US20100058794A1

US20100058794A1 - Low profile evaporative cooler

Info

Publication number: US20100058794A1
Application number: US12/231,725
Authority: US
Inventors: Mohinder S. Bhatti; Ilya Reyzin; Shrikant M. Joshi
Original assignee: Delphi Technologies Inc
Current assignee: Delphi Technologies Inc
Priority date: 2008-09-05
Filing date: 2008-09-05
Publication date: 2010-03-11

Abstract

An evaporative cooler assembly includes a plurality of tubes extending from a refrigerant tank in a spaced relationship to one another with each tube defining a wet air passage. Each pair of adjacent tubes defines a dry air passage extending transversely to the tubes. Each tube includes a plurality of orifices each in fluid communication with the corresponding wet air passage and the adjacent dry air passage. A pair of air ducts are disposed on the refrigerant tank with the tubes being disposed between the air ducts and the air ducts being in fluid communication with the dry air passages whereby a dry air stream flows sequentially through a portion of the dry air passages and into one of the air ducts and through another portion of the dry air passages and into the other air duct until the dry air stream flows out of a dry air outlet as conditioned air.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The subject invention relates to conditioning air, and more specifically, to conditioning air using the principles of evaporative cooling.
2. Description of the Prior Art
It is known to cool air by flowing the air over an evaporator comprising a set of tubes carrying a refrigerant. The heat is transferred from the air to the refrigerant flowing within the tubes to cool the air. The refrigerant then passes through a compressor and is compressed into a superheated vapor. The heat must then be dissipated from the superheated refrigerant vapor before the refrigerant can be used to cool additional air. Typically, the heat is dissipated into the atmosphere by transferring the heat from the superheated refrigerant vapor to ambient air flowing over a condenser comprising a set of condensing tubes carrying the superheated refrigerant vapor. As the refrigerant cools, it condenses back into a liquid.
A significant drawback to the system as described above is the requirement of a chemical refrigerant and a compressor. Chemical refrigerants generally are not environmentally friendly, and compressors consume energy and tend to make the systems bulky. Accordingly, systems that do not require a chemical refrigerant or a compressor have been developed. An example of such a system is a heat and mass exchanger as disclosed in U.S. patent application No. 11/801,545. The heat and mass exchanger as disclosed by Bhatti et al. comprises a refrigerant tank having a top surface and defining a refrigerant cavity for housing a refrigerant. The top surface of the refrigerant tank defines a plurality of tube slots. A plurality of tubes each defining a wet air passage extend between a refrigerant inlet end and a wet air outlet end for producing a wet air stream. Each of the tubes extend from one of the tube slots and transversely to the refrigerant tank in a spaced relationship to one another with the wet air passages being in fluid communication with the refrigerant cavity. A plurality of cooling fins extending between adjacent tubes to define a plurality of dry air passages extending transversely to the tubes for receiving a dry air stream. Each of the tubes includes a plurality of orifices each in fluid communication with the corresponding wet air passage and the adjacent dry air passage. In operation, a dry air stream is flowed into the dry air passages whereby a portion of the dry air stream is diverted through the orifices and into the wet air passages. The wet air stream is cooled by the refrigerant, generally water, in the refrigerant cavity thereby dissipating heat from the dry air stream in the dry air passages. The wet air stream is expelled from the wet air outlet end of each tube as exhaust, and the dry air stream is output from the dry air passages as dry, conditioned air.
While the heat and mass exchanger as disclosed by Bhatti et al. effectively eliminates the need for a chemical refrigerant and a compressor, it tends to be bulky in order to provided the required amount of conditioning. Accordingly, there remains a need for a more efficient evaporative cooler assembly.

SUMMARY OF THE INVENTION

The present invention provides for such an evaporative cooler assembly improved by disposing a first air duct defining a first duct passage on the top surface of the refrigerant tank and adjacent the tubes with the first duct passage being in fluid communication with the dry air passages for receiving the dry air stream. In operation, the dry air stream flows through a first portion of the dry air passages and into the first duct passage defined by the first air duct and is deflected by the first air duct into a second portion of the dry air passages to be output as conditioned air.
The present invention improves upon the prior art by flowing the dry air stream through the dry air passages a plurality of times. Accordingly, an evaporative cooler having a lower profile can more efficiently condition the dry air stream.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective and cross-sectional view of an evaporative cooler assembly;

FIG. 2 is a perspective and exploded view of an evaporative cooler assembly; and

FIG. 3 is a fragmentary view of an evaporative cooler assembly.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, an evaporative cooler assembly 20 for conditioning air is shown generally.
The assembly 20 includes a refrigerant tank 22 having a top surface 24 extending between a pair of tank ends 26. The refrigerant tank 22 defines a refrigerant cavity 28 for housing a refrigerant, and generally has a rectangular cross-section. The refrigerant is preferably water, however, those skilled in the art appreciate other refrigerants can also be used. The top surface 24 of the refrigerant tank 22 defines a plurality of tube slots 30. The tube slots 30 are preferably spaced axially along the top surface 24 of the refrigerant tank 22 between the tank ends 26. The tube slots 30 are generally rectangular for receiving a plurality of generally rectangular tubes 32, however, those skilled in the art appreciate tube slots 30 of different shapes can also be used.
The plurality of tubes 32 each have an interior surface 34 and are generally rectangular in cross-section for being received by the tube slots 30. Each tube 32 defines a wet air passage 36 extending between a refrigerant inlet end 38 and a wet air outlet end 40 for producing a wet air stream. In an embodiment of the assembly 20, the refrigerant inlet end 38 of each tube 32 is disposed in the refrigerant cavity 28 for contacting the refrigerant, and each of the tubes 32 extend through one of the tube slots 30 in a spaced relationship to one another with the wet air passages 36 being in fluid communication with the refrigerant cavity 28. In another embodiment of the assembly 20, the refrigerant inlet end 38 of each tube 32 is disposed on the top surface 24 of the refrigerant tank 22 with each wet air passage 36 aligned with one of the tube slots 30 and the tubes 32 extending from the tube slots 30 in a space relationship to one another with the wet air passages 36 being in fluid communication with the refrigerant cavity 28. The tubes 32 preferably extend in a parallel relationship to one another and perpendicularly from the refrigerant tank 22. Each of the tubes 32 also preferably include at least one divider 42 extending between the refrigerant inlet end 38 and the wet air outlet end 40 to define a plurality of the wet air passages 36 and for reinforcing the tube 32.
A wicking material 44 is generally disposed on the interior surface 34 of each of the tubes 32 and on each divider 42 for conveying refrigerant from the refrigerant cavity 28 into the tubes 32. Additionally, in the embodiment of the assembly 20 wherein each refrigerant inlet end 38 is disposed on the top surface 24 of the refrigerant tank 22, the wicking material 44 is also preferably disposed on the interior surface of the refrigerant tank 22 for conveying the refrigerant from the refrigerant cavity 28 to the tubes 32.
A plurality of cooling fins 46 extend between adjacent tubes 32 to define a plurality of dry air passages 48 for receiving a dry air stream and for transferring heat from the dry air stream to the tubes 32. The dry air passages 48 generally extend transversely to the tubes 32 and are preferably parallel to the tank ends 26. While the cooling fins 46 are shown as serpentine fins in the Figures, those skilled in the art appreciate additional types of cooling fins can also be used.
Each of the tubes 32 define a plurality of orifices 50 in fluid communication with the corresponding wet air passages 36 and the adjacent dry air passages 48 for diverting a portion of the dry air stream from the dry air passages 48 to the wet air passages 36 for producing the wet air stream. The orifices 50 are shown in the Figures as being circular, however, those skilled in the art appreciate that orifices 50 having a different shape can also be used.
A plurality of top plates 52 each extend between the wet air outlet ends 40 of adjacent tubes 32. The top plates 52 define a portion of the dry air passages 48 and add structural support to the assembly 20.
A first air duct 54 defining a first duct passage 56 is disposed on the top surface 24 of the refrigerant tank 22 and adjacent the tubes 32 with the first duct passage 56 being in fluid communication with the dry air passages 48 for receiving the dry air stream. The first air duct 56 generally receives the dry air stream from a portion of the dry air passages 48 and deflects the dry air stream into another, adjacent portion of the dry air passages 48. In an embodiment of the assembly 20 as shown in FIG. 1, a second air duct 58 defining a second duct passage 60 is disposed on the top surface 24 of the refrigerant tank 22 and adjacent the tubes 32 with the tubes 32 being disposed between the air ducts and the second duct passage 60 being in fluid communication with the dry air passages 48 for receiving the dry air stream that is deflected by the first air duct 54 into another, adjacent portion of the dry air passages 48. The first and second air ducts are shown in the Figures as having rectangular cross-sections, however, those skilled in the art appreciate air ducts having different cross-sections can also be used.
A plurality of flow separators 62 are spaced axially along the top surface 24 of the refrigerant tank 22 and disposed alternately in the air ducts as shown in FIG. 1 for diverting the dry air stream in the air ducts. The flow separators 62 are spaced axially along the top surface 24 of the refrigerant tank 22 and disposed alternately in the air ducts for causing the dry air stream to sequentially wind from one of the air ducts to a portion of the dry air passages 48 to the other of the air ducts to another, adjacent portion of the dry air passages 48.
In an embodiment of the assembly 20 as shown in FIG. 1, one of the air ducts is spaced from each of the tank ends 26 to define a dry air inlet 64 and a dry air outlet 66. In an alternative embodiment of the assembly 20, one of the air ducts defines a dry air inlet 64 and the other of the air ducts defines a dry air outlet 66.
In operation, the dry air inlet 64 receives a dry air stream. The dry air stream flows into a portion of the dry air passages 48, and a portion of the dry air stream is diverted through the orifices 50 of the tubes 32 adjacent the portion of the dry air passages 48 and into the wet air passages 36 defined by the tubes 32 adjacent the portion of the dry air passages 48 to form a wet air stream. The wicking material 44 in the tubes 32 adjacent the portion of the dry air passages 48 wicks the refrigerant from the refrigerant cavity 28 and into the wet air passages 36 defined by the tubes 32. The wet air stream flows over the refrigerant causing the refrigerant to evaporate thereby dissipating heat from the dry air stream in the dry air passages 48. The wet air stream is output through the wet air outlet ends 40 of each of the tubes 32 as exhaust, and the dry air stream flows into one of the air ducts. The dry air stream flows through the corresponding duct passage 56, 60 and is deflected by one of the flow separators 62 disposed in the corresponding air duct 54, 58 and through another, adjacent portion of the dry air passages 48 and into the other of the duct passages defined by the other of the air ducts. The dry air passage 48 is then deflected by one of the flow separators 62 disposed in the other of the air ducts. The dry air stream continues flowing between the air ducts and through the dry air passages 48 until the dry air stream reaches the dry air outlet 66. The lowest temperature of the dry air stream leaving the evaporative cooling assembly 20 equals the dew point temperature of the incoming ambient air (T_dpi) defined by the equation:
$\begin{matrix} T_{dpi} = T_{wt} {1 - \frac{1}{α} \ln [\frac{(P_{a} / P_{wt}) ω_{i}}{ω_{i} + (M_{w} / M_{a})}]}^{- 3 / 4} & (1) \end{matrix}$
wherein:

- T_wtis the triple-point temperature of water=491.6880° R;
- α is the dimensionless constant for water=15.0197;
- P_ais the atmospheric pressure=14.696 psia;
- P_wtis the triple-point pressure of water=0.088663 psia;
- ω_iis the absolute humidity of the incoming ambient air into the evaporative cooler assembly 20;
- M_wis the molecular weight of water=18.0152 lb/lb-mole; and
- M_ais the molecular weight of air=28.9645 lb/lb-mole.

The absolute humidity of the incoming ambient air (ω_i) into the evaporative cooler assembly 20 is further defined by the equation:
$\begin{matrix} ω_{i} = \frac{(M_{w} / M_{a}) φ_{i}}{(P_{a} / P_{wi}) - φ_{i}} & (2) \end{matrix}$
wherein:

- φ_iis the relative of the incoming ambient air into the evaporative cooler assembly 20; and
- P_wiis the vapor pressure of water in the incoming ambient air into the evaporative cooler assembly 20; it is defined by the equation:

$\begin{matrix} P_{wi} = P_{wt} \exp {α [1 - {(\frac{T_{wt}}{T_{i}})}^{4 / 3}]} & (3) \end{matrix}$
wherein:

- T_iis the dry bulb temperature of the incoming ambient air into the evaporative cooler assembly 20.

Additionally, the temperature of the wet air stream (T_wo) of the evaporative cooler assembly 20 is defined by the equation:
$\begin{matrix} T_{wo} = T_{i} - \frac{1}{2} (A + \sqrt{(A^{2} + 4 B)}) & (4) \end{matrix}$
wherein A and B are the constraints dependent on the psychrometric parameters as defined by the equations below:
$\begin{matrix} A = \frac{\begin{matrix} (\frac{{\dot{m}}_{da}}{{\dot{m}}_{wa}}) (c_{fw} - c_{pw}) (T_{i} - T_{dpi}) - c_{pw} T_{i} + \\ c_{fw} (T_{i} - T_{fpw}) - {β (1 - \frac{T_{i}}{T_{c}})}^{3 / 8} (1 + \frac{ω_{i} c_{pw}}{c_{pa}}) - h_{gwi} \end{matrix}}{c_{fw} - c_{pw}} & (5) \end{matrix}$
wherein:

- {dot over (m)}_dais the mass flow rate of the dry air stream through the evaporative cooler assembly 20;
- {dot over (m)}_wais the mass flow rate of the wet air stream through the evaporative cooler assembly 20;
- c_fwis the specific heat of liquid water=1 Btu/lb ° F.;
- c_pwis the isobaric specific heat of water vapor=0.444 Btu/lb ° F.;
- T_fpwis the normal freezing point of water=32° F.;
- β is the constant for water=1339.2 Btu/lb;
- T_cis the critical temperature of water=1165.11° R;
- c_pais the isobaric specific heat of air=0.240 Btu/lb ° F and
- h_gwiis the specific enthalpy of water vapor at 0° F.=1061 Btu/lb.

The constant B is further defined by the equation:
$\begin{matrix} B = \frac{({\dot{m}}_{da} / {\dot{m}}_{wa}) (T_{i} - T_{dpi}) ⌊ c_{pw} T_{i} - c_{fw} (T_{i} - T_{fpw}) + h_{gwi} ⌋}{c_{fw} - c_{pw}} & (6) \end{matrix}$
and the ratio of absolute humidity ω_woof wet air stream leaving the evaporative cooler assembly 20 to the absolute humidity ω_iof the ambient air stream entering the evaporative cooler assembly 20 is further defined by the equation:
$\begin{matrix} \frac{ω_{wo}}{ω_{i}} = 1 + \frac{(c_{pw} + c_{pa} / ω_{i}) (T_{i} - T_{wo})}{h_{gwi} + c_{pw} T_{wi} - c_{fw} (T_{wo} - T_{fpw})} & (7) \end{matrix}$
wherein all the symbols have been previously defined.
While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. An evaporative cooler assembly for conditioning air comprising:

a refrigerant tank having a top surface and defining a refrigerant cavity for housing a refrigerant;

said top surface of said refrigerant tank defining a plurality of tube slots;

a plurality of tubes each defining a wet air passage extending between a refrigerant inlet end and a wet air outlet end for producing a wet air stream;

each of said tubes extending from one of said tube slots and transversely to said refrigerant tank in a spaced relationship to one another with said wet air passages being in fluid communication with said refrigerant cavity;

each pair of adjacent tubes defining a dry air passage extending transversely to said tubes for receiving a dry air stream;

each of said tubes including a plurality of orifices in fluid communication with said corresponding wet air passage and said adjacent dry air passage for diverting a portion of the dry air stream from said dry air passage to said wet air passage for producing the wet air stream; and

a first air duct defining a first duct passage disposed on said top surface of said refrigerant tank and adjacent said tubes with said first duct passage being in fluid communication with said dry air, passages for receiving the dry air stream;

whereby the dry air stream flows through a first portion of said dry air passages and into said first duct passage defined by said first air duct and is deflected by said first air duct into a second portion of said dry air passages to be output as conditioned air.

2. The assembly as set forth in claim 1 including a second air duct defining a second duct passage disposed on said top surface of said refrigerant tank and adjacent said tubes with said tubes being disposed between said air ducts and said second duct passage being in fluid communication with said dry air passages for receiving the dry air stream.

3. The assembly as set forth in claim 2 including a plurality of flow separators being spaced axially along said top surface of said refrigerant tank and disposed alternately in said air ducts for diverting the dry air stream in said air ducts whereby the dry air stream sequentially flows through a portion of said dry air passages and into one of said-duct passages defined by said corresponding air duct and is deflected by one of said flow separators disposed in said corresponding air duct and through another portion of said dry air passages and into the other of said duct passages defined by the other of said air ducts and is deflected by one of said flow separators disposed in the other of said air ducts.

4. The assembly as set forth in claim 3 wherein said refrigerant tank extends between a pair of tank ends and one of said air ducts is spaced from each of said tank ends to define a dry air inlet and a dry air outlet.

5. The assembly as set forth in claim 3 wherein one of said air ducts defines a dry air inlet and the other of said air ducts defines a dry air outlet.

6. The assembly as set forth in claim 3 including a plurality of cooling fins extending between adjacent tubes to define a plurality of said dry air passages extending transversely to said tubes between said adjacent tubes for receiving the dry air stream.

7. The assembly as set forth in claim 3 wherein said refrigerant inlet end of each tube is disposed in said refrigerant cavity for contacting the refrigerant and each of said tubes extends through one of said tube slots.

8. The assembly as set forth in claim 3 wherein said tubes extend perpendicularly to said refrigerant tank.

9. The assembly as set forth in claim 3 wherein said tubes extend in a parallel relationship.

10. The assembly as set forth in claim 3 wherein said refrigerant tank extends between a pair of tank ends and said dry air passages extend parallel to said tank ends.

11. The assembly as set forth in claim 3 wherein each of said tubes have an interior surface and including a wicking material disposed on said interior surface of each of said tubes for conveying refrigerant from said refrigerant cavity into said tubes.

12. The assembly as set forth in claim 3 wherein each of said tubes include at least one divider extending between said refrigerant inlet end and said wet air outlet end to define a plurality of said wet air passages and for reinforcing said tube.

13. The assembly as set forth in claim 12 including a wicking material disposed on said dividers of each of said tubes for conveying refrigerant from said refrigerant cavity into said tubes.

14. The assembly as set forth in claim 3 wherein said tube slots are spaced axially along said top surface of said refrigerant tank.

15. The assembly as set forth in claim 3 including a plurality of top plates each extending between said wet air outlet ends of adjacent tubes.

16. The assembly as set forth in claim 3 wherein said tubes are generally rectangular in cross-section and said tube slots are generally rectangular.

17. The assembly as set forth in claim 3 wherein said refrigerant tank has a rectangular cross-section.

18. An evaporative cooler assembly for conditioning air comprising:

a refrigerant tank having a top surface extending between a pair of tank ends and a rectangular cross-section and defining a refrigerant cavity for housing a refrigerant;

said top surface of said refrigerant tank defining a plurality of tube slots being generally rectangular and spaced axially along said top surface of said refrigerant tank between said tank ends;

a plurality of tubes each having an interior surface and a generally rectangular cross-section and defining a wet air passage extending between a refrigerant inlet end and a wet air outlet end for producing a wet air stream,

said refrigerant inlet end of each tube disposed in said refrigerant cavity for contacting said refrigerant;

each of said tubes extending through one of said tube slots and perpendicularly to said refrigerant tank in a spaced and parallel relationship to one another with said wet air passages being in fluid communication with said refrigerant cavity;

each of said tubes including at least one divider extending between said refrigerant inlet end and said wet air outlet end to define a plurality of said wet air passages and for reinforcing said tube;

a wicking material disposed on said interior surface and said dividers of each of said tubes for conveying refrigerant from said refrigerant cavity into said tubes;

a plurality of cooling fins extending between adjacent tubes to define a plurality of dry air passages extending transversely to said tubes and parallel to said tank ends for receiving a dry air stream and for transferring heat from the dry air stream to said tubes;

a plurality of top plates each extending between said wet air outlet ends of adjacent tubes;

each of said tubes defining a plurality of orifices in fluid communication with said corresponding wet air passages and said adjacent dry air passages for diverting a portion of the dry air stream from said dry air passages to said wet air passages for producing the wet air stream;

a first air duct defining a first duct passage disposed on said top surface of said refrigerant tank and adjacent said tubes with said first duct passage being in fluid communication with said dry air passages for receiving the dry air stream;

a second air duct defining a second duct passage disposed on said top surface of said refrigerant tank and adjacent said tubes with said tubes being disposed between said air ducts and said second duct passage being in fluid communication with said dry air passages for receiving the dry air stream;

a plurality of flow separators being spaced axially along said top surface of said refrigerant tank and disposed alternately in said air ducts for diverting the dry air stream in said air ducts; and

one of said air ducts being spaced from each of said tank ends to define a dry air inlet and a dry air outlet;

whereby the dry air stream flows through said dry air inlet and sequentially through a portion of said dry air passages and into one of said duct passages defined by said corresponding air duct and is deflected by one of said flow separators disposed in said corresponding air duct and through another portion of said dry air passages and into the other of said duct passages defined by the other of said air ducts and is deflected by one of said flow separators disposed in the other of said air ducts until the dry air stream flows out of said dry air outlet as conditioned air.