Abstract:
This invention relates to an airconditioning system which uses a plurality of absorption chiller-cells, for refrigerating an antifreeze fluid that is circulated through fan-coil units of an airconditioning system. The anti-freeze fluid passes through refrigerant evaporators in each cell structure in a consecutive order for lowering the temperature of the antifreeze fluid gradually. More particularly, it relates to an absorption chiller-cell system having a plurality of evaporators employing multi-refrigerant circulation circuits in an absorption cycle to produce sufficient refrigerant for the airconditioning system. The invention enables the physical size of the system to be relatively small, so that the system can replace conventional electric airconditioning units for home applications. In further aspects, this invention provides an airconditioning system which includes a plurality of absorption chiller-cells that produce various kinds of capacity of the system by combining more or less numbers of chiller-cells, the invention provides also an easier and simpler solution for maintenance or replacement of chiller-cells.

Description:
This is a continuation-In-Part of our copending patent application, Ser. No. 09/504,149 filed on Feb. 15, 2000. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to an airconditioning system utilizing a plurality of absorption chiller-cells for refrigerating a second coolant medium such as an anti-freeze solution to obtain a sufficient low temperature for the indoor fan-coil units of an airconditioning system, by circulating and exchanging heat of the second coolant medium gradually from the first absorption chiller-cell and through up to numbers of absorption chiller-cells in a consecutive order, for providing an accumulative chilling effect, to give more efficient and faster cooling. 
     Further the invention provides a method and apparatus for operating an absorption chiller-cell, utilizing an absorption refrigeration means which has a plurality of evaporator means. The apparatus employs multi-refrigerant circulation circuits in an absorption cycles so as to enable the physical size of the system to be smaller and the cooling capacity larger, when compared to existing absorption systems. This invention also provides an airconditioning system wherein absorption chiller-cells produce various different capacities by combining various numbers of chiller cells, chiller cells maintenance or replacement is easily accomplished. 
     Various systems have been devised before to make an airconditioning system utilizing an absorption refrigeration means. One known arrangement is to use water as the refrigerant and lithium bromide as the absorbent. However, this system is not suitable for home use due to its physical size and a complex construction required to solve the crystallization problem. There is also the risk of freezing due to the use of water as the refrigerant. 
     Another known airconditioning system uses a solution pair of ammonia as refrigerant and water absorbent. This system is relatively small compared to the system using LiBr (lithium bromide) and water, but still too big to replace the present electric airconditioning unit for home or apartment application. The main problem of the prior art absorption refrigeration cycle, is the technical difficulty in producing enough refrigerant at low temperature somewhat below that of the heat load with a small physical system. The prior art, including numerous patents and studies, is mainly concerned with the technology of improving the coefficient of performance (COP) of an absorption refrigeration system regardless of the physical size of the system. Conventional absorption refrigeration systems are not easily maintained or operated, and are therefore not adaptable for home applications. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide an airconditioning system utilizing an absorption refrigeration means having a plurality of absorption chiller-cell structures for chilling a sufficient quantity of an antifreeze solution to a sufficient low temperature for the fan-coil units of an airconditioning system. Another object is to provide a method and apparatus for operating an absorption refrigeration system having a plurality of evaporators that provide an improved cooling capacity with a limited physical size refrigeration system. Still another object is to provide an absorption refrigeration system having a reduced physical size whereby the system can replace the cooling unit of the conventional electric airconditioning system for home use. Still another object is to provide an air conditioning system which is capable of increasing or decreasing its cooling capacity by increasing or decreasing the number of chiller-cell units to produce various different airconditioning system capacities. Still another object is to provide an absorption airconditioning system which will be easier to maintain and repair. 
     The outstanding characteristic of the invention is that the refrigerating means comprises a plurality of absorption chiller-cell structures for refrigerating an antifreeze fluid to sufficient low temperature; the anti freeze fluid is circulated through each absorption chiller-cell in consecutive order, to produce enough refrigerant volume to meet the cooling capacity requirements of the air conditioning system. 
     Another outstanding characteristic of the invention is to provide an airconditioning system based on the diffusion absorption (DA) cycle by employing multi-refrigerant circulation circuits in an absorption cycle. The DA technology is based on the Platen-Muntecs cycle and is currently manufactured internationally for hotel room and recreational vehicle refrigerators. The unique features of the new technology are (1) it can be gas-fired with no electric input required and (2) machines based on a DA cycle are essentially silent. Until the present invention it was thought that the DA cycle should consist of one refrigerant loop circuit, one solution loop circuit and one gas loop circuit; the single loop arrangement is not suitable for airconditioning systems due to its poor cooling capacity. The present invention employs multiple loop technology, i.e. multiple evaporators and multiple condensers. 
     Another unique characteristic of the invention is the method of heat exchange between an antifreeze and each absorption chiller-cell, employing tube-in-tube principles to create a plural evaporator and associated heat exchanging chambers. The antifreeze solution exchanges heat with the evaporating refrigerant by flowing as a liquid film along the outside surface of each evaporator tube. The temperature and volume of the antifreeze solution is controlled by using multiple evaporators in parallel flow relation, and passing the antifreeze solution in serial fashion through separate heat exchangers associated with the respective evaporators, whereby the antifreeze solution is cooled in stages. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram of an absorption chiller-cell refrigeration system of the present invention. 
     FIG. 2 is a diagram of a double effect absorption chiller system of the present invention. 
     FIG. 3 is a diagram of an air conditioning system embodying the present invention. 
     FIG. 4 is a detailed schematic diagram of two evaporators arranged in parallel flow relation, according to the invention. Each evaporator has an associated heat exchanging chamber. 
     FIG. 5 is a detailed diagram of an embodiment of a heat exchange chamber of the invention in a consecutive order. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the preferred embodiment of the invention, the ammonia is the refrigerant and water is the absorbent. FIG. 1 shows a systematic diagram of the absorption refrigeration system in conformity with the invention. The absorption refrigeration system comprises a plurality of absorption chiller-cells  10 - 1 ,  10 - 2 ,  10 - 3 ,  10 -N. Each chiller-cell comprises Absorber means  11 , absorber vessel  12 , heating means  23 , plural generator means  13 - 1 ,  13 - 2 , with rectifier  14 - 1 ,  14 - 2 , plural condenser means  16 - 1 ,  16 - 2 , plural evaporators  17 - 1 ,  17 - 2 ,  17 - 3 ,  17 - 4 , with heat exchange chambers  18 - 1 ,  18 - 2 ,  18 - 3 ,  18 - 4 , for exchanging heat between the evaporator and antifreeze fluid flowing through the heat exchange chambers. A central processing unit  20  with thermo sensors  19 - 1 ,  19 - 2 ,  19 - 3 ,  19 - 4 , and heating control means  19 - 5  is employed to control the system. 
     Referring to FIG. 4 each heat exchange chamber comprises an evaporator tube  17 - 1 ,  17 - 2 , in a tube  13 - 1 ,  18 - 2  of a heat exchanger chamber which has a fluid inlet  20 - 1 ,  20 - 2 , a fluid outlet  21 - 1 ,  21 - 2 , and an antifreeze fluid flow path therebetween. In the preferred embodiment of the invention, this system uses a three component working fluid, consisting of the refrigerant (ammonia), the absorbent (water) and an auxiliary gas (hydrogen). The refrigerant serves as a transporting medium to carry energy from a-low temperature source to a high temperature sink. The water absorbs the refrigerant at low temperature and low partial pressure, and releases it at high temperature against high partial pressure. The auxiliary gas provides pressure equalization for working fluid between the condenser and evaporator. 
     The number of possible working fluid combinations is infinite, but in practice, the combination in wide commercial use is ammonia-water-hydrogen. Helium can also be used as the auxiliary gas, with a performance penalty. A thermodynamic representation of the invention is illustrated in FIG.  1 . The representative chiller-cell uses a single refrigeration cycle with multi-refrigerant circulation loop circuits that include generator means  13 - 1 ,  13 - 2 , and plural evaporators  17 - 1 ,  17 - 2 ,  17 - 3 ,  17 - 4  in the loop circuit. This arrangement results in a significantly increased cooling effect by cooling the anti freeze coolant in stages. This circuit produces the desired working temperature in each evaporator in a different manner than the prior absorption refrigeration concepts, resulting in a different relationship between the components in each refrigeration circuit. 
     The conventional diffusion absorption (DA) cycle has three fluid loop circuits, consisting of an ammonia loop circuit, a gas loop circuit and ammonia-water solution loop circuit. The ammonia loop circuit includes all the components, since ammonia circulates through all the components. Ammonia-Water solution circuit flows through the solution loop circuit, which includes the generator (bubble pump), absorber and solution heat exchanger, The auxiliary gas circulates through the gas loop circuit, which includes the evaporator, absorber and auxiliary gas heat exchanger. The conventional DA cycle has only one ammonia loop circuit employing only one evaporating means, so that the performance is limited and not enough to feed the cooling capacity of an airconditioning system. 
     The present invention configures multi-ammonia loop circuits at a DA cycle for feeding multi-evaporator means to produce enough ammonia vapor for operating a plurality of heat exchange chambers, i.e. by transferring heat to the evaporator tubes from an antifreeze solution that flows through the serially connected heat exchange chambers  18 - 1 ,  18 - 2 ,  18 - 3 ,  18 - 4  by a circulation pump. As shown in FIG. 1, a preferred absorption solution mixture (ammonia and water) and the auxiliary gas (hydrogen gas) are collected in the absorber vessel  12 . These are at sufficient pressure to condense ammonia at room temperature. When heat from the heating means  23  is supplied to the generator means  13 - 1 ,  13 - 2 , bubbles of ammonia gas are produced and rise. The vapor contains a small quantity of water vapor which can be removed by passing the mixed vapor through the rectifier tubes  14 - 1 ,  14 - 2 , by heat rejection. The small amount of water in the ammonia runs back and drains to the absorber vessel  12  through rectifiers, leaving the dry ammonia vapor to pass to the condensers  16 - 1 ,  16 - 2 . While the ammonia vapor passes into the finned condensers  16 - 1 ,  16 - 2 , air circulating over the fins of the condensers removes heat from ammonia vapor, which condenses into liquid ammonia. The ammonia flows through the evaporators  17 - 1 ,  17 - 2 ,  17 - 3 ,  17 - 4 ., to cool an anti-freeze solution flowing serially through heat exchangers  18 - 1 ,  18 - 2 ,  18 - 3  and  18 - 4 . 
     The evaporators are supplied with hydrogen, by tube  24 . The hydrogen passes across the surface of the ammonia and returns back into absorber vessel  12 , to lower the ammonia vapor pressure enough to allow the liquid ammonia to evaporate. The evaporation of the ammonia extracts heat from the evaporator tubes. This, in turn, extracts heat from the antifreeze fluid in the heat exchange chambers  18 - 1 ,  18 - 2 ,  13 - 3 ,  18 - 4 , lowering the temperature of the antifreeze fluid. The ammonia-rich gas mixture leaves the bottom of the evaporators  17 - 1 ,  17 - 2 ,  17 - 3 ,  17 - 4 , and passes down through the tube  25 - 1  to the absorber  11 . In the absorber  11 , the ammonia is absorbed from the gas by the liquid solution. The auxiliary gas, which is almost insoluble in the liquid is free to rise up from the top of the absorber  11  and pass into the evaporators  17 - 1 ,  17 - 2 ,  17 - 3 ,  17 - 4 , together with some residential ammonia vapor. The hydrogen and ammonia gas circulation loop is driven by natural convection, caused primarily by the large density differences associated with the ammonia fraction in the vapor. 
     The liquid circulation in the cycle is driven by the heat-powered bubble pump shown schematically in FIG.  1 . This cycle operates continuously as long as the tubes of the generator  13 - 1 ,  13 - 2 , means is heated. The thermostats  19 - 1 ,  19 - 2 ,  19 - 3 ,  19 - 4 , which control the heat source  19 - 5  through controller  20 , regulate the temperature of the antifreeze fluid. The antifreeze fluid is circulated from the first heat exchange chamber  18 - 1  of the first evaporator  17 - 1 , through the second heat exchange chamber  18 - 2  of the second evaporator  17 - 2 , through the third heat exchange chamber  18 - 3  in the third evaporator  17 - 3 , and finally through the fourth heat exchange chamber  13 - 4  of the fourth evaporator  17 - 4  by a pump, so that the fluid temperature is lowered gradually. 
     Ammonia-poor hydrogen enters into each of the evaporators, and the auxiliary gas atmosphere accommodates the partial pressure of the ammonia vapor in accordance with Dalton&#39;s law. As the ammonia evaporates into the hydrogen, the partial pressure of the ammonia gas rises, and the evaporation temperature also rises. Thus, the plural evaporators  17 - 1 ,  17 - 2 ,  17 - 3 ,  17 - 4  (employing a multi-refrigerant circulation circuit in an absorption cycle) significantly increases the cooling capacity for the airconditioning application, when compared to the prior art, which employs a single evaporator means in an absorption cycle. 
     According to the invention, the cooling capacity of each chiller-cell depends on the number of evaporators and the refrigerant loop circuit in an absorption cycle. Depending on cooling capacity needed for an appropriate temperature level, the system can adjust the number of chiller cells. If the air space to be cooled is small, for example, four chiller cells are available. Meanwhile, if the space to be cooled is large, more chiller cells can be used, to adjust the cooling capacity. 
     As shown schematically in FIG. 2, another useful embodiment of the invention comprises a first diffusion absorption refrigeration system (or circuit) that includes a multiple refrigerant generator  25 . The generator feeds heated refrigerant vapor through three tube systems in heat exchangers  27  and  29 . Each tube system supplies refrigerant to at least one evaporator and at least one condenser. Heat exchangers  27  and  29  act as refrigerant generators for a second absorption refrigeration system (or circuit). Refrigerant in the second circuit is heated by the tubes of the first heat exchanger  27  of the first diffusion absorption system after the refrigerant solution has been pre-heated by the tubes in the second heat exchanger  29 . 
     The second refrigeration circuit includes a condenser  16 - 1  and evaporator  17 - 1 . 
     The FIG. 2 system includes four evaporators  17 - 1 ,  17 - 2 ,  17 - 3 ,  17 - 4  that are individually supplied with liquid refrigerant from four condensers  16 - 1 ,  16 - 2 ,  16 - 3  and  16 - 4 . The evaporators are arranged in parallel flow relation for achieving a gradual staged cooling of the liquid coolant (antifreeze solution) flowing serially through the associated heat exchangers  18 - 1 ,  18 - 2 ,  18 - 3 ,  18 - 4 . 
     FIG. 3 illustrates schematically one embodiment of the invention which can be used either for cooling or heating. If it needs to be installed for both heating and cooling the room, an interceptive valve  109  and antifreeze heating means  108  can be linked to the IN/out pipe of the chiller-cell. When heating the room, an antifreeze supply pipe of each chiller-cell is turned off by interceptive valve  109 , while it turns on to operate a pump  105  to circulate the antifreeze, which is heated by heating means  108 . The heated fluid is pumped through fan-coil units  106 - 1 ,  106 - 2 , and  106 - 3 . 
     The antifreeze is employed as a second refrigerant of the system to protect its chiller-cell and heat exchange chambers against freezing in winter. The temperature and circulation speed of the antifreeze are controlled by a central processing unit  112 . When after-service is required, the servicing procedure is relatively-simple and doesn&#39;t require stopping all functions of the system because only the problemed chiller-cell needs to be replaced. 
     The invention, in overcoming all of the aforesaid draw-backs of the prior art, presents a new technology, with a small sized improved absorption refrigeration means having multi-evaporators to produce various kinds of capacity of absorption airconditioning systems by combining more or less numbers of small sized chiller-cell type cooling means, rather than a single type large sized Cooling means with a fixed cooling capacity. Further, the system provides a more efficient heat-transfer by circulating antifreeze to extract heat by the evaporation of the refrigerant, thereby lowering gradually the temperature and making a faster and more efficient staged cooling effect. Further, the cooling capacity can be adjusted by adding or subtracting chiller-cells. The foregoing description has been set forth merely to illustrate the invention and is not intended to be limiting. It is herein understood that although the present invention has been specifically disclosed with the preferred embodiments and examples, modifications and variations of the concepts of the described embodiments may be resorted to by those persons skilled in the art. Such modifications and variations are considered to be within the scope of the invention and the appended claims.