Patent Application
20090178426
The invention relates to an evaporative heat exchanger for cooling a refrigerant; more specifically, to an evaporative heat exchanger having an integrated outboard refrigerant cooling section.
An indirect evaporative cooler is a heat exchange device comprising a dry air stream and a wet air stream flowing in two separate sets of channels. The heat from the dry air stream is conducted across the dry channel walls to the wet air stream in the wet channels. This heat causes evaporation of the liquid water in the wet air stream resulting in cooling of the dry air stream and humidification of the wet air stream. The cooling of the dry air stream is alluded to as the indirect evaporative cooling of the air since the dry air stream does not come in direct contact with the evaporating water. In an indirect evaporative cooler there is also cooling of the wet air stream in addition to humidification. This is referred to as the direct evaporative cooling of the air since in this case there is a direct contact between the air and the evaporating water.
An indirect evaporative cooler can be employed to cool the condenser of a vapor compression refrigeration or air conditioning system. The vapor compression system comprises a condenser, an expansion device, an evaporator and a compressor. The working fluid of the vapor compression system is a refrigerant, such as R-134a, which is capable of undergoing liquid-to-vapor transformation in the evaporator and vapor-to-liquid transformation in the condenser. The compressor—located between the evaporator and the condenser—provides the motive power for the circulation of the refrigerant in a closed loop and the expansion device—located between the condenser and the evaporator—causes expansion of the high pressure mixture of liquid-vapor refrigerant from the condenser into the evaporator.
The most common method of condensing the refrigerant in the condenser is by forcing the ambient air through the fins on the exterior of the condenser. The ambient air at relatively high temperature is not as effective as cooler air in condensing the refrigerant. Another common method of condensing the refrigerant in the condenser is by spraying liquid water on the exterior of the condenser. A drawback of this method is that the water consumption is excessive. Motivated by these considerations evaporatively cooled air is utilized to condense the refrigerant vapor.
Shown in
It has been proposed to provide a condenser cooling concept that utilizes the principle of evaporating a liquid to cool a hot refrigerant, which has a higher pressure than ambient air. To contain the higher pressure refrigerant, the refrigerant channels are formed of a higher strength heat transfer material such as aluminum to provide the structural integrity required. The wet and dry channels of the associated evaporative cooler are formed of a plastic or cellulose material. Working air is passed through the refrigerant condenser, which includes a complex network of wet and dry channels inter crossed with the refrigerant channels, incrementally cooling the refrigerant. The refrigerant channels are bundled near the center of the evaporative cooler, thereby, limiting the heat transfer area for evaporative cooling.
There exists a need for an evaporatively cooled condenser that may provide improved heat transfer efficiency for cooling a refrigerant; there also exists a need for an evaporative cooler that can accommodate a high pressure refrigerant. There is also a need for an evaporatively cooled condenser that is simpler and cost effective to manufacture; and there is a further need for an evaporatively cooled condenser that is scalable in size.
The present invention provides an evaporatively cooled condenser that includes a stack of alternating wet and dry plates that utilizes the principles of evaporative cooling to remove heat from a hot refrigerant with a higher than ambient pressure.
The evaporative heat exchanger includes a dry plate having an air flow section and an integral refrigeration cooling section. The air flow section includes a dry side that defines a plurality of dry channels in a first direction, a wet side, and a series of varying sized ports for air distribution located along the bottom of the dry channel. The outboard refrigerant cooling section has refrigerant passageways and is structurally integral with the air flow section to provide efficient thermal conductivity for heat transfer.
The evaporative heat exchanger also includes a wet plate having a wet surface that is adjacent to and cooperates with the wet side of the dry plate to define a plurality of wet air flow conduits in a second direction, which is substantially perpendicular to the first direction. The wet air flow conduits are adapted to contain an evaporative liquid such as water capable of undergoing liquid-to-vapor transformation. Each wet plate further includes a dry surface adjacent to and cooperates with the dry side of the next alternatively stacked dry plate to define a plurality of dry air flow conduits in the first direction. The wet flow conduits communicate with the dry air flow conduits through the ports.
An evaporative liquid, such as water, is provided to the wet plates. Concurrently, an air stream of low humidity is induced through the heat exchanger core defined by the stack of wet and dry plate. As the low humidity air evaporates the liquid provided to the surface of wet plate, the temperatures of the liquid and wet and dry plates are reduced due to removal of latent heat therefrom resulting in evaporation of water from liquid to vapor state. The cooling of the heat exchanger in turn removes heat from the hot refrigerant flowing in the passageways of the integral outboard refrigerant cooling section
Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of the preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings.
This invention will be further described with reference to the accompanying drawings in which:
Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, an evaporative refrigerant cooler 90 constructed in accordance with the subject invention, is generally shown in
In reference to
Protruding from wet surface 110 of wet plate 100 is a plurality of substantially parallel channel guides 115 that extends the width of core 15. Channel guides 115 cooperate with wet surface 110 to define a series of substantially parallel wet channels 125. Wet channels 125 have opposing ends 130c, 130d located outboard of core 15 in the third and fourth directions C, D. The opposing ends 130c, 130d are open to ambient atmosphere. Located on either edge of wet plate 100 in first and second direction A, B is wet plate wall 117 that has a height X that is greater than or equal to the height Y of channel guides 115. Wet surface 110 may have a layer of wicking material (not shown) for the even distribution of evaporative liquid throughout the surface areas of wet channel 125. As an alternative, wet surface 110 may be sand-blasted or chemically etched to provide a textured surface for the even distribution of liquid. Located substantially midway along the width of each channel guide 115 is notch 135. Notches 135 are axially aligned parallel to longitudinal axis 20.
Also shown in
Dry channels 225 have air inlet end 230 for accepting air flow along the longitudinal axis 20, from the second direction B to first direction A. On the opposing end is air outlet end 235. Positioned in series along dry channel 225 are ports 242 for the separation and diversion of an air stream to wet side 210. The open area of ports 242 may increase along dry channel 225 toward first direction A in the direction of air flow. The optimal ratio for the area of the largest port opening compared to the area of the smallest port opening is in the range of 1.125 to 2.000 for uniform distribution of air distribution to each wet channel.
Located on both outboard edges of dry plate 200 in the third direction C and fourth direction D are refrigerant cooling sections 600. Refrigerant cooling section 600 is integrally formed with and is a continuous seamless part of dry plate 200. In reference to
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As redistributed air stream 500 flows through wet air flow conduit 140, the relatively low humidity air causes the evaporative liquid to change from a liquid state to a gaseous state. As the physical state of the liquid changes into a gaseous state, the temperatures of wet plate 100, dry plate 200, and air stream 500 are reduced due to the heat absorption by the evaporating liquid.
Some thermal energy from hot refrigerant flowing through refrigerant cooling section 600 is conducted through the body of dry plate 200 and rejected to the dry air flow in dry air conduit 240 with the assistance of fins 215. The bulk of thermal energy from refrigerant cooling section 600 is rejected by forced convection to the cooler wet air stream 500 as it flows over the bottom surface 630 of the refrigerant cooling section 600 through the wet conduits 140.
As the air stream 500 flows down dry air flow channel 240 toward first direction A, the air stream 500 becomes progressively cooler resulting in a temperature gradient where the temperature of the evaporative cooler is lower in the first direction A as compared to the second direction B. As the diverted air stream 500 moves from the latitudinal axis 25 toward wet air outlet 145, the temperature of the evaporative cooler 10 becomes progressively cooler toward the outboard ends. Outlet ends 235 may be blocked to divert all of air stream 500 to wet air flow conduits 140 for maximum cooling of refrigerant as shown in
In reference to
The outboard location of refrigerant cooling section 600 provides sufficient surface area for heat to be released to the exposed end surface 615 by radiation and natural convection to the surrounding environment. Concurrently heat is conducted through dry plate 200 from second and third directions C, D toward longitudinal axis, during which time a portion of heat is released to the cooler air stream 500 in dry air flow conduits 240 with the assistance of fins 215. As air flow 500 flows through wet flow conduit 140, it removes heat by forced convection from the wet side 210 of dry plate 200 and bottom surface 630 of refrigerant cooler 600.
An advantage of the refrigerant cooling section being located outboard of the evaporative refrigerant cooler is that it allows heat to be removed by a combination radiation, conduction, and convection.
Another advantage of the evaporative refrigerant cooler is that the refrigerant cooling section is formed integrally with dry plate 200; whereby, there is no resistance of heat flow from the refrigerant cooling section through the dry plate to the fins for dissipation to air stream in dry flow conduits 240.
Still another advantage of the evaporative refrigerant cooler is that the refrigerant cooling section is formed of a material that is heat conductive and able to withstand the pressure requirements of hot refrigerants.
Yet another advantage of the evaporative refrigerant cooler is that wet plate 100 and dry plate 200 may be formed of a heat conductive material such as copper, aluminum, or brass that allows the plates to be extruded, assembled, and brazed with known methods in the art.
Still yet another advantage of the evaporative refrigerant cooler is that the unit is scalable to be fitted on a roof top or within a motor vehicle, depending on cooling needs.
Another advantage is that the evaporative refrigerant cooler can cool the refrigerant and condition air for another purpose.
While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.
