Abstract:
A refrigeration process comprising: compressing low pressure vapor refrigerant to a higher temperature and pressure vapor, compressing low pressure vapor refrigerant to a higher temperature and pressure vapor, condensing the higher pressure vapor refrigerant into a liquid refrigerant at the higher pressure, thermally isolating the higher pressure liquid, cooling the thermally isolated liquid refrigerant while remaining thermally isolated and then allowing thermal contact of the remaining low temperature and pressure liquid and a cooled substance causing the low temperature and pressure liquid to further reversibly boil to a vapor at the low pressure.

Description:
This application claims the benefit of the following U.S. Provisional Patent Applications: Ser. No. 60/154,027, filed Sep. 16, 1999, and Ser. No. 60/168,335 filed Dec. 1, 1999. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention pertains to a novel liquid vapor refrigeration cycle which evaporates the liquid leaving the condenser by thermally isolating the liquid from energy loss during the evaporative cooling of the liquid as it is cooled below the condensing temperature. This allows a refrigerator to achieve efficiency greater than has been achieved in the past, and as a result of its greater efficiency it is also possible to achieve lower temperatures than before. 
   2. Description of the Related Art 
   Most prior art liquid-vapor refrigerant systems have attempted to eliminate the energy wasted during expansion of the liquid across an expansion valve by incorporating expansion engines, or have attempted to continuously remove the energy in the warm condensate liquid with an auxiliary refrigeration system which is continuously operating at a higher coefficient of performance. The expansion engines have the disadvantage that the expanded refrigerant must then be recompressed by the compressor at a lower COP (coefficient of performance). Mechanically sub-cooled systems have the added disadvantage that they have losses due to expansion valves and the heat exchanger. 
   U.S. Pat. No. 3,766,745 by inventor Lester K. Quick describes an invention that overcomes the need for a heat exchange to cool the warm liquid at a better COP (coefficient of performance). However, U.S. Pat. No. 3,766,745 still has the major disadvantage of prior art systems of irreversible free expansion into a tank and at the expansion valves, which causes the major inefficiency in the Quick invention and all other liquid vapor prior art systems. U.S. Pat. No. 3,766,745 also utilizes expansion valves at the evaporators, which also result in the irreversible free expansion of the refrigerant. This system allows energy exchange from the liquid being expanded and the liquid and gas molecules which have gone through the expansion. This means that the potential energy which is in the liquid is wasted by accelerating molecules randomly. This is a consequence of the liquid not being thermally isolated during the expansion process. 
   U.S. Pat. No. 4,014,182 by inventor Eric Granryd describes an invention, which contains an evaporator, a condenser, a compressor and a closed vessel which receives condensed refrigerant from the condenser. The vessel has outlets connected to the compressor and to the evaporator. Communication between the vessel and the compressor is established for a regulated period to lower the pressure in the vessel, causing the refrigerant therein to boil and cool. During most of this period, communication between the evaporator and the compressor is closed and thereafter is opened. This patent uses a batch process to cool the warm refrigerant. 
   U.S. Pat. No. 4,014,182 does address the problem of irreversibility at the expansion valve and offers a solution which, however, introduces several other irreversibilities, and hence inefficiencies, into the system that have not been previously recognized. One of the irreversibilities introduced by Granryd comes about in the vessel, which contains the evaporating refrigerant. The refrigerant is placed in the vessel and refrigerated. As it cools, it also cools the walls of the vessel. When the cool liquid is ejected and the next batch of warm liquid is placed into the vessel, the vessel is at a low temperature and the energy from the warm liquid flows from the refrigerant into the walls. Thus, the previous liquid cooling cycle was used to remove part of the energy in the injected warm liquid refrigerant at a lower COP than would be possible if the transfer of energy from the vessel walls had not taken place. Since the cost of removing the energy at the end of the cycle is the greatest, this means that the portion of the cycle, which would benefit the most from this approach, is actually costing the most. Also, some of the vapor from the condenser condenses on the cool walls of the vessel, which actually adds more heat load to the refrigeration system; this is also an additional irreversible process. Thus, if appreciable energy exchange is allowed to take place between the liquid and the cooling vessel surroundings, the process is made more irreversible and thus more inefficient. It is therefore, important to minimize the relative amount of energy which is transferred in and out of the liquid before, during, and after the liquid cooling process, as is disclosed in the present invention. 
   In the current invention the liquid is allowed to expand reversibly by evaporative cooling in a container from which the liquid is thermally isolated. The cool liquid is then delivered to the evaporator for cooling the cooled substance without the need of an expansion throttling valve, or the pressure reducing device of U.S. Pat. No. 3,766,745, or the heat exchangers used in sub-cooling systems. 
   Thermally isolative cooling process is the process of minimizing energy flow from the condensate liquid during the period which it is cooled in a cooling vessel. This means that the amount of energy flowing to or from the liquid as the result of contact with its surroundings, per unit mass of refrigerant circulated, should be small during this process in order to obtain a high efficiency. 
   The problem of losing energy from the liquid when it enters the liquid cooling container because the cooler is cold from the previous cycle was not recognized by Granryd in U.S. Pat. No. 4,014,182. Neither was the problem of vapor entering the cooling vessel from the condenser and condensing on the cool walls of the cooling vessel, thereby adding energy to the cycle and causing the compressor to remove more energy than a conventional refrigeration cycle. Therefore, the solution of providing a thermally isolated inner surface for the liquid cooling container, which would isolate the liquid thermally from the cooling vessel and limit the energy exchanged with the liquid, was not proposed by Granryd. Granryd did propose the use of insulation on the tank but did not teach the use of thermal isolation of the liquid within the container, i.e., the liquid has to be thermally isolated against the flow of energy to or from the cooling vessel during the reversible process of evaporation. If it is not thermally isolated the process will not be reversible and, thus, be more inefficient. 
   One embodiment of the current invention solves the problems presented by the Granryd patent by replacing the liquid cooling vessel with a container, which thermally isolates the liquid refrigerant from its surroundings during the liquid cooling process. This eliminates the irreversible free expansion that has taken place in most prior art systems and replaces it with a reversible expansion process, which achieves a larger efficiency. It also eliminates the irreversible transfer of energy from the liquid to the surroundings by thermally isolating the liquid from the container by using a thermally non-conducting liner. Irreversible expansion which was present in U.S. Pat. No. 4,014,182 due to the thermal conduction between the vessel used to expand the refrigerant and the refrigerant is eliminated in the current invention. The current invention also eliminates the problem in U.S. Pat. No. 4,014,182 of vapor condensation on the cool walls of the cooling vessel, which took place during part of the cycle. 
   Tests on a system constructed in accordance with U.S. Pat. No. 4,014,182 indicate that the operational cost of a system constructed in this way will exceed the cost of operation of a conventional refrigeration system which is equipped with an expansion valve. This could explain why such a system has not achieved commercial success in the 22 years since the issuance of U.S. Pat. No. 4,014,182. The current invention demonstrates the solution to a long felt need by discovering and solving the problems of inefficiency in refrigeration systems, which have gone unrecognized for those 22 years. 
   The current invention also solves the problem of moving the liquid from the condenser to the liquid cooling container and then to the evaporator. This problem was not recognized previously, and therefore, no solutions exist to this problem in the prior art. 
   Finally, the problem of irreversibility at the expansion valve in a liquid vapor system has not been solved successfully prior to this invention. A common attempt in the past to overcome the inefficiency due to the irreversible nature of the expansion through the expansion valve has been to utilize the energy that is lost by running an engine with the wasted energy. The solution utilized in the current invention offers greater efficiency than can be achieved by the expansion engine solution because it is a more reversible process, because the use of an expansion engine still requires that the gas used for expansion must still be compressed by the compressor. This means that the inefficiency of the engine is magnified by inefficiency of the compressor resulting in an efficiency less than the current invention. 

   
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       FIG. 1  is a schematic of refrigeration system deploying adiabatic cooling of the liquid refrigerant. ..\Drawings\Novel Refrigeration Cycle.cdr 
   

   SUMMARY OF THE INVENTION 
   The current invention is a refrigeration process which utilizes a reversible adiabatic liquid cooling process. This is done by eliminating the free expansion at the expansion valve in a closed loop liquid vapor system, and replaces it with a thermally isolative cooling process which is the process of minimizing energy flow from the condensate liquid during the period which it is cooled in a cooling vessel. 
   
     
       
             
           
             
             
           
             
             
           
         
             
                 
             
             
               Table of Numbers 
             
           
        
         
             
               Number 
               Description 
             
             
                 
             
           
        
         
             
               10 
               Compressor 
             
             
               20 
               Discharge line from compressor 
             
             
               30 
               condenser 
             
             
               40 
               Condenser fan 
             
             
               50 
               Condenser air temperature sensor 
             
             
               60 
               Line connecting condenser and receiver 
             
             
               70 
               Receiver (liquid reservoir) 
             
             
               80 
               Liquid level sensor in the receiver 
             
             
               90 
               Pressure transducer on the liquid tube leaving the receiver 
             
             
               100 
               Solenoid valve on the liquid tube leaving the receiver 
             
             
               120 
               Supply tube to liquid cooler 
             
             
               130 
               Liquid tube temperature sensor 
             
             
               140 
               Liquid cooler container 
             
             
               141 
               Thermally isolating Inner liner of liquid cooler container 
             
             
               150 
               Liquid level sensor in the liquid cooler 
             
             
               160 
               Tube connecting suction solenoid 170 and liquid cooler 
             
             
                 
               container 140 
             
             
               161 
               Tube connecting suction solenoid 170 and suction tube 
             
             
                 
               280 
             
             
               170 
               Suction solenoid for liquid cooler container 
             
             
               180 
               Solenoid check valve leaving the liquid cooler 
             
             
               181 
               Liquid tube leaving the liquid cooler 
             
             
               190 
               Temperature sensor on the liquid cooler 
             
             
               200 
               Liquid tube connecting liquid cooler to evaporator metering 
             
             
                 
               valve 
             
             
               210 
               Liquid metering valve 
             
             
               215 
               Tube connecting evaporator metering valve and evaporator 
             
             
               216 
               Liquid metering tube 
             
             
               217 
               evaporator inlet temperature sensor 
             
             
               220 
               Evaporator 
             
             
               230 
               Evaporator fan 
             
             
               240 
               Refrigerator air temperature sensor 
             
             
               260 
               Evaporator outlet temperature 
             
             
               270 
               Suction 1 way valve from evaporator 
             
             
               280 
               Suction tube 
             
             
               290 
               Suction pressure transducer 
             
             
               380 
               Suction temperature transducer 
             
             
               390 
               Tube from high pressure to supply solenoid 400 
             
             
               400 
               Liquid cooler container pressurization feed line solenoid 
             
             
               410 
               Liquid cooler container pressurization feed line 
             
             
               420 
               Pressure transducer for liquid cooler container 
             
             
               430 
               Air passing over the condenser 
             
             
               440 
               Refrigerator air circulated over the evaporator 
             
             
               450 
               Refrigerated area 
             
             
               500 
               Micro-processor controller 
             
             
               510 
               Micro-processor controller outputs 
             
             
               520 
               Micro-processor controller inputs 
             
             
                 
             
           
        
       
     
   
                                         Table of Elements                                    Compressor   10           Condenser   30           Liquid cooler container Pressurization           Liquid cooler Liquid level sensor   150           Means for filling liquid cooler   500, 510, 520, 150           Pressurization means   410, 400, 390, 170, 100,           Receiver liquid level sensor   80           Thermally isolative cooling container   140           Thermally isolative liner   141                        
Objectives and Advantages
 
   
     
       
             
           
             
             
           
         
             
                 
             
             
               Table of Functions, purposes, objectives, goals, tasks 
             
           
        
         
             
               Objectives 
               Solution 
             
             
                 
             
             
               Save Energy 
               Thermally isolate the condensate liquid 
             
             
               By achieving adiabatic 
               during cooling (expansion) of condensate 
             
             
               expansion in a refrigeration 
               liquid 
             
             
               system 140, 141 
               Contain Thermally isolated liquid during 
             
             
                 
               cooling of the liquid 
             
             
               Save additional energy 
               turn off fans during the liquid cooling phase 
             
             
               500, 510, 520, 230 
               of adiabatic expansion 
             
             
               Achieve lower 
               Contain thermally isolated liquid during 
             
             
               temperatures in a 
               cooling of the liquid 
             
             
               refrigeration system by 
             
             
               achieving adiabatic 
             
             
               expansion 140, 141 
             
             
               Achieve lower 
               turn off fans during the liquid cooling phase 
             
             
               temperatures in a 
               of adiabatic expansion 
             
             
               refrigeration system by 
             
             
               achieving adiabatic 
             
             
               expansion 140, 141 
             
             
                 
             
           
        
       
     
   
   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a schematic of a refrigeration system operating with a single compressor and single evaporator which utilizes one embodiment of the current invention of the reversible adiabatic liquid cooling process. This is done by introducing a control system and a separate thermal isolated vessel within which the liquid is evaporatively cooled, and from which the liquid is thermally isolated, thus eliminating the major portion of the irreversible free expansion at the expansion valve in a closed loop liquid vapor system. The process implemented and controlled by a micro-controller  500  with inputs  520  taken from transducers and outputs  510  used to operate motors, solenoids and other output type functions. Multiple or mixed refrigerants may be used without deviating from the invention. 
   Compressing: In  FIG. 1  micro-controller  500  turns on compressor  10  through outputs  510  which compresses low pressure vapor entering from vapor tube  280  to a high pressure vapor and transmits it to the condenser  30  through high pressure vapor tube  20 . Temperature sensor  380  and pressure sensor  380  provide information to micro-controller  500  through inputs  520 . Micro-controller  500  turns off compressor  10  when the pressure at pressure transducer  290  or the temperature at temperature transducer  240  falls below preset values or determines that liquid exists at temperature probe  380  or pressure transducer  290 . Various types of compressors may be added in parallel or series without deviating from the invention. 
   Condensing: The high temperature and pressure vapor is cooled and condensed in condenser  30  by the circulation of cooler ambient air by a fan  40 . Temperature sensors  50 ,  130  and pressure sensors  90  and  290  are used to provide the temperature and pressure information to micro-controller  500  through inputs  520 . The pressure at pressure transducer  90  is maintained by micro-controller  500  at a pressure 20 psi greater than the pressure at pressure transducer  290  by increasing the speed of fan  40  if the pressure differential is greater than 20 psi and decreasing the speed if the pressure differential is less than 20 psi. The liquid condensed by condenser  30  is transmitted through tube  60  to a liquid receiver tank  70 . A liquid level sensor  80  supplies information to inputs  520  of micro-controller  500  which determines the amount of liquid in receiver tank  70 . Liquid tubes and  120 ,  90 , and solenoid valve  100  are used to transport liquid from receiver tank  70  to the liquid cooling container  140  which thermally isolates the liquid with a thermally non-conductive inner liner  141 . 
   Thermally Isolative cooling process: One of the novel and key features of this invention is the reversible expansion of the condensed liquid. Reversible expansion is the evaporation of the liquid with minimal transfer of energy between the surroundings and the liquid or the vapor to which the liquid is being expanded. The micro-controller  500  checks the pressure in liquid cooler  140  and in the receiver  70  to determine whether the pressure is lower in the liquid cooler by comparing the difference in pressure transducers  90  and  420 . If the liquid cooler is not at a pressure lower than in the receiver, the pressure in the cooler is lowered by momentarily opening valve  170 . When it is determined that the pressure in the liquid cooler is lower than in the receiver, liquid is transferred into the liquid cooling container  140  in a reversible way (i.e., without the transfer of energy to or from the liquid), through open solenoid valve  100  and liquid tubes  90  and  120  until such time as the level reaches a preset level detected by liquid level switch  150 . The liquid cooling container  140  contains a thermo-isolative inner lining  141  which prevents energy transfer from the liquid to or from the walls of the liquid cooling container  140 . Valves  180 ,  170  and  400  remain closed until the preset level is reached. When micro-controller  500  determines the preset level is reached, the liquid cooling phase begins which allows the energy to be removed from the liquid at the highest COP (coefficient of performance) possible by evaporating the thermally isolated liquid. Valves  180  and  100  are closed and valve  170  is opened by the outputs  520  of micro-controller  500  allowing suction of compressor  10  on the liquid cooling container  140 , which results in evaporation of the liquid at a rapid rate. Valve  400  remains closed by micro-controller  500  and vapor is passed from tube  160  through valve  170 , and through tube  161  to tube  280 , and then to the suction side of compressor  10 . At this point, check valve  270  becomes reverse biased and does not pass vapor from tube  250  into tube  280 . 
   Since the liquid cooling container  140  has a thermo-isolative liner  141  on its inside walls, neither the liquid cooling container nor the thermo-isolative liner  141  give up or take in appreciable energy as the container  140  receives liquid which is alternately heated and cooled by the process. This allows the liquid to be expanded in a manner, which is more reversible than described in U.S. Pat. No. 4,014,182. Multiple containers with thermo-isolative liners may be used to expand the liquid, which would allow the continuous supply of liquid to evaporators. The inventor is also defining the term thermo-isolative to mean that only small amounts of energy are transferred. 
   In this embodiment the liquid is being thermally isolated from its surroundings by providing a thermo-isolative lining inside the liquid cooling container. It is also possible to incorporate the invention in other embodiments, which will only transfer small amounts of energy from the liquid to its surroundings during the cooling of the liquid. This is accomplished by thermally isolating the liquid by isolating means and the scope of this invention is intended to cover the methods of transferring minimal amounts of energy to and from the liquid or resulting vapor during the cooling of the liquid. In another embodiment the entire liquid cooling container  140  would be made out of a material of low thermal conductivity, such as epoxy. Yet another possible embodiment would be to create a vapor barrier between a thin conductive lining and the vessel. 
   In another embodiment the thermally isolative cooling process may also be done by decreasing the time in which the liquid is cooled. If the liquid is in contact with the surface of a container for only a short amount of time, then the amount of energy lost to the container could be small per unit of refrigerant mass circulated, and would satisfy the inventor&#39;s definition of a thermo-isolative process. 
   In another embodiment the thermally isolative cooling process may be done by a separate evaporative system which would indirectly cool the liquid with a heat exchanger. This system would be designed to transfer only a small amount of energy to or from the liquid and the separate heat exchanger or other heat exchange mediums at times other than when the liquid is cooled. Although a system practicing the current invention with a separate evaporator and system would not have the efficiency of the first embodiment described, it would be a considerable improvement over prior art systems. These systems would fall under the inventor&#39;s definition of “thermally isolating the liquid during the liquid cooling phase”. 
   Compressing the liquid from the liquid cooling container  140 : Compressor  10  may be of constant speed or of the variable speed type. Under variable speed operation, the speed may be initially reduced by micro-controller  500  since the volumetric efficiency is greatly increased during the first part of the liquid cooling cycle, and then increased toward the end of the cooling cycle. Alternatively, the compressor speed my be set by micro-controller  500  through one of the outputs  510  to achieve the maximum power, such that it is controlled to slower speeds when the liquid cooling cycle is first started and faster speeds as the liquid cooling cycle approaches the temperature of evaporator  220 . It is also possible to achieve a similar benefit by using unloaders to reduce the load on a compressor during the first part of the cycle. This would achieve a further benefit of not overloading the compressor during the period which low compression ratios are present on the compressor. 
   Transfer of Liquid to the cooling evaporator: When micro-controller  500  determines that the pressure and temperature of the liquid in the liquid cooling container  140  approach either a preset point, or the temperature and pressure of evaporator cooling coil  220  the cool liquid is transferred into evaporator cooling coil  220 . This is accomplished by pressurizing container  140  with high pressure vapor from the high pressure receive tank  70 . Micro-controller  500  opens valve  400  and high pressure vapor travels through tube  390 , valve  400  and restricted tube  410 . Tube  410  is restricted since it is not desirable to have pressurization by large volumes of vapor, which would increase the amount of condensing in liquid cooling container  140  during this phase of the cycle. The cold liquid is then transferred through tube  181 , valve  180 , tube  200 , metering valve  210 , tube  215 , and restriction tube  216  into cooling evaporator  220 . Receivers tanks before and/or after the liquid cooler container  140  may also be used to even the flow from the condenser and to the evaporator. 
   Evaporate liquid in cooling evaporator: Micro-controller  500  allows the liquid to enter evaporator coil  220  through metering valve  210  until the amount of liquid is sufficient to provide cooling at a low pressure/low temperature in order to cool the ambient air  440  circulated by fan  230  which is also controlled by micro-controller  500 . It is at this point that all prior art systems have incorporated free irreversible expansion by expanding the liquid at a high pressure and or temperature through an expansion valve. The current invention minimizes this loss by expanding the liquid in a reversible manner rather than the irreversible free expansion across an expansion valve. Temperature sensor  260  is used by micro-controller  500  to determine the degree of superheat leaving evaporator cooling coil  220 . If the superheat decreases at the outlet of evaporator cooling coil  220  towards zero, micro-controller  500 , through metering valve  210 , decreases the amount of liquid flowing into the evaporator cooling coil  220 . Conversely, if the superheat increases above a desirable value, metering valve  210  increases the amount of liquid flowing into the evaporator. Fan  230  may be cycled off during the liquid cooling phase if a single compressor is being used to compress the refrigerant from the liquid cooler and the evaporator. Fan  230  may also be cycled off when the temperature is adequate and the compressor is cycled off. The cycling of fan  230  saves energy by initially not consuming the energy and also by not having to remove that energy from the system cooled by the evaporator. It should be noted that multiple evaporators may be added in parallel or series. It is possible in some embodiments that the cooling evaporator function is done by the liquid cooler, i.e., the substance being cooled is brought into thermal contact with the liquid in the liquid cooler after the liquid has been cooled. 
   Compress vapor from the cooling evaporator: During the filling of the liquid cooling container  140  check valve  270  is forward biased and compressor  10  is receiving gas refrigerant through tube  250  from evaporator cooling coil  220  and compressing it into line  20 . During the liquid cooling phase in the liquid cooling container  140  the check valve  270  is reverse biased and there is no flow through tube  250  because the pressure in tube  280  is above the pressure in tube  250 . During the evaporator cooling phase, check valve  270  is also forward biased and compressor  10  receives vapor from the evaporator coil  220 . 
   It should be obvious to someone skilled in the art that multiple evaporators may be used to refrigerate in different areas. It should also be obvious to someone skilled in the art that the invention may have more than one compressor and that the compressors may be piped in a way that allows independent suction and compression of the evaporation from the liquid cooling container  140  and the evaporators cooling coil.