WO2025170772A1

WO2025170772A1 - Augmented system and method for ultra-high heat flux exchange

Info

Publication number: WO2025170772A1
Application number: PCT/US2025/012931
Authority: WO
Inventors: Peiwen Li
Original assignee: University of Arizona
Current assignee: University of Arizona
Priority date: 2024-02-07
Filing date: 2025-01-24
Publication date: 2025-08-14
Anticipated expiration: 2026-08-07

Abstract

A heat-exchange cell and a heat-exchange apparatus including at least one such cell. The cell employs the principle of jet impingement of a gas-mix coolant (with the heat-transfer coefficient of about 8-10 kW/(m²°C) onto judiciously structured heat-exchange surface(s) carried out my multiple coolant jet tubes, the return of coolant fluid in a direction opposite to the direction of jet(s) and optional additional heat-transfer enhancement structural features of the cell to achieve a heat transfer coefficient of jet impingement flow of up to 10 kW/(m²°C). The heat-exchange apparatus in built by judicious stacking multiple cells. Method of carrying heat-exchange process.

Description

AUGMENTED SYSTEM AND METHOD FOR ULTRA-HIGH HEAT FLUX EXCHANGE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This Patent Application claims priority from and benefit of the US Provisional Patent Application no. 63/550,770 filed on February 07, 2024, the disclosure of which is incorporated herein by reference.

RELATED ART

[0002] Heat transfer is the process of exchanging thermal energy between physical systems. (Generally, such process is classified according to various enabling mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes, for example .) The problem of increasing the efficiency of heat transfer - whether during the process of collection of solar energy or in a process of advection, for example - remains persisting.

[0003] One of recognized engineering tricks played to increase the heat transfer coefficient is to judiciously structure the surface participating in heat transfer - by, for example, augmenting it. (The most common illustration is provided by the “finned” - that is, containing fins - surface of a thermoelectric cooler used in electronics.)

[0004] Tire potential impact of technologies turning on developing the ultra-high heat flux exchange capabilities extend across multiple industrial areas, including applications in compact heat exchangers for recuperators and waste heat recovery, ultra-high flux solar thermal energy harvesting, or scaling down for heat sinks to cool electronic devices, among others. The dramatic improvement in the efficiency of heat exchange for industrial waste heat utilization and solar thermal energy harvesting will assist the industry in achieving the goal of decarbonization.

SUMMARY OF THE INVENTION

[0005] Embodiments of the invention provide an article of manufacture configured to operate as a heat-exchanger that contains at least a base heat-exchange cell. Such cell includes a supporting substrate, a coolant-in port, a coolant-out port, and an array of jet tubes attached to the supporting substrate and fluidly connected to the coolant-in port (here, each jet tube of such array is configured to transport, in a first direction, a coolant fluid received through the coolant-in port to a heat-transfer surface of the cell through an output end of such jet tube. Tire cell additionally includes an array of fluidreturning tubes attached to the supporting substrate and fluidly connected to the coolant-out port (here, each fluid-returning tube of such array of fluid-returning tubes is configured to receive the coolant fluid, which has interacted with the heat-transfer surface, at an input end of such fluid-returning tube and to transport such coolant fluid in a second direction towards the coolant-out port). The first and second directions are opposite to one another. Each fluid-returning tube encloses at least a portion of a respectively corresponding jet tube. At least one embodiment of the article is structured to satisfy one or more of the following conditions: a fluid-returning tube of the array of fluid-returning tubes is substantially co-axial with the respectively corresponding jet tube of the array of jet tubes: at least one of a fluid-returning tube of the array of fluid-returning tubes and a jet tube of the array of jet tubes is substantially cylindrical; and a first axis of a first jet tube of the array of jet tubes is substantially not parallel to a second axis of a second jet tube of the array of jet tubes. Additionally or in the alternative (and when the first axis of the first jet tube is substantially not parallel to the second axis of the second jet tube), the supporting substrate may have a non-zero curvature in a plane containing at least one of the first and second axes, and/or - when the first axis is substantially not parallel to the second axis - the supporting substrate may be dimensioned as a tubular element having a cross-section with a perimeter defined by a closed line. (In the latter case, a perimeter of the cross-section may be dimensioned to be substantially elliptical or polygonal.) Optionally, substantially even’ implementation of the article of manufacture may be configured to satisfy one of the following conditions: - the output end of a chosen jet tube is open and configured to face the input end of a chosen fluid-returning tube that is fluidly sealed, to thereby direct a jet of coolant fluid exiting the output of the chosen jet tube end to directly impinge onto a sealing surface of the input end of the chosen fluid-returning tube; and - the output end of the chosen jet tube and the input end of the chosen fluid-returning tube are open to direct the jet of coolant fluid exiting the output of the jet tube away from the output end of the chosen fluid-returning tube. (Here, when the first condition is satisfied, a surface of the fluid-returning tube may be configured as the heat-transfer surface of the heat-exchange apparatus.) Alternatively or in addition, substantially every implementation of the article of manufacture may additionally include a substantially fluidly-sealed housing configured to enclose both the array of jet tubes and the array of fluid-returning tubes (such housing generally includes a housing wall and a housing cap). When such housing is present, an embodiment of the article may be structured to satisfy one of the following conditions: (i) a surface of a fluid-returning tube of the array of fluid-returning tubes is configured as a heat-transfer surface, and (ii) the housing cap, facing open ends of jet tubes of the array of jet tubes, is configured as the heat-transfer surface. When such housing is present, the article may be optionally configured to include an auxiliary fluid-in port and an auxiliary fluid-out port (in at least one of the housing wall and the housing cap) and a manifold plate or membrane that has multiple openings therethrough configured to fluidly connect each of the auxiliary fluid-in port and the auxiliary fluid-out port with fluid-returning tubes of the array of fluid-returning tubes. Alternatively or in addition, substantially every implementation of the article of manufacture may include an auxiliary heat-exchange cell that is configured substantially identically to the base heat-exchange cell and that is structurally cooperated with the base heat-exchange cell such as (a) to have an array of fluidreturning tubes of the auxiliary heat-exchange cell face towards the array of fluid-returning tubes of the base heat-exchange cell and to be separated from the array of fluid-returning tubes of the base heatexchange cell by a manifold plate or membrane having multiple openings therethrough, and/or (b) to have the array of fluid-returning tubes of the auxiliary' heat-exchange cell face away from the array of fluidreturning tubes of the heat-exchange cell and to be separated from the array of fluid-returning tubes of the heat-exchange cell by the supporting substrate. Alternatively or in addition, substantially every implementation of the article of manufacture may be configured to satisfy at least one of the following conditions: the (1) article of manufacture includes a source of coolant fluid (such, as, for example, a nitrogen gas and/or a helium gas) and (2) the article of manufacture includes an auxiliary fluid-in port, an auxiliary' fluid-out port, and a manifold plate or membrane having multiple opening therethrough configured to fluidly connect each of the auxiliary fluid-in port and the auxiliary' fluid-out port with fluidreturning tubes of the array of fluid-returning tubes.

[0006] Embodiments of the invention further provide a method for carrying out a heat-exchange process (which method in at least one specific case may be effectuated with the use of substantially every embodiment of the article of manufacture alluded to above). Such method includes at least a step of impinging a coolant fluid (which has been jetted out of a corresponding output end of each jet tube of an array of jet tubes in a first direction) onto a corresponding heat-transfer surface, and a step of transferring the coolant fluid (which has interacted with the corresponding heat-transfer surface) in a second direction that is opposite to the first direction inside corresponding fluid-returning tubes of an array of fluid-returning tubes. (Here, there is a one-to-one correspondence between the fluidreturning tubes of the array of fluid returning tubes and jet tubes of the array of jet tubes - that is, each jet tube is matched with exactly one corresponding fluid-returning tube, thereby ensuring that each jet tube and each corresponding fluid-returning tube is counted only once when counting a group of tubes. Moreover, each of the fluid-returning tubes encloses and/or houses therein at least a portion of a corresponding jet tube therein.) In at least one case, the step of impinging may include impinging the coolant fluid directly onto the heat-transfer surface without interacting the coolant fluid with an element of the article of manufacture between the output end of the jet tube and the heat-transfer surface; and/or the step of delivering may include delivering the coolant fluid to each jet tube of the array of jet tubes through multiple coolant-in ports fonned in a supporting substrate, wherein the supporting substrate carries at a body of the supporting substrate both the array of jet tubes and the array of fluid-returning tubes, while the method further includes a step of removing the coolant fluid that has propagated through at least one jet tube and through at least one corresponding fluid-returning tube through multiple coolant- out ports formed in the supporting substate. Optionally, the multiple coolant-in ports and the multiple coolant-out ports of the article of manufacture may be positioned at and distributed along a perimeter of the supporting substrate substantially evenly and in alternating fashion. Optionally, propagation of a coolant fluid through the supporting substrate may include propagating the coolant fluid through the supporting substrate dimensioned as a hollow tubular element, in which case the step of delivering is carried out substantially inwardly towards an axis of the hollow tubular element, or substantially outwardly away from the axis of the hollow tubular element, or both substantially outwardly away from the axis of the hollow tubular element and substantially inwardly towards the axis of the tubular element. When the supporting substrate is structured at a hollow tubular element, it may have a cross section with a substantially polygonal outer perimeter or with a substantially elliptical outer perimeter. Alternatively or in addition, the step of delivering the cooling fluid may be carried out through a delivery passage that fluidly connects a coolant-in port with a jet tube of the array of jet tubes, and a step of removing the cooling fluid may be carried out through a removal passage that is fluidly connecting a fluid-returning tube with a coolant-out port, while the delivery passage and the removal passage do not intersect one another to prevent mixing of an in-flowing portion of the coolant fluid with an out-flowing portion of the coolant fluid in the body of the supporting substrate. Optionally, at least one embodiment of the method is configured to satisfy at least one of the following conditions: (A) a fluid-returning tube of the array of fluid-returning tubes is substantially co-axial with the respectively corresponding jet tube; (B) at least one of a fluid-returning tube of the array of fluid-returning tubes and a jet tube of the array of jet tubes is substantially cylindrical; (C) a first axis of a first jet tube is substantially not parallel to a second axis of a second jet tube; (D) each fluid-retuning tube has a sealed end that is individually sealed with a corresponding heat-transfer surface of a plurality of heat-transfer surfaces: and (E) each fluid- retuning tube has a corresponding open input end (where the corresponding heat-transfer surface is a single heat-transfer surface common to or shared by all pairs of a fluid-returning tube of the array of fluidreturning tubes and a corresponding jet tube of the array of jet tubes). In such embodiment of the method, when condition (D) is satisfied, the method may be devoid of (that is, not include) a process of mixing a portion of the coolant fluid jetting out of an output end of a first jet tube with a portion of the coolant fluid jetting out of an output end of a second jet tube prior to delivering such coolant fluid to a coolant-out port of the apparatus; and/or, when condition (E) is satisfied, the method may include a process of mixing the portion of the coolant fluid jetting out of an output end of the first jet tube with the portion of the coolant fluid jetting out of an output end of a second jet tube prior to delivering the coolant fluid to the coolant- out port of the heat-exchange cell. Optionally, when condition (D) is satisfied, the method may be configured to additionally include a step of delivering an auxiliary fluid through an auxiliary fluid-in port in a wall and/or a cap of a housing shell that covers the array of fluid-returning tubes having sealed ends; and a step of transferring the auxiliary fluid through multiple openings fonned through a manifold plate or a membrane that is separated from the supporting substrate by the array of fluid-returning tubes. In at least one specific implementation that involves the use of auxiliary fluid, the method may additionally include the step of interacting the auxiliary fluid with the heat-transfer surface and the step of expelling such auxiliary fluid from the volume through an auxiliary fluid-out port fonned in the wall of the housing shell without mixing the auxiliary fluid with the coolant fluid. Alternatively or in addition, substantially every implementation of the method may include a step of transferring heat energy from an auxiliary fluid (which circulates through a volume of a shell side of the heat-exchange article of manufacture employed to carry out the method that is fluidly separated from the array of jet tubes) to the heat-transfer surface; and a step of transmitting the heat energy through the heat-transfer surface to the coolant fluid that includes gas contained in a volume of a tube side of the article of manufacture. Optionally, substantially every implementation of the method may include a step of jetting out the coolant fluid from the array of jet tubes (here, when a first axis of a first jet tube of the array of jet tubes is substantially not parallel to a second axis of a second jet tube of the array of jet tubes, the supporting substrate of the heat-exchange article of manufacture employed to carry out the method is configured to have a non-zero curvature in a plane containing at least one of the first and second axes). Optionally, substantially every implementation of the method may include a step of operating the heat-exchange article of manufacture that includes multiple combinations of arrays of jet tubes with corresponding arrays of fluid-returning tubes and where such combinations are stacked on top of another in a specific fashion. In the formed stack, first and second combinations of the multiple combinations of the alluded to arrays share a supporting substrate carrying respective arrays of jet tubes and respective arrays of fluid-returning tubes, and/or at least two combinations of such multiple combinations that have different supporting substrates while respective arrays of fluid-returning tubes of such at least two combinations arc facing one another.

BRIEF DESCRIPTION OF THE DRAWINGS

[0001] The invention will be more fully understood by referring to the following Detailed Description of Specific Embodiments in conjunction with the Drawings, of which:

[0007] FIGs. 1A, IB provide examples of related designs of a heat-exchange cell (or heater transfer cell, or heat transfer unit - which terms may be used herein interchangeably) employing multiple jet impingements onto judiciously structured heat-transfer surfaces. Structure of FIG. 1A enables jet impingements onto dead-ended fluid-returning tubes that receive sunlight. Structure of FIG. IB enables jet impingements onto a plate configured as a common cap of the housing structured covering the tubular elements of the cell and shared by the array of jet tubes and the array of fluid-returning tubes and placed to absorb energy incident thereon from outside of the housing of the heat-transfer cell.

[0008] FIG. 1C illustrates a schematic view of the embodiments of FIGs. 1A, IB along an axis transverse to the supporting substrate of the embodiments.

[0009] FIG. ID presents a schematic of a heat-transfer cell configured to implement coolant jet impingement in tubes and heat delivered to material particles contained at tube bank.

[0010] FIG. IE illustrated an outside -flux-of-energy-facing side (for example, a sun-facing side) of a 3D-printed mini model of a heat-transfer cell implementing the design of FIG. 1 A.

[0011] FIGs. 2 A, 2B illustrate possible configurations of optional fins for fluid-returning tubes of an embodiment of a heat-exchange unit of the invention. FIG. 2A: helically-dimensioned fins on inner surfaces of open-ended fluid-returning tubes of FIG. IB; FIG. 2B: outwardly pointing substantially- planar fins on outer surfaces of open-ended fluid returning tubes of FIG. IB.

[0012] FIG. 2C illustrates schematically optional inner fins at an inner surface of a dead-end of a fluid-returning tube of an embodiment of FIG. IB.

[0013] FIG. 3 depicts schematically a related embodiment of a heat-exchange cell structured to employ, in addition to an array of combinations of jet tubes with respectively corresponding fluidreturning tubes, shell-side portion that includes a housing shell covering the array and a manifold separating a portion of the volume of the housing for delivery of an auxiliary fluid through port(s) that are spatially distinct from the coolant-in port(s).FIGs. 4 and 5 illustrate embodiments of a heat-exchange apparatus formed by stacking multiple heat-exchange cells in a judicial fashion to share supporting substrate and/or a liquid-side of a given embodiment.

[0014] FIGs. 4 and 5 illustrate emb odiments of a heat-exchange apparatus or device that is formed by stacking-up and/or appropriately combining constituent heat-exchange cells structured according to the idea of the present invention.

[0015] FIG. 6 schematically illustrates an embodiment in which an overall supporting substrate is arranged from the constituent panels of supporting substrates to form a substantially tubular element.

[0016] Generally, the sizes and relative scales of elements in Drawings may be set to be different from actual ones to appropriately facilitate simplicity, clarity, and understanding of the Drawings. For the same reason, not all elements present in one Drawing may necessarily be shown in another. Generally, unless specified otherwise, dimensions if shown are shown in mm and are not limiting but provide only specific example(s). DETAILED DESCRIPTION

[0017] The proposed solution to persisting practical limitations of conventional heat exchangers stems from the realization that a combination of a jet impingement of the used coolant onto a judiciously augmented heat-transfer surface(s) with additional heat-transfer enhancement geometry of a heatexchange cell (such as, in one example, locating the coolant jet-forming tubes at least partially inside the tube structured to provide for return of the coolant from the heat-transfer surfaces enables highly effective heat transfer with a heat transfer coefficient that is enhanced as compared to that achieved in related art with industrial heat exchangers. Moreover, the proposed designs lend themselves to tire used of additive manufacturing technologies to enable the relatively easy and cost-effective fabrication of fins on the used augmented heat transfer surfaces, thereby adding further advantages to the heat transfer technology.

[0018] To this end, FIGs. 1A, IB provide examples of related designs 100, 100’ of a base heat-exchange cell. In one configuration, a cell so designed may be used to collect energy from the concentrated ultra-high solar flux incident onto the heat-transfer surface(s).

[0019] The advantages of the technology proposed and discussed in this disclosure stems from the utilization, in the base heat-exchange or heat-transfer cell 100, 100’ (see FIGs. 1A, IB) of an array of jets of a coolant fluid (in one specific example - the chosen gas) that is directed to impinge, in the form of multiple jets, from the open ends of jet tubes upon heat-exchange surface(s) of the corresponding cell and to be collected and returned to the coolant storage (not shown) via multiple an respectively- corresponding to jet tubes fluid-returning tubes. Depending on the specifics of a particular design, heatexchange surface(s) receiving the coolant jets from the open output ends of the jet tubes are structured to be either (i) common to - that is, shared by - all of involved fluid-returning tubes or (ii) in one specific implementation, as will be discussed in more details below, when the fluid-returning tubes are dead- ended. are individual to and one-to-one corresponding to a combination of a given jet tube and a given fluid-returning tube (in which case the individual heat-exchange surfaces is provided at least partially by the dead ends of the fluid-returning tubes).

[0020] A portion of an embodiment of a heat-transfer apparatus (structured according to the idea of the invention and shown in FIG. 1A) includes the base heat-transfer cell 100 that combines a supporting substrate 134 (carrying at different levels or depths therein various fluid-delivery passages), multiple combinations of jet tubes 110, and respectively -corresponding fluid-returning tubes 120 (arranged one inside the other in each of the multiple combination). The multiplicity of the jet tubes 110 forms an array of jet tubes, the multiplicity of the fluid-returning tubes 120 forms an array of fluid- returning tubes, and the multiplicity of the combinations of one-to-one corresponding jet tubes and fluidreturning tubes forms an array of combinations of tubes.

[0021] The coolant (which may also be referred to herein as a coolant fluid) is delivered to the jet tunes through the coolant-in port(s) 130 connecting corresponding delivery⁷ passage(s) 132 in the supporting substrate 134 with ambient environment, is propagated towards the input ends of jet tubes 110 via fluid delivery⁷ passage(s) 132 and then through the jet tubes HO to be jetted out of the open ends 110A of the jet tubes 110 onto individual (to each of the jet tubes 110) heat-exchange surfaces formed by dead (or closed) ends 122 of the fluid-returning tubes 120. The skilled person will readily appreciate that the embodiment 100 is configured to provide for formation and impinging of a corresponding jet flow (produced by a given jet tube 110 that is an inner tube of a given combination of the tubes) onto an inner surface of a dead-end of the corresponding fluid -returning tube. Phrased differently, the output end of a chosen jet tube is open and configured to face the input end of a chosen fluid-returning tube that is fluidly sealed, as a result of which a jet of coolant fluid exiting the output of the chosen jet tube end directly impinges, in operation of the base cell 100, onto a sealing surface of the input end of the chosen fluidreturning tube.

[0022] Having interacted with such individual heat-exchange surfaces 122, the coolant is then collected through the fluid-returning tubes 120. Here, specifically, the coolant from each jet is collected through the annulus between the jet-inducing tube 110 and the corresponding fluid-returning tube 120 after the coolant has interacted with the dead-end of tire tube 120. Thereafter, the coolant is expelled through the fluid-returning passage(s) 136 and the coolant-out port(s) 138. The delivery passage(s) 132 and the return passage(s) 136 are configured such as to not overlap, thereby preventing the coolant fluid delivered to the jet tubes and that returned after interaction with the heat-exchange surface(s) from mixing with one another.

[0023] In at least one mode of operation, the cell 100 is exposed to a flux of outside energy - for example, to receive solar flux (that may have been already spatially concentrated) incident on the outer surface of the fluid-returning tubes 120 and. in particular, on the dead ends 122 of such tubes 120.

[0024] FIG. IB illustrates a related structure 100’ of a base heat-exchange cell, in which the fluidreturning tubes 120’ of the array of combinations of tubes (each combination including a jet tube 110 and the respectively-corresponding fluid returning tube 120') are open-ended, thereby enabling multiple jets from the corresponding jet tubes 110 to impinge directly onto the shared by the tubes element 114 that is configured as a cap of the housing of the base heat-exchange cell 100’ that covers and fluidly seals the array of combination of tubes from the ambient environment. The cap 114 is configured, therefore, as a common to the fluid-returning tubes 120’ heat-exchange element of the base cell 100’. (In this implementation, the coolant fluid delivered to the heat-exchange surface of the cap 114 from each jet is also collected through the annulus between a given jet-inducing tube 110 and the one-to-one corresponding outer fluid-returning tube with the open end that encloses at least a portion of the respective jet-inducing tube 110.) Here, both the output end of the chosen jet tube and the input end of the corresponding fluid-returning tube are open to direct the jet of coolant fluid exiting the output of the jet tube away from the output end 9the one leading to the fluid passage directly connected to a coolant-out port 138) of the corresponding fluid-returning tube.

[0025] FIG. 1C presents a schematic illustration combining cross-sectional views of the embodiments 100, 100’ as seen along an axis that is perpendicular to the surface of the supporting substrate 134 (here, the Y- axis of the local system of coordinates).

[0026] FIG. ID is a schematic of a heat -exchange cell employing the design of the embodiment 100, in which the energy (as illustrated - solar energy) transferred through the dead-ends of the fluidreturning tubes is further transferred to material particles (such as, for example, particles of silica from about 0. 1 to about 1.0 mm in size) disposed and essentially enclosed at the tube bank or volume between the supporting substrate and the separator element 144. Here, the ability to have high heat transfer coefficient using jet impingement flow and to accommodate the requirement for particle thermal storage provides a big operational advantage for the embodiment of FIG. ID. A trial model has been 3D-printed using plastic (as seen substantially along the Y-axis in FIG. IE) to demonstrate the design of 2D-array of combination of jet tubes enclosed within respectively -corresponding fluid-returning tubes of FIG. 1A. [0027] As the skilled person will readily appreciate, the axes along which the jet tubes and respectively-corresponding fluid-return tubes are extending from the supporting substrate are not necessarily parallel to one another. Similarly, when the housing with the cap (configured as a common heat-exchange surface for an array of tubes) is employed such as in the embodiment 100’) the common to different fluid-returning tubes heat-exchange surface is not necessarily substantially planar (as shown in the example of FIG. IB): it may be curved (whether convex or concave as seen from inside the heatexchange cell) and in a specific case form a portion of a surface of a sphere, for example such as in the case when the cap is dimensioned as a portion of a spherical shellnone of these specific cases is shown in the Figures for the simplicity of illustrations). Furthermore, the inner surface of the cap 114 - the one facing the tubes 110, 120’ - may be additionally structured to include a prc-dctcrmingly sized surface relief, to be ‘‘dimpled” or to include protrusions / fins extending towards the array of tubes 110, 120, for example (not shown) to further increase the efficiency of heat transfer as compared with that provided by the implementation of the jet-impingement alone.

[0028] Therefore, in at least one specific implementation of a heat-exchange cell, a fluid-returning tube may be substantially co-axial with the respectively corresponding jet tube of the array of jet tubes, and/or at least one of a fluid-returning tube of the array of fluid-returning tubes and a jet tube of the array of jet tubes may be substantially cylindrical, and/or a first axis of one jet tube may be substantially not parallel to a second axis of another jet tube of the array of jet tubes and, optionally, the supporting substrate may have a non-zero curvature in a plane containing at least one of these first and second axes. The skilled person will readily appreciate that, with such structural arrangement(s), each individual jet of coolant has a respectively corresponding and individually controlled heat-exchange surface.

[0029] Overall, the fluid-returning tubes 120, 120’ of embodiments of a heat-exchange cell structure according to the idea of the invention are fonned in a specifically structured array such that each of the fluid-returning tubes houses at least a portion of the respectively-corresponding jet tube inside the fluid-returning tube and, optionally, is complemented with fins at inside and/or outside surfaces of such fluid-returning tube (which fins may be formed via, for example, 3D printing fabrication). To this end, FIGs. 2A and 2B provide but two non-limiting examples 210A, 220A of such fins on open-ended fluid returning tubes 210, 220, while FIG. 2C illustrate one possible design of inwardly pointing fins 230 on the inner surface of the dead-end 122 of the tube 120 of an embodiment employing the structure 100.

[0030] Notably, it is well recognized (see, for example, T. Muszynski, R. Andrzejczyk, Applied Thermal Engr., 100 (2016) 105-113) that the jet impingement-based heat transfer approach has not been innovatively used in constructing heat exchangers. Instead - and in regrettable contradistinction with the proposed methodology - traditional manufacturing technologies, which rely on welding to add features to heat exchangers, make it exceptionally challenging to incorporate fins on heat transfer surfaces, as required for heat transfer enhancement and surface augmentation. Consequently, the improvement in heat transfer coefficient in traditional heat exchangers is typically limited to less than 70% (see B. Pidaparthi et al., ASME J. of Energy Resources Technology, DOI: 10.1115/1.4063207), with heat transfer surface augmentation practically restricted to a coefficient of 2, resulting in an NTU typically smaller than 2.8 (see A.R.S. Masitah et al., Energy Research Journal, DOI: 10.3844/eijsp.2015.7.14).

[0031] In at least one specific implementation of the idea of the invention (that utilizes a high thermal conductivity gas such as helium (He) or a mixture of He and nitrogen (N₂) as a coolant and that is implemented as part of a solar energy receiver) to operate with the heat transfer coefficient of at least 10 kW/(m^{2 o}C) to achieve a solar heat flux of about 0.8-1 .0 MWm or higher. In particular, as was experimentally determined, about 40% of mass concentration of He in the gas mixture of (He + N₂ ) results in dramatic improvement of the thermal conductivity of such gas mixture In this specific case, the jet impingement based heat-transfer cell structure (made, for example, from metallic thermally conductive materials such as Al, Cu, steal, and various high-temperature alloys) that is similar to that of FIG. IB contains a dimpled inner surface of the cap 114 to have a Nusselt number (dimensionless heat transfer coefficient, Nu = -~-ⁱ) of around 250 at the stagnation zone on the target surface (the surface on which the jet of coolant is impinging), which is much higher than that achie ved with the lateral flow of the coolant liquid over the target surface. (As the skilled person recognizes, a stagnation point is the center point of a target surface corresponding to the jet’s center point. The stagnation zone is the area of substantially the same size as a footprint of the jet at the target surface.) Here, h represents the heat transfer coefficient, D, is the diameter of the jet flow at the jet exit, k is the thermal conductivity of the fluid in the jet

[0032] The proposed configuration achieves a remarkably high convective heat transfer coefficient for the tube-side coolant fluid propagating on the tube-side of an embodiment of the heattransfer cell. The jet impingement can attain a heat transfer coefficient at the stagnation region 5- 10 times higher than that in the region of regular lateral flow on a surface (see, for example, P. W. Li, W. Q. Tao, Wanne-und Stoffubertragung, 1994, vol. 29, pp. 463-470). The augmentation of the heat-transfer surface area (due to the use of fluid-returning tubes 120) can be as much as 100 times higher as compared to the nominal surface area (which is the cross-section area of the tubes), consequently leading to an overall increase in the heat transfer rate by up to 100 times, of the proposed configuration of a heat exchanger may be successfully used in industry to extract heat from flue gases which may come from steel mills, power plants, or cement production plant, for example.

[0033] In yet another specific case, a given supporting substrate of an embodiment of a heatexchange cell may be “folded” and/or “bent” upon itself or arranged from the constituent panels of supporting substrates to form a substantially tubular element (optionally, with a quasi -elliptically or a polygonally shaped cross-section, thereby having a perimeter defined by a closed line) such that the array of fluid-returning tubes and the array of jet tubes carried by the supporting substrate extends from such substrate either inwardly (towards the axis of the tubular element) or outwardly (away from the axis of the tubular element), thereby fonning a folded heat-exchange unit. A schematic illustration of such structure is presented in FIG. 6 showing a “tower” type heat-exchange apparatus 600 with the axis 610. [0034] A portion of an article of manufacture that includes a related embodiment of the heatexchange cell configured according to the idea of the invention is schematically illustrated in FIG. 3.

Here, the body of the cell 300 (still containing the array of jet tubes such as tubes 110 enveloped with and housed within the corresponding closed-end fluid-returning tubes such as tubes 120, similar to that of FIG. 1 A) is functionally complemented with the housing or shell 304 that is attached to the supporting substrate 134 to fluidly enclose and cover and seal the array of combinations of tubes 110, 120. Furthermore, a portion of the volume limited by the housing is separated from the array of the combination of tubes with a manifold / membrane 310 having throughout openings in it to enable delivery of auxiliary fluid towards the tubes of the cell: through the corresponding auxiliary fluid-in port(s) 314 and then through the multiple openings in the manifold 310. Operationally, therefore, the structure 300 can be viewed as including a tube-side 318 (enabling the circulation of a chosen coolant between the coolant-in pot(s) 130 and the coolant-out port(s) 138, as discussed above) and a shell-side 322.

After interacting with the outer surface(s) of the fluid-returning tubes (the sealed ends of which form at least parts of corresponding heat-exchange surfaces), the auxiliary liquid is extracted from the volume of the liquid-side of the heat-exchange unit through the auxiliary fluid-out port(s) 326. The geometric configuration of the supporting substrate of the cell 300 can be substantially similar to that of the supporting substrate of embodiments 100, 100’: it can be substantially planar, or bent, or even folded upon itself.

[0035] Tire above arrangements of a heat exchange unit result in a high heat transfer coefficient from tire jet impingement combined with fins and a substantial increase in heat transfer surface area facilitated by the array of tubes. Tire jet impingement can attain a heat transfer coefficient at the stagnation region 5- 10 times higher than that in the region of regular lateral flow on a surface . The heat transfer surface area augmentation due to the use of array of housed-in-one-another tubes can be as much as 100 times higher compared to the nominal surface area (which is the cross-section area of the tubes), consequently leading to an overall increase in the heat transfer rate by up to 100 times. This type of heat exchanger may be used in industry to extract heat from flue gases which may come from steel mills, power plants, or cement production plant, etc.

[0036] FIGs. 4 and 5 schematically illustrate related embodiments of a heat-exchange apparatus 400 each of which is formed by stacking-up and/or appropriately combining individual heat-exchange cells (such as those described above).

[0037] FIG. 4 depicts the situation in which two arrays of combinations of open-ended fluidreturning tubes 120 and jet tubes 110 (compare with FIG. IB) are carried by the same supporting substrate and face away from one another. In particular, the first array of tube combinations is extended from the supporting substrate structure 434 in the +Y direction (according to the chosen local system of coordinates) towards the upper cap 414A of the housing structure and the second array of tube combinations extends from the same supporting substrate structure 434 in the -Y direction towards the lower cap 414B of the housing structure of the apparatus 400. The substrate structure 434 is generally dimensioned in a fashion similar to that of the supporting substrate 134; as shown in FIG. 4, however, the upper and lower portions of the apparatus 400 share the coolant -in port(s) 130 but have spatially- independent coolant-out port(s) 138.

[0038] FIG. 5 schematically illustrates the idea of fonning the heat-exchange apparatus by operationally appropriate stacking-up of the individual heat-exchange cells that similarly structured - for example, substantially according to the embodiment of FIG. 3. Here, as shown, the first and second cells 510, 520 can be assembled back-to-back so that the tube-side flow of the cells 510, 520 is shared (that is, one supporting substrate structure 534 is shared by two different sets of arrays of tubes. The housing structures of the cells 510, 520 are separate from one another but are attached to the same, common to the cells 510, 520 supporting substrate structure 534. Similarly, the shell-side flow of the second and third cells 520, 530 (at the lower portion of the embodiment 500) can be coupled and shared. Here, the housing structure corresponding to the cells 520, 530 may be shared between these cells - as shown in the example of FIG. 5. In the same manner, more individual heat-exchange cells can be operationally coupled together to form a large compact heat exchange apparatus as needed. Accordingly, in at least one implementation, a heat-exchange apparatus may include an auxiliary’ heat-exchange cell that is configured substantially identically to the base heat-exchange cell and that is structurally cooperated with the base heat-exchange cell such as to satisfy at least one of the following conditions: (a) to have an array of fluidreturning tubes of the auxiliary heat-exchange cell face towards the array of fluid-returning tubes of the base heat-exchange cell and to be separated from the array of fluid-returning tubes of the base heatexchange cell by a manifold plate or membrane having multiple openings therethrough, and to have the array of fluid-returning tubes of the auxiliary’ heat-exchange cell face away from the array of fluidreturning tubes of the heat-exchange cell and to be separated from the array of fluid-returning tubes of the heat-exchange cell by the supporting substrate.

[0039] Overall, as the skilled artisan will readily appreciate, the operation of an embodiment of a heatexchange apparatus or an article of manufacture (yvhich incorporates at least one embodiment of an individual heat-exchange cell discussed above) generally entails: (i) impinging a coolant fluid, which has been jetted out of a corresponding output end of each jet tube of an array of jet tubes in a first direction, onto a corresponding heat-transfer surface; and (ii) transferring the coolant fluid, which has interacted with the corresponding heat-transfer surface, in a second direction that is opposite to the first direction inside corresponding fluid-returning tubes of an array of fluid-returning tubes. Here, there is a one-to-one correspondence between the fluid-returning tubes of the array of fluid returning tubes and jet tubes of the array of jet tubes and each of the fluid-returning tubes encloses and/or contains at least a portion of a corresponding jet tube therein.

[0040] For fabrication of an embodiment of the invention, carbon steel, stainless steel, nickel-based alloys, or refractory metals might be used, depending, for example, on the requirement for corrosion resistance and lifespan over operationally significant time (such as twenty years). Under conventional fabrication technology based on welding, smooth tubes are typically used; however, with additive manufacturing technology (3D printing) being applied, fins may be fabricated at the inner and outer surface of the tubes, which can further enhance the heat transfer for both the flows of the heat exchanger. With additive manufacturing, materials at the inner and outer surface of the tubes might be different for different requirement of corrosion resistivity under different fluid environment.

[0041] Referring again to the embodiment of FIG. 1A, in one specific application the same heat transfer configuration using a bundle of tubes (with optional fins) and configured to jet impingement heat transfer as discussed above can be applied to the case of receiving ultra-high heat flux that might be coming from concentrated sunlight, incident onto the outer surface of the fluid-returning tubes. For example, a heat flux of 1.0 MW/m² can be due to 1000 times of direct sunlight (typically in energy density of 1.0 kW/m²) being concentrated. Due to the enhanced heat transfer on the fluid side and augmentation of the heat transfer surface area, a heat flux target of 1.0-2.0 MW/m2 (equivalent to 1000 to 2000 times of sunlight being concentrated) can be reasonably set as the goal for industrial application that can provide high temperature gas or liquid that carries thermal energy (up to 1000 °C) to feed to applications such as cement production , or elsewhere where such heat is needed.

[0042] Referring again to embodiments of FIGs. IB, 4 for example, one may consider the case when the heat flux of solar energy is applied to the common (shared, as an external cover, by multiple tubes) plate / heat-transfer surface 114, 414A, 414B where the heat flux may be from concentrated solar energy or from the heat generation of fuel cells or electronics devices, etc., depending on the specific application. A typical volume of one unit of the heat exchanger 100, 100, 300 may be about 0.5m x 0.5m x 0.06m, while the three-unit-coupled heat exchanger 500 of FIG. 5 may be about 0.5m x 0.5m x 0.18m. [0043] Generally, embodiments of the invention demonstrate elevated target level of performance as comparison with those employing conventional regular lateral flows of coolant. From the features of jet impingement heat transfer, about 500% of heat transfer coefficient (U) improvement is demonstrated at the impinged areas (dead-ends) of the fluid-returning tubes while at the remaining surfaces of the fluid-returning tubes, heat transfer coefficient can be improved by 30-50% higher in case of the addition of fins. About 10 to 100 times of the increase of the heat transfer surface area (A) due to the use of tubes will also make the NTU (number of transfer unit) being larger than 3.0 and stretch to 3.5, and the heat exchanger effectiveness (E) is expected to be no less than 0.90.

[0044] For example, in the case of use of the embodiment of FIG. IE with (Hc+N_; ) gas mix introduced as a coolant, one conceived application scenario of the current proposed technology may be to collect solar thermal energy for direct high temperature gas Brayton cycle with combination of Rankine cycle and phase-change-material (PCM) based thermal storage, to provide high temperature heat (at the level of 800-850 °C) for Brayton gas cycle and Rankine steam cycle combined power generation with extended operation due to thermal storage using phase change materials like NaCl at melting point of 801 °C. A preliminary study was conducted (see. for example, Sheng Li t al., Helium Gas Brayton Cycle and Rankine Cycle Combined System with PCM Thermal Storage for Efficient CSP System, ES2024-130951, 2024 ASME Energy Sustainability conference, Anaheim, CA, July 15-17, 2024., the disclosure of which is incorporated by reference herein) to demonstrate solar to electrical energy conversion efficiency of 36.2% for such a system. Because of the PCM thermal storage material NaCl and off-the-shelf devices like gas turbines, steam turbines, and steam generators, the goal of LCOE of $0.05/kWh electric for baseload power is achievable. (As is known in related art. LCOE - or levelized cost of energy - is a measure used for comparison of different types of techniques used to collect solar energy or electricity, for example. Capital investment, maintenance for operation, and lifetime are all accounted for under the LCOE metric to calculate the cost of the harvested energy or electricity.)

[0045] Overall, the proposed innovative designs for heat exchangers are non-traditional, utilizing impinging flow or jet impingement on the heat transfer surface to maximize heat transfer enhancement. Notably, employing multiple jet impingement tubes can significantly augment the heat transfer surface area. Additionally, modem additive manufacturing technology enables the fabrication of fins on the heat transfer surfaces, providing a unique advantage over traditional heat exchanger technology. Through the design, fabrication, and experimental tests of the newly invented heat exchangers in the proposed project, we anticipate a significant impact on the design and manufacturing of industrial heat exchangers. More importantly, this innovation is poised to greatly improve the performance of modem heat exchangers, a critical component in the energy industry for thermal energy utilization, harvesting thermal energy from renewable sources, and advancing decarbonization efforts.

[0046] For the purposes of this disclosure and the appended claims, the use of the terms "substantially", "approximately", "about" and similar tenns in reference to a descriptor of a value, element, property or characteristic at hand is intended to emphasize that the value, element, property, or characteristic referred to, while not necessarily being exactly as stated, would nevertheless be considered, for practical purposes, as stated by a person of skill in the art. These terms, as applied to a specified characteristic or quality descriptor means "mostly", "mainly", "considerably", "by and large", "essentially", "to great or significant extent", "largely but not necessarily wholly the same" such as to reasonably denote language of approximation and describe the specified characteristic or descriptor so that its scope would be understood by a person of ordinary skill in the art. [0047] The use of these terms in describing a chosen characteristic or concept neither implies nor provides any basis for indefiniteness and for adding a numerical limitation to the specified characteristic or descriptor. As understood by a skilled artisan, the practical deviation of the exact value or characteristic of such value, element, or property from that stated falls and may van' within a numerical range defined by an experimental measurement error that is typical when using a measurement method accepted in the art for such purposes. In some specific cases, which are within the scope of the invention, the terms "approximately" and "about", when used in reference to a numerical value, represent a range of plus or minus 20% with respect to the specified value, more preferably plus or minus 10%, even more preferably plus or minus 5%, most preferably plus or minus 2% with respect to the specified value.

[0048] References made throughout this specification to "one embodiment." "an embodiment," "a related embodiment," or similar language mean that a particular feature, structure, or characteristic described in connection with the referred to "embodiment" is included in at least one embodiment of the present invention. Thus, appearances of these phrases and terms may, but do not necessarily, refer to the same implementation. It is to be understood that no portion of disclosure, taken on its own and in possible connection w ith a figure, is intended to provide a complete description of all features of the invention.

[0049] It is also to be understood that no single drawing is intended to support a complete description of all features of the invention. In other words, a given drawing is generally descriptive of only some, and generally not all, features of the invention. A given drawing and an associated portion of the disclosure containing a description referencing such drawing may not, generally, contain all elements of a particular view or all features that can be presented is this view, for purposes of simplifying the given drawing and discussion, and to direct the discussion to particular elements that are featured in this drawing. A skilled artisan will recognize that the invention may possibly be practiced without one or more of the specific features, elements, components, structures, details, or characteristics, or with the use of other methods, components, materials, and so forth. Therefore, although a particular detail of an embodiment of the invention may not be necessarily shown in each and every drawing describing such embodiment, the presence of this detail in the drawing may be implied unless the context of tire description requires otherwise. In other instances, well known structures, details, materials, or operations may be not shown in a given drawing or described in detail to avoid obscuring aspects of an embodiment of the invention that arc being discussed.

[0050] The term such as “element A and/or element B” is defined to have the same meaning as the term “at least one of element A and element B”. Tire invention as recited in claims appended to this disclosure is intended to be assessed in light of the disclosure as a whole, including features disclosed in prior art to which reference is made.

[0051] While the invention is described through the above-described exemplar, embodiments, it will be understood by those of ordinary skill in the art that modifications to, and variations of, the illustrated embodiments may be made without departing from the inventive concepts disclosed herein. Accordingly, the invention should not be viewed as being limited to the disclosed embodiment s).

Claims

1. An article of manufacture comprising: a base heat-exchange cell that includes a supporting substrate, a coolant-in port, a coolant-out port, an array of jet tubes attached to the supporting substrate and fluidly connected to the coolant-in port, wherein each jet tube of the array of jet tubes is configured to transport, in a first direction, a coolant fluid received through the coolant-in port to a heattransfer surface through an output end of such jet tube, and an array of fluid-returning tubes attached to the supporting substrate and fluidly- connected to the coolant-out port, wherein each fluid-returning tube of the array of fluid-returning tubes is configured to receive the coolant fluid, which has interacted with tire heattransfer surface, at an input end of such fluid-returning tube and to transport said coolant fluid in a second direction towards the coolant-out port, wherein the first and second directions are opposite to one another, and wherein each fluid-returning tube encloses at least a portion of a respectively corresponding jet tube.

2. An article of manufacture according to claim 1, wherein:

(2A) a fluid-returning tube of the array of fluid-returning tubes is substantially co-axial with the respectively corresponding jet tube of the array of jet tubes; and/or

(2B) at least one of a fluid-returning tube of tire array of fluid-returning tubes and a jet tube of the array of jet tubes is substantially cylindrical; and/or

(2C) a first axis of a first jet tube of the array of jet tubes is substantially not parallel to a second axis of a second jet tube of the array of jet tubes.

3. An article of manufacture according to claim 2, wherein, when the first axis of the first jet tube is substantially not parallel to the second axis of the second jet tube, the supporting substrate has a non-zero curvature in a plane containing at least one of said first and second axes.

4. An article of manufacture according to claim 2, wherein, when the first axis is substantially not parallel to the second axis, tire supporting substrate is dimensioned as a tubular element having a crosssection with a perimeter defined by a closed line.

5. An article of manufacture according to claim 4, wherein the cross-section is substantially elliptical or polygonal.

6. An article of manufacture according to claim 1, wherein one of the following conditions is satisfied: condition (6 A) the output end of a chosen jet tube is open and configured to face the input end of a chosen fluid-returning tube that is fluidly sealed, to thereby direct a jet of coolant fluid exiting the output of the chosen jet tube end to directly impinge onto a sealing surface of the input end of the chosen fluid-returning tube; and condition (6B) both the output end of the chosen jet tube and the input end of the chosen fluidreturning tube are open, and wherein the article of manufacture is structured to direct the jet of coolant fluid exiting the output of the jet tube away from the input end of the chosen fluid-returning tube.

7. An article of manufacture according to claim 6, wherein, when condition (6A) is satisfied, a surface of the fluid-returning tube is configured as the heat-transfer surface.

8. An article of manufacture according to claim 1, further comprising a substantially fluidly-sealed housing configured to enclose both the array of jet tubes and the array of fluid-returning tubes, the housing including a housing wall and a housing cap.

9. An article of manufacture according to claim 8, wherein:

(9A) a surface of a fluid-returning tube of the array of fluid-returning tubes is configured as a heat-transfer surface; or (9B) the housing cap, facing open ends of jet tubes of the array of jet tubes, is configured as the heat-transfer surface.

10. An article of manufacture according to claim 8, further comprising: an auxiliary fluid-in port and an auxiliary fluid-out port in at least one of the housing wall and the housing cap, and a manifold plate or membrane having multiple openings therethrough configured to fluidly connect each of the auxiliary fluid-in port and the auxiliary fluid-out port with fluid-returning tubes of the array of fluid-returning tubes.

11. An article of manufacture according to claim 1, further comprising an auxiliary heat-exchange cell that is configured substantially identically to the base heat-exchange cell and that is structurally cooperated with the base heat-exchange cell such as:

( 11 A) to have an array of fluid-returning tubes of the auxiliary heat-exchange cell face towards the array of fluid-returning tubes of the base heat-exchange cell and to be separated from the array of fluid-returning tubes of the base heat-exchange cell by a manifold plate or membrane having multiple openings therethrough, and/or

(1 IB) to have the array of fluid-returning tubes of the auxiliary heat-exchange cell face away from the array of fluid-returning tubes of the heat-exchange cell and to be separated from the array of fluid-returning tubes of the heat-exchange cell by the supporting substrate.

12. An article of manufacture according to claim 1 , wherein at least one of the following conditions is satisfied: condition ( 12A): the article of manufacture further comprises a source of coolant fluid, wherein the coolant fluid includes a nitrogen gas and/or a helium gas, and condition (12B): when the article of manufacture comprises an auxiliary fluid-in port, an auxiliary fluid-out port, and a manifold plate or membrane having multiple opening therethrough configured to fluidly connect each of the auxiliary fluid-in port and the auxiliary fluid-out port with fluidreturning tubes of the array of fluid-returning tubes, the article of manufacture further comprises a source of auxiliary fluid.

13. A method for earn ing out a heat-exchange process, the method comprising: with the use of the article of manufacture according to claim 1 : impinging a coolant fluid, which has been jetted out of a corresponding output end of each jet tube of an array of jet tubes in a first direction, onto a corresponding heat-transfer surface: and transferring the coolant fluid, which has interacted with the corresponding heat-transfer surface, in a second direction inside corresponding fluid-returning tubes of an array of fluid-returning tubes; wherein there is a one-to-one correspondence between the fluid-returning tubes of the array of fluid returning tubes and jet tubes of the array of jet tubes, wherein each of the fluid-returning tubes encloses at least a portion of a corresponding jet tube therein, and wherein the first direction and the second direction are opposite directions.

14. A method according to claim 13, wherein the impinging includes impinging the coolant fluid directly onto the heat-transfer surface without interacting the coolant fluid with an element of the article of manufacture between the output end of the jet tube and the heat-transfer surface.

15. A method according to claim 13, comprising: delivering the coolant fluid to said each jet tube of the array of jet tubes through multiple coolantin ports formed in a supporting substrate, wherein the supporting substrate carries within a body of the supporting substrate both the array of jet tubes and the array of fluid-returning tubes; and removing the coolant fluid that has propagated through at least one jet tube and through at least one corresponding fluid-returning tube through multiple coolant-out ports formed in the supporting substate.

16. A method according to claim 15, wherein the multiple coolant-in ports and the multiple coolant- out ports of the article of manufacture are positioned at and distributed along a perimeter of the supporting substrate substantially evenly and in alternating fashion.

17. A method according to claim 15, wherein the supporting substrate is dimensioned as a hollow tubular element, and wherein said delivering is carried out

(i) substantially inwardly towards an axis of tire hollow tubular element; or

(ii) substantially outwardly away from the axis of the hollow tubular element; or (iii) both substantially outwardly away from the axis of the hollow tubular element and substantially inwardly towards said axis.

18. A method according to claim 17, wherein said hollow tubular element has a cross section with a substantially polygonal outer perimeter or with a substantially elliptical outer perimeter.

19. A method according to claim 15, wherein: a delivery passage that is configured to carry out said delivering substrate and that fluidly connects a coolant-in port with a jet tube of the array of jet tubes, and a removal passage that is configured to carry out said removing and fluidly connecting a fluidreturning tube with a coolant-out port do not intersect one another to prevent mixing of an in-flowing portion of the coolant fluid with an out-flowing portion of the coolant fluid in the body of the supporting substrate.

20. A method according to claim 13, wherein at least one of the following conditions is satisfied: condition (20A): a fluid-returning tube of the array of fluid-returning tubes is substantially co-axial with the respectively corresponding jet tube; condition (20B): at least one of a fluid-returning tube of the array of fluid-returning tubes and a jet tube of the array of jet tubes is substantially cylindrical; condition (20C) a first axis of a first jet tube is substantially not parallel to a second axis of a second jet tube; condition (20D): each fluid-retuning tube has a sealed end that is individually sealed with a corresponding heat-transfer surface of a plurality of heat-transfer surfaces; and/or condition (20E): each fluid-retuning tube has a corresponding open input end, wherein the corresponding heat-transfer surface is a single heat-transfer surface common to or shared by all pairs of a fluid-returning tube of the array of fluid-returning tubes and a corresponding jet tube of the array of jet tubes.

21. A method according to claim 20, wherein, when condition (20D) is satisfied, the method further comprises not mixing a portion of the coolant fluid jetting out of an output end of a first jet tube with a portion of the coolant fluid jetting out of an output end of a second jet tube prior to delivering said coolant fluid to a coolant-out port of the apparatus; and/or wherein, when condition (20E) is satisfied, the method further comprises: mixing the portion of the coolant fluid jetting out of an output end of the first jet tube with the portion of the coolant fluid jetting out of an output end of a second jet tube prior to delivering said coolant fluid to the coolant-out port of the apparatus.

22. A method according to claim 20, wherein, when the condition (20D) is satisfied, the method further comprising: delivering an auxiliary liquid through a liquid-in port in a wall and/or a cap of a housing shell covering the array of fluid-returning tubes having sealed ends: and transferring the auxiliary liquid through multiple openings formed through a manifold plate or a membrane that is separated from the supporting substrate by the array of fluid-returning tubes.

23. A method according to claim 22, further comprising: interacting the auxiliary liquid with the heat-transfer surface; and expelling said auxiliary liquid from the volume through a liquid-out port formed in the wall of the housing shell without mixing the auxiliary liquid with the coolant fluid.

24. A method according to claim 13, further comprising: transferring heat energy from an auxiliary liquid, which circulates through a volume of a shell side of the article of manufacture that is fluidly separated from the array of jet tubes, to the heat-transfer surface; and transmitting the heat energy through the heat-transfer surface to a coolant fluid that comprises a gas contained in a volume of a tube side of the article of manufacture.

25. A method according to claim 13, comprising jetting out the coolant fluid from the array of jet tubes, wherein, when a first axis of a first jet tube of the array of jet tubes is substantially not parallel to a second axis of a second jet tube of the array of jet tubes, the supporting substrate has a non-zero curvature in a plane containing at least one of said first and second axes.

26. A method according to claim 13, comprising operating the article of manufacture that comprises multiple combinations of arrays of jet tubes with corresponding arrays of fluid-returning tubes, wherein said combinations are stacked on top of another such that the article of manufacture includes: (26 A) first and second combinations of said multiple combinations that share a supporting substrate carrying respective arrays of jet tubes and respective arrays of fluid-returning tubes, and/or

(26B) two combinations of said multiple combinations that have different supporting substrates but respective arrays of fluid-returning tubes of which are facing one another.