Heat exchanger configuration with porous layer

Abstract

To provide a heat exchanger which can inhibit mixing of coolants.SOLUTION: A heat exchanger disclosed herein is made up of a hot flow channel, a cold flow channel, and a porous layer provided between the hot flow channel and the cold flow channel. The heat exchanger is a plate heat exchanger comprising a hot plate and a cold plate. The hot flow channel is formed as first guide channels on a surface of the hot plate, and the cold flow channel is formed as second guide channels on a surface of the cold plate. A porous thermally insulative layer is disposed between the hot plate and the cold plate.SELECTED DRAWING: Figure 2

Description

[Background technology]

[0001] A heat exchanger is a device that allows the transfer of thermal energy from the core of an operating nuclear reactor to a secondary fluid, where the thermal energy can be captured and used for a useful purpose. In some cases, the thermal energy is used to generate steam, which can be used to generate electricity, such as through a steam turbine.

[0002] Heat exchangers are often exposed to large temperature gradients that can cause thermal stresses in the heat exchanger components. If the temperature gradient is high enough, the thermal stresses can cause leaks that promote mixing of the two working fluids. In some cases, the two working fluids passing through the heat exchanger may react unfavorably if allowed to mix.

[0003] Furthermore, in some cases, when the working fluid passing through a heat exchanger reaches a temperature below the freezing temperature of the working fluid, it may begin to solidify, reducing the effectiveness of the heat exchanger in transferring thermal energy.

[0004] It would be advantageous if the above problems were addressed, such as by providing additional strength to the heat exchanger to withstand cyclic thermal stresses, reducing leakage and mixing of two or more working fluids, and reducing freezing of the working fluids.

[0005] These and other advantages will become apparent with reference to the following description and accompanying drawings. Summary of the Invention

[0006] According to some embodiments, a heat exchanger that can be used in a nuclear reactor is described. The heat exchanger includes a hot flow channel, a cold flow channel fluidly separated from the hot flow channel, and a porous thermal insulation layer disposed between the hot and cold flow channels. The porous thermal insulation layer can include an inlet, an outlet, and a fluid passage between the inlet and the outlet. The porous thermal insulation layer is configured to flow a control gas through the fluid passage, the control gas being configured to affect a thermal energy transfer efficiency of the porous thermal insulation layer.

[0007] In some cases, the control gas is used for leak detection of the first fluid, the second fluid, or both. In other words, if there is a breach in the hot or cold flow path, the control gas can be monitored for the presence of fluid in the control gas exit stream. In some cases, the control gas is used to capture fission products or activation products, such as tritium.

[0008] The control gas can be a mixture of two or more gases, and mixing control can be provided to vary the mixture of the two or more gases to change the thermal energy transfer efficiency of the porous thermal insulation layer. In some cases, the control gas is a mixture of argon and helium. Mixing control can be used to vary the proportion of argon and helium in the control gas, which also changes the heat transfer properties of the control gas.

[0009] In some embodiments, the porous thermal insulation layer is formed of a metal or metal alloy and defines an open pore structure. Alternatively, it may be formed of a ceramic material. The porous thermal insulation layer may be formed by an additive manufacturing process. The additive manufacturing process may include 3D printing or molding.

[0010] In some cases, the porous thermal insulation layer reduces the efficiency of thermal energy transfer from the hot flow path to the cold flow path.

[0011] The heat exchanger may be a plate heat exchanger including a hot plate and a cold plate, with the hot flow passages formed as first guide passages on the surface of the hot plate and the cold flow passages formed as second guide passages on the surface of the cold plate. Alternatively, the heat exchanger may be a shell and tube heat exchanger.

[0012] In the case of a plate heat exchanger, a porous thermal insulation layer may be placed between the hot and cold plates to provide an additional boundary that inhibits mixing of the hot and cold fluids.

[0013] For example, a porous thermal insulation layer may further separate the hot and coolant flow paths, allowing the hot and coolant flow paths to respond independently to thermal gradients that exist across the heat exchanger.

[0014] According to some embodiments, a method for reducing thermal energy transfer efficiency in a heat exchanger includes: providing a hot flow path; providing a cold flow channel fluidly separated from the hot flow path; and providing a porous thermal insulation layer between the hot flow path and the cold flow path.

[0015] Providing a porous thermal insulation layer can include providing an open pore structure of metal between the hot and cold flow paths. The method can further include providing an inlet on one side of the porous thermal insulation layer and an outlet on the other side of the porous thermal insulation layer.

[0016] A control gas may be introduced through the inlet, through the porous thermal insulation layer, and through the outlet.

[0017] In some cases, the method includes controlling the thermal energy transfer efficiency of the heat exchanger by varying a mixture of a control gas. For example, the control gas can be a mixture of two or more gases, and varying the mixture of the control gas can change the thermal energy transfer efficiency of the heat exchanger. In some cases, the control gas is a mixture of argon and helium, although any suitable gas or mixture of gases can be used.

[0018] In some examples, the control gas can be tested for the presence of a fugitive substance in the heat exchanger. The fugitive substance can be the first fluid, the second fluid, or both. The method can also include selecting the control gas to attract and capture tritium. The control gas can be captured after flowing through the heat exchanger, and the tritium can be removed. [Brief explanation of the drawings]

[0019] The detailed description is set forth with reference to the accompanying drawings, in which the leftmost digit(s) of a reference number identifies the figure in which the reference number first appears. Use of the same reference number in different figures indicates similar or identical components or features.

[0020] [Figure 1A] 1 is a schematic diagram of a plate heat exchanger for transferring thermal energy from a hot fluid to a cold fluid, according to some embodiments.

[0021] [Figure 1B] FIG. 1 is a schematic diagram of a hot flow plate with channels according to some embodiments.

[0022] [Figure 1C] FIG. 2 is a schematic diagram of a porous layer that may be disposed between a hot flow plate and a cold flow plate in a plate heat exchanger according to some embodiments.

[0023] [Figure 1D] FIG. 1 is a schematic diagram of a cold flow plate with channels, according to some embodiments.

[0024] [Figure 2] FIG. 1 is a schematic diagram of a plate heat exchanger with a porous layer between the hot and cold flow plates according to some embodiments.

[0025] [Figure 3A] 1 illustrates an exemplary porous layer that can be used in a heat exchanger, according to some embodiments.

[0026] [Figure 3B] 1 illustrates an exemplary porous layer that can be used in a heat exchanger, according to some embodiments.

[0027] [Figure 3C] 1 illustrates an exemplary porous layer that can be used in a heat exchanger, according to some embodiments.

[0028] [Figure 3D] 1 illustrates an exemplary porous layer that may be used in a heat exchanger according to some embodiments.

[0029] [Figure 4] 1 shows a scanning electron image of a porous structure that can be used as a layer in a heat exchanger according to some embodiments.

[0030] [Figure 5] 1 illustrates a cross-sectional view of a double shell and tube heat exchanger with a porous layer between the shell and the tubes, according to some embodiments.

[0031] [Figure 6] 1 illustrates a process flow for reducing the heat transfer efficiency of a heat exchanger according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present disclosure generally relates to heat exchanger devices. Heat exchangers can be used in any application where thermal energy transfer between a first fluid and a second fluid is desired. While much of the following disclosure is provided in the context of nuclear reactors, it should be understood that nearly any application utilizing a heat exchanger can benefit from the embodiments described and claimed herein. The present invention also relates to configurations that can reduce the efficiency of a heat exchanger, thereby reducing thermal stresses and temperature gradients across the heat exchanger. While a significant amount of research has been conducted to improve the efficiency of heat exchangers, even using foam materials to increase surface area and promote conduction, according to some embodiments, a layer of porous material is positioned between the hot and cold flow paths to reduce heat transfer, thereby reducing the thermal energy transfer efficiency of the heat exchanger. Providing a porous layer has the additional benefit of providing flexibility to the heat exchanger to better absorb thermal stresses imparted to the heat exchanger, which can cause failure of one or more components and allow mixing of working fluids.

[0033] In some cases, the working fluids in the heat exchangers are different fluids and may include salt and sodium. For example, in a molten salt reactor (MSR), fuel salt provides both the fuel and the primary coolant for the reactor core. In some cases, fuel salt is the first working fluid, and a secondary coolant receives thermal energy from the fuel salt. The secondary coolant may be any suitable coolant, such as, for example, salt, sodium, or some other desired coolant.

[0034] In some nuclear reactors, sodium is the primary coolant in the reactor, receiving thermal energy from the reactor core. The sodium enters a heat exchanger as the first working fluid and provides thermal energy to a second working fluid, which may be sodium, salt, or other suitable coolant.

[0035] As used herein, the term "primary coolant" is a broad term and refers to a fluid that receives thermal energy from the reactor core to manage the reactor core temperature. The primary coolant may be any suitable coolant, such as, for example, salt, sodium, lead, lead-bismuth eutectic, heavy water, light water, gas, or some other suitable coolant. The primary coolant in the reactor vessel is also referred to herein as the first working fluid in the heat exchanger. While the exemplary embodiment references a single heat exchanger as an example, it should be understood and appreciated that a nuclear reactor can include any number of heat exchangers that function to transfer thermal energy from the primary coolant to the secondary coolant. Furthermore, the heat exchanger may be made up of several heat exchanger cores that all cooperate to handle the reactor's thermal load. While any of these configurations are equally applicable to the disclosure herein, for efficiency, a single heat exchanger will be used in describing the exemplary embodiment. References to a first fluid and / or a second fluid in the heat exchanger will also be made throughout this description. It should be understood that the terms "first fluid" and "second fluid" may be used interchangeably with the terms "primary coolant" and "secondary coolant."

[0036] In some embodiments, a small heat exchanger is provided within the reactor vessel of a nuclear reactor to transfer heat from the primary coolant to the secondary coolant in the core. In some cases, the heat exchanger transfers thermal energy from sodium to salt. For example, in a sodium-cooled fast reactor ("SFR"), sodium may be used as the primary coolant within the reactor vessel. As sodium circulates throughout the reactor vessel by either natural circulation, one or more circulation pumps, or a combination of circulation modalities, sodium near more reactive regions receives thermal energy and becomes heated. The heated sodium flows through the heat exchanger, and thermal energy is transferred from the primary sodium coolant to the secondary coolant (possibly sodium, salt, or other secondary coolant).

[0037] In a molten salt reactor (MSR), fuel salt is used as both the fuel and the primary coolant, which is circulated through the reactor vessel via natural circulation, one or more pumps, or a combination thereof. The fuel salt passes through the reactor core, where it heats up as it receives thermal energy from the fission reaction. The fuel salt is then routed to a heat exchanger, which transfers the thermal energy to the secondary coolant (salt, sodium, or other coolant circulating through the heat exchanger). In some cases, the secondary coolant may have a higher thermal conductivity than the fuel salt. As an example, sodium has a thermal conductivity approximately 100 times higher than many cooling salts. In a salt-to-sodium heat exchanger, it is desirable to control the transfer of thermal energy from the salt to the sodium. For example, if heat transfer is too efficient, the fuel salt may cool below its freezing point, begin to increase in viscosity, and / or flow through the heat exchanger may decrease, exacerbating the problem of fuel salt freezing within the heat exchanger. Of course, stopping the primary coolant from flowing through the heat exchanger can lead to other undesirable problems, particularly heat buildup within the reactor vessel.

[0038] Therefore, in some instances, it may be important to control, limit, slow down, or otherwise influence the transfer of thermal energy within a heat exchanger from the primary coolant to the secondary coolant.

[0039] Plate heat exchangers may be used to transfer thermal energy from a primary coolant to a secondary coolant. In some cases, the plate heat exchanger may have two inlets and two outlets. For example, the plate heat exchanger may have an inlet and an outlet for the primary coolant and an inlet and an outlet for the secondary coolant. The flow paths of these liquids may be defined by channels within each plate of the heat exchanger, which keep the coolants fluidically separated and maintain heat transfer as the plates transfer thermal energy from a hot fluid to a cold fluid.

[0040] In some cases, it is desirable to maintain separation between the primary and secondary coolants. For example, in some cases, the primary and secondary coolants may react when mixed. Plate heat exchangers typically provide separation between the primary and secondary coolant flow paths. However, due to cyclic thermal stresses applied to the heat exchanger, the separation between the plates may fail, such as by plastic deformation, which allows the primary and secondary coolants to mix. In many plate heat exchangers, the hot flow channels are formed on one surface of the plates and the cold flow channels are formed on the opposite side of the plates. As a result, the thickness of the plates provides separation between the hot and cold fluids. If one or more plates fail, the fluids can mix.

[0041] Therefore, it may be desirable to further inhibit coolant mixing, for example, by reducing the thermal stresses applied to the heat exchanger, providing additional separation between the fluid flow paths, and / or allowing elastic deformation within the heat exchanger to compensate for cyclic thermal stresses. According to some embodiments, all of these benefits are provided by forming a porous layer between the hot and cold flow paths.

[0042] 1A-1D show layers of a plate heat exchanger 100. According to some embodiments, the plate heat exchanger is formed from multiple metal plates bonded together. Fluid passages are formed in the surfaces of the plates to form fluid flow paths for hot and cold fluids. The hot flow plate 102 and the cold flow plate 104 are typically in a heat transfer relationship, such as by conduction, where thermal energy is transferred from the hot flow plate 102 to the cold flow plate 104. Often, the hot flow plate 102 and the cold flow plate 104 are bonded directly to each other, but in other cases, a single plate has channels formed in both surfaces of the plate, with one surface portion of the hot flow path and the opposite surface forming part of the cold flow path.

[0043] One potential concern with this arrangement is that cyclical thermal stresses may cause weakening and eventual failure of one or more plates, allowing the primary and secondary coolants to mix. Therefore, in some embodiments, a porous layer 106 is disposed between the hot flow plate 102 and the cold flow plate 104. This provides separation between the hot flow plate 102 and the cold flow plate 104, which provides an additional barrier to mixing between the primary and secondary coolants. For example, there must be a simultaneous failure of both the hot flow plate 102 and the adjacent cold flow plate 104 for the primary and secondary coolants to mix.

[0044] The porous layer 106 may be any suitable porous material, and in some cases is a porous metal. The porous layer 106 may be formed by any suitable process and any suitable material. For example, the porous layer 106 may be formed by one or more of an additive manufacturing process (e.g., 3D printing), sintering, thermal spraying, foaming, powder metallurgy, or injection molding, to name a few. In some cases, the porous layer 106 forms an open pore structure in which the pores are interconnected to form fluid passages therebetween. In some cases, the porous layer 106 forms a third fluid passage having a third fluid inlet and a third fluid outlet for passing a third fluid through the porous layer 106 of the heat exchanger 100.

[0045] The porous layer 106 may be formed to have any pattern, such as a regular pattern that may be formed by additive manufacturing or molding. The porous layer 106 may additionally or alternatively be formed in a random pattern, such as via sintering, thermal spraying, powder metallurgy, foaming, or other suitable process.

[0046] In some cases, a third inlet and outlet may be provided, with a third fluid flow path defined by the porous layer 106. The third fluid may be provided for any of several purposes, such as to detect leaks in either the primary or secondary coolant heat exchangers, to remove fission products or activation products (e.g., tritium), to modify the heat transfer characteristics of the heat exchangers, or other purposes. In some cases, hydrogen may be used as the third fluid in the heat exchangers. In some cases, CO2 may be used as the third fluid in the heat exchangers. In some cases, helium may be used as the third fluid in the heat exchangers. In some cases, argon may be used as the third fluid in the heat exchangers. In some cases, a mixture of gases is fed through the porous layer of the heat exchangers.

[0047] In either case, the third fluid may be used for leak detection. For example, one or more detectors may be placed in the third fluid stream downstream of the heat exchanger, and the third fluid may be tested for the inclusion of one or more substances that were not present in the third fluid before entering the heat exchanger. For example, the third fluid may be tested for salts after passing through the heat exchanger, and the presence of salts (whether in liquid or vapor form) in the third fluid may be an indication of a salt leak in the heat exchanger.

[0048] The hot flow plate 102 and the cold flow plate 104 may have fluid channels formed therein, which may be formed by machining, chemical etching, laser etching, or some other suitable process. The plates may provide heat transfer between the primary and secondary coolant, such as through material conduction. In some cases, the plates may be fused together to form a monolithic structure. As shown, primary reactor coolant enters the heat exchanger at an inlet 110, where it flows through channels 112 in the plates and exits the opposite side of the heat exchanger at an outlet 114.

[0049] 1D shows the cold flow plate 104 having a second inlet 116 for secondary coolant fluid. A secondary coolant fluid outlet 118 allows the secondary coolant to exit the heat exchanger 100. In some cases, the secondary coolant loop includes coaxial pipes, with an inner pipe extending through an outer pipe. The inner pipe may be coupled to the inlet of the heat exchanger and the outer pipe may be coupled to the outlet of the heat exchanger, in which case the inlet and outlet of the cold plate 104 may be formed on the same side of the heat exchanger.

[0050] Suitable heat exchangers 100 include, but are not limited to, printed circuit heat exchangers, plate heat exchangers, molded plate heat exchangers, or hybrid heat exchangers, where two or more media flow on opposite sides of one or more joined plates. The cooling media can be under high pressure, but in some embodiments is at low pressure. The working fluid, which in some embodiments is salt and sodium, can be made to flow on both sides of one or more joined plates through a 2D or 3D plate pattern. The 2D or 3D plate pattern can be configured to create a desired thermal length and pressure drop.

[0051] The nuclear reactor may be any suitable reactor for utilizing the improvements possible with the embodiments described herein. For example, without limitation, the described embodiments may be used with an SFR, an MSR, or any other nuclear reactor, and the reactor may be a pool-type or loop-type reactor. Of course, other types of nuclear reactors may be used, and any suitable primary and secondary coolants may be used. In some cases, the described heat exchanger is a salt / sodium heat exchanger, in which salt is the primary coolant and sodium is the secondary coolant. In other cases, the heat exchanger is a salt / salt heat exchanger, a sodium / salt heat exchanger, a sodium / sodium heat exchanger, a salt / lead heat exchanger, a lead / salt heat exchanger, a sodium / water heat exchanger, a salt / lead-bismuth eutectic heat exchanger, or a lead-bismuth eutectic-to-salt heat exchanger. Of course, any two working fluids may be used in a heat exchanger according to embodiments, and the working fluids may be the same or different fluids.

[0052] The heat exchanger 100 may be formed from a series of parallel plates 102, 104 having surface grooves 112 positioned adjacent to one another to form a series of flow paths when the plates 102 are joined together. The surface grooves 112 may be photochemically etched, mechanically formed, or formed by some other process into the surfaces of the plates and may be sized and positioned to provide desired flow characteristics, such as fluid path length and pressure drop.

[0053] In many cases, the plates 102, 104 are diffusion bonded together, which is a solid-state welding process that restores the bond to parent metal strength, allows for superior high temperature flow performance, and allows for design optimization of 2D and / or 3D fluid passages through the heat exchanger 100. However, in some cases, a porous layer 106 is provided between each of the hot flow plates and the cold flow plate.

[0054] In some embodiments, headers or manifolds (not shown) may be attached to the fluid inlets 110 or outlets 114 that provide a fluid communication path simultaneously through all layers of the heat exchanger 100. Alternatively, or additionally, ports may be constructed during the plate forming stage to provide integral headers for the heat exchanger 100. In some cases, the heat exchanger 100 may be semi-ported, with a mix of headers and ports connected by manifolds.

[0055] An acceptable pressure drop can be specified, with lower pressure drops typically being desirable to reduce capital and operating costs. In some embodiments, the pressure drop across the primary refrigerant flow path of heat exchanger 100 is less than about 6 psi, or less than about 5 psi, or less than about 4 psi, or less than about 3 psi. Lower pressure drops typically require shorter flow lengths and lower refrigerant viscosities, which directly affect the heat transfer coefficient. Pressure drop can be adjusted by varying the flow length, fluid viscosity, and / or flow path width and depth dimensions, and overall heat transfer can similarly be affected by varying the number of layers and heat transfer area.

[0056] Plate surface types can be tailored for specific purposes and can be formed to increase surface density and heat transfer coefficient, and can be formed as fins with any suitable configuration, such as sawtooth, herringbone, or perforated. Of course, other configurations are possible and contemplated herein. In combination or alternatively, passages can be formed directly in the plate by any suitable method, in some cases by photochemical etching.

[0057] The passages can be of any suitable size and cross-sectional shape. In some embodiments, the formed flow channels are semicircular with a radius of about 0.5 mm, or about 0.75 mm, or about 1 mm. Of course, other suitable cross-sectional shapes and sizes are contemplated, depending on the design flow parameters of the heat exchanger.

[0058] 2 shows a heat exchanger 100 formed by joining together alternating hot flow plates 102, cold flow plates 104, and porous layers 106. As shown, the porous layers 106 create a separation between the hot flow plates 102 and cold flow plates 104. In this manner, failure of a single plate does not result in mixing of the primary and secondary coolants, but rather allows leaking fluid to enter the space created by the porous layers 106.

[0059] Additionally, in some cases, the porous layer 106 may include a control gas. The control gas may be any suitable gas or mixture of gases. In some cases, the control gas is a mixture of inert gases, such as argon or nitrogen. The mixture ratio of the control gas may be varied to control the heat transfer coefficient in the porous layer, which allows for fine tuning of the heat transfer efficiency between the primary and secondary coolants.

[0060] For example, in some cases, the control gas is a mixture of argon and helium, and the mixture can be controlled to affect the effective conductivity of the porous layer. Thermal energy transfer into the gas can be relatively low compared to conduction through the porous layer; however, by varying the mixture of the control gas, it is possible to actively control the efficiency of thermal energy transfer through the porous layer. Using a mixture of argon and helium as an example, a suitable mixture can be between 100% argon and 100% helium, or any mixture ratio therebetween. In some cases, the mixture can be approximately 50% argon and 50% helium. Generally, helium has a much higher thermal conductivity than argon, and a control gas with a higher percentage of helium provides improved heat transfer characteristics, while a lower percentage of helium provides reduced heat transfer characteristics. The control gas can be any suitable mixture of gases and can include any of several gases, such as nitrogen, argon, helium, CO2, or other inert gases. Laboratory tests have been conducted, and it has been observed that by varying the control gas mixture in the porous layer 106, heat transfer can be affected by up to 10% or more. Depending on the control gas used within the porous layer 106, the thermal energy transfer efficiency between the hot flow plate 102 and the cold flow plate 104 can be reduced by 10% or more.

[0061] The porous layer provides gas separation between the hot flow plate 102 and the cold flow plate 104, which reduces heat transfer efficiency compared to directly bonding the hot flow plate 102 to the cold flow plate 104. In other words, the porous layer 106 creates insulation between the hot flow plate 102 and the cold flow plate 104, thereby reducing thermal energy transfer efficiency.

[0062] Additionally, the control gas can be monitored to test for failures in one or more of the hot flow plates 102 or cold flow plates 104. For example, the control gas can be monitored for leaks of the primary or secondary coolant. As the control gas exits the heat exchanger, it can be tested for the presence of primary coolant, secondary coolant, or both to determine if a failure has occurred within the heat exchanger. As previously mentioned, mixing of the primary and secondary coolants is inhibited by the porous layer, which provides an additional boundary between the primary and secondary coolants.

[0063] The thermal stresses exhibited by a heat exchanger are directly proportional to the thermal gradient between the hot and cold flow plates 102, 104 and the efficiency of heat transfer. In some cases, the thermal stresses can be severe, causing thermal expansion and contraction of different parts of the heat exchanger when experiencing temperature gradients. In many typical heat exchangers, components are tightly bonded together, and thermal stresses can lead to thermal fatigue cracking and catastrophic failure. The mechanical properties of heat exchanger materials degrade over time when the material is exposed above a certain temperature. Similarly, the ultimate strength of the material decreases due to aging of the material at high temperatures. This exacerbates the occurrence of plastic deformation in thermal fatigue.

[0064] The porous layer 106 provides the additional benefit of allowing relative movement between the hot flow plate 102 and the cold flow plate 104 due to thermal stresses. The porous layer 106 provides compliance that allows the hot flow plate 102 to deform significantly independent of the cold flow plate 104. In other words, the porous layer 106 is a cushion that absorbs excessive stresses experienced by the heat exchanger 100. Through experimentation, it has been observed that the porous layer elastically collapses individual pores, absorbing thermal stresses and strains. In some cases, the porous layer 106 provides sufficient flexibility to allow the hot flow plate 102 and the cold flow plate 104 to expand and contract independently. This, among other things, allows the hot flow plate 102 and the cold flow plate 104 to be formed of different materials, if desired. In some cases, the hot flow plate 102 is formed of a first material, and the cold flow plate 104 is formed of a second material that is different from the first material. In some cases, the second material has a different thermal expansion coefficient than the first material. In some cases, the second material has a higher coefficient of thermal expansion than the first material.

[0065] 3A-3D are exemplary porous layers 106 that may be used with the embodiments described herein. Figures 3A and 3B show a porous layer 106 with a random pore structure. The random pore structure may be formed by any suitable technique, such as foaming, sintering, powder metallurgy, spraying, or other suitable process. The porous layer 106 may be formed from any suitable material, and in some cases is formed from a metal, ceramic, or a combination thereof. In some cases, the porous layer is formed from a nickel-based alloy or steel.

[0066] 3C and 3D show porous layer 106 having a uniform pore distribution. The uniform pore distribution can be provided by any suitable process, such as material removal or additive manufacturing techniques. Exemplary manufacturing techniques include 3D printing, metal powder fusion, electron beam melting, injection molding, and other suitable techniques.

[0067] According to any of the embodiments described herein, the porous layer can be formed according to design criteria such as pressure drop, density, crush strength, or other properties. In some cases, the degree of porosity is controlled to result in an open pore structure in which adjacent pores are interconnected to provide a fluid pathway through the porous layer. In some cases, the porous layer 106 is up to 95% porous, or up to 85% porous, or up to about 75% porous, or up to about 70% porous, or up to about 60% porous, or up to about 50% porous, or up to about 40% porous. In some cases, the porosity of the porous layer 106 is within a range from about 40% porous to about 70% porous. In some cases, the porosity is balanced against the resulting crush strength of the porous layer 106. Additionally, the greater the porosity, the less heat conduction through the porous layer 106, and the selection of the control gas can have a significant impact on the overall heat transfer efficiency through the porous layer 106.

[0068] In some embodiments, the porous layer 106 is in fluid communication with an inlet manifold or plenum that supplies a control gas to an inlet on one side of the porous layer. An outlet may be formed on the opposite side of the porous layer 106, which may be an outlet manifold or plenum. Providing an inlet and an outlet in the porous layer defines a flow direction, and as with any of the embodiments described herein, the control gas passes through the porous layer 106 and can be used for leak detection. Additionally, the porous layer further separates the primary coolant from the secondary coolant. As the control gas exits the heat exchanger, it can be tested for the inclusion of primary and / or secondary coolant materials. For example, helium can pass through the porous layer and be tested for the presence of primary and / or secondary coolant at its exit.

[0069] In some cases, a control gas may be selected and used to capture fission or activation products, for example, a control gas may be used to capture and remove products, such as tritium, from a heat exchanger before transferring them from the primary coolant to the secondary coolant.

[0070] It should be understood that the control gas may be changed over time. For example, to control the thermal energy transfer efficiency of the porous layer 106, the mixture of two gases may be changed, and the mixture ratio may be changed over time as follows: Furthermore, the first control gas may be purged by injecting a second control gas, and the second control gas may be different from the first control gas. In other words, the first control gas may be introduced a first time, and the second control gas may be introduced a second time after the first time.

[0071] In some embodiments, the porous layer may not be a continuous shape, but rather may be formed by discrete particles that define flow paths between the particles. As an example, the porous layer may be formed by agglomerating pebble material, powder, or spherical particles between the hot flow plate 102 and the cold flow plate 104 to provide many of the advantages and benefits described herein.

[0072] In some cases, the porous layer 106 may not be bonded to the hot flow plate 102 and / or the cold flow plate 104. For example, the hot flow plate 102 and the cold flow plate 104 may be bonded to the heat exchanger shell to define a space between the hot flow plate 102 and the cold flow plate 104, and the space therebetween may be filled with the porous layer material, which may be a powder, pebbles, or particles with some other suitable form that provides an open pore structure to provide flow paths through the porous layer 106.

[0073] 4 shows an enlarged view of the open pore structure formed in the metal porous layer 400. The metal porous layer 400 may be used with any of the embodiments described herein to provide the described benefits and advantages. In some examples, the metal porous layer 400 is formed from a suitable metal and is formed with an open pore structure that may be between about 30% and 80% porous, or between 40% and 70% porous, or between 50% and 60% porous.

[0074] In some examples, the porous layer 400 is composed of metal ligaments 402 that form a porous structure. The metal ligaments 402 may provide elasticity to accommodate differential thermal expansion and contraction between the hot and cold flow plates. The metal ligaments 402 may provide sufficient crush strength to maintain the size and shape of the porous metal layer 400. The metal ligaments may be formed of any suitable material, which may be different from the material from which the heat exchanger is made. The metal ligaments 402 may be formed by any suitable process, such as, for example, drawing, spinning, foaming, printing, sintering, bubbling, or any other suitable process.

[0075] FIG. 5 shows a cross-sectional view of a dual-pipe and shell heat exchanger 500 with a porous layer 506. While the example shows a single tube within the shell, it should be understood that any number of tubes may pass through the shell. The hot flow tubes 502 provide a flow path for the primary coolant, and the cold flow shell 504 is configured to provide a cold flow path 508 for the secondary coolant. The porous layer 506 may be disposed between the hot flow tubes 502 and the cold flow shell 504 to provide the benefits described herein. For example, the porous layer 506 provides a dual containment barrier that inhibits mixing of the primary and secondary coolants; provides flexibility to allow independent expansion and contraction of the hot flow tubes 502 and the cold flow shell 504 in response to thermal stresses caused by temperature gradients across the heat exchanger 500; and provides a third flow path for introducing control gases, such as for controlling the heat transfer efficiency of the heat exchanger, testing the primary and / or secondary coolants for leaks, and removing fission and / or activation products.

[0076] In some embodiments, there are structural supports extending between the walls of the hot flow tubes 502 and the cold flow shell 504 to provide structural supports for the heat exchanger 500. In some cases, the structural supports maintain a desired spacing between the hot flow tubes 502 and the cold flow shell 504 to allow a porous layer to be disposed between the hot flow tubes 502 and the cold flow shell 504. In some cases, the porous layer 506 can be formed from particulate matter, powder, or other loose structure that can be added to the heat exchanger 500 between the hot flow tubes 502 and the cold flow shell 504.

[0077] 6 illustrates an example process for reducing thermal energy transfer efficiency in a heat exchanger. At block 602, a heat exchanger includes a hot flow path, such as for containing a primary coolant.

[0078] At block 604, the heat exchanger is provided with a cold flow path, such as for containing a secondary coolant, which may be the same as or different from the primary coolant.

[0079] A porous thermal insulation layer is provided between the hot and cold flow paths at block 606. The porous thermal insulation layer provides thermal insulation and provides a gas gap between the hot and cold flow paths to reduce the thermal energy transfer efficiency of the heat exchanger.

[0080] Optionally, a control gas may be passed through the porous insulating layer at block 608. The control gas may be a single gas or a mixture of two or more gases.

[0081] Optionally, the control gas mixture may be varied to affect the efficiency of thermal energy transfer between the hot and cold flow paths at block 610. For example, if the control gas includes two gases with different thermal conductivities, increasing the proportion of one of the gases will decrease the thermal energy transfer efficiency of the heat exchanger, while increasing the proportion of the other gas will increase the thermal energy transfer efficiency of the heat exchanger.

[0082] This disclosure presents exemplary embodiments and is therefore not intended to limit the scope of the disclosed embodiments and the appended claims in any way. The embodiments have been described above with the aid of functional building blocks that illustrate implementations of particular components, functions, and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of description. Alternative boundaries may be defined within which the specified functions and their relationships are appropriately performed.

[0083] The foregoing description of specific embodiments will make fully apparent the general nature of the disclosed embodiments such that others, by applying the knowledge of those skilled in the art, can readily modify and / or adapt the specific embodiments to various applications without undue experimentation and without departing from the general concepts of the disclosed embodiments. Such adaptations and modifications are therefore intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. The phraseology or terminology used herein is for the purpose of description and not limitation, as would be interpreted by one of ordinary skill in the relevant art in light of the teaching and guidance presented herein.

[0084] The breadth and scope of the disclosed embodiments should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

[0085] In particular, conditional language such as "can," "could," "might," or "could," unless expressly stated otherwise or understood otherwise within the context of use, is intended to generally convey that certain embodiments may include particular features, elements, and / or operations, while other implementations may not include particular features, elements, and / or operations. Thus, such conditional language does not generally imply that features, elements, and / or operations are required in one or more implementations, or that one or more implementations necessarily include logic for determining whether those features, elements, and / or operations are included in or performed in a particular implementation, with or without user input or prompting.

[0086] Those skilled in the art will recognize that any process or method disclosed herein can be modified in many ways. The process parameters and sequence of steps described and / or illustrated herein are given by way of example only and can be modified as needed. For example, although the steps described and / or illustrated herein may be shown or described in a particular order, these steps do not necessarily have to be performed in the order shown or described.

[0087] The various exemplary methods described and / or illustrated herein may omit one or more of the steps described or illustrated herein or may include additional steps in addition to those disclosed. Furthermore, the steps of any method disclosed herein may be combined with any one or more steps of any other method disclosed herein.

[0088] Of course, it is not possible to describe every conceivable combination of elements and / or methodologies for the purpose of describing various features of the present disclosure, and one of ordinary skill in the art will recognize that many more combinations and permutations of the disclosed features are possible. Accordingly, various modifications can be made to the present disclosure without departing from the scope or spirit of the present disclosure. Moreover, other embodiments of the present disclosure will be apparent from consideration of the specification and accompanying drawings, as well as from practice of the disclosed embodiments presented herein. The examples presented in the specification and accompanying drawings are to be considered in all respects as illustrative and not restrictive. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0089] Unless otherwise specified, the terms "connected" and "coupled" (and their derivatives) as used in the specification are to be construed as permitting both direct and indirect (i.e., via other elements or components) connections. Furthermore, the term "a" or "an" as used in the specification is to be construed as meaning "at least one." Finally, for ease of use, the terms "comprise" and "have" (and their derivatives) as used in the specification are interchangeable with the term "have," and have the same meaning. From the above and the accompanying drawings, it will be understood that specific embodiments have been described herein for illustrative purposes, but that various changes can be made without departing from the spirit and scope of the appended claims and the elements described therein. Furthermore, while certain aspects are presented below in certain claim forms, the inventors contemplate the various aspects in any available claim form. For example, while only some aspects may currently be described as embodied in a particular configuration, other aspects may likewise be embodied. Various modifications and variations may be made that will be apparent to those skilled in the art having the benefit of this disclosure. All such modifications and variations are intended to be included and, therefore, the above description should be regarded in an illustrative rather than a limiting sense.

[0090] A heat exchanger according to a first aspect of the present invention is a heat exchanger for a nuclear reactor, comprising: high temperature flow path; a cold flow path fluidly separated from the hot flow path; and a porous thermal insulation layer disposed between the hot flow path and the cold flow path, the porous thermal insulation layer comprising: entrance; Exit; and a fluid passage between the inlet and the outlet; the porous thermal insulation layer is configured to flow a control gas through the fluid passages, the control gas being configured to affect a thermal energy transfer efficiency of the porous thermal insulation layer. Porous thermal insulation layer;

[0091] A heat exchanger according to a second aspect of the present invention is the heat exchanger of the first aspect, wherein the control gas is used for leak detection of the first fluid, the second fluid, or both.

[0092] A heat exchanger according to a third aspect of the present invention is the heat exchanger of the first aspect, wherein the control gas is used to capture fission products or activation products.

[0093] A fourth aspect of the present invention relates to the heat exchanger of the third aspect, wherein the control gas captures tritium.

[0094] A fifth aspect of the present invention relates to the heat exchanger of the first aspect, wherein the control gas is a mixture of two or more gases.

[0095] A heat exchanger according to aspect 6 of the present invention is the same as in aspect 5, further including a mixing control configured to change the mixture of the two or more gases to change the thermal energy transfer efficiency of the porous thermal insulation layer.

[0096] A seventh aspect of the present invention relates to the heat exchanger of the fifth aspect, wherein the control gas contains argon and helium.

[0097] A heat exchanger according to an eighth aspect of the present invention is the heat exchanger of the first aspect, wherein the porous thermal insulation layer is formed from a metal or a metal alloy and defines an open pore structure.

[0098] A ninth aspect of the present invention relates to the heat exchanger of the first aspect, wherein the porous thermal insulation layer is formed by an additive manufacturing process.

[0099] A tenth aspect of the present invention relates to the heat exchanger of the first aspect, wherein the porous thermal insulation layer reduces the efficiency of thermal energy transfer from the high-temperature flow path to the low-temperature flow path.

[0100] In a heat exchanger according to aspect 11 of the present invention, in aspect 1, the heat exchanger is a plate heat exchanger having a high-temperature plate and a low-temperature plate, and the high-temperature flow path is formed as a first guide flow path on the surface of the high-temperature plate, and the low-temperature flow path is formed as a second guide flow path on the surface of the low-temperature plate.

[0101] A heat exchanger according to a twelfth aspect of the present invention is the heat exchanger of the eleventh aspect, wherein the porous thermal insulation layer is disposed between the high-temperature plate and the low-temperature plate.

[0102] In a heat exchanger according to aspect 13 of the present invention, in aspect 1, the porous thermal insulation layer separates the high-temperature flow path and the low-temperature flow path, allowing the high-temperature flow path and the low-temperature flow path to respond independently to thermal gradients that exist across the heat exchanger.

[0103] A fourteenth aspect of the present invention provides a method for reducing thermal energy transfer efficiency in a heat exchanger, comprising: providing a high temperature flow path; providing a cold flow path fluidly separated from the hot flow path; and providing a porous thermal insulation layer between the hot flow path and the cold flow path.

[0104] In a method according to aspect 15 of the present invention, in aspect 14, providing the porous thermal insulation layer includes providing an open pore structure of metal between the high-temperature flow path and the low-temperature flow path.

[0105] In a method according to aspect 16 of the present invention, in aspect 14, providing the porous thermal insulation layer further includes providing an inlet on one side of the porous thermal insulation layer and providing an outlet on the other side of the porous thermal insulation layer.

[0106] A seventeenth aspect of the present invention relates to the method of the sixteenth aspect, further comprising flowing a control gas from the inlet, through the porous thermal insulation layer, and through the outlet.

[0107] An eighteenth aspect of the present invention relates to the method of the seventeenth aspect, further comprising controlling the thermal energy transfer efficiency of the heat exchanger by changing the mixture of the control gas.

[0108] A nineteenth aspect of the present invention relates to the method of the eighteenth aspect, wherein the control gas is a mixture of argon and helium.

[0109] A twentieth aspect of the present invention relates to the method of the seventeenth aspect, further comprising testing the control gas for the presence of a leaking material in the heat exchanger.

Claims

1. 1. A heat exchanger for a nuclear reactor comprising: High temperature flow path; a cold flow path fluidly separated from the hot flow path; and a porous thermal insulation layer disposed between the hot flow path and the cold flow path, the porous thermal insulation layer comprising: entrance; Exit; and a fluid passage between the inlet and the outlet; the porous thermal insulation layer is configured to flow a control gas through the fluid passages, the control gas being configured to affect a thermal energy transfer efficiency of the porous thermal insulation layer. a porous thermal insulation layer; the heat exchanger is a plate heat exchanger having a high-temperature plate and a low-temperature plate, the high-temperature flow path is formed as a first guide flow path on a surface of the high-temperature plate, and the low-temperature flow path is formed as a second guide flow path on a surface of the low-temperature plate; The porous thermal insulation layer is disposed between the hot plate and the cold plate to allow relative movement between the hot plate and the cold plate.

2. The control gas is used to detect leaks of the first fluid, the second fluid, or both. The heat exchanger of claim 1 .

Images