ABSORPTION COOLING SYSTEM
The absorption cooling system is capable of continuous operation both day and night while using only solar power for its basic operation. The system is an absorption type system using phase changes of aqua-ammonia and a storage system for storing chilled refrigerant for operations when solar power is not available. When solar power is available during the day, the system operates according to the principles of absorption cooling systems, and also stores a reserve of chilled refrigerant in the storage unit. The stored refrigerant then continues the absorption process during the night when solar energy is not available, thereby providing uninterrupted cooling during the day, and also at night when solar energy is not available.
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1. Field of the Invention
The present invention relates generally to mechanical cooling and refrigeration systems, and particularly to an absorption cooling system using aqua-ammonia as the refrigerant.
2. Description of the Related Art
Solar energy has great potential as a renewable energy source that can be effectively utilized to power refrigeration and air conditioning systems, among other purposes. However, the biggest challenge in utilizing solar energy for uninterrupted cooling is its unavailability at night. There are essentially two types of operation for refrigeration and air conditioning systems, i.e., continuous operation and intermittent operation. Continuously operating systems have comparatively high coefficients of performance, and are also generally more compact than systems using other principles of operation. While such continuously operating systems may be capable of operating both day and night if supplied with uninterrupted power, if they are powered by solar energy, they can only provide cooling during the time that solar energy is available, so they cannot be used to achieve uninterrupted cooling around the clock.
Intermittent operating cooling systems generally require fewer components for operation and may be configured so that they do not require any electrical or other power input for their operation (other than ventilation fans for air circulation in the volume being cooled). However, such intermittent cooling systems have comparatively poor coefficients of performance, are relatively large in size, and can generally only provide cooling effect during cooler times of day, i.e., at night.
Thus, an absorption cooling system solving the aforementioned problems is desired.
SUMMARY OF THE INVENTIONThe absorption cooling system is a relatively compact assembly essentially comprising five basic units, i.e., a generator unit, a condenser unit, an evaporator unit, an absorption unit, and a storage unit. The system does not require a separate heat rejection system. The configuration is such that heat can be rejected directly from the system. Thus, no intermediate cooling system is required for operation. Two pumps are used for the operation of the system. These pumps are used alternately during day and night operations.
The generator unit comprises a plurality of heating tubes, a liquid-liquid heat exchanger, a rectifier, and a dephlegmator in combination, in a single unit. The condenser unit includes a condenser, a liquid ammonia tank, and a vapor-liquid heat exchanger, in a single unit. The evaporator unit comprises only the evaporator, while the absorber unit comprises only the absorber. The storage unit provides for storage of both strong (i.e., having a relatively low percentage of water) and weak (i.e., having a higher percentage of water) aqua-ammonia (i.e., ammonium hydroxide) solutions. Induced draft fans are used for heat rejection from the system to the ambient air. The generator and condenser units operate only during the period when solar energy is available, whereas the absorption and evaporator units continue their operation throughout the day and night in cooperation with the storage unit and pumps to achieve an uninterrupted supply of cooled air.
These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.
Similar reference characters denote corresponding features consistently throughout the attached drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTSThe absorption cooling system 100 as illustrated in
The description of the various components and their operation will begin with the generator unit 200 of
The lower portion 204 of the generator 200 contains a first plurality of heat exchange tubes 212 therein. The tubes 212 are arranged in a sinusoidal array, generally as shown in
The temperature differential between the solar collector fluid and the aqua-ammonia solution at the upper or inlet portion and the lower or outlet portion of the heat exchange tubes 212 results in greater heating of the aqua-ammonia liquid around the upper portion of the heat exchanger 212. This greater heating drives off more ammonia vapor from the liquid refrigerant near the upper portion of the heat exchanger tubes 212. The relatively lower temperature differential in the lower portion of the tubes 212 does not generate as much heat, so comparatively less ammonia vapor is driven off from the aqua-ammonia liquid in the lowermost portion of the case 202. As the strong aqua-ammonia solution moves from the upper portion to the lower portion of the heat exchanger tubes 212 while continuously driving off ammonia vapors, this results in a relatively weak aqua-ammonia solution near the lowermost portion of the case 202.
Nevertheless, circulation within the generator 200 around the heat exchanger tubes 212 results in the aqua-ammonia liquid in the lowermost portion of the generator containing a larger fraction of water. This liquid is circulated through a second plurality of heat exchange tubes 220 in the upper portion 206 of the generator 200, due to the pump 708 of the plumbing system 700, shown in
The return tubes 222a through 222e are connected to a header 224 formed along the second side 210 of the case 202. The aqua-ammonia liquid flows from the tubes 222a through 222e into the lower end of the header 224, and rises in the header 224 as the liquid is drawn into the second plurality of heat exchanger tubes 220 due to the pump 708 (
Due to the heat generated within the generator 200, nearly all of the aqua-ammonia vapors generated in the lower portion 204 move to the upper portion 206 of the generator 200. Additional strong or concentrated ammonia liquid is pumped into the generator unit 200 through an inlet pipe 230. This additional liquid results from mixing concentrated ammonia liquid supplied from the tank system 600 of
The two vapor outlets 240a, 240b pass the concentrated ammonia vapor to a condenser unit 300.
The lower portion 304 of the liquid ammonia tank 302 includes a plurality of vapor-liquid heat exchanger tubes 316 therein, which are disposed in a sinusoidal array, much like the first and second heat exchanger tubes 212 and 220 of the generator unit 200. These tubes 316 are connected to the evaporator 400. This portion of the operation is explained further below. A baffle 318 is placed immediately above the heat exchanger tubes 316. A plurality of vapor condenser tubes 320 is disposed across each of the air channels. These condenser tubes 320 are shown in end view in the cross section elevation of
The condenser unit 300 receives the rich, heated ammonia vapor from the generator 200 through the vapor outlets 240a and 240b that extend from the upper portion of the generator 200 to the central upper tank portion 306, as shown in
The cooled, concentrated liquid ammonia flows from the lower tank 304 of the condenser unit 300 through an outlet tube 322 containing a throttling valve or expansion valve (not shown). The outlet tube 322 also comprises the inlet tube to the evaporator unit 400, shown in
A plurality of coolant tubes 406 is disposed within the evaporator tank 402, preferably in a sinusoidal array, as shown in
Under some operating conditions, the ammonia entering the evaporator unit 400 may comprise a certain fraction that remains in a vapor state. The evaporator tank 402 also serves as a separator for the segregation of the liquid phase from the vapor phase. As the cooling effect is produced from the vaporizing of chilled liquid ammonia, it is preferable that the tubes 406 only come into contact with the liquid phase. Eventually, the liquid ammonia may fill the evaporator tank 400, in which case proper segregation of the liquid and vapor phases may not occur. This can greatly reduce the cooling effect to the coolant tubes 406. Accordingly, a flotation control valve is provided at the ammonia fluid inlet 404. The valve comprises a float 412 that rides between two guides or supports 414. If too much liquid ammonia enters the tank 402, the float 412 will rise to cover the inlet 404 until sufficient ammonia escapes the tank 402 through the ammonia fluid outlet 416. Thus, precooled ammonia flows from the liquid tank 302 of the condenser unit 300 to the evaporator unit 400 via the exit tube or line 322 (
An absorption unit 500 is illustrated in partial section in
During daytime operations, i.e., when solar heating is available from the solar collector 214, the absorption unit 500 accepts a weak liquid aqua-ammonia solution from the exit manifold and pipe 228 of the generator unit 200, through a valve and plumbing network described further below, into a first (fluid) inlet 514. However, at night when no solar heating is available, the absorption unit 500 receives weak liquid aqua-ammonia solution from the storage tank system 600 (shown in
The storage tank system 600 for storing various concentrations of aqua-ammonia solution is shown in
Each of the tanks 602 and 604 has its own dedicated inlet and outlet. During daytime operation the strong aqua-ammonia solution is drawn from the outer tank outlet 616. The aqua-ammonia from this source ultimately is delivered to the upper inlet 230 of the generator unit 200. Weaker aqua-ammonia solution is returned from the exit manifold and pipe 228 of the generator unit 200, back to the second or inner tank inlet 618. At night the flow to and from the tanks 602 and 604 is reversed, so that relatively weak aqua-ammonia solution is drawn from the second or inner tank outlet 620 and delivered to the first (fluid) inlet 514 of the absorption unit 500. Relatively strong aqua-ammonia solution is returned from the outlet or return line 518 of the absorption unit 500, and back to the return inlet 622 of the first or outer tank 602.
Daylight operation utilizes the solar collector 214 to heat a working fluid. The heat energy is transferred to the ammonia fluid in the generator 200, as noted further above. A relatively strong ammonia solution is supplied to the generator 200 from both the first or outer tank outlet 616 and the outlet 518 of the absorption unit 500. The first tank outlet is connected to a first delivery pipe 702 (mostly concealed by other pipes, only its leftmost portion being visible in
The flow is considerably different for night operation, when the solar collector 214 is ineffective. At night, the relatively weak ammonia solution is drawn from the second or inner tank outlet 620 by a second pump 716, and passes through a fourth delivery pipe 718 and valve 720. Upon leaving the second pump 716, the ammonia solution passes through another valve 722 and a tee, and on through yet another valve 724 to the inlet 516 of the absorption unit 500 (
The above-described absorption cooling system 100 requires relatively little energy for its operation, in comparison to systems using large compressors to produce high working pressures in portions of the system. Although the first pump 708 used for daytime operation does operate to increase the working pressure of the fluid passing therethrough, the pressures produced and the corresponding power required are relatively low. Accordingly, the power required for daytime operation of the first pump 708, the fans 314 of the condenser unit 300, and the fan 512 of the absorption unit 500 may be provided by a plurality of solar panels 730, as shown in
It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.
Claims
1. An absorption cooling system, comprising:
- a generator unit;
- a condenser unit communicating with the generator unit;
- an evaporator unit communicating with the condenser unit;
- an absorption unit communicating with the generator unit and with the condenser unit;
- a first storage tank communicating with the generator unit and the absorption unit;
- a second storage tank being concentric to and disposed within the first storage tank, the second storage tank communicating with the generator unit and the absorption unit, wherein the second storage tank has an open upper end positioned beneath a closed upper end of said first storage tank, a gap being defined therebetween for the flow of aqua-ammonia vapor between said first and second storage tanks, an annular ammonia storage volume being defined between sidewalls of said first and second storage tanks;
- a first pump disposed between the generator unit and the first storage tank; and
- a second pump disposed between the absorption unit and the second storage tank.
2. The absorption cooling system according to claim 1, wherein the generator unit comprises:
- a case having a lower portion, an upper portion, a first side, and a second side opposite the first side;
- a heated fluid inlet and a heated fluid outlet extending from the lower portion of the case;
- a first plurality of heat exchange tubes disposed in the lower portion of the case, the tubes being disposed in a sinusoidal path between the heated fluid inlet and the heated fluid outlet;
- a second plurality of heat exchange tubes disposed in the upper portion of the case, the second plurality of tubes forming a sinusoidal path;
- a header disposed in the second side of the case, the header having a plurality of return tubes communicating with the lower portion of the case, the header further communicating with the second plurality of heat exchange tubes;
- a vapor chamber disposed above the second plurality of heat exchange tubes;
- a rectifier and dephlegmator disposed within the vapor chamber about the second plurality of heat exchange tubes; and
- at least one vapor outlet extending from the upper portion of the case.
3. The absorption cooling system according to claim 2, farther comprising:
- a solar collector communicating with the heated fluid inlet and the heated fluid outlet of the generator case; and
- a solar panel communicating with the first pump and the second pump.
4. The absorption cooling system according to claim 1, wherein the condenser unit comprises:
- a liquid tank having a lower portion and an upper portion, the upper portion having first and second air channels disposed therethrough;
- first and second vapor inlet tubes extending from the upper portion of the tank;
- a plurality of vapor-liquid heat exchanger tubes disposed in the lower portion of the liquid tank in a sinusoidal array;
- a plurality of condenser tubes disposed across each of the air channels, the condenser tubes communicating with the lower portion of the tank; and
- first and second condenser fans disposed in the first and second air channels, respectively, of the tank.
5. The absorption cooling system according to claim 1, wherein the evaporator unit comprises:
- an evaporator tank;
- a plurality of coolant tubes disposed within the evaporator tank, the coolant tubes being in a sinusoidal array;
- a fluid inlet disposed in the evaporator tank;
- a flotation control valve disposed in the evaporator tank at the fluid inlet; and
- a fluid outlet disposed in the evaporator tank.
6. The absorption cooling system according to claim 1, wherein the absorption unit comprises:
- a closed case having a first end and a second end opposite the first end;
- a plurality of airflow tubes disposed through the case, the airflow tubes extending from the first end to the second end;
- an airflow fan disposed in the second end of the case, the airflow fan selectively drawing air through the airflow tubes;
- a vapor inlet tube extending from the case;
- a fluid inlet tube extending from the case; and
- a fluid outlet tube extending from the case.
7. The absorption cooling system according to claim 1, further comprising aqua-ammonia fluid selectively circulating within the generator unit, the absorption unit, the condenser unit, the evaporator unit, the first storage tank, the second storage tank, the first pump, and the second pump.
8. An absorption cooling system, comprising:
- a generator unit having:
- a case having a lower portion, an upper portion, a first side, and a second side opposite the first side;
- a heated fluid inlet and a heated fluid outlet extending from the lower portion of the case;
- a first plurality of heat exchange tubes disposed in the lower portion of the case in a sinusoidal path between the heated fluid inlet and the heated fluid outlet;
- a second plurality of heat exchange tubes disposed in a sinusoidal path in the upper portion of the case;
- a header disposed in the second side of the case, the header having a plurality of return tubes communicating with the lower portion of the case, the header also communicating with the second plurality of heat exchange tubes;
- a vapor chamber disposed above the second plurality of heat exchange tubes;
- a rectifier and dephlegmator disposed within the vapor chamber and about the second plurality of heat exchange tubes;
- at least one vapor outlet extending from the upper portion of the case;
- a condenser unit communicating with the generator unit;
- an evaporator unit communicating with the condenser unit;
- an absorption unit communicating with the generator unit and with the condenser unit;
- a storage tank system communicating with the absorption unit and with the generator unit, wherein the storage tank system comprises a first storage tank communicating with the generator unit and the absorption unit and a second storage tank being concentric to and disposed within the first storage tank, the second storage tank communicating with the generator unit and the absorption unit, wherein the second storage tank has an open upper end positioned beneath a closed upper end of said first storage tank, a gap being defined therebetween for the flow of aqua-ammonia vapor between said first and second storage tanks, an annular ammonia storage volume being defined between sidewalls of said first and second storage tanks; and
- a pump system communicating with the storage tank system, the generator unit, and the absorption unit, wherein the pump system comprises a first pump disposed between the generator unit and the first storage tank and a second pump disposed between the absorption unit and the second storage tank.
9. The absorption cooling system according to claim 8, further comprising:
- a solar collector communicating with the heated fluid inlet and the heated fluid outlet of the generator case; and
- a solar panel communicating with the pump system.
10. (canceled)
11. The absorption cooling system according to claim 8, wherein the condenser unit comprises:
- a liquid tank having a lower portion and an upper portion, the upper portion having first and second air channels disposed therethrough;
- first and second vapor inlet tubes extending from the upper portion of the tank;
- a plurality of vapor-liquid heat exchanger tubes disposed in a sinusoidal array in the lower portion of the liquid tank;
- a plurality of condenser tubes disposed across each of the air channels, the condenser tubes communicating with the lower portion of the tank; and
- first and second condenser fans disposed in the first and second air channels, respectively, of the tank.
12. The absorption cooling system according to claim 8, wherein the evaporator unit comprises:
- an evaporator tank;
- a plurality of coolant tubes disposed in a sinusoidal array in a sinusoidal array within the evaporator tank;
- a fluid inlet disposed in the evaporator tank;
- a flotation control valve disposed in the evaporator tank at the fluid inlet; and
- a fluid outlet disposed in the evaporator tank.
13. The absorption cooling system according to claim 8, wherein the absorption unit comprises:
- a closed case having a first end and a second end opposite the first end;
- a plurality of airflow tubes disposed through the case, the airflow tubes extending from the first end to the second end;
- an airflow fan disposed in the second end of the case, the airflow fan selectively drawing air through the airflow tubes;
- a vapor inlet tube extending from the case;
- a fluid inlet tube extending from the case; and
- a fluid outlet tube extending from the case.
14. The absorption cooling system according to claim 8, further comprising aqua-ammonia fluid selectively circulating within the generator unit, the absorption unit, the condenser unit, the evaporator unit, the storage tank system, and the pump system.
15. An absorption cooling system, comprising:
- a generator unit;
- a condenser unit communicating with the generator unit, the condenser unit having:
- a liquid tank having a lower portion and an upper portion, the upper portion having first and second air channels disposed therethrough;
- first and second vapor inlet tubes extending from the upper portion of the tank;
- a plurality of vapor-liquid heat exchanger tubes disposed in a sinusoidal array in the lower portion of the liquid tank;
- a plurality of condenser tubes disposed across each of the air channels, the condenser tubes communicating with the lower portion of the tank;
- first and second condenser fans disposed in the first and second air channels, respectively, of the tank;
- an evaporator unit communicating with the condenser unit;
- an absorption unit communicating with the generator unit and with the condenser unit;
- a storage tank system communicating with the absorption unit and with the generator unit, wherein the storage tank system comprises a first storage tank communicating with the generator unit and the absorption unit and a second storage tank being concentric to and disposed within the first storage tank, the second storage tank communicating with the generator unit and the absorption unit, wherein the second storage tank has an open upper end positioned beneath a closed upper end of said first storage tank, a gap being defined therebetween for the flow of aqua-ammonia vapor between said first and second storage tanks, an annular ammonia storage volume being defined between sidewalls of said first and second storage tanks;
- a pump system communicating with the storage tank system, the generator unit, and the absorption unit, wherein the pump system comprises a first pump disposed between the generator unit and the first storage tank and a second pump disposed between the absorption unit and the second storage tank; and
- a solar panel communicating with the pump system.
16. (canceled)
17. The absorption cooling system according to claim 15, wherein the generator unit further comprises:
- a case having a lower portion, an upper portion, a first side, and a second side opposite the first side;
- a heated fluid inlet and a heated fluid outlet extending from the lower portion of the case;
- a solar collector communicating with the heated fluid inlet and the heated fluid outlet of the generator case;
- a first plurality of heat exchange tubes disposed in the lower portion of the case, the heat exchanges tubes being in a sinusoidal path between the heated fluid inlet and the heated fluid outlet;
- a second plurality of heat exchange tubes disposed in a sinusoidal path in the upper portion of the case;
- a header disposed in the second side of the case, the header having a plurality of return tubes communicating with the lower portion of the case, the header further communicating with the second plurality of heat exchange tubes;
- a vapor chamber disposed above the second plurality of heat exchange tubes;
- a rectifier and dephlegmator disposed within the vapor chamber about the second plurality of heat exchange tubes; and
- at least one vapor outlet extending from the upper portion of the case.
18. The absorption cooling system according to claim 15, wherein the evaporator unit comprises:
- an evaporator tank;
- a plurality of coolant tubes disposed in a sinusoidal array within the evaporator tank;
- a fluid inlet disposed in the evaporator tank;
- a flotation control valve disposed in the evaporator tank, at the fluid inlet; and
- a fluid outlet disposed in the evaporator tank.
19. The absorption cooling system according to claim 15, wherein the absorption unit comprises:
- a closed case having a first end and a second end opposite the first end;
- a plurality of airflow tubes disposed through the case, the airflow tubes extending from the first end to the second end;
- an airflow fan disposed in the second end of the case, the airflow fan selectively drawing air through the airflow tubes;
- a vapor inlet tube extending from the case;
- a fluid inlet tube extending from the case; and
- a fluid outlet tube extending from the case.
20. The absorption cooling system according to claim 15, further comprising aqua-ammonia fluid selectively circulating within the generator unit, the absorption unit, the condenser unit, the evaporator unit, the storage tank system, and the pump system.
Type: Application
Filed: Mar 18, 2013
Publication Date: Sep 18, 2014
Applicant:
Inventors: SEID AHMED MOHAMMED SAID (DHAHRAN), MAGED AHMED EL-SHAARAWI (DHAHRAN), MUHAMMAD UMAR SIDDIQUI (DHAHRAN)
Application Number: 13/846,797
International Classification: F25B 15/00 (20060101);