Refrigeration – Processes – Circulating external gas
Reexamination Certificate
1998-07-31
2002-08-06
Doerrler, William (Department: 3744)
Refrigeration
Processes
Circulating external gas
C062S305000, C062S476000, C062S502000
Reexamination Certificate
active
06427453
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to vapor-compression evaporative cooling systems that use water as a refrigerant in an open system, and in particular, to vapor-compression evaporative cooling systems capable of processing large volumetric flow rates of water vapor and removing noncondensibles from the system and to methods using such systems. This invention also relates to low-friction, positive-displacement compressors useful in such cooling systems and to means for removing noncondensibles from such cooling systems.
2. Description of the Background
Conventional vapor-compression air conditioning systems employ a working fluid such as chlorofluorocarbons (CFCs). Liquid CFC is introduced into a low-pressure heat exchanger where it absorbs heat at a low temperature and vaporizes. A compressor repressurizes the vapors that are introduced to a high-pressure heat exchanger where heat is rejected to the environment and the vapors condense. The condensate is reintroduced into the low-pressure heat exchanger, thus completing the cycle.
The use of CFCs raises two important environmental concerns. First, CFCs are stable enough to enter the stratosphere where they decompose to chlorine free radicals that catalyze the destruction of ozone. This is unfortunate because ozone absorbs ultraviolet radiation which damages DNA in plants and animals. Second, CFCs absorb infrared radiation which contributes to global warming.
Because CFCs cannot be released into the environment, they must be contained within the air conditioning system. The evaporator and condenser heat exchangers have a sizable temperature difference between the ambient environment and the working fluid (about 10 to 15° C.) which greatly reduces the Carnot efficiency. Further limiting the efficiency is the fact that the condenser rejects heat at the dry-bulb temperature. The wet-bulb temperature is generally about 5-30° C. less than the dry-bulb temperature. Thus, if heat were rejected at the wet-bulb temperature, the Carnot efficiency could be improved even more.
In addition, compressors used in conventional systems typically have compressing components that are in direct contact with each other. The close fit between components has heretofore been necessary to prevent blow-by of high-pressure compressed vapors. However, the friction resulting from the close contact between components reduces efficiency, creates heat and causes wear on the components.
Although the use of water in place of CFCs as the air-conditioning working fluid has been considered, proposed systems have been generally unworkable because the vapor density is very low requiring large volumes of water vapor to be compressed.
One study by the Thermal Storage Applications Research Center of the University of Wisconsin,
The Use of Water as a Refrigerant
, Report No. TSARC
92-1
, March 1992, studied the use of water as a refrigerant. This study concluded that for water-based air conditioning, positive displacement compressors are not suitable for use in such systems. Rather, only dynamic compressors are suitable.
Although “swamp cooler” air conditioners are employed in arid regions of the United States that have low wet-bulb temperatures, they have limited usefulness. In swamp coolers, ambient air is contacted with water which evaporates and cools the air. No external power is required other than for air-handling blowers. Unfortunately, these simple devices are restricted to regions of low humidity (e.g., Arizona, New Mexico) and are not suitable for many regions of the world. Further, although the air is cooler, it has increased humidity which can make the air feel “clammy.”
SUMMARY OF THE INVENTION
There is therefore a need for an environmentally friendly, efficient and economical means for air conditioning in all types of climates. The present invention overcomes the above noted deficiencies in the art by providing air conditioning systems that use water as the working fluid rather than CFCs, thus eliminating potential CFC emissions. These systems are not limited to regions of low humidity. The present invention is directed to cooling systems that are 1.7 to 3.9 times more efficient than conventional air conditioning systems and that have manufacturing costs less than, or competitive with, conventional air conditioning systems.
In addition, unlike the teachings of the literature, it has been discovered that high-volume, low-pressure positive displacement compressors can be utilized in cooling systems that use water as the working fluid. It has further been discovered that because of the relatively low pressures (i.e., 0.2-0.7 psia) in the compressors of the cooling systems of the present invention, the gaps between the compressing components can be comparatively large, and that such large gaps are not only acceptable, but actually can be beneficial from both an efficiency and wear standpoint. Because of the low friction, the novel compressors can be scaled up to the necessary size. For example, such a gap-containing, positive displacement compressor can process the 1400 ft
3
/min of low-pressure water vapor needed to produce 3 tons of cooling.
In addition, it has been discovered that water, with or without suitable wicking material, cat be used to fill the gaps between the components, and thereby create an effective, but low-friction seal between the compressing components. Thus, the present invention is also directed to novel positive displacement compressors which are useful in air conditioning systems using water as the working fluid. These compressors include novel compressors which are useful in the disclosed systems as well as in other applications. The present invention is also directed to novel pumps useful for removing noncondensibles from the disclosed cooling systems as well as in other applications. Finally, the present invention is directed to novel seals and mounting apparatus useful in the disclosed compressors.
In accordance with one embodiment of the present invention, a vapor-compression evaporative air conditioning system is provided that comprises: an evaporator; a room air contactor for directly exchanging heat between room air and a quantity of water from the evaporator; means for compressing a volume of water vapor, thereby creating a vacuum on the water in the evaporator, the means for compressing comprising a positive displacement compressor, the compressor comprising an inlet and an outlet, wherein low-pressure water vapors from the evaporator enter the inlet and compressed water vapors exit the outlet; a condenser for receiving the compressed water vapors; means for reducing a water content of the vapors exiting the condenser; means for removing noncondensibles from the condenser, and an ambient air contactor for directly exchanging heat between the ambient air and water from the condenser. The positive displacement compressor is preferably a low-friction compressor comprising at least two compressing components, which do not substantially contact one another. The advantages of this system include that it is an efficient low-friction system capable of functioning in humid environments.
The compressing components may comprise an inner gerotor, an outer gerotor and a housing; an orbiting (or mobile) scroll, a stationary (or fixed) scroll and a housing; a housing and a piston a housing, a rotor, and a flap; an inner drum, an outer drum and a swinging vane; or a housing, a rotor and a sliding vane. In a preferred embodiment there is a gap between at least two of the compressing components. Water or water and a wick may be used as a sealant in the gap.
In one embodiment of this system, the means for compressing water vapor comprises a gerotor compressor comprising an inner gerotor and an outer gerotor, the inner gerotor disposed within the outer gerotor, each gerotor comprising a plurality of teeth. The inner gerotor has one less tooth than the outer gerotor, thereby creating a void volume between the inner gerotor and the outer gerotor. An inlet port and a discharge port communicate with the
Davison Richard
Holtzapple Mark T.
Rabroker G. Andrew
Baker & Botts L.L.P.
Doerrler William
Shulman Mark
The Texas A&M University System
LandOfFree
Vapor-compression evaporative air conditioning systems and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vapor-compression evaporative air conditioning systems and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vapor-compression evaporative air conditioning systems and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2897712