterized by simplifying the design of the pressure-bearing boundary, wherein the simplification is that the pressure-bearing outer cylinder (9) is removed, and the heat exchange unit, the inflow header and the outflow header are directly used as the pressure-bearing boundary, and are suitable for common high-temperature and common high-pressure application conditions.

4. The design scheme of the direct current and countercurrent pore canal type heat exchanger/evaporator as claimed in claim 3, wherein the upper heat exchange unit, the middle heat exchange unit and the lower heat exchange unit are designed in a modified way, and the modified points are that the working surfaces of the heat exchange units B1 and B2 are modified into outer cylindrical and inner cylindrical working surfaces (annular heat exchanger) or outer and inner cylindrical surfaces (sector heat exchanger).

5. A once-through, counter-flow, channel heat exchanger/evaporator design as claimed in claim 1, claim 2, claim 3, claim 4 wherein the lower heat exchange unit is configured with a modified simplification wherein the two outlet flow faces of the lower heat exchange unit B1, B2 block one of them and remove one side secondary outlet header and secondary outlet conduit to flow out of only one of them.

6. The design scheme of the direct current counterflow pore channel type heat exchanger/evaporator as claimed in claim 1, claim 2, claim 3, claim 4 and claim 5, characterized in that the built-in pore channels of the upper heat exchange unit and the lower heat exchange unit are designed in a modified way, the primary side pore channels of the upper heat exchange unit can be arranged into arc-shaped flow channels, curved flow channels or a plurality of folded flow channels from the surface B1 to the surface A2, and the flow channels are parallel to each other and do not penetrate each other; the primary side pore channels of the lower heat exchange unit can be arranged into arc-shaped channels, curved channels or a plurality of folded surface channels from the surface A1 to the surface B1 (or the surface B2), and the channels are parallel to each other and are not communicated with each other; the arc-shaped flow channel, the curved-surface flow channel or the plurality of folded-surface flow channels can be formed through 3D printing or photochemical etching.

7. A design scheme of a once-through counterflow tunnel heat exchanger/evaporator as claimed in claim 1, claim 2, claim 3, claim 4 and claim 5, as shown in fig. 1, fig. 2 and fig. 3, characterized in that the once-through counterflow tunnel for heat transfer is specifically designed according to the heat transfer performance of the structural material and the pressure-bearing function of the working medium, and at the same time, considering the convenience of tunnel processing process and sometimes the flow resistance characteristic of the tunnel. The cross-sectional shape of the porthole can be generally circular, oblong, oval, semicircular, rectangular, rhombic, triangular, polygonal, irregular, etc. The direct-current countercurrent pore canal can also be designed into a non-uniform cross-section shape along the flowing direction of the working medium, such as a continuous conical pore canal; the non-circular pore canal is easy to generate stress concentration and micro defects in the processing process, and is not recommended to be selected under the high-pressure working condition; circular, oblong, elliptical or semicircular channel cross-sections are preferred. If the primary side pore channel and the secondary side pore channel are oval or semicircular, the diameter (2a) of the long axis of the oval and the diameter chord (2r) of the semicircle are suggested to be parallel to the inflow direction of the primary side of the heat exchange unit, so that the number of the heat exchange pore channels can be increased under the condition of ensuring the heat transfer coefficient and the pressure bearing function, and the heat exchange area is increased. The internal flow channel of the pore channel can be understood as or equal to the inner wall of the heat transfer pipe, the two functional structures are completely similar, the size and the dimension of the pore channel are determined by combining the heat transfer performance of working fluid and the pressure bearing function of heat exchange materials, wall thickness inter-pore bridges (H1, H2) are reserved between the pore channel and the pore channel to meet the requirement of pressure bearing strength, and a certain wall thickness inter-pore bridge (H3) is arranged between the primary side pore channel and the secondary side pore channel to prevent the working medium at a high pressure end from leaking to a lower pressure medium end; in general, small-sized pores or micropores can bear high pressure or extremely high pressure, and can not cause the breakage and leakage of pore channels, but the flow resistance of the pores or micropores is larger. The heat exchange area of the pore canal is generally the product of the perimeter of the cross section of the pore canal and the length of the path of the pore canal, and the path of the pore canal in the heat exchange unit can be designed and arranged along a straight line or can be designed and arranged in a path bending way; the straight-through hole channel is convenient for processing and forming in various processing modes and controlling the form and position tolerance precision, and the bent hole channel is limited in general processing technology and high in processing cost. The surface roughness of the inner wall of the duct influences the flow resistance, and the flow resistance of the smooth inner wall surface is generally smaller. After the size and the cross-sectional shape of the direct current countercurrent pore channel are designed and determined, technical requirements on the straightness and the surface roughness of the pore channel are required to be provided on a design drawing; a plurality of pore channels of a primary side or a secondary side are generally arranged in the heat exchange unit, the technical requirements of position tolerance and parallelism form and position tolerance should be provided between the pore channel of the primary side and the axial lead of the pore channel, and the technical requirements of position tolerance and parallelism form and position tolerance between the pore channel of the secondary side and the pore channel are also provided between the pore channel of the secondary side; the technical requirements of form and position tolerance of position degree and verticality (or space included angle precision) are required to be provided between the primary side pore canal and the secondary side pore canal. The processing precision requirements aim at ensuring the quality level of the pore channels and preventing the wall thickness of the material between the pore channels from being reduced and weakened due to processing deviation in the pore channel processing process so as to generate the accident of broken pipe and pressure loss. According to the size and the cross section shape of the pore channel, the porous ceramic is processed and formed by adopting deep hole drilling, 3D printing additive manufacturing, multilayer board chemical etching, vacuum diffusion welding, wire cutting and other modes.

Images