HIGH-TEMPERATURE AND HIGH-PRESSURE HEAT EXCHANGER

Abstract

A high gravimetric and volumetric power density heat exchanger is provided for high-temperature and high-pressure applications with counter-flowing hot and cold agents that enter via respective inlet headers, transit parallel and adjacent flow passages, and exit via respective outlet headers. One or more headers for conveying one of the substances may be situated within the flow of the other substance. Structures within the flow passages promote the transfer of heat while limiting pressure drop on one or both sides. The structures may include microscale pins, an array of pins (with specified aspect ratios and spacing), a lattice of interconnected pins, parallel ridges, and/or other features. Through an additive manufacturing process, the headers are monolithically integrated into the heat exchanger instead of being separately constructed and attached.

Description

BACKGROUND

This disclosure relates to the fields of mechanical engineering and thermodynamics. More particularly, heat exchangers for high-temperature and high-pressure applications are provided with integrated header-core architectures that yield high volumetric power density within compact designs and that may be constructed using additive manufacturing. The heat exchangers may be used in various applications that feature extreme temperatures and pressures, such as nuclear power generation, petrochemical and chemical processes, and solar thermal power generation.

For example, concentrating solar power (CSP) systems, when coupled with thermal storage, enable the generation of electricity during periods of little or no sunlight. Thermal storage can replace the traditional and expensive battery storage of converted energy, but may complicate the process of converting the solar energy into electrical energy. In particular, a primary heat exchanger is required that can absorb the collected thermal energy for use in a power-generation cycle. For example, the thermal energy may be stored in the form of molten salt or some other heated fluid, and a heat exchanger must be able to efficiently transfer the heat of the molten salt to a receiving agent such as supercritical carbon dioxide (sCO₂).

Conventional heat exchangers are unable to handle operating environments of solar power systems that feature surface temperatures up to approximately 720° C. in the molten salt, pressures of 200-250 bar for the sCO₂, and the potential for damage by the corrosive salt. Today's CSP systems exhibit these conditions for extended periods of time.

Existing microlamination and printed circuit heat exchangers operate at lower temperatures, suffer from relatively high pressure drops of the process fluid, and/or yield relatively low efficiency. In addition, such heat exchangers suffer from weaknesses inherent in the manner in which they are manufactured. For example, headers for admitting or expelling contents of the heat exchanger (e.g., the receiving agent) are usually constructed separate from the body of the heat exchanger and attached using brazing or welding. The attachment area is thus vulnerable to failure before integral parts of the heat exchanger.

SUMMARY

In some embodiments, an additively manufactured heat exchanger is provided for extended operation within a high-temperature and/or high-pressure operating environment. The heat exchanger facilitates the transfer of heat energy from a hot agent (e.g., molten salt, fluidized metallic or ceramic particles, liquid sodium, supercritical carbon dioxide or sCO₂) to a cold agent (e.g., molten salt, sCO₂) that can be used to store the heat energy and/or drive an electrical power generator.

The heat exchanger features a cold side for containing and conveying the cold agent, and a hot side for containing and conveying the hot agent. The agents generally flow in opposite directions within adjacent passages that feature structural details that promote the transfer of heat from the hot side to the cold side. For example, cold-side passages may feature arrays of microscale pins that are shaped and sized to transfer absorbed heat to the cold agent, but without permitting a significant pressure drop within the cold side (e.g., less than 2%). Meanwhile, hot-side passages may also feature microscale pins that are constructed in an interlocking or lattice structure or, alternatively, an arrangement of parallel ridges or fins, to transfer heat away from the hot agent. Structures within the two different types of passages may therefore be the same or different, depending upon constraints placed upon the two sides, the nature of the hot and cold agents, and/or other factors. Cold-side passages and/or hot-side passages are enclosed within plates aligned in parallel.

In some embodiments, the heat exchanger may be constructed monolithically via additive manufacturing, using powdered metal and/or metal superalloys (e.g., of Nickel and/or Cobalt). Thus, headers for inputting and outputting either or both agents may be formed as integral parts of the heat exchanger instead of being attached separately and causing vulnerable joints susceptible to wear and stress. Moreover, one or both headers for one of the agents may be positioned within the flow of the other agent.

In some embodiments, a heat exchanger design is scalable by increasing or decreasing the number of cold-side and hot-side passages or, more specifically, by increasing or decreasing the number of plates that contain the passages. The design may be further scalable by stacking multiple heat exchangers or heat exchanger units to form an assembly.

DESCRIPTION OF THE FIGURES

The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

FIG. 1A is a perspective view of a heat exchanger, in accordance with some embodiments.

FIG. 1B further illustrates the heat exchanger with cutaway views, in accordance with some embodiments.

FIG. 2A is another view of the heat exchanger of FIG. 1A, in accordance with some embodiments.

FIG. 2B illustrates alternative designs for the walls of hot-side passages within the heat exchanger of FIG. 1A, in accordance with some embodiments.

FIG. 3A is a perspective view of a heat exchanger, in accordance with some embodiments.

FIG. 3B is a cutaway view of the outlet header of the heat exchanger of FIG. 3A, in accordance with some embodiments.

FIG. 3C is a cutaway view of a cold-side passage of the heat exchanger of FIG. 3A, in accordance with some embodiments.

FIG. 4A is another view of the heat exchanger of FIG. 3A, in accordance with some embodiments.

FIG. 4B is another cutaway view of the outlet header of the heat exchanger of FIG. 3A, in accordance with some embodiments.

FIG. 5A is a front perspective view of a heat exchanger, in accordance with some embodiments.

FIG. 5B is a rear perspective view of the heat exchanger of FIG. 5A, with a cutaway view of the outlet header, in accordance with some embodiments.

FIG. 5C is a rear perspective view of an assembly comprising the heat exchanger of FIG. 5A, in accordance with some embodiments.

FIG. 5D is a further view of the heat exchanger of FIG. 5A, with cutaway views of hot-side and cold-side passages, in accordance with some embodiments.

FIGS. 6A-C are detail views of the structure of hot-side and cold side passages of a heat exchanger, in accordance with some embodiments.

FIG. 7A is a front perspective view of a heat exchanger, in accordance with some embodiments.

FIG. 7B separately illustrates the cold and hot sides of the heat exchanger of FIG. 7A, in accordance with some embodiments.

FIG. 7C illustrates a cross-section of the heat exchanger of FIG. 7A, with detail view of the headers, in accordance with some embodiments.

FIG. 7D is a front perspective view of the heat exchanger housed with an enclosure, in accordance with some embodiments.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled in the art to make and use the disclosed embodiments, and is provided in the context of one or more particular applications and their requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the scope of those that are disclosed. Thus, the present invention or inventions are not intended to be limited to the embodiments shown, but rather are to be accorded the widest scope consistent with the disclosure.

Overview

In some embodiments, a compact additively manufactured heat exchanger is provided for use in solar energy systems and/or other environments (e.g., nuclear, chemical, and/or petrochemical processes). In illustrative deployments, the heat exchanger operates at temperatures up to approximately 800° C. and/or internal pressures up to approximately 250 bar, and may have an operating lifetime of approximately 40,000 hours.

The hot side of the heat exchanger accommodates a flow of molten salt and/or some other hot fluid or fluidiform agent (e.g., molten salt, fluidized metallic or ceramic particles, liquid sodium, supercritical carbon dioxide or sCO₂). In some implementations, the molten salt may be composed of 20% NaCl, 40% KCl, and 40% MgCl₂ per mole, and enter the heat exchanger with an inlet temperature (T_H,in) of approximately 720° C. and a pressure (P_H,in) of approximately 10⁵ Pa or 1 bar (e.g., ambient pressure). In some alternative implementations, however, the hot agent may be pressurized, at approximately 80 bar for example.

The cold side of the heat exchanger may be occupied by super-critical carbon dioxide (sCO₂) and/or some other cold fluid or fluidiform agent (e.g., molten salt). In an illustrative implementation, the sCO₂ enters the heat exchanger with a temperature (T_C,in) of approximately 500° C. and a pressure (P_C,in) of 200-250 bar.

The terms ‘hot’ and ‘cold’ as used herein are relative unless otherwise noted. In other words, while the ‘hot’ side may be considered objectively hot (based on input temperatures in the range of 600-800° C.), the ‘cold’ side is cold relative to the hot side, and is not necessarily objectively cold. The hot and cold agents flow generally in opposing directions through adjacent passages of the heat exchanger, which feature structural details (e.g., channels, ridges, pins, rods, a lattice) for conducting or recuperating heat from the hot side to the cold side.

The heat exchanger may be fabricated via laser powder bed additive manufacturing (3D printing) using metals (e.g., nickel, iron-nickel, cobalt) and/or metal superalloys. Illustrative powder alloys that may be employed in an additive manufacturing process to produce a heat exchanger described below include Haynes® 230®, Haynes 282®, Inconel® alloy 600, Inconel alloy 718, Inconel alloy 740H®, Pearl® Micro MHA3300®, and EOS® Titanium Ti64, although other powder alloys may also be suitable. A LPBF (Laser Powder Bed Fusion) metal 3D printer, such as the EOS M 290, EOS M 400-4, SLM NXG XII 600, GE Concept Laser X Line 2000R, or another model having similar functionality, may be employed to fabricate the heat exchanger.

One or more heat exchangers disclosed herein enable scalable, modular and integrated designs. They are scalable in that volumes of the hot and/or cold side may be scaled up or down horizontally (e.g., by adding or removing cold plates that enclose cold-side passages and/or hot plates that enclose hot-side passages) and/or vertically (e.g., by adding additional heat exchanger units or cores). They are modular in that the hot agent and the cold agent flow through separate modules (e.g., headers, plates), and they are integrated in that the core and headers can be additively manufactured as a monolithic entity. In some embodiments, headers for either the hot agent or the cold agent may be designed for immersion within the stream or flow of the other agent. Embodiments of heat exchangers disclosed herein provide significant power densities (e.g., greater than 10 MW/m³), greater than 90% effectiveness, greater than 99.9% part densities, and less than 0.5 bar pressure drop on the cold side and/or the hot side.

Moreover, the design features of the hot-side and cold-side passages of the disclosed heat exchangers are independent of each other (i.e., they may have the same or different designs) and the aspect ratios and pitch (e.g., spacing) of pins, ridges, channels and/or other features of the passages are also independent. By modifying the designs accordingly, constraints may be more easily satisfied regarding maximum pressure drops and/or heat transfer effectiveness. For example, one side may be designed (e.g., in terms of aspect ratios and pitches of passage features) to limit pressure drop while the other side may be designed to enhance or promote more effective heat transfer.

Compact High-Pressure and High-Temperature Heat Exchanger

In different embodiments, a heat exchanger may feature different designs but overlapping features that promote the benefits of low pressure drop, high effectiveness, and high power density. For example, the disclosed heat exchangers feature separate sides for the hot and cold agents (i.e., hot sides and cold sides), and each side includes passages for conveying the agent between the side's inlet and outlet, with each passage for a given agent being generally parallel and adjacent to passage for the other agent. However, the agents generally flow in opposite directions to maximize their time of exposure to each other, and their passages may be configured differently, such as with different structural features for shedding or absorbing heat.

Thus, different embodiments of the cold side may feature different configurations of pins or pin arrays in terms of size, shape, aspect ratio, pitch, placement, orientation, etc. Similarly, different embodiments of the hot side may feature different configurations of channels, fins, ridges, rods, pins, a lattice of interlocking pins, etc.

FIGS. 1A and 1B are perspective views of a heat exchanger, with cutaways disclosing internal details, according to some embodiments.

As shown in FIG. 1A, molten salt or another heated fluidiform agent enters heat exchanger 100 via inlet 102 and exits outlet 104 after being channeled through passages (i.e., hot-side passages) between and defined by hollow plates 126 and body 120. Meanwhile, super-critical CO₂ or another cold fluidiform agent enters via inlet 112 of inlet header 122, flows through passages (i.e., cold-side passages) within plates 126, and exits outlet 114 of outlet header 124. Plates 126 may be termed cold plates because they enclose passages through which the cold agent passes.

FIG. 1B provides another cutaway view of heat exchanger 100 showing plates that encompass cold-side passages 116 and also showing hot-side passages 106 interleaved with the plates. FIG. 1B also includes a detail view showing hot-side passage 106a (for conducting the molten salt) and cold-side passages 116a, 116b (for conveying the sCO₂). Hot-side passage 106a is sandwiched between adjacent plates 126 that enclose separate and adjacent cold-side passages 116a and 116b, and comprises multiple ridges or fins 108 for channeling the molten salt and/or facilitating the transfer of heat to adjacent cold-side passages.

Each cold-side passage 116 comprises an array of pins or protrusions 118 to facilitate heat transfer and assist in vortex shedding within the flow of the cold agent. Each plate 126 of heat exchanger 100 encloses one cold-side passage 116, with constituent pins 118, within walls that feature external ridges 108. Each hot-side passage 106 and cold-side passage 116 therefore abuts two passages of the other type, except for passages at the outer sides of heat exchanger 100, and the hot and cold agents flow in opposing directions in the two different types of passages.

Pins in cold-side passages in some implementations of heat exchanger 100 are approximately 2 mm in diameter at their base and approximately 1.8 mm tall, and are separated by a transverse pitch of approximately 2.5 mm and a longitudinal pitch of approximately 5 mm. In other implementations, pin diameters may vary from about 0.25 mm to about 1.5 mm, and pin heights may vary from about 0.5 mm to about 2.0 mm. Pins may taper somewhat, so that they are thicker at their bases and tops (where they connect to the walls of the cold-side passage in which they are located) and thinner in the middle.

Cross-sections of pins may be circular, elliptical, partially circular and partially elliptical, or have different shapes when viewed along their vertical axes. The width of a cold-side passage in these embodiments effectively matches the height of the passage's pin array because the pins extend from one wall of the passage to the other. Those walls, which separate the enclosed cold-side passage from adjacent hot passages, may be approximately 0.25 mm to 1.5 mm thick, and so a given plate 126 may be approximately 1.0 to 5.0 mm wide. The width of a hot-side passage (i.e., the lateral space between adjacent plates 126) may be approximately 1.0 mm.

Surface roughness on both cold and hot sides may be approximately 60 μm, but range from about 30 to 150 μm. Different configurations may be produced for different operating environments. For example, at higher temperatures the transverse pitch and/or longitudinal pitch distances between pins 118 may decrease.

FIGS. 2A and 2B provide alternative views of heat exchanger 100 of FIGS. 1A and 1B. FIG. 2A illustrates the core of heat exchanger 100 and details of a hot-side passage 106 and cold-side passages 116, without arrowheads showing the directional flows of the molten salt and the sCO₂.

FIG. 2B illustrates alternative patterns for ridges 108 of hot-side passages 106. The illustrated designs include straight ridges 130, offset ridges 132, and contoured ridges 134. Although contoured ridges 134 provide for extended contact between the counter-flowing hot and cold agents, and therefore greater heat transfer, this option may cause a greater pressure drop in the molten salt (i.e., the hot side) than other designs. In contrast, straight ridges 130 yield the lowest drop in pressure of the hot agent and may additionally promote drainage of the hot agent from heat exchanger 100.

Heat exchanger 100 of FIGS. 1A-B and 2A-B may be considered compact because, in some embodiments, it features a length (e.g., from inlet 102 to outlet 104) of approximately 20 cm, a width in the range of 10-20 cm, and a height of approximately 5-7 cm. By way of illustration, with a 10 cm width, 40 plates (plates 126) may be contained within body 120. The mass flow rate on the hot side may vary from approximately 0.235 kg/s to 0.986 kg/s. The cold side mass flow rate may be approximately 0.2 kg/s and may be fixed.

Depending upon the internal volume of heat exchanger 100, which, for measurement purposes, includes only body 120 and not the headers, volumetric power densities in of 10 to 20 MW/m³ may be achieved. The actual value obtained depends upon the heat capacity rates of the hot (Ch) and cold (C) sides or the ratio (C_r) between the two rates. The principal factor affecting this ratio may be the outlet temperature of the cold agent. For example, the effectiveness of the heat transfer process may exceed 90% when the outlet temperature (at outlet 114) is at or above approximately 700° C. (with an inlet temperature at inlet 112 of approximately 500° C.).

Another factor that helps improve the effectiveness and the heat transfer process is the surface roughness within the hot and/or cold-side passages. This is an inherent consequence of the additive manufacturing process and yet helps increase the volumetric power density.

FIG. 3A is a perspective view of a heat exchanger, with a cutaway disclosing internal details, according to some embodiments.

In these embodiments, molten salt or another heated agent enters inlet 302 of heat exchanger 300, flows through rectangular or semi-rectangular channels (i.e., hot-side passages), then exits outlet 304. Supercritical carbon dioxide (sCO₂) enters inlet 312 of inlet header 322, flows through arrays of microscale pins (i.e., cold-side passages), then exits outlet 314 of outlet header 324.

In an illustrative implementation, T_H,in=720° C., P_H,in=1 bar, T_C,in=500° C., and P_C,in=200 bar (all values are approximate and may vary in other implementations). Further, the length (from inlet 302 to outlet 304), width, and height (without headers 322, 324) of the illustrated heat exchanger may be approximately 24 cm, 10 cm, and 5 cm, respectively. Note, however, that the width may be increased by installing additional plates (i.e., cold-side passages).

As the cutaway view in FIG. 3A shows, cold-side passage 316a feature one or more arrays of pins 318 that promote absorption of heat by the sCO₂, increase flow distribution, and facilitate vortex shedding. Hot-side passages 306 feature channels or ridges 308 to further promote heat transfer. Body 320 thus encompasses multiple (cold) plates 326, with each plate enclosing one cold-side passage 316 and abutting adjacent hot-side passages 306. Ridges 308 may be substantially straight, and parallel to one another; this feature facilitates drainage of the molten salt when heat exchanger 300 is idle and oriented vertically.

It may be noted that the cold agent enters and exits the heat exchanger orthogonal to its eventual flow through body 320 (i.e., within plates or cold plates 326). Thus, while it flows counter to the hot agent in the body, when transitioning between a header and the body it travels cross-flow rather than counter-flow.

FIGS. 3B and 3C are cut-away and detail views of heat exchanger 300 of FIG. 3A according to some implementations, and demonstrate how the counter-flowing sCO₂ within a given cold-side passage 316a transitions to a cross-flow at the end of its plate 326a and exits via outlet header 324. In particular, as the sCO₂ stream approaches the end of passage 316a, flow guides 340 help redirect the stream through conical outlet tubes 346 and into outlet chamber 342, from which it exits via outlet 314. Chamber 342 includes multiple support pillars 344. Pillars 344 may be shaped to hinder the flow of the cold agent as little as possible (e.g., with elliptical cross-sections have a major axis parallel to the flow).

The interface or transition from inlet header 322 to cold-side passage 316a may mirror the configuration illustrated in FIGS. 3B and 3C. In particular, inlet header 322 may comprise a chamber that is perforated with inlet tubes corresponding to outlet tubes 346, and the cold-side passage may feature additional flow guides 340 for transitioning the sCO₂ stream from a cross-flow orientation as it enters plate 326a to a counter-flow relative to adjacent hot-side passages.

FIGS. 4A-B provide alternative views of heat exchanger 300 of FIGS. 3A-C.

FIG. 4A illustrates heat exchanger 300, hot-side passages 306 and cold-side passages 316, without arrowheads showing the directional flows of the molten salt and the sCO₂. FIG. 4A also illustrates a portion of a pin array of a cold-side passage, and demonstrates how pin diameter 362, transverse pitch 364, and longitudinal pitch 366 are oriented and measured, assuming the sCO₂ stream passes horizontally (i.e., orthogonal to transverse pitch 364 and parallel to longitudinal pitch 366).

FIG. 4B shows another cutaway view of outlet header 324 and a detail view of a cross-section of chamber 342 of the outlet header. The detail view is rotated about a vertical axis to better show details such as support pillar 344 and conical outlet tubes 346. Although heat exchanger 300 is depicted as including six outlet tubes for each plate 326, in other embodiments more or fewer tubes may be incorporated.

By additively manufacturing heat exchanger 300, headers 322 and 324 can be integrated into the heat exchanger instead of being separately constructed and attached. Additive manufacturing (AM) also enables independent variations in the aspect ratio and/or pitch ratio of pins on the cold side, and for any desired variations between the cold-side and hot-side passages. AM also makes it easy to change the number of plates within the heat exchanger and adjust the volume (e.g., depth) of the sCO₂ headers.

Heat exchangers such as heat exchanger 300 of FIGS. 3A-C and 4A-B are designed to combine low cost with high power density, while restricting the pressure drop in the cold side to no more than 2%. For example, a Gen 1 heat exchanger may exhibit an operating effectiveness in excess of 90% at lower cost than heat exchanger 100 of FIG. 1, while providing a volumetric power density in excess of 10 MW/m³; the power density measurement for heat exchanger 300 includes input and output header volumes.

Testing of heat exchanger 300 may involve variations in characteristics such as plate spacing (i.e., spacing between plates 326, which is equivalent to the width of hot-side passages), spacing between ridges within hot-side passages, designs for pin arrays in cold-side passages, inlet temperatures of the molten salt and sCO₂, mass flow rates, and other aspects of the heat exchanger. Testing and simulation involving pin arrays, for example, determined that pins with circular cross-sections within a hexagonal array helped limit the maximum stress within the pin arrays. Moreover, an effective pin configuration featured a pin diameter of 1.2 mm, pin height of 1.8 mm, fillet radii of 0.4 to 0.8 mm, transverse and longitudinal pitches of 2.05 and 1.76 respectively, and a wall thickness (i.e., thickness of each wall of a plate) of 0.5 mm.

FIG. 5A is a front perspective view of a heat exchanger according to some embodiments.

In these embodiments, most or all of the cold side of heat exchanger 500 is situated within the flow of the heated agent (e.g., molten salt), except possibly inlet 512 and outlet 514 for admitting and expelling the cold agent (e.g., sCO₂). Inlet header 522 and outlet header 524, however, are within the molten salt stream, which first contacts the cold side at outlet header 524, flows through channels (i.e., hot-side passages) defined by cold plates 526, and over inlet header 522.

Because headers 522, 524 are additively constructed as integral parts of heat exchanger 500 instead of being constructed separately and then attached to the heat exchanger (e.g., via brazing or welding), there are no vulnerable joints between the headers and the body of the heat exchanger. In addition, the headers are constructed with aerodynamic (e.g., elliptical) cross-sections to reduce the drag imparted to the molten salt stream.

Meanwhile, after entering the heat exchanger via inlet 512, the sCO₂ flows through plates 526 to outlet header before exiting. The design of heat exchanger 500, with headers that are immersed in the molten salt stream, thus features greater counter-flow and less cross-flow between the hot and cold agents compared to heat exchangers discussed above. Although not shown in the figures, heat exchanger 500 may be enclosed within an enclosure that has an inlet and an outlet for the molten salt.

FIG. 5B is a rear perspective view of heat exchanger 500 of FIG. 5A, with a cutaway disclosing internal details, according to some embodiments. After flowing over and under outlet header 524, the molten salt flows through passages 506 (e.g., hot-side passage 506a) between plates 526, some or all of which feature ridges 508 on external surfaces.

The detail view in FIG. 5B illustrates the interface between outlet header 524, a hot-side passage 506a, and a cold-side passage 516a. As in other embodiments, the cold-side passage features an array of pins 518 and flow guides 540 for assisting the sCO₂ stream. Note that the flow guides not only help direct the sCO₂ stream, but also act as pins for promoting the transfer of heat from the molten salt to the sCO₂.

FIG. 5C is a rear perspective view of a heat exchanger assembly comprising a combination of multiple heat exchangers 500, according to some embodiments. Each individual heat exchanger 500 within assembly 550 is connected or coupled to at least one other heat exchanger 500, such that the molten salt or other hot agent continues to flow through the hot-side passages and between the stacked heat exchangers. The entire assembly may be housed within a suitable enclosure for admitting and expelling the molten and closely surrounding heat exchanger assembly 550 to facilitate the desired heat transfer.

It should be noted that in addition to scaling heat exchanger assembly 550 vertically by adding additional heat exchanger cores or bodies, an individual heat exchanger 500 may be scaled horizontally by increasing the number of cold plates containing cold-side passages, which inherently also increases the number of hot-side passages.

FIG. 5D is a view of heat exchanger 500 of FIG. 5A with detail views showing the structure of hot-side passages and cold-side passages, according to some embodiments. In particular, a first detail view provides a close-up look at ridge 508a, multiple plates 526 connected to and via ridge 508a, and hot-side passages 506 between the plates. It will be recalled that each plate 526 houses a cold-side passage.

Additional detail views in FIG. 5D illustrate structural details of hot-side passage 506a and cold-side passage 516a that share a common wall 560a. Cold-side passage 516a incorporates an array of pins similar or identical to pins employed in other embodiments. Hot-side passage 506a, however, incorporates a lattice structure of slanted pins that are inclined at approximately 45° in both the direction of flow of the molten salt and the transverse direction. The lattice structure exhibits more surface area than the ridges of previously described heat exchangers and therefore better promotes the transfer of heat from the hot-side passages to the cold-side passages. Note, however, that the exterior walls of the outermost plates may feature ridges instead of the lattice structure. Thus, in different implementations, a hot-side passage may feature a lattice structure, one or more ridges, or a combination of ridges and lattice.

Table 1 lists effective ranges of values for various parameters regarding heat exchanger 500, as well as suggested values for each parameter. Among these parameters, L_HX, W_HX and H_HX represent the length, width, and height of the heat exchanger. W_H and W_C represent the widths of the hot-side and cold-side passages, and D_pin,C and D_pin,H represent the diameters of pins in the cold-side pin arrays and the hot-side lattices respectively. β_T represents the transverse pitch ratio of the cold-side pin arrays, and t_wall represents the thickness of plate walls, which separate hot-side and cold-side passages. Mass flow rates on the hot side (e.g., of molten salt) and the cold side (e.g., of sCO₂) are represented as {dot over (m)}_H and {dot over (m)}_C, respectively. Values of the identified parameters in other implementations may vary.

	TABLE 1
	Parameter	Range of Values	Suggested Value
	LHX (cm)	16.00-35.00	18
	WHX (cm)	10.00-18.00	10
	HHX (cm)	5.00-6.00	5
	WH (mm)	1.00-1.80	1.80
	WC (mm)	0.75-2.50	1.80
	Dpin, H (mm)	0.75-1.25	1.00
	Dpin, C (mm)	0.50-1.50	1.20
	βT	1.34-2.05	2.05
	twall (mm)	0.30-1.50	0.5
	{dot over (m)}H (g/sec)	97-141	115
	{dot over (m)}C (g/sec)	80	80

Modeling and testing of heat exchanger 500 yielded volumetric power densities on the order of 18.6 MW/m³ including headers 522, 524. An effectiveness of heat transfer of approximately 90% was achieved at a heat capacity rate ratio (C_r) of 0.8 between the hot and cold agents. With fixed input temperatures of approximately 720° C. on the hot side and approximately 500° C. on the cold side, the value of C_r and performance of heat exchanger 500 depend upon the value of {dot over (m)}_H.

In the illustrated embodiments of heat exchanger 500, each (cold) plate encompasses a cold-side passage having a primary portion that is approximately 18 cm long (and 5 cm tall), within which the sCO₂ travels counter-flow with the molten salt. In addition, each plate includes diagonal sections approximately 2.3 cm long that couple the primary portion with the inlet and outlet headers, within which the sCO₂ travels cross-flow in comparison to the molten salt. Twenty-six plates were included in some models of heat exchanger 500.

FIGS. 6A-C are detail views of a hot-side passage and walls defining the passage, according to some embodiments.

FIG. 6A is a perspective view showing hot-side passage 606a, surrounding walls 660a and 660b of adjacent plates defining cold-side passages 616a, 616b, and features of the hot-side and cold-side passages. In particular, and as previously discussed, hot-side passage 606a features a lattice structure 608 of angled (e.g., at 45°) and shaped (e.g., elliptical) pins that connect walls 660a, 660b. Cold-side passages 616a, 616b feature arrays of pins that connect the walls of the plates that enclose the separate passages.

FIG. 6B is a side view of the components depicted in FIG. 6A, and FIG. 6C is a front view. These views further demonstrate the form of lattice 608. In alternative embodiments, the pins may have different cross-sections and/or may be angled differently.

FIG. 7A is a perspective view of a heat exchanger having a radial design, according to some embodiments.

As in other embodiments, heat exchanger 700 includes hot-side inlet 702 and hot-side outlet 704, but also includes hot-side inlet header 706 and hot-side outlet header 708. The heat exchanger also includes cold-side inlet 712 and cold-side outlet 714, as well as cold-side inlet header 722 and cold-side outlet header 724. Using additive manufacturing, all headers may be integrally constructed as part of the heat exchanger.

It may be noted that the headers of heat exchanger 700 are curved in a coordinated and concentric manner, with cold-side plates 726 and hot-side plates 728 radially extending between hot-side outlet header 708 and cold-side inlet header 722 on one end and hot-side inlet header 706 and cold-side outlet header 724 on the other end. Thus, in the illustrated embodiments, both the hot agent (e.g., molten salt) and the cold agent (e.g., sCO₂) flow in closed flow passages (i.e., within hot plates 728 and cold plates 726, respectively). In addition, the hot agent flows through the cold headers within isolated tubes.

FIG. 7B provides perspective views of the cold-side and the hot-side of heat exchanger 700, according to some embodiments. More particularly, the view of cold side 700a shows only the portions of heat exchanger 700 that enclose the cold agent, while the view of hot side 700b shows only the portions of heat exchanger 700 that enclose the hot agent.

Thus, in addition to the inlets, outlets, and headers, these figures show cold-side plates (or cold plates) 726, hot-side plates (or hot plates) 728, cold-side tubes 746, and hot-side tubes 748. Cold-side tubes 746 convey the cold agent from cold-side inlet header 722 to cold-side plates 726 (through hot-side outlet header 708), and between cold-side plates 726 and cold-side outlet header 724. Hot-side tubes 748 convey the hot agent from hot-side inlet header 706 to hot-side plates 728 (through cold-side outlet header 724), and between hot-side plates 728 and hot-side outlet header 708.

FIG. 7C shows a cross-section of heat exchanger 700 with the perspective indicated by the dashed line in FIG. 7B, according to some embodiments. In these embodiments the illustrated plate (e.g., a hot plate) features an array of pins 718 along the length of the plate, between hot-side outlet header 708 and cold-side outlet header 724.

Thus, hot-side inlet header 706 appears on the far right and, as the detail view reveals, features a lattice of pins or rods as well as openings to hot-side tubes 748, which transect cold-side outlet header 724 to lead from hot-side inlet header 706 to a hot-side passage enclosed in a hot-side plate. Also shown connected to cold-side outlet header 724 are portions of several cold-side tubes 746 for an adjacent cold plate.

On the far left of the cross-sectional view is cold-side inlet header 722, which also features a lattice of pins or rods. Also shown are openings to cold-side tubes 746 that transect hot-side outlet-header 708 to connect cold-side inlet header 722 to a cold-side passage enclosed in a cold-side plate 726. Also shown connected to hot-side outlet header 708 are portions of several hot-side tubes 748.

FIG. 7D is a perspective view of body 720 that encloses heat exchanger 700, according to some embodiments. In these embodiments, the body provides openings for the inlets and outlets, but otherwise encapsulates the core of the heat exchanger (i.e., the headers, plates, and tubes).

Table 2 lists suggested values for various parameters regarding heat exchanger 700. Among these parameters, L_HX, W_HX, H_HX-H and H_HX-P represent the length and width of the heat exchanger, as well as the height of the heat exchanger at the headers (H_HX-H) and the plates (H_HX-P). L_HX-P represents the length of the cold and hot plates (e.g., the core of the heat exchanger). W_H and W_C represent the widths of the hot-side and cold-side passages, and D_pin,C and D_pin,H represent the diameters of pins in the cold-side arrays and the hot-side lattices respectively. β_T represents the transverse pitch ratio of the cold-side pin arrays, and t_wall represents the thickness of plate walls, which separate hot-side and cold-side passages. Mass flow rates on the hot side (e.g., of molten salt) and the cold side (e.g., of sCO₂) are represented as m_H and {dot over (m)}_C, respectively. Values of these parameters in other implementations may vary.

TABLE 2
Parameter                Suggested Value
LHX (cm)                 22
LHX-P (cm)               12
WHX (cm)                 25
HHX-H (cm)               9
HHX-P (cm)               6
WH (mm)                  1.2
WC (mm)                  1.2
Dpin, H (mm)             1.2
Dpin, C (mm)             1.2
βT                       2.23
twall (mm)               0.5
{dot over (m)}H (kg/sec) 0.6
{dot over (m)}C (kg/sec) 0.6

Modeling and testing of heat exchanger 500 yielded volumetric power densities on the order of 18.6 MW/m³ (including headers 522, 524). An effectiveness of heat transfer of approximately 90% was achieved at a heat capacity rate ratio (C_r) of 0.8 between the hot and cold agents. With fixed input temperatures of approximately 720° C. on the hot side and approximately 500° C. on the cold side, the value of C_r and performance of heat exchanger 500 depend upon the value of {dot over (m)}_H. Pressure drops may be approximately 1.5 bar on the hot side (with an input pressure of 80 bar) and 0.9 bar on the cold side (with an input pressure of 250 bar).

An environment in which one or more embodiments described above are executed may incorporate a general-purpose computer or a special-purpose device such as a hand-held computer or communication device. Some details of such devices (e.g., processor, memory, data storage, display) may be omitted for the sake of clarity. A component such as a processor or memory to which one or more tasks or functions are attributed may be a general component temporarily configured to perform the specified task or function, or may be a specific component manufactured to perform the task or function. The term “processor” as used herein refers to one or more electronic circuits, devices, chips, processing cores and/or other components configured to process data and/or computer program code.

The foregoing embodiments have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit this disclosure to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. The scope is defined by the appended claims, not the preceding disclosure.

Claims

1. A heat exchanger device, comprising: a first pathway for conveying a first substance, the first pathway comprising: a first plurality of plates, wherein each plate encloses a first flow passage that includes a plurality of first structures;a first inlet header configured to receive the first substance and direct the first substance through the first flow passages in the first plurality of plates; anda first outlet header configured to receive the first substance from the first flow passages and expel the first substance from the device; anda second pathway for conveying a second substance, the second pathway comprising: a plurality of second flow passages between adjacent plates in the first plurality of plates, wherein each second flow passage includes a plurality of second structures;a second inlet header configured to receive the second substance and direct the second substance through the second flow passages; anda second outlet header configured to receive the second substance from the second flow passages and expel the second substance from the device.

2. The device of claim 1, wherein the first flow passages convey the first substance and the second flow passages convey the second substance in substantially opposite directions.

3. The device of claim 1, wherein the first substance has a relatively high pressure and a relatively low temperature at the first inlet header, in comparison to the second substance at the second inlet header.

4. The device of claim 3, wherein: the first inlet header receives the first substance at a pressure up to approximately 250 bar; andthe second inlet header receives the second substance at a temperature up to approximately 800° C.

5. The device of claim 1, wherein the plurality of first structures comprises microscale pins.

6. The device of claim 5, wherein the microscale pins have predetermined aspect ratios and spacing.

7. The device of claim 5, wherein the microscale pins connect opposing walls of the plate.

8. The device of claim 1, wherein the plurality of second structures comprises two or more parallel ridges.

9. The device of claim 1, wherein the plurality of second structures comprises interlocking pins that form a lattice structure.

10. The device of claim 1, wherein: the device further comprises a second plurality of plates enclosing the second flow passages; andthe first plurality of plates and the second plurality of plates are radially aligned between (a) the first inlet header and the second outlet header and (b) the second inlet header and the first outlet header.

11. The device of claim 10, wherein: the plurality of second structures of one or more second flow passages converge in a direction of flow of the second substance through the second flow passages to control pressure loss of the second substance.

12. The device of claim 1, wherein one or more of the first flow passages and the second flow passages have variable converging and/or diverging cross-sections that control loss of pressure of one or more of the first substance and the second substance.

13. The device of claim 1, wherein the device is devoid of braze joints and weld joints.

14. The device of claim 1, wherein the device is fabricated monolithically via a metal laser powder-based fusion additive manufacturing process.

15. The device of claim 1, wherein the first substance comprises one or more of: supercritical carbon dioxide; andmolten salt.

16. The device of claim 1, wherein the second substance comprises one or more of: molten salt;fluidized metallic particles;fluidized ceramic particles;liquid sodium; anda supercritical gas.

17. A heat exchanger apparatus, comprising: a first inlet header for inletting a first fluidiform substance;a second inlet header for inletting a second fluidiform substance;a first outlet header for outputting the first fluidiform substance;a second outlet header for outputting the second fluidiform substance;a plurality of first passages through which the first substance flows between the first inlet header and the second inlet header; anda plurality of second passages through which the second substance flows between the second inlet header and the second outlet header;wherein the plurality of first passages and the plurality of second passages are parallel to and interleaved with each other.

18. The apparatus of claim 17, further comprising: a plurality of first plates, wherein each first plate encloses one of the first passages.

19. The apparatus of claim 18, wherein each first passage comprises microscale structures that connect opposing walls of the plate.

20. The apparatus of claim 19, wherein the microscale structures include an array of pins having predetermined aspect ratios and spacing.

21. The apparatus of claim 18, further comprising: a plurality of second plates, wherein each second plate encloses one of the second passages.

22. The apparatus of claim 21, wherein each second passage comprises microscale structures that connect opposing walls of the plate.

23. The apparatus of claim 22, wherein the microscale structures include a lattice of interconnecting pins.

24. The apparatus of claim 17, wherein the first inlet header and/or the first outlet header are exposed to a flow of the second substance before and/or after the second substance flows through the plurality of second passages.

25. The apparatus of claim 17, wherein the apparatus has a radial configuration in which: one of the inlet headers and one of the outlet headers form an inner arc;the other of the inlet headers and the other of the outlet headers form an outer arc; andthe plurality of first passages and the plurality of second passages are radially aligned between the inner arc and the outer arc.