Abstract:
The present invention provides an air-conditioning system capable of continuous heating operation over an outdoor temperature range of 20 degree to negative 40 degree Celsius. The present invention utilizes at least two sets of the evaporators capable of cross-reverse refrigerant circulation and cross-air defrosting process, which alternately generates the heat energy required for the defrosting process and the air-conditioning, and said air-conditioning system can apply a combination of the two defrost methods to raise overall heating efficiency.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a forced-air-defrost type air-conditioning system, more particularly to a cross-reverse type air-conditioning system capable of the cross-reverse defrosting process and the cross-air defrosting process. 
         [0002]    The present invention can be applied on residential, agriculture, and industrial purposes. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention is a divisional application of the patent application No. 20070137238 filed on Dec. 20, 2005, entitled “Multi-range cross defrosting heat pump system and humidity control system.” 
         [0004]    Current available heat pump requires different types of compressors for different range of working environment temperature; therefore, the user may need to install multiple air-conditioning systems such as a combination of a heat pump and a gas heater for different range of working temperature. One of the reasons is the low efficiency of the heat pump under low working temperature; another reason is the need for interrupting operation due to the frost conditions on evaporators. 
         [0005]    The current defrosting methods such as electrical defrost system and reverse-circulation defrost system require the heat pump to stop operation while defrosting. Therefore, it is one objective of the present invention to provide an air-condition heat pump capable of uninterrupted operation during system defrosting process. 
         [0006]    Another objective of the present invention is to provide the most efficient control methods for cross defrosting heat pump system under different temperature and humidity conditions; most heat pumps require the heat energy from other source to maintain the heating efficiency while the present invention defrosts with the heat energy absorbed from the environment and the heat energy generated by the compressor. 
         [0007]    Current compressors have very low efficiency under low temperature range, the current two-stage compressors utilize two compression strokes to increase system efficiency, however, the current two-stage compressors can not operate under different temperature range, in other words, the two-stage compressor can not operate under the environment that does not require pressure boosting; therefore it is another objective of the present invention to provide a multi-stage pressure boosting heat pump system capable of adjusting the level of pressure boosting in order to operate under a wide range of working environment temperature. 
         [0008]    In general, current heat pump system has very limited range of working temperatures due to the limitation and the operation efficiency of the compressor; however, in many circumstances, the environment temperature may vary from negative 40 degree to 20 degree Celsius, therefore it is main objective of the present invention to provide a multi-range cross defrosting heat pump capable of operating under a wide range of working environment temperature at high efficiency. 
       SUMMARY OF THE INVENTION 
       [0009]    1. It is the primary objective of the present invention to provide a cross-reverse type air-conditioning system capable of defrosting with cross-reverse refrigerant circulation and cross-air defrosting process. 
         [0010]    2. It is the secondary objective of the present invention to provide the control method for the cross-reverse type air-conditioning system to prevent the evaporators from malfunctioning. 
         [0011]    3. It is the third objective of the present invention to provide a cross-reverse type air-conditioning system capable for frost-prevention over an outdoor temperature range 20 degree Celsius to negative 40 degree Celsius. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1A  to  FIG. 1I  are the illustrative diagrams of the cross-reverse type air-conditioning system. The control logic table of cross-reverse type air-conditioning system is provided in Table. 1 as a reference to  FIG. 1A  to  FIG. 1E . 
           [0013]      FIG. 1F  is an exemplary construction scheme of the cross-reverse type air-conditioning system utilizing rotary valves. 
           [0014]      FIG. 1H  and  FIG. 1J  are construction schemes of the cross-reverse type air-conditioning system utilizing more than two evaporators. 
           [0015]      FIG. 1I  is another possible modified construction scheme based on the cross-reverse type air-conditioning system. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    The first embodiment of present invention is shown in  FIG. 1A  to  FIG. 1F  and the table 1 is used as a reference to understand the control method of the present invention. As shown in the table 1, the present invention includes a combination of the two defrosting methods, the first defrosting method can be applied to the operation environment where the outdoor temperature is from 20 degree Celsius to 0 degree Celsius, the second defrosting method can be applied to the operation environment where the outdoor temperature is from 10 degree to negative 40 degree Celsius; the threshold of switching the system from the first defrosting method to the second defrosting method can be adjusted according to the operating condition. However, for the ease of comprehension, the following embodiments will be explained with a threshold of 5 degree Celsius for the system to switch from the first defrosting method to the second defrosting method. 
         [0017]    Now referring to  FIG. 1A  and the table 1, the cross-reverse type air-conditioning system comprising the following basic components: main compressor  101 , main condenser  102 , first evaporator  121 , second evaporator  122 , main expansion valve  103 , first upper-flow control valve  131 , second upper-flow control valve  132 , first lower-flow control valve  171 , second lower-flow control valve  172 , first reverse-flow control valve  151 , second reverse-flow control valve  152 , first expansion valve  141 , second expansion valve  142 , first one-way valve  161 , second one-way valve  162 , first venting fan (not shown), second venting fan (not shown), separate insulation means (not shown) for each evaporator. 
         [0018]    Now referring to  FIG. 1A  for the full capacity heating operation of the cross-reverse type air-conditioning system; the refrigerant-flow of the first evaporator  121  and the refrigerant-flow of the second evaporator  122  are enabled, so that both the first evaporator  121  and the second evaporator  122  are absorbing the heat from the outdoor-air-flow for the evaporating process therein; the first upper-flow control valve  131  and the first lower-flow control valve  171  are open to enable the refrigerant-flow of the first evaporator  121 ; the second upper-flow control valve  132  and the second lower-flow control valve  172  are open to enable the refrigerant flow of the second evaporator  122 ; all the control valves for cross-reverse refrigerant circulation are shut to disable the hot refrigerant flow from the main compressor  101  to the first evaporator  121  and the second evaporator  122 ; the first reverse-flow control valve  151  and second reverse-flow control valve  152  are shut. The refrigerant in said two evaporators absorbs heat from the outdoor-air-flow and next, the evaporated refrigerant is pressurized in main compressor  101 , and next the main condenser  102  releases the heat energy for the air-conditioning. 
         [0019]    Now referring to  FIG. 1B  and  FIG. 1C  for the first defrosting method of the cross-reverse type air-conditioning system, said first defrosting method can also be called as cross-air defrosting process; when the first defrosting method is employed, said system operates with a defrost-cycle which is depending on the outdoor temperature and the humidity. An exemplary defrost-cycle is provided as follow; the first evaporator  121  and the second evaporator  122  operate with the evaporation process for 5 minutes as shown in  FIG. 1A , and next the first evaporator  121  defrosts with the first defrosting method as shown in  FIG. 1B , and next the second evaporator  122  defrosts with the first defrosting method as shown in  FIG. 1C , and then said system repeats the defrost-cycle until further change in the outdoor temperature is detected. 
         [0020]    As shown in  FIG. 1B , the first evaporator is defrosting with the first defrosting method; the refrigerant flow of the first evaporator  121  is disabled by the first upper-flow control valve  131  and first lower-flow control valve  171 , the first venting fan will operate at full speed to draw the outdoor air through the first evaporator  121  to melt the frost thereon; the second evaporator  122  will continue the evaporation process to provide a sufficient refrigerant flow to the main compressor  101 , the main condenser  102  will continue to generate the heat energy required for the air-conditioning. 
         [0021]    As shown in  FIG. 1C , the second evaporator is defrosting with the first defrosting method, the refrigerant flow of the second evaporator  122  is disabled by the second upper-flow control valve  132  and the second lower-flow control valve  172 , the second venting fan will operate at full speed to draw the outdoor air through the second evaporator  122  to melt the frost thereon; the first evaporator  121  will continue the evaporation process to provide a sufficient refrigerant flow to the main compressor  101 , the main condenser  102  will continue to generate the heat energy required for the air-conditioning. 
         [0022]    When the outdoor temperature reaches the threshold, at which the first defrosting method cannot provide enough heat energy with the outdoor air, the system can switch to the second defrosting method as shown in  FIG. 1D  and  FIG. 1E , and said second defrosting method is also called as the cross-reverse defrosting process. The cross-reverse defrosting process also operate in a similar defrost-cycle as the first defrosting method, an exemplary defrost-cycle is provided as follows; the first evaporator  121  and the second evaporator  122  together operate to generate heat energy as shown in  FIG. 1A  for 10 minute, and next the first evaporator  121  defrosts with the cross-reverse defrosting process as shown in  FIG. 1D  for 3 minute, and next the second evaporator  122  defrosts with the cross-reverse defrosting process as shown in  FIG. 1E  for 3 minute, and next the system repeats the cycle until further change in the outdoor environment is detected. 
         [0023]    As shown in  FIG. 1D , the first evaporator  121  is defrosting with the second defrosting method, the cross-reverse defrosting process; the first evaporator  121  will stop the evaporation process and disable the refrigerant-flow from the main expansion valve  103  by shutting the first upper-flow control valve  131  and first lower-flow control valve  171 . The cross-reverse refrigerant circulation will be initiated by opening the first reverse-flow control valve  151 , providing a refrigerant passage from the main compressor  101  to the first evaporator  121 , so the pressurized refrigerant from the discharge port of the main compressor  101  will now flow to the main condenser  102  and the first evaporator  121 ; said pressurized refrigerant will condense in the first evaporator  121  to heat up and melt the accumulated ice on the first evaporator  121 , and said refrigerant-flow of the first evaporator  121  will exit through the first expansion valve  141  and the first one-way valve into the second evaporator  122 ; the second evaporator  122  will now receive both the refrigerant-flow from the main expansion valve  103  and the refrigerant-flow from the first one-way valve  161 ; in other words, the main condenser  102  and the first evaporator  121  will be condensing refrigerant to generate heat energy for the air-conditioning and the cross-reverse defrosting process respectively, while the second evaporator  122  will be evaporating the refrigerant by absorbing the heat from the outdoor-air-flow; the first venting fan will stop or spin slowly to conserve the heat energy in the first evaporator  121 , the second venting fan will be operating at full speed to provide a sufficient flow of the outdoor air for the evaporating process of the second evaporator  122 . 
         [0024]    As shown in  FIG. 1E , the second evaporator  122  is defrosting with the second defrosting method, the cross-reverse defrosting process; the second evaporator  122  will stop the evaporation process and disable the refrigerant-flow from the main expansion valve  103  by shutting the second upper-flow control valve  132  and second lower-flow control valve  172 . The cross-reverse refrigerant circulation will be initiated by opening the second reverse-flow control valve  152 , providing a refrigerant passage from the main compressor  101  to the second evaporator  122 , so the pressurized refrigerant from the discharge port of the main compressor  101  will now flow to the main condenser  102  and the second evaporator  122 ; said pressurized refrigerant will condense in the second evaporator  122  to heat up and melt the accumulated ice on the second evaporator  122 , and said refrigerant-flow of the second evaporator  122  will exit through the second expansion valve  142  and the second one-way valve  162  into the first evaporator  121 ; the first evaporator  121  will now receive both the refrigerant-flow from the main expansion valve  103  and the refrigerant-flow from the second one-way valve  162 ; in other words, the main condenser  102  and the second evaporator  122  will be condensing refrigerant to generate heat energy for the air-conditioning and the cross-reverse defrosting process respectively, while the first evaporator  121  will be evaporating refrigerant by absorbing the heat from the outdoor-air-flow; the first venting fan will stop or spin slow to conserve the heat energy in the second evaporator  122 , the first venting fan will be operating at full speed to provide a sufficient flow of the outdoor air for the evaporating process of the first evaporator  121 . 
         [0025]    Under the operating condition where the outdoor temperature is below 0 degree Celsius, the cross-reverse type air-conditioning system has to continue the cross-reverse refrigerant circulation at an appropriate time interval to prevent any of the evaporators from being completely frosted; in order to maximize the efficiency of heat absorption, the cross-reverse defrosting air-condition system can employed more than 2 evaporators for reducing the time required for each defrosting process intervals; in other words, for a cross-reverse type air-conditioning system with three evaporators, the first evaporator will defrost with the cross-reverse defrosting process while the second evaporator and the third evaporator are continuing the evaporating process for a time interval, and next the second evaporator will defrost with the cross-reverse defrosting process while the first evaporator and the third evaporator are continuing the evaporating process for a time interval, and next the third evaporator will defrost with the cross-reverse defrosting process while the first evaporator and the second evaporator are continuing the evaporating process for a time interval. Various time schedule can be used to maximize the heating efficiency of the present invention, however, it should be noted that the time interval for switching between the defrosting process of each evaporator should not be overestimated to cause all the evaporators being heavily frosted at the same time because the present invention is mostly used in the cold region, and the malfunction of the indoor heating can be fatal for the residential use in the crucial weather. 
         [0026]    A construction scheme is shown in  FIG. 1H  for the cross-reverse type air-conditioning system with more than two evaporators. When each evaporator is defrosting with first defrosting method, that evaporator stops its refrigerant-flow by shutting its associated upper-flow control valve and lower-flow control valve, and its associated venting fan is operating at full speed to defrost with the outdoor-air-flow. A construction scheme is shown in  FIG. 1.J  for the cross-reverse type air-conditioning system with four evaporators and the cross-reverse refrigerant circuit. 
         [0027]    When each evaporator is defrosting with second defrosting method, its associated upper-flow control valve and lower-flow control valve are shut, and its reverse-flow control valve is open to provide direct passage between that evaporator and discharge port of the main compressor; its associated venting fan will stop or spin slowly to conserve the heat within the heat insulated space of that evaporator. The second defrosting method utilizes the heat absorbed from the other evaporators and the heat generated from the main compressor to melt the ice on the evaporator that is defrosting. 
         [0028]    An exemplary defrost-cycle is provide for the cross-reverse type air-conditioning system with 3 evaporators; all evaporators are evaporating refrigerant at full capacity for 5 minutes, then the first evaporator defrosts for 5 minute, and next the second evaporator defrosts for 5 minute, and next the third evaporator defrosts for 5 minutes, thus completed one cycle and the system will detect if the outdoor temperature has raised or decreased over the threshold for switching to another defrost method. 
         [0029]    For easier maintenance, most control valves can be combined into one single rotary valve or other multi-port control valve means. A control valve construction scheme of the cross-reverse type air-conditioning system with rotary valves is provided in  FIG. 1F , wherein first reverse-flow control valve  151  and first upper-flow control valve  131  are replaced with first rotary upper-flow control valve  131  capable of same functions, first lower-flow control valve  171  and first one-way valve  161  can be replaced with first rotary lower-flow control valve  171  capable of same functions. Another construction scheme is provided in  FIG. 1I , wherein the pressurized refrigerant enters the defrosting evaporator from the discharge port of the defrosting evaporator during the cross-reverse defrosting process. Many other construction schemes and control valve means are possible to perform the same task based on the present invention and should be considered within the scope of the present invention. 
         [0030]    The system can also further employ a defrosting process sensor means to detect if the evaporator has melted all the ice thereon, if no further defrosting is required, the system will reset to the next step of the defrost-cycle. The defrosting process sensor means can be a refrigerant pressure or refrigerant temperature sensor. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Control logics of Cross-reverse type air-conditioning system 
               
             
          
           
               
                   
                   
                 Full capacity 
                 Cross-air defrosting 
                 Cross-air defrosting 
                 Cross-reverse defrosting 
                 Cross-reverse defrosting 
               
               
                   
                   
                 Heating 
                 process of 
                 process of 
                 process of 
                 process of 
               
               
                 Label 
                 Component Name 
                 Operation 
                 First evaporator 
                 Second evaporator 
                 First evaporator 
                 Second evaporator 
               
               
                   
               
               
                 102 
                 Main condenser 
                 Condensation 
                 Condensation 
                 Condensation 
                 Condensation 
                 Condensation 
               
               
                   
                   
                 Process 
                 Process 
                 Process 
                 Process 
                 Process 
               
               
                 121 
                 First evaporator 
                 Evaporation 
                 Defrosting with 
                 Evaporation 
                 Cross Reverse 
                 Evaporation 
               
               
                   
                   
                 Process 
                 Outdoor-air-flow 
                 Process 
                 Defrosting 
                 Process 
               
               
                   
                   
                   
                 (no refrigerant flow) 
               
               
                 122 
                 Second evaporator 
                 Evaporation 
                 Evaporation 
                 Defrosting with 
                 Evaporation 
                 Cross Reverse 
               
               
                   
                   
                 Process 
                 Process 
                 Outdoor-air-flow 
                 Process 
                 Defrosting 
               
               
                   
                   
                   
                   
                 (no refrigerant flow) 
               
               
                 151 
                 First reverse-flow 
                 Closed 
                 Closed 
                 Closed 
                 Open 
                 Closed 
               
               
                   
                 control valve 
               
               
                 152 
                 Second reverse-flow 
                 Closed 
                 Closed 
                 Closed 
                 Closed 
                 Open 
               
               
                   
                 control valve 
               
               
                 131 
                 First upper-flow 
                 Open 
                 Closed 
                 Open 
                 Closed 
                 Open 
               
               
                   
                 control valve 
               
               
                 171 
                 First lower-flow 
                 Open 
                 NA 
                 Open 
                 Closed 
                 Open 
               
               
                   
                 control valve 
                   
                 (preferably closed) 
               
               
                 132 
                 Second upper-flow 
                 Open 
                 Open 
                 Closed 
                 Open 
                 Closed 
               
               
                   
                 control valve 
               
               
                 172 
                 Second lower-flow 
                 Open 
                 Open 
                 NA 
                 Open 
                 Closed 
               
               
                   
                 control valve 
                   
                   
                 (preferably closed) 
               
               
                   
                 First venting fan 
                 Full speed 
                 Full speed 
                 Full speed 
                 Decreasing speed 
                 Full speed 
               
               
                   
                 Second venting fan 
                 Full speed 
                 Full speed 
                 Full speed 
                 Full speed 
                 Decreasing speed