US20170010046A1

US20170010046A1 - Heat Exchanger

Info

Publication number: US20170010046A1
Application number: US15/186,645
Authority: US
Inventors: Peter Hofbauer
Original assignee: THERMOLIFT Inc
Current assignee: THERMOLIFT Inc
Priority date: 2015-07-08
Filing date: 2016-06-20
Publication date: 2017-01-12

Abstract

Newly-developed manufacturing techniques have opened up new possibilities in fabricating designs of components that were previously infeasible. One such component is a heat exchanger. A crossflow heat exchanger is disclosed that includes a plurality of internal passages for conducting a first fluid. The internal passages that form a spiral with adjacent passages separated by a gap of a predetermined distance or less. The second fluid passes through the gaps. The internal passages may be a plurality of parallel passages arranged along a first line. From upstream to downstream, each of the passages form an inlet spiral connected to an inner ring connected to an outlet spiral. The gaps are less than a predetermined distance related to a Reynolds number that is less than that at which laminar flow exists.

Description

FIELD

The present disclosure relates to heat exchangers for special applications such as a heat pump.

BACKGROUND

There are many heat exchanger configurations that have been used over the years. Many of these designs have been constrained by manufacturing limitations. However, with the advent of new manufacturing techniques, heat exchangers that might have not been conceived of previously might now be fabricated.

SUMMARY

A heat pump presently being developed has a heat exchanger specification of high effectiveness and favorable packaging. A heat exchanger having such characteristics is disclosed herein as one example of such a heat exchanger to provide the desired characteristics for the heat pump.
A cross flow heat exchanger is disclosed that has an inlet for a first fluid, an outlet for the first fluid, an inlet spiral having a plurality of passages therein, an inlet manifold fluidly coupling the inlet with the plurality of passages of the inlet spiral, an outlet spiral having a plurality of passages therein, and an outlet manifold fluidly coupling the outlet with the plurality of passages of the outlet spiral. The passages of the inlet spiral are fluidly coupled to the passages of the outlet spiral. Interior walls of the passages of the inlet and outlet spirals are in contact with the first fluid. The exterior walls of the inlet and outlet spirals are in contact with a second fluid. The inlet spiral is nested with the outlet spiral. A gap between adjacent turns of the inlet and outlet spirals is less than a predetermined distance.
The predetermined distance is less than a distance at which a predetermined Reynolds number exists. The predetermined Reynolds number is that which is defined to lead to laminar flow for the given geometry of the gaps.
The crossflow heat exchanger may include a plurality of braces mechanically coupling adjacent turns of the inlet and outlet spirals.
In some embodiments, the passages of the inlet spiral and the passages of the outlet spiral are fluidly coupled via a collector ring. In another embodiment, the passages of the inlet spiral and the passages of the outlet spiral are coupled via a transition section.
In some embodiments, the passages of the inlet spiral are arranged along a first line, the passages of the outlet spiral are arranged along a second line, and the first line and the second line are parallel.
The passages of the inlet and outlet spirals are circular, elliptical, polygonal, or any suitable shape.
A heat pump is disclosed that includes a cylinder, a hot displacer disposed in the cylinder, a cold displacer disposed in the cylinder, and a crossflow heat exchanger disposed between the hot displacer and the cold displacer. The crossflow heat exchanger includes: an inlet spiral having a rectangular cross section and defining a plurality of passages arranged longitudinally, an inlet manifold coupled to an upstream end of the inlet spiral with the inlet spiral defining an inlet volume that fluidly couples with the plurality of passages of the inlet spiral, an outlet spiral having a rectangular cross section and defining a plurality of passages arranged longitudinally, and an outlet manifold coupled to a downstream of the outlet spiral with the outlet spiral defining an outlet volume that fluidly couples with the plurality of passages of the outlet spiral, wherein the passages of the inlet spiral are fluidly coupled to the passages of the outlet spiral.
The passages of the inlet spiral are coupled to the passages of the outlet spiral via a transition section, a central collector ring, or any suitable transition.
Turns of the inlet spiral interleave with turns of the outlet spiral, and gaps exists between adjacent turns.
The cylinder is filled with a working fluid. And reciprocation of one of the displacers in the cylinder causes the working fluid to pass through the gaps.
A pressurized fluid supply is coupled to the inlet manifold.
Turns of the inlet spiral interleave with turns of the outlet spiral, and a gap exists between adjacent turns. The heat exchanger further includes a plurality of braces mechanically coupling adjacent turns.
A liquid flows from the inlet manifold into passages in the inlet spiral into passages in the inlet ring into passages in the outlet spiral into the outlet manifold.
A crossover passage in parallel with gaps between inlet spirals through which the second fluid may bypass the heat exchanger.
Newer fabrication techniques, such as 3-dimensional printing and hydroforming, facilitate manufacture complicated shapes is facilitated. Some of the embodiments in the present disclosure, which may have been very difficult to fabricate with prior fabrication techniques, may now be readily fabricated via such newer methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a heat exchanger according to an embodiment of the disclosure;

FIG. 2 is a core of the heat exchanger of FIG. 1;

FIG. 3 is a cross-sectional, isometric view of the heat exchanger of FIG. 1;

FIG. 4 a cross-sectional view of a portion of the heat exchanger of FIG. 1;

FIGS. 5-9 are illustrations of alternative cross-sectional shapes for inlet and outlet spirals of a heat exchanger;

FIGS. 10-12 are representations of alternative embodiments of heat exchanger spirals;

FIG. 13 is a schematic of a heat pump with a centrally-located heat exchanger;

FIG. 14 is a cross-sectional view of a heat exchanger showing a bypass passage;

FIGS. 15-17 illustrate various stages of an embodiment in which a heat exchanger is assembled using sintering; and

FIG. 18 is an illustration of a spiral heat exchanger according to an embodiment of the disclosure.

DETAILED DESCRIPTION

As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce alternative embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. Those of ordinary skill in the art may recognize similar applications or implementations whether or not explicitly described or illustrated.
FIG. 1 shows a top view of a heat exchanger 100, which has a frame 102 having two nested spirals 110 and 112. The term involute is an alternative term for spiral. In some applications, frame 102 of heat exchanger 100 is welded to a cylinder (not shown) in which it is disposed. In other applications, frame 102 is a sealing member and has any number of O-rings, or other suitable type of seals in grooves in frame 102, to seal against a cylinder (not shown). Inlet spiral 110 has three turns 111 interleaved with turns 113 of outlet spiral 112. A spiral may alternately called and involute.
A gap 106 between adjacent turns has a distance 108 less than a predetermined distance. In one embodiment, a liquid circulates in passages within spirals 110 and 112 and a gas travels through gaps 106 (into, or out of, the plane of FIG. 1) between adjacent turns of spirals 110 and 112. The predetermined distance, in one embodiment, is a distance in which laminar flow would exist if the length of the flow were to be enough to set up laminar flow. There is a Reynolds number which is based on the geometry, the velocity expected, and parameters of the fluid itself, below which is defined to provide laminar flow. Braces 104 are provided to maintain the gaps of predetermined distance of spirals 110 and 112 with a gap that is less than or equal to the gap that provides laminar flow. Manifold housing 114 is an inlet area and manifold housing 116 is an outlet area, which will be discussed below. A central collector 118 has an internal passage that fluidly couples with passages in spirals 110 and 112.
In FIG. 2, a representation of a core 120 of heat exchanger 100 (of FIG. 1). The core is essentially the “negative” of heat exchanger 100, i.e., the part where the fluid would flow inside heat exchanger 100. Core 120 has an inlet 122 and an outlet 124. Inlet 122 leads to an inlet spiral passages (only one of which is visible) 132 via an adapter 136 to a central collector 134. The fluid moves from central collector 134 to outlet spiral passages (only one of which is visible) 130 via an adapter 138. Outlet spiral passages 130 fluidly couple to outlet 124. Inlet spiral passages 132 interleave with outlet spiral passages 130, although offset by 180 degrees in the embodiment shown in FIG. 2. The three-turn embodiment with 180 degree offset in FIG. 2 is provided by way of example only and not intended to be limiting as the turns can be any suitable number and the offset can be altered to accommodate desired inlet and outlet locations or for other purposes.
In FIG. 3, an isometric view of a section of heat exchanger 100 is shown. The cross section is taken through two of braces 104. In FIG. 2, outlet spiral passage 130 appears as a single spiral. However, in the embodiment in FIG. 3, there are four parallel outlet spirals passages arranged along a line, such as illustrated with one of the turns shown arranged along dash dot line 140. In place of four openings along line 140, a single slot could be provided. However, in some embodiments in which the pressure difference between the inside and the outside is great, a plurality of passages essentially provides bracing and prevents collapse that might occur with a single slot. Similarly, inlet spiral passage 132 has four parallel spirals. The passages of one of the turns is shown lying in a line, as illustrated with dash-dot line 142. Central collector 134 is shown as a single slot. Thus, the four passages of the inlet spiral passage 132 combine to form a single slot passage of central collector 134 and then manifolds into four passages of outlet spiral passage 130. Central collector 134 has beefier walls than spiral passages 130 and 132. If thinner walls for the central collector are desired, the central collector may alternatively have a plurality of passages that correspond to the passages in the spirals.
In FIG. 4, a portion of heat exchanger 100 is shown in cross section. An inlet 152 leads to a manifold 154 that fluidly couples with inlet spiral passages 132. A similar manifold is provided for the outlet spiral passages (not shown).
The cross section of heat exchanger 100 shown in FIG. 3 is taken through brace 104. Thus, passages 132 appear to be in a block with an array of passages. In FIG. 5, a single turn of a spiral 200 is shown in cross section with the cross section taken at a place away from a brace. Within that turn are multiple circular passages 200. In an alternative, passage 206 in turn 204 are substantially square. Passages 206 have rounded corners to avoid stress risers. In turn 208, passages 210 are substantially rectangular. Any suitable passage shape can be used. In the embodiments shown in FIGS. 3-7 the spiral has straight sides. However, in an alternative configuration shown in FIG. 9, adjacent turns 220 and 222 of spirals have a gap distance 224 that is consistent along the gap.
An alternative heat exchanger 240 configuration is also contemplated, as shown in FIG. 10. Heat exchanger 240 has an inlet spiral 242 interleaved with an outlet spiral 244. In the embodiment in FIG. 10, the spirals are not regular, but have kinks in them. Herein, such a configuration or other similar configurations with slight kinks are called spirals. Heat exchanger 240 has a central opening 248 to accommodate a post. In other configurations, opening 248 is filled with a plug so that gasses flow through the gaps between adjacent turns of the spirals. The gaps in FIG. 10 are exaggerated for illustration convenience. The gaps are to be consistent and are generally narrow. To fill any blank spaces that would allow gases to flow rather than between the spirals, plugs 250 and 252 are provided. A transition section 246 is provided to connect inlet spiral 242 with outlet spiral 244. Another heat exchanger 260 alternative is shown in FIG. 11 with inlet spiral 262, outlet spiral 264, plugs 270 and 272, opening to accommodate a post 268, and transition section 266. And yet, another alternative heat exchanger 280 is shown in FIG. 12. Heat exchange 280 has: inlet spiral 282, outlet spiral 284, plugs 290 and 292, opening to accommodate a post 288, and transition section 296.
The illustrations in FIGS. 10-12 show the inlet and outlet spirals to be single lines for illustration simplicity. In reality, the turns of the spirals are wider than is implied in the Figures and the gap between adjacent turns is a predetermined width. That predetermined width is based on the properties of the gas that travels through the gap and the velocity of the gas traveling through the gap such that the Reynolds number is in a range defined to provide laminar flow.
An illustration of a heat pump 300 is shown in cross section in FIG. 13. Heat pump 300 has a cylinder 302 in which a hot displacer 304 and a cold displacer reciprocate. A heat exchanger 310 is located within cylinder 302. A top edge of heat exchanger 310 is substantially at the bottom end of travel of hot displacer 304; a bottom edge of heat exchanger 310 is substantially at the top of travel of cold displacer 306. Heat exchanger 310 has an inlet 314 and an outlet 316 and passages fluidly coupling inlet 314 with outlet 316. The fluid within heat exchanger 310 is a liquid, but alternatively a gas. Flow within heat exchanger 310 is in the plane of such heat exchanger. Flow on the exterior surface is substantially perpendicular to the flow with heat exchanger 10. Gas flows through gaps 312.
If both cold and hot displacers 304 and 306 move upward or downward, the gases flow from one side of heat exchanger 310 to the other side. If only one of the displacers moves, the gases that flow through heat exchanger 310 bypasses the cylinder. That is, for example, if cold displacer 306 moves upwardly while hot displacer 304 is stationary, gases from the volume within cylinder 302 that is above displacer 306 flow through gaps 312 into the volume above heat exchanger 310 through a bypass tube 340, a regenerator 342, a bypass tube 344, and a heat exchanger 346 then into the volume within cylinder 302 that is below displacer 306. Gases reverse that flow path when hot displacer 304 moves upwardly while hot displacer 306 is stationary. Another bypass path is provided that has a bypass tube 334, a regenerator 332, a bypass tube 330, and a heat exchanger 336. These elements provide desired function in the context of a heat pump, in particular a Vuilleumier heat pump, further description of which can be found elsewhere. The heat exchanger disclosed herein is suitable for such a heat pump, but this is a non-limiting application.
In FIG. 14, a cross section through a heat exchanger 400 shows bypass passages 430 and 440. There are a plurality of such passages around the periphery of heat exchanger 400. The cross section in FIG. 14 happens to cut through two such passages 430 and 440. Unlike the cross section in FIG. 3 that is through a brace section, the cross section of FIG. 14 is away from the brace section. A turn of the inlet spiral in which passage 402 is located is displaced by a gap 406 from a turn of the outlet spiral in which passage 404 is located.
One of the processes by which a heat exchanger according to the present disclosure can be manufactured is via 3D printing. Alternatively, a sintering process is used. In FIG. 15, two portions 450 are shown in cross section. The two portions 450 are shown sintered together at interface 452 in FIG. 16. An assembly 456 of a grid of such portions 450 is shown in which the portions are sintered at interfaces 452 and interfaces 454. Gaps 458 less than a predetermined width are provided between each column.
In some applications, it is desirable to have an annular heat exchanger, such as a heat exchanger 500 shown in FIG. 18. An inlet 502 leads inwardly and couples to a turnaround 504 which causes heat exchanger 500 to spiral outwardly to outlet 506. Heat exchanger 500 allows for space 510 in the center to provide the annular shape. In the case of a Vuilleumier heat pump, displacers can reciprocate through the middle of heat exchanger 500.
While the best mode has been described in detail with respect to particular embodiments, those familiar with the art will recognize various alternative designs and embodiments within the scope of the following claims. While various embodiments may have been described as providing advantages or being preferred over other embodiments with respect to one or more desired characteristics, one or more characteristics may be compromised to achieve desired system attributes, which depend on the specific application and implementation. These attributes include, but are not limited to: cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. The embodiments described herein that are characterized as less desirable than other embodiments or prior art with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.

Claims

We claim:

1. A crossflow heat exchanger, comprising:

an inlet for a first fluid;

an outlet for the first fluid;

an inlet spiral having a plurality of passages therein;

an inlet manifold fluidly coupling the inlet with the plurality of passages of the inlet spiral;

an outlet spiral having a plurality of passages therein; and

an outlet manifold fluidly coupling the outlet with the plurality of passages of the outlet spiral, wherein:

the passages of the inlet spiral are fluidly coupled to the passages of the outlet spiral;

interior walls of the passages of the inlet and outlet spirals are in contact with the first fluid;

the exterior walls of the inlet and outlet spirals are in contact with a second fluid;

the inlet spiral is nested with the outlet spiral; and

a gap between adjacent turns of the inlet and outlet spirals is less than a predetermined distance.

2. The crossflow heat exchanger of claim 1 wherein the predetermined distance is less than a distance at which a predetermined Reynolds number exists.

3. The crossflow heat exchanger of claim 2 wherein the predetermined Reynolds number is that which is defined to lead to laminar flow for the given geometry of the gaps.

4. The crossflow heat exchanger of claim 1, further comprising: a plurality of braces mechanically coupling adjacent turns of the inlet and outlet spirals.

5. The crossflow heat exchanger of claim 1 wherein the passages of the inlet spiral and the passages of the outlet spiral are fluidly coupled via a collector ring.

6. The crossflow heat exchanger of claim 1 wherein the passages of the inlet spiral and the passages of the outlet spiral are coupled via a transition section.

7. The crossflow heat exchanger of claim 1 wherein the passages of the inlet spiral are arranged along a first line; the passages of the outlet spiral are arranged along a second line; and the first line and the second line are parallel.

8. The crossflow heat exchanger of claim 1 wherein a cross section of the passages of the inlet and outlet spirals are one of: circular, elliptical, and polygonal.

9. A crossflow heat exchanger, comprising:

an inlet spiral having a rectangular cross section and defining a plurality of passages arranged longitudinally;

an inlet manifold coupled to an upstream end of the inlet spiral with the inlet spiral defining an inlet volume that fluidly couples with the plurality of passages of the inlet spiral;

an outlet spiral having a rectangular cross section and defining a plurality of passages arranged longitudinally;

an outlet manifold coupled to a downstream end of the outlet spiral with the outlet spiral defining an outlet volume that fluidly couples with the plurality of passages of the outlet spiral;

a collector ring having a rectangular cross section and defining a plurality of passages longitudinally, wherein:

the plurality of passages of the collector ring have inlets and outlets;

the inlets of the passages in the collector ring couple with downstream ends of the plurality of passages in the inlet spiral; and

the outlets of the passages in the outer ring couple with upstream ends of the plurality of passages in the outlet spiral.

10. The heat exchanger of claim 9 wherein turns of the inlet spiral interleave with turns of the outlet spiral and the inlet and outlet spirals have a least one kink around the circumference.

11. The heat exchanger of claim 10 wherein a gap between adjacent turns of the inlet and outlet spirals is less than a predetermined distance.

12. The heat exchanger of claim 10 wherein:

turns of the inlet spiral interleave with turns of the outlet spiral; and

a gap exists between adjacent turns, the heat exchanger further comprising:

a plurality of braces mechanically coupling adjacent turns.

13. The heat exchanger of claim 10 wherein:

turns of the inlet spiral interleave with turns of the outlet spiral; and

a gap exists between adjacent turns, the heat exchanger further comprising:

a plurality of braces extending radially and mechanically coupling a plurality of turns.

14. The heat exchanger of claim 10 wherein a fluid flows from the inlet manifold into passages in the inlet spiral into passages in the inlet ring into passages in the outlet spiral into the outlet manifold.

15. The heat exchanger of claim 14 wherein the fluid is a liquid.

16. The heat exchanger of claim 9 wherein:

a gap exists between adjacent turns; and

a gas flows through the gaps.

17. A heat pump, comprising:

a cylinder;

a hot displacer disposed in the cylinder;

a cold displacer disposed in the cylinder; and

a crossflow heat exchanger disposed between the hot displacer and the cold displacer, the crossflow heat exchanger comprising:

an outlet spiral having a rectangular cross section and defining a plurality of passages arranged longitudinally; and

an outlet manifold coupled to a downstream end of the outlet spiral with the outlet spiral defining an outlet volume that fluidly couples with the plurality of passages of the outlet spiral, wherein the passages of the inlet spiral are fluidly coupled to the passages of the outlet spiral.

18. The heat pump of claim 17 wherein the passages of the inlet spiral are coupled to the passages of the outlet spiral via a transition section.

19. The heat pump of claim 17 wherein:

turns of the inlet spiral interleave with turns of the outlet spiral;

gaps exists between adjacent turns;

the cylinder is filled with a working fluid; and

reciprocation of one of the displacers in the cylinder causes the working fluid to pass through the gaps.

20. The heat pump of claim 17 wherein:

turns of the inlet spiral interleave with turns of the outlet spiral; and

a gap exists between adjacent turns, the heat exchanger further comprising:

a plurality of braces mechanically coupling adjacent turns.