US20140096555A1

US20140096555A1 - Plate evaporative condenser and cooler

Info

Publication number: US20140096555A1
Application number: US13/648,607
Authority: US
Inventors: Zahid Ayub; Peng Peng
Original assignee: American Sino Heat Transfer LLC
Current assignee: American Sino Heat Transfer LLC
Priority date: 2012-10-10
Filing date: 2012-10-10
Publication date: 2014-04-10

Abstract

An evaporator condenser has a condenser unit which has plural plate units separated from one another by air gaps. Each plate unit has first and second plates that are coupled together about a perimeter thereof. Each plate unit has a first edge and an opposite second edge. The first and second plates are coupled together along at least one line so as to form a first channel that extends from the first edge to the second edge in the second channel by communicates with the first channel and extends back to the first edge. The channels decrease in volume from an inlet to an outlet.

Description

FIELD OF THE INVENTION

The present invention relates to heat exchangers and more particularly to evaporative condensers and coolers.

BACKGROUND OF THE INVENTION

Evaporative condensers are condensers where water is sprayed onto a heat exchanger to condense a gas into a liquid. For example, in a refrigeration system, a compressor compresses a heat exchange fluid, such as ammonia. The output of the compressor is hot, high pressure ammonia gas. The gas is provided to a condenser, where it condenses into a liquid. The liquid ammonia then passes through an expansion valve, where it drops in pressure and decreases in temperature to provide refrigeration.
In a conventional evaporative condenser, the heat exchanger for the fluid is a set of coils or tubes. The ammonia gas flows into the coils and condensed or liquid ammonia flows out.
It is desirable to make improvements over the conventional coil condenser.

SUMMARY OF THE INVENTION

An evaporative condenser comprises a condenser unit and a water sprayer located above the condenser unit. A fill section is located below the condenser unit. A basin is located below the fill section. At least one fan flows air through the condenser unit and the fill section. The condenser unit comprises plural plate units separated from one another by air gaps. Each plate unit comprises first and second plates coupled together about a perimeter thereof. Each plate unit has a first edge and an opposite second edge. Each plate unit has an inlet and an outlet. The first and second plates are coupled together along at least one line so as to form a first channel that extends from the first edge to the second edge and a second channel that communicates with the first channel and extends back to the first edge. The first and second plates are coupled together at spots located in the channel.
In accordance with one aspect, the first channel extends from the inlet. A third channel extends to the outlet. The first channel has a larger volume than the third channel.
In accordance with another aspect, there is an intermediate channel between the first and third channels. The intermediate channel has a smaller volume than the first channel and a larger volume than the third channel.
In accordance with another aspect, the at least one line extends from the first edge toward the second edge. The first channel is bounded by the one line and an outside edge. A second line extends from the second edge toward the first edge. The second channel is bounded by the one line and the second line.
In accordance with another aspect, the one line and the second line are discontinuous.
In accordance with still another aspect, the one line has gaps that decrease in size from the first edge to the second edge and the second line has gaps that decrease in size from the second edge to the first edge.
In accordance with another aspect, the one line has gaps of equal size and the second line has gaps of equal size. The gaps of the second line are misaligned with the gaps of the one line in a direction perpendicular to the first and second edges.
In accordance with another aspect, the first channel extends from the inlet. A third channel extends to the outlet. The third channel has a third line that extends from one of the first or second edges to the other of the first or second edges. The one line has a first gap for the second edge. The third line has a third gap with the other of the first or second edges. The first gap is larger than the third gap.
In accordance with another aspect, the one line is continuous.
In accordance with another aspect, the one line is discontinuous.
In accordance with another aspect, the plates in each plate unit are coupled together at spots located in the first and second channels. The spots are arranged in a triangular pattern. The triangular pattern has triangles with bases that are parallel to the flow of fluid through the first and second channels.
In accordance with another aspect, the plates in each plate unit are coupled together at spots located in the first and second channels. The spots are arranged in a triangular pattern. The triangular pattern has triangles with bases that are perpendicular to the flow of fluid through the first and second channels.
In accordance with another aspect, the plates in each plate unit are coupled together at spots located in the first and second channels. The spots are arranged in a rectangular pattern. The rectangular pattern has a side that is parallel to the fluid flow through the first and second channels.
In accordance with another aspect, the plates in each plate unit are coupled together at spots located in the first and second channels. The spots are arranged in a rectangular pattern. The rectangular pattern has a side that is angled 15 to 60 degrees to fluid flow through the first and second channels.
In accordance with another aspect, each of the plate units has sides. The plate units are oriented with respect to each other along adjacent sides. Frames extend across the plate units and are coupled thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an evaporative condenser.

FIG. 2 is a side view of a plate unit, in accordance with one embodiment.

FIG. 3 is a cross-sectional view of the plate unit, taken along lines III-III of FIG. 2.

FIG. 4 is a side view of a plate unit, in accordance with another embodiment.

FIG. 5 is a side view of a plate unit, in accordance with another embodiment.

FIG. 6 is a side view of a plate unit, in accordance with another embodiment.

FIG. 7 is an end view of the plate assembly.

FIG. 8 is a side view of a plate unit, in accordance with another embodiment.

FIG. 9 is a side view of a plate unit, in accordance with another embodiment.

FIGS. 9A and 9B are side views of a plate unit, in accordance with other embodiments.

FIG. 10 is a side view of a plate unit, in accordance with another embodiment.

FIG. 11 is a side view of a plate unit, in accordance with another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an evaporative condenser 11. Water is sprayed onto a plate assembly 13 which is a heat exchanger. A fan 15 draws air 17 through the wetted plate assembly 13 to provide evaporative cooling and condensing of a fluid inside of the plate assembly (typically from a gas into a liquid). The plate assembly 13 provides an efficient, cost effective condenser.
The various components of the evaporative condenser 11 will now be described. The evaporative condenser 11 has a housing 19. The plate assembly 13 is located in the housing. Below the plate assembly is a fill or stuffing section 21. The fill section 21 has layers that expose descending water to air flow. The layers can be made of plastic, etc. Below the fill section 21 is a basin 23 to catch the water. The housing also has a plenum 25 that communicates with the plate assembly section and the fill section. The fan 15 draws air through the plate assembly 13, in through the fill section 21, through demisters 27 or dehydrators, into the plenum 25 and out of the housing.
The plate assembly 13 includes a number of plate units 31 vertically oriented and spaced apart from each other. Referring to FIGS. 2 and 3, a plate unit 31 is shown. Each plate unit has two plates 33, each of generally rectangular shape. Each plate 33 is metal, such as carbon steel or stainless steel. The plates are coupled together along their outside edges 35A, 35B, 35C, 35D, with edge or perimeter welds. Once coupled together, the plates form an interior cavity 37. An inlet pipe 39 is provided at one corner of the plate unit. An outlet pipe 41 is provided at another corner of the plate unit. The inlet and outlet can be on the same side 35A as shown in FIG. 2, or in opposite corners. The inlet and outlet pipes 39, 41 communicate with the interior cavity 37.
Channels 43 are formed in the interior cavity 37 by welding the plates together along inside locations. In the embodiment shown in FIG. 2, the fluid flows from the inlet pipe in the first edge 35A, in one channel to the opposite, or second edge 35C, and enters the adjacent channel where it flows back to the first edge 35A and so on in a zig-zag manner to the outlet 41. The channels are made by lines 45 of welding (in the example shown in FIG. 2, there are weld lines 45A, 45B, 45C, 45D, 45E, 45F and 45G). Thus, the channel receiving fluid from the inlet pipe 39 is bounded by the outside edge 35D and a weld line 45A extending from the first edge 35A toward the second edge 35C. The weld line 45A stops short of the second edge 35C leaving a gap 47A to allow fluid to exit the inlet channel and enter the next channel. A second weld line 45B extends from the second edge 35C toward the first edge 35A. This next channel is formed by the first and second weld lines 45A, 45B. The second weld line 45B stops short of the first edge 35A, leaving a gap.
Thus, the channels 43 are formed by the weld lines 45A-45G and the outside edges.
The volumes of the individual channels 43 change from the inlet to the outlet. Because the plate unit operates as a condenser, the volumes of the channels are larger near the inlet 39 than near the outlet 41. For example, and referring to the orientation of FIG. 2, the height of the first two channels near the inlet (the channels bound by the edge 35D and the weld line 45A and the channel between weld lines 45A, 45B), is A, with the height of the next few channels (bounded by weld lines 45B and 45C; 45C and 45D; 45D and 45E; and 45E and 45F) is B, where A>B. The height of the channels nearest the outlet (bounded by weld lines 45F and 45G and 45G and edge 35B) is C, where B>C. Because the lengths of the channels are equal (from edge 35A to edge 35C), the distance between the weld lines determines the channel volumes. Alternatively, the cross-sectional areas of the channels decrease from the inlet 39 to the outlet 41 where the cross-section is perpendicular to the general flow of fluid in the channels.
Likewise, the gaps 47 at the ends of the weld lines, leading from one channel to the next, change size, diminishing from the inlet to the outlet. The first two gaps 47A nearest the inlet are larger than the next few gaps 47B. The gap or gaps 47C nearest the outlet is the smallest, with 47A>47B>47C.
If the plate unit operates as a cooler instead of a condenser, the flow through the plate unit is reversed, from the smaller channels to the larger channels to accommodate the expansion fluid. If no phase change occurs in the plate unit, then the channels will be of equal dimensions.
In addition to the weld lines 45, spot welding 49 is used in or along the channels. The spot welds enhance heat transfer by creating elliptical cross-sections of the channels (see FIG. 3). Elliptical cross-sections of the channels are more efficient at heat transfer than are circular cross-sections.
Fluid in the channels flow generally from one edge 35A to the opposite edge 35C and back, and parallel to the weld lines 45. Spot welding contributes to turbulent flow of fluid in the channels. As the fluid flows in the channels, a spot weld 49 diverts flow around the weld. Such turbulent flow enhances heat transfer.
The spot welds 49 can be arranged in pattern or configuration. In FIG. 2, spot welds are arranged in a triangular pattern, with each spot weld forming an apex of an equilateral triangle. (In FIGS. 2, 4-6, dashed lines between spot welds 49 indicate the pattern). The triangles have bases 51 that are parallel to the general fluid flow in the channels. FIG. 4 illustrates a spot weld pattern where the triangles are rotated 90 degrees so that the triangle bases 51 are perpendicular to the general fluid flow in the channels. The pattern of FIG. 4 presents a different aspect of the triangles of fluid flowing in the channels around the spot welds than the pattern of FIG. 2.
FIG. 5 illustrates a spot weld pattern in a rectangular arrangement. The sides 53 of the rectangles are parallel to the edges 35 (35C, 35D) of the plate unit. FIG. 6 illustrates a rectangular spot weld pattern rotated from that of FIG. 5. FIG. 6 shows the sides 53 oriented at 45 degrees relative to the weld lines 45. However, the sides 53 could be oriented 15 to 60 degrees.
The distance between spot welds 49 can be varied according to the design. The spot welds can be spaced apart a constant distance. Alternatively, the spot welds can be located closer together in the channels nearest the outlet than in the channels nearest the inlet.
After the plate unit has been welded, the plates are positioned together with little volume in the interior cavity. Pressurized air is introduced into the interior cavity through the inlet or outlet. This causes the unwelded portions of the plates to expand outward as shown in FIG. 3.
The individual plate units 31 are assembled together into the plate assembly 13. The plate units are parallel to each other and separated from the adjacent plate units by gaps for air circulation. Frames 55 extend across the edges of plate units 31 to join them together (see FIG. 7). The frames 55 contact the outside edges 35 of the plate units 31. The frames can be angle iron. Alternatively, each frame can have notches 57 therein for receiving an edge of a plate unit. The plate units may be welded to the frames. The inlet pipes and outlet pipes are coupled to respective headers 59 (see FIG. 1). The plate assembly 13 is mounted in the housing 19.
In operation, referring back to FIG. 1, water is sprayed from spray heads 61 onto the plate units 13. The water moves down the plate units. Air is drawn across the plate units by the fan 15. Fluid in the plate units enters the inlets as a gas and leaves the outlets as a liquid. The water, now hot, falls onto the fill section 21, where it is cooled by air flowing across the fill section. The water then falls into the basin 23, where a pump 63 returns it to the spray head 65. A float switch 65 controls the pump.
FIG. 8 illustrates another embodiment of the plate unit 31. The plate units of FIGS. 8-10 are designed to handle an excess amount of gas. In FIG. 2, the weld lines 45 dividing the channels 43 are continuous. In FIG. 8, the weld lines 71 are discontinuous for those weld lines located closest to the inlet 39. Gaps 73 are provided in the weld lines 71, wherein fluid can flow through the gaps 73 from one channel to the next. As the weld lines extend from the first edge 35A, there is a gap a, then gap b, gap c and gap d between the end of the weld line and the second edge 35C. The next weld line extends from the second edge 35C and has a gap a, then gap b, gap c and gap d. For the gaps, a>b>c>d. Subsequent weld lines 45 can be solid because the volume of gas diminishes.
FIG. 9 shows another embodiment of the plate unit 31 where the first two weld lines 71 have gaps 73 of uniform dimension. The gaps in the second weld line are vertically staggered (referring to the orientation shown in the drawing) from the gaps of the first weld line. Subsequent weld lines 45 are solid.
FIG. 9A shows an alternate embodiment to FIG. 9. The embodiment of FIG. 9A has the first two weld lines 71 with gaps 73 but lacks subsequent solid weld lines. FIG. 9B shows another embodiment which has a single weld line 71 with gaps 73 but no subsequent weld lines.
FIG. 10 shows another embodiment of the plate unit 31 where the first weld line 71 is discontinuous and nonparallel to the other weld lines. The weld line extends from the first edge 35A toward the second edge 35C and inclines upward toward the upper edge 35D so as to reduce the volume of the inlet channel at the second edge. The gaps 73 can be of the same size or decreasing in size: a>b>c>d>e. Subsequent weld lines 45 are continuous and parallel.
FIG. 11 shows another embodiment of the plate unit 31. A series of weld lines 71 is provided near the upper edge 35D. The weld lines 71 are separated by gaps 73. The weld lines have first and second ends 81, 83. The first ends 81 are progressively closer to the upper edge 35D for those weld lines 81 that are closer to the second edge 35B than to the first edge 35A. Likewise, the second ends 83 are progressively closer to the upper edge 35D for those weld lines 81 that are closer to the second edge 35B. Also the second ends 83 are closer to the upper edge 35D than are the first ends 81.
Thus, by providing plate units 31 for the condenser, the condenser component can be made inexpensively since the plate units are simply welded around the perimeter edges and then the interior so as to form channels and also spot welding to increase the turbulence of flow of fluid inside the plate units. The plate units 31 are then assembled together into a plate assembly 13 in an inexpensive manner.
The plate assembly provides an efficient heat exchanger as the exterior of the plate units has large surface areas for being wetted with the water spray, while the interior provides elliptically shaped channels to increase the surface area with the fluid inside. In addition, the spot welding provides turbulence for fluid flow.
The foregoing disclosure and showings made in the drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense.

Claims

1. An evaporative condenser, comprising:

a) a condenser unit;

b) a water sprayer located above the condenser unit;

c) a fill section located below the condenser unit;

d) a basin located below the fill section;

e) at least one fan for flowing air through the condenser unit and the fill section;

f) the condenser unit comprising plural plate units, separated from one another by air gaps, with each plate unit comprising first and second plates coupled together about a perimeter thereof, each plate unit having a first edge and an opposite second edge, each plate unit having an inlet and an outlet, the first and second plates coupled together along at least one line so as to form a first channel that extends from the first edge to the second edge and a second channel that communicates with the first channel and extends back to the first edge, the first and second plates coupled together at spots located in the channel.

2. The evaporative condenser of claim 1 wherein the first channel extends from the inlet, further comprising a third channel that extends to the outlet, the first channel having a larger volume than the third channel.

3. The evaporative condenser of claim 2 further comprising an intermediate channel between the first and third channels, the intermediate channel having a smaller volume than the first channel and having a larger volume than the third channel.

4. The evaporative condenser of claim 1 wherein the at least one line extends from the first edge toward the second edge, the first channel bounded by the one line and an outside edge, further comprising a second line extending from the second edge toward the first edge, the second channel bounded by the one line and the second line.

5. The evaporative condenser of claim 4 wherein the one line and the second line are discontinuous.

6. The evaporative condenser of claim 5 wherein the one line has gaps that decrease in size from the first edge to the second edge and the second line has gaps that decrease in size from the second edge to the first edge.

7. The evaporative condenser of claim 6 wherein the one line has gaps of equal size and the second line has gaps of equal size, the gaps of the second line being misaligned with the gaps of the one line in a direction perpendicular to the first and second edges.

8. The evaporative condenser of claim 4 wherein the first channel extends from the inlet, further comprising a third channel that extends to the outlet, the third channel having a third line that extends from one of the first or second edges to the other of the first or second edges, the one line having a first gap for the second edge, the third line having a third gap with the other of the first or second edges, the first gap being larger than the third gap.

9. The evaporative condenser of claim 1 wherein the one line is continuous.

10. The evaporative condenser of claim 1 wherein the one line is discontinuous.

11. The evaporative condenser of claim 1 wherein the plates in each plate unit are coupled together at spots located in the first and second channels, the spots arranged in a triangular pattern, which triangular pattern has triangles with bases that are parallel to the flow of fluid through the first and second channels.

12. The evaporative condenser of claim 1 wherein the plates in each plate unit are coupled together at spots located in the first and second channels, the spots arranged in a triangular pattern, which triangular pattern has triangles with bases that are perpendicular to the flow of fluid through the first and second channels.

13. The evaporative condenser of claim 1 wherein the plates in each plate unit are coupled together at spots located in the first and second channels, the spots arranged in a rectangular pattern, which rectangular pattern has a side that is parallel to fluid flow through the first and second channels.

14. The evaporative condenser of claim 1 wherein the plates in each plate unit are coupled together at spots located in the first and second channels, the spots arranged in a rectangular pattern, which rectangular pattern has a side that is angled 15 to 60 degrees to fluid flow through the first and second channels.

15. The evaporative condenser of claim 1 wherein each of the plate units has sides, the plate units are oriented with respect to each other along adjacent sides, further comprising frames extending across the plate units and coupled thereto.