Abstract:
The present invention provides an air-condition heat pump system and two-stage defrosting control method for continuous operation under an environment temperature range from 20 degree to negative 40 degree Celsius or lower. The heat pump system employs different defrosting methods under different temperature and humidity conditions. A ventilation and humidity control system is also provided for implementing the cross defrosting heat pump system within an indoor dimension.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a multi-range air-condition heat pump, more particularly to a multi-range air-condition heat pump capable of uninterrupted operation. The present invention can be applied on residential, agriculture, commercial transportation, and industrial purposes. More particularly, the present invention can be used for air-conditioning, refrigeration. 
   BACKGROUND OF THE INVENTION 
   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. 
   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. 
   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. 
   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. 
   Current ventilation and humidity control systems can not fully utilize the heat energy in the indoor air exhaust; therefore it is yet another objective to provide a ventilation and humidity control system to combine with the multi-range cross defrosting heat pump systems of the present invention. The ventilation and humidity control system recycles the heat energy from the indoor exhaust and adjusts the ventilation rate according to the humidity percentage. For the human comfort in most indoor space, the ventilation rate required is directly proportional to the humidity percentage, the ventilation and humidity control system of the present invention raises the ventilation rate by automatically adjusting the defrosting duration, since the multi-range cross defrosting heat pump system of the present invention requires more defrosting time when the humidity percentage of the working environment is high. 
   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 
   1. It is a primary object of the present invention to provide a multi-range cross defrosting heat pump system capable of operating under various range of temperature. 
   2. It is a second object of the present invention to provide a multi-range cross defrosting heat pump system capable of uninterrupted continuous operation during defrosting process. 
   3. It is another object of the present invention to provide the most efficient defrosting control method for the multi-range cross defrosting heat pump system which is capable of defrosting with the heat energy absorbed from the environment and the heat energy generated from the compressor, therefore minimizing the energy required for defrosting process. 
   4. It is yet another object of the present invention to provide a ventilation and humidity control system that can combine and fully utilize the multi-range cross defrosting heat pump of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  to  FIG. 1E  shows the first embodiment of the present invention, which is the multi-range cross-defrosting humidity control system constructed of the cross-reverse refrigerant circulation; the control logic table is provided in Table. 1 as a reference to  FIG. 1A  to  FIG. 1E . 
       FIG. 1A  is an operation scheme of the first embodiment, in which all the evaporators are evaporating the refrigerant therein. 
       FIG. 1B  and  FIG. 1C  are the operation schemes of the first defrosting method, which is also called as the cross-air defrosting process. 
       FIG. 1D  and  FIG. 1E  are the operation schemes of the second defrosting method, which is also called as the high speed cross reverse defrosting process. 
       FIG. 2A  to  FIG. 2E  shows the second embodiment of present invention, which is the multi-range cross-defrosting humidity control system constructed of the one-body defrost condenser; the control logic table is provided in Table. 2 as a reference to  FIG. 2A  to  FIG. 2E . 
       FIG. 2A  is an operation scheme of the second embodiment, in which all the evaporators are evaporating the refrigerant therein. 
       FIG. 2B  and  FIG. 2C  are the operation schemes of the first defrosting method, which is also called as the cross-air defrosting process. 
       FIG. 2D  and  FIG. 2E  are the operation schemes of the second defrosting method, which is also called as the high speed cross defrosting process. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention includes two main embodiments, the first embodiment is the multi-range cross-defrosting humidity control system constructed with the cross reverse refrigerant circulation, the second embodiment is the multi-range cross-defrosting humidity control system constructed with the one-body defrost condenser. 
   Now referring to  FIG. 1A  to  FIG. 1E  and Table 1 for the first embodiment: 
   The basic operation scheme is shown in  FIG. 1A  to  FIG. 1E , the multi-range cross-defrosting humidity control system operates with a control system that change the defrosting methods according to the outdoor temperature and humidity; when the outdoor temperature is in the range of 20 degree Celsius to 0 degree Celsius, the control system can apply the first defrosting method, which is also called as the cross-air defrosting process; when the outdoor temperature is in the range of 10 degree to negative 40 degree or lower, the control system can apply the second defrosting method, which is also called as the high speed cross-reverse defrosting process; the threshold at which the control system switch between the first defrosting method and the second defrosting method can be adjust at any point between 10 degree Celsius to 0 degree Celsius; for the ease of comprehension, the threshold will be set as 5 degree Celsius, it should be understood that this threshold value should be adjusted according to the heating need and the humidity of the outdoor environment for the best heating efficiency and the indoor humidity control. 
   As shown in  FIG. 1A , the cross reverse defrosting humidity control 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 valve  131 , second upper-flow valve  132 , first lower-flow valve  171 , second lower-flow valve  172 , first reverse-flow valve  151 , second reverse-flow valve  152 , first expansion valve  141 , second expansion valve  142 , first one-way valve  161 , second one-way valve  162 , first venting fan  191 , second venting fan  192 , separate heat insulation for each evaporator, first indoor-air-intake fan  181 , second indoor-air-intake fan  182 , first outdoor-air-intake valve  195 , second outdoor-air-intake valve  196 , first indoor-air-intake valve  181 , second indoor-air-intake valve  182 , first temperature sensor  193 , second temperature sensor  194 , outdoor temperature sensor (not shown). 
   The basic concept of the cross-air defrosting process is to block the refrigerant-flow of the frosted evaporator, and a controlled amount of the outdoor air will flow through that frosted evaporator to heat up the frost thereon, while the other evaporator will operate with the evaporation process to provide the evaporated refrigerant to the main compressor  101  for the pressurization process, the main condenser  102  will carry on the condensation process for the air-conditioning; the cross-air defrosting process requires a defrost-cycle of alternating operation, a defrost cycle is provided as follows, the first evaporator  121  defrosts with cross-air defrosting process for 5 minute as in  FIG. 1B , and next the second evaporator  122  defrosts with the cross-air defrosting process for 5 minute as in  FIG. 1C , and next the first evaporator  121  and the second evaporator  122  all resume the evaporation process for 10 minute as in  FIG. 1A , and next the control system repeats the defrost cycle or switch to another defrosting method if a change in the outdoor temperature is detected. 
   Now referring to  FIG. 1A , in which the first evaporator  121  and the second evaporator  122  are absorbing the heat from the outdoor-air-flow with the evaporation process; the cross reverse refrigerant circulation is disabled by shutting the first reverse-flow valve  151  and the second reverse-flow valve  152 ; now the refrigerant is circulating as follows, the refrigerant is pressurized in the main compressor  101  and condensed in the main condenser  102 , and next the first evaporator  121  and the second evaporator  122  will be evaporating refrigerant to provide the evaporated refrigerant to the main compressor  101 ; the first indoor-air-intake fan  181  and the second indoor-air-intake fan  182  are stopped to disable the indoor-air-flows of the first evaporator  121  and the second evaporator  122 ; the first outdoor-air-intake valve  131  and the second outdoor-air-intake valve  132  are open to admit the outdoor-air-flow into the first evaporator  121  and the second evaporator  122 . 
   Now referring to  FIG. 1B  and  FIG. 1C  for the first defrosting method of the cross reverse defrosting humidity control system, said first defrosting method is also called as the cross-air defrosting process; the control system can employ said cross-air defrosting process when the outdoor temperature is between 20 degree Celsius and 0 degree Celsius; during the defrost-cycle of the cross-air defrosting process, the control system will defrost each evaporator with a defrost cycle as follows; the first evaporator  121  defrosts with the cross-air defrosting process for 5 minute as shown in  FIG. 1B , and next the second evaporator  122  defrosts with the cross-air defrosting process for 5 minute as shown in  FIG. 1C , and next the first evaporator  121  and the second evaporator  122  will resume the evaporation process as shown in  FIG. 1A  or repeat the defrost-cycle if the condition required. 
   As shown in  FIG. 1B  is the cross-air defrosting process of the first evaporator  121 ; the refrigerant-flow of the first evaporator  121  is disabled by shutting the first upper-flow valve  131  and first lower-flow valve  171 , the first venting fan  191  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 operate with the evaporation process to provide a sufficient flow of evaporated refrigerant to the main compressor  101 , the main condenser  102  will continue to generate the heat energy required for the air-conditioning. 
   As shown in  FIG. 1C  is the cross-air defrosting process of the second evaporator  122 ; the refrigerant-flow of the second evaporator  122  is disabled by shutting the second upper-flow valve  132  and the second lower-flow valve  172 , the second venting fan  192  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 operate with the evaporation process to provide a sufficient flow of evaporated refrigerant to the main compressor  101 , the main condenser  102  will continue to generate the heat energy required for the air-conditioning. 
   Now referring to  FIG. 1D  and  FIG. 1E . When the outdoor temperature reaches the threshold, at which the cross-air defrosting method cannot provide enough heat energy with the outdoor air, the control 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 high speed cross reverse defrosting process, the applicable range of the high speed cross reverse defrosting process is from 10 degree Celsius to negative 40 degree Celsius and lower; the high speed cross reverse defrosting process also operates in a similar defrost-cycle as the first defrosting method, a defrost-cycle is provided as follows; the first evaporator  121  and the second evaporator  122  operate with the evaporation process to absorb the heat energy from the outdoor-air-flow as shown in  FIG. 1A  for 10 minute, and next the first evaporator  121  defrosts with the high speed cross reverse defrosting process as shown in  FIG. 1D  for 2 minute, and next the second evaporator  122  defrosts with the high speed cross reverse defrosting process as shown in  FIG. 1E  for 2 minute, and next the control system repeats the defrost-cycle until further change in the outdoor environment is detected. 
   The basic concept of the high speed cross reverse defrosting process is to transfer a controlled amount of the indoor air into the heat insulated space of the evaporator that is defrosting, and at the same time a controlled amount of the pressurized refrigerant will be distributed into the evaporator that is defrosting, the accumulated frost on said evaporator will melt by the heat generated from condensation process and the heat energy of the indoor air, therefore, the required time for the defrosting process will be greatly shortened, and the indoor air will be ventilated during this process; the other evaporator of the system will continue the evaporation process with the outdoor-air-flow, the main compressor and the main condenser will also continue their operations to generate the heat energy for the air-conditioning. The defrost-cycle of the high speed cross reverse defrosting process requires each evaporator to alternate its operation at a time interval, and the detailed control scheme is provide in  FIG. 1D  and  FIG. 1E . 
   As shown in  FIG. 1D , the first evaporator  121  is defrosting with the high speed cross reverse defrosting process; the first evaporator  121  will stop the evaporation process and disable the refrigerant passage from the main expansion valve  103  by shutting the first upper-flow valve  131  and first lower-flow valve  171 . The cross reverse refrigerant circulation will be initiated by opening the first reverse-flow valve  151 , providing a refrigerant passage from the main compressor  101  to the first evaporator  121 , so that the pressurized refrigerant from the main compressor  101  will now be distributed 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  161  into the second evaporator  122 ; the first outdoor-air-intake valve  195  will be shut to stop the outdoor-air-flow of the first evaporator  121 , the first venting fan  191  will stop or spin slowly to conserve the heat inside the heat insulated space of the first evaporator  121 , thus creating a hot environment inside the heat insulated space of the first evaporator  121 ; the first evaporator  121  will now be defrosting with the heat energy of the condensation process and the indoor-air-flow; the second evaporator  122  will 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 high speed cross reverse defrosting process respectively, while the second evaporator  122  will be operating with the evaporation process by absorbing the heat from the outdoor-air-flow; the second venting fan  192  will be operating at full speed to provide a sufficient flow of the outdoor air for the evaporating process of the second evaporator  122 . 
   As shown in  FIG. 1E , the second evaporator  122  is defrosting with the high speed cross reverse defrosting process; the second evaporator  122  will stop the evaporation process and disable the refrigerant passage from the main expansion valve  103  by shutting the second upper-flow valve  132  and second lower-flow valve  172 . The cross reverse refrigerant circulation will be initiated by opening the second reverse-flow valve  152 , providing a refrigerant passage from the main compressor  101  to the second evaporator  122 , so the pressurized refrigerant from the main compressor  101  will now be distributed 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 first evaporator  121 , 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 second outdoor-air-intake valve  196  will be shut to stop the outdoor-air-flow into the heat insulated space of the second evaporator  122 , the second venting fan  192  will stop or spin slowly to conserve the heat inside the heat insulated space of the second evaporator  122 , thus creating a hot environment inside the heat insulated space of the second evaporator  122 ; the second evaporator  122  will now be defrosting with the heat energy of the condensation process and the indoor-air-flow; the first evaporator  121  will 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 the heat energy for the air-conditioning and the high speed cross reverse defrosting process respectively, while the first evaporator  121  will be operating with the evaporation process by absorbing the heat from the outdoor-air-flow; the first venting fan  191  will be operating at full speed to provide a sufficient flow of the outdoor air for the evaporating process of the first evaporator  121 . 
   The first embodiment of the present invention can be further extended with additional evaporators. And the control system can adjust accordingly to the basic concept of the present invention; when one of the evaporators is frosted and requires to defrost with the second defrosting method, said frosted evaporator will block the refrigerant-flow from the main expansion valve and initiate the refrigerant-flow from the main compressor with its associated control valves, said frosted evaporator will initiate the condensation process with the pressurized refrigerant from the main compressor, and the heat insulated space of said frosted evaporator will block the flow of the outdoor air and admit a controlled amount of indoor air with its associated air-intake means, at the same time all other evaporators can continue the evaporation process to absorb heat energy from the outdoor-air-flow, the main compressor and the main condenser will continue their operation for the air-conditioning; the control system will also operate in a similar defrost-cycle, a defrost-cycle is as follows, all evaporators operate with the evaporation process for 10 minute, and next the first evaporator defrosts for 2 minute, next the second evaporator defrosts for 2 minute, and next the third evaporator defrosts for 2 minute, and next the fourth evaporator defrosts for 2 minute, and next the control system repeats the defrost-cycle or adjust its operation if further change in the outdoor temperature is detected. 
   For easier maintenance, most control valves can be combined into one single rotary valve or other multi-port control valve means. An alternative scheme of the control valve means is provided as follows, wherein the first reverse-flow valve  151  and the first upper-flow valve  131  are replaced with the first rotary upper-flow valve capable of same functions, the first lower-flow valve  171  and the first one-way valve  161  can be replaced with the first rotary lower-flow valve capable of same functions. 
   Many other construction schemes and control valve means are possible to perform the same task based on the principle of present invention and should be considered within the scope of the present invention. 
   Now referring to the second embodiment as shown in  FIG. 2A  to  FIG. 2E  for the multi-range cross-defrosting humidity control system constructed of the one-body defrost condenser. 
   The second embodiment also operate with a control system that changes the defrosting methods according to the outdoor temperature and humidity; when the outdoor temperature is in the range of 20 degree Celsius to 0 degree Celsius, the control system can apply the first defrosting method, which is also called as the cross-air defrosting process; when the outdoor temperature is in the range of 10 degree to negative 40 degree or lower, the control system can apply the second defrosting method, which is also called as the high speed cross-defrosting process; the threshold at which the control system switches between the cross-air defrosting process and the high speed cross-defrosting process can be adjust at any point between 10 degree Celsius to 0 degree Celsius. 
   The second embodiment as shown in  FIG. 2A , the cross-defrosting humidity control system comprising the following basic components: main compressor  201 , main condenser  202 , first evaporator  221 , second evaporator  222 , main expansion valve  203 , first upper-flow valve  231 , second upper-flow valve  232 , first defrost-flow valve  251 , second defrost-flow valve  252 , first expansion valve  241 , second expansion valve  242 , first defrost-condenser  223 , second defrost-condenser  224 , first venting fan  291 , second venting fan  292 , separate heat insulation for each evaporator, first indoor-air-intake fan  283 , second indoor-air-intake fan  284 , first outdoor-air-intake valve  295 , second outdoor-air-intake valve  296 , first indoor-air-intake valve  281 , second indoor-air-intake valve  282 , first temperature sensor  293 , second temperature sensor  294 , outdoor temperature sensor (not shown). 
   The first evaporator  221  and the first defrost-condenser  223  are constructed together to maximize the heat transfer rate between each other, therefore, the heat energy will be transfer from the first defrost-condenser  223  to the first evaporator  221  through the radiator fins they shared during the high speed cross defrosting process of the first evaporator  221 . 
   The second evaporator  222  and the second defrost-condenser  224  are also constructed together in the same manner for maximizing the heat transfer rate between each other. 
   Now referring to  FIG. 2A  for the full capacity heating operation when both the first evaporator  221  and second evaporator  222  are operating with the evaporation process; the refrigerant-flow of the first evaporator  221  and the refrigerant-flow of the second evaporator  222  are enabled by opening the first upper-flow valve  231  and second upper-flow valve  232 ; the refrigerant circuits for the high speed cross-defrosting process are disabled by shutting the first defrost-flow valve  251  and the second defrost-flow valve  252 ; the heat insulated space of the first evaporator  221  and the second evaporator  222  will block the indoor-air-flow and admit the outdoor-air-flow for absorbing heat, the first indoor-air-intake fan  283  and the second indoor-air-intake fan  284  will be disabled to block the indoor-air-flow into the first evaporator  221  and the second evaporator  222 , the first outdoor-air-intake valve  295  and the second outdoor-air-intake valve  296  will be open, the first venting fan  291  and the second venting fan  292  will be operating to draw the outdoor-air-flow into the heat insulated space of the first evaporator  221  and the heat insulated space of the second evaporator  222 ; the main compressor  201  and the main condenser  202  will be operating with the pressurization process and the condensation process respectively to provide the heat energy for the air-conditioning. 
   Now referring to  FIG. 2B  and  FIG. 2C  for the cross-air defrosting process of the second embodiment; the control system can employ said cross-air defrosting process when the outdoor temperature is between 20 degree Celsius and 0 degree Celsius; during the defrost-cycle of the cross-air defrosting process, the control system will defrost each evaporator with a defrost-cycle as follows; the first evaporator  221  defrosts with the cross-air defrosting process for 5 minute as shown in  FIG. 2B , and next the second evaporator  222  defrosts with the cross-air defrosting process for 5 minute as shown in  FIG. 2C , and next the first evaporator  221  and the second evaporator  222  will resume the evaporation process as shown in  FIG. 2A  or repeat the defrost-cycle if the condition required. 
   As shown in  FIG. 2B , the first evaporator  221  is defrosting with the cross-air defrosting process; the refrigerant-flow of the first evaporator is disabled by shutting the first upper-flow valve  231 , the outdoor-air-flow will be drawn into the heat insulated space of the first evaporator  221 , and the frost on the first evaporator  221  will melt by the absorbing the heat energy of the outdoor-air-flow; the second evaporator  222  will operate with the evaporation process to provide the evaporated refrigerant to the main compressor  201 ; the main compressor  201  and the main condenser  202  will continue the pressurization process and the condensation process respectively for the air-conditioning; the refrigerant circuits for the high speed cross-defrosting process are disabled by shutting the first defrost-flow valve  251  and the second defrost-flow valve  252 . 
   As shown in  FIG. 2C , the second evaporator  222  is defrosting with the cross-air defrosting process; the refrigerant flow of the second evaporator  222  is disabled by shutting the second upper-flow valve  232 , the outdoor-air-flow will be drawn into the heat insulated space of the second evaporator  222 , and the frost on the second evaporator  222  will melt by the absorbing the heat energy of the outdoor-air-flow; the first evaporator  221  will operate with the evaporation process to provide the evaporated refrigerant to the main compressor  201 ; the main compressor  201  and the main condenser  202  will continue the pressurization process and the condensation process respectively for the air-conditioning; the refrigerant circuits for the high speed cross-defrosting process are disabled by shutting the first defrost-flow valve  251  and the second defrost-flow valve  252 . 
   Now referring to  FIG. 2D  and  FIG. 2E . When the outdoor temperature reaches the threshold for initiating the high speed cross defrosting process, the control system will operate with a defrost-cycle of the high speed cross defrosting process, a defrost-cycle is provided as follows; the first evaporator  221  and the second evaporator  222  operate with the evaporation process to absorb the heat energy from the outdoor-air-flow as shown in  FIG. 2A  for 10 minute, and next the first evaporator  221  defrosts with the high speed cross defrosting process as shown in  FIG. 2D  for 2 minute, and next the second evaporator  222  defrosts with the high speed cross defrosting process as shown in  FIG. 2E  for 2 minute, and next the system repeats the defrost-cycle until further change in the outdoor environment is detected. 
   The basic concept of the high speed cross defrosting process is to transfer a controlled amount of the indoor air into the heat insulated space of the evaporator that is defrosting, and at the same time a controlled amount of the pressurized refrigerant will be distributed into the defrost-condenser associated with the evaporator that is defrosting, the accumulated frost on said evaporator will melt by the heat current transferred from its associated defrost-condenser and the heat energy of the indoor air, therefore, the required time for the defrosting process will be greatly shortened, and the indoor air will be ventilated during this process; the other evaporator of the system will continue the evaporation process with the outdoor-air-flow, the main compressor and the main condenser will also continue their operation to generate the heat energy for the air-conditioning. The defrost-cycle of the high speed cross defrosting process requires each evaporator to alternate its operation at a time interval, and the detailed control scheme is provide in  FIG. 2D  and  FIG. 2E . 
   As shown in  FIG. 2D , the first evaporator  221  is defrosting with the high speed cross defrosting process; the first evaporator  221  will stop the evaporation process and disable the refrigerant passage from the main expansion valve  203  by shutting the first upper-flow valve  231 ; the first defrost-condenser  223  will be enabled by opening the first defrost-flow valve  251 , providing a refrigerant passage from the main compressor  201  to the first defrost-condenser  223 , so the pressurized refrigerant from the main compressor  201  will now be distributed to the main condenser  202  and the first defrost-condenser  223 ; said pressurized refrigerant will condense in the first defrost-condenser  223  to heat up and melt the accumulated frost on the first evaporator  221 , and said refrigerant-flow of the first defrost-condenser  223  will exit through the first expansion valve  241  into the second evaporator  222 ; the first outdoor-air-intake valve  295  will be shut to stop the outdoor-air-flow of the first evaporator  221 , the first venting fan  291  will stop or spin slowly to conserve the heat inside the heat insulated space of the first evaporator  221 , thus creating a hot environment inside the heat insulated space of the first evaporator  221 ; the first evaporator  221  will now be defrosting with the heat energy of the condensation process of the first defrost-condenser  223  and the indoor-air-flow; the second evaporator  222  will receive the refrigerant-flow from the main expansion valve  103  and the refrigerant-flow from the first expansion valve  241 ; in other words, the main condenser  202  and the first defrost-condenser  223  will be condensing refrigerant to generate heat energy for the air-conditioning and the high speed cross defrosting process respectively, while the second evaporator  222  will be operating with the evaporation process by absorbing the heat from the outdoor-air-flow; the second venting fan  292  will be operating at full speed to provide a sufficient flow of the outdoor air for the evaporating process of the second evaporator  222 ; the second defrost-condenser  224  is disabled by shutting the second defrost-flow valve  252 . 
   As shown in  FIG. 2E , the second evaporator  222  is defrosting with the high speed cross defrosting process; the second evaporator  222  will stop the evaporation process and disable the refrigerant passage from the main expansion valve  203  by shutting the second upper-flow valve  232 ; the second defrost-condenser  224  will be enabled by opening the second defrost-flow valve  252 , providing a refrigerant passage from the main compressor  201  to the second defrost-condenser  224 , so the pressurized refrigerant from the main compressor  201  will now be distributed to the main condenser  202  and the second defrost-condenser  224 ; said pressurized refrigerant will condense in the second defrost-condenser  224  to heat up and melt the accumulated frost on the second evaporator  222 , and said refrigerant-flow of the second defrost-condenser  224  will exit through the second expansion valve  242  into the first evaporator  221 ; the second outdoor-air-intake valve  296  will be shut to stop the outdoor-air-flow of the second evaporator  222 , the second venting fan  292  will stop or spin slowly to conserve the heat inside the heat insulated space of the second evaporator  222 , thus creating a hot environment inside the heat insulated space of the second evaporator  222 ; the second evaporator  222  will now be defrosting with the heat energy of the condensation process of the second defrost-condenser  224  and the indoor-air-flow; the first evaporator  221  will receive the refrigerant-flow from the main expansion valve  203  and the refrigerant-flow from the second expansion valve  242 ; in other words, the main condenser  202  and the second defrost-condenser  224  will be condensing refrigerant to generate heat energy for the air-conditioning and the high speed cross defrosting process respectively, while the first evaporator  221  will be operating with the evaporation process by absorbing the heat from the outdoor-air-flow; the first venting fan  291  will be operating at full speed to provide a sufficient flow of the outdoor air for the evaporating process of the first evaporator  221 ; the first defrost-condenser  223  is disabled by shutting the first defrost-flow valve  251 . 
   The second embodiment of the present invention can be further extended with additional evaporators and additional defrost-condensers, and the control system can adjust accordingly to the basic concept of the present invention; when one of the evaporators is frosted and requires to defrost with the high speed cross defrosting process, said frosted evaporator will block the refrigerant passage from the main expansion valve with its associated control valves, and the defrost-condenser associated with said frosted evaporator will initiate the refrigerant-flow from the main compressor with its associated control valves, said defrost condenser will initiate the condensation process with the pressurized refrigerant from the main compressor, and the heat insulated space of said frosted evaporator will block the flow of the outdoor air and admit a controlled amount of indoor air with its associated air-intake means, at the same time all other evaporators can continue the evaporation process to absorb heat energy from the outdoor-air-flow, the main compressor and the main condenser will continue their operation for the air-conditioning; the control system will also operate in a defrost-cycle, wherein each evaporator will take turns to operate with the high speed cross defrosting process, a defrost cycle is as follows, all evaporators operate with the evaporation process for 10 minute, and next the first evaporator defrosts for 2 minute, next the second evaporator defrosts for 2 minute, and next the third evaporator defrosts for 2 minute, and next the fourth evaporator defrosts for 2 minute, and next the control system repeats the defrost-cycle or adjust its operation if further change in the outdoor temperature is detected. 
   The control system can further employ the sensor means for the progress of the defrosting process to detect if the evaporator has melted all the frost thereon, if all the frost has melted, the control system can be reset to the next step of the defrost-cycle; said sensor means can be a pressure or temperature sensor in the evaporator. 
   A special ventilation operation mode can also be implanted in the control system as an additional function, said operation mode is called as the forced-ventilation mode, wherein a controlled amount of the outdoor-air-flow and a controlled amount of the indoor-air-flow are admitted into the evaporators that are operating with the evaporation process, therefore the indoor air will be drawn out of the indoor space for the ventilation purpose, while the heat insulated space of each evaporator will have an air flow of higher temperature, thus ventilating the indoor air with a high energy recovery rate. 
   It should be understood that the threshold temperatures for initiating each stage of defrosting are different for each regions in the world, wherein the humidity and frosting condition are the main factor for selecting the appropriate threshold for each defrosting method and operation mode. 
   
     
       
             
           
             
             
             
             
             
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               Control Logics of First Embodiment 
             
           
        
         
             
                 
                 
               All evaporators 
               Cross-air defrost 
               Cross-air defrost 
               Cross reverse 
               Cross reverse 
             
             
                 
                 
               operating at 
               process of 
               process of 
               defrost process of 
               defrost process of 
             
             
               Label 
               Component Name 
               full capacity 
               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 
               Evaporating 
               High speed 
               Evaporating 
             
             
                 
                 
               Process 
               Outdoor-air-flow 
               Process 
               cross reverse 
               Process 
             
             
                 
                 
                 
                 
                 
               Defrosting 
             
             
               122 
               Second evaporator 
               Evaporating 
               Evaporating 
               Defrosting with 
               Evaporating 
               High speed 
             
             
                 
                 
               Process 
               Process 
               Outdoor-air-flow 
               Process 
               cross reverse 
             
             
                 
                 
                 
                 
                 
                 
               Defrosting 
             
             
               151 
               First reverse-flow valve 
               Closed 
               Closed 
               Closed 
               Open 
               Closed 
             
             
               152 
               Second reverse-flow valve 
               Closed 
               Closed 
               Closed 
               Closed 
               Open 
             
             
               131 
               First upper-flow valve 
               Open 
               Closed 
               Open 
               Closed 
               Open 
             
             
               171 
               First lower-flow valve 
               Open 
               Closed 
               Open 
               Closed 
               Open 
             
             
               132 
               Second upper-flow valve 
               Open 
               Open 
               Closed 
               Open 
               Closed 
             
             
               172 
               Second lower-flow valve 
               Open 
               Open 
               Closed 
               Open 
               Closed 
             
             
               191 
               First venting fan 
               Full speed 
               Full speed 
               Full speed 
               Decreasing speed 
               Full speed 
             
             
               192 
               Second venting fan 
               Full speed 
               Full speed 
               Full speed 
               Full speed 
               Decreasing speed 
             
             
               183 
               First indoor-air-intake fan 
               Disabled 
               Disabled 
               Disabled 
               Operating at a 
               Disabled 
             
             
                 
                 
                 
                 
                 
               controlled speed 
             
             
               184 
               Second indoor-air-intake fan 
               Disabled 
               Disabled 
               Disabled 
               Disabled 
               Operating at a 
             
             
                 
                 
                 
                 
                 
                 
               controlled speed 
             
             
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
             
             
             
             
           
         
             
               TABLE 2 
             
           
           
             
                 
             
             
               Control Logics of Second Embodiment 
             
           
        
         
             
                 
                 
               All evaporators 
               Cross-air defrost 
               Cross-air defrost 
               Cross reverse 
               Cross reverse 
             
             
                 
                 
               operating at 
               process of 
               process of 
               defrost process of 
               defrost process of 
             
             
               Label 
               Component Name 
               full capacity 
               First evaporator 
               Second evaporator 
               First evaporator 
               Second evaporator 
             
             
                 
             
             
               202 
               Main condenser 
               Condensation 
               Condensation 
               Condensation 
               Condensation 
               Condensation 
             
             
                 
                 
               Process 
               Process 
               Process 
               Process 
               Process 
             
             
               221 
               First evaporator 
               Evaporation 
               Defrosting with 
               Evaporating 
               High speed 
               Evaporating 
             
             
                 
                 
               Process 
               Outdoor-air-flow 
               Process 
               Cross-Defrosting 
               Process 
             
             
               222 
               Second evaporator 
               Evaporating 
               Evaporating 
               Defrosting with 
               Evaporating 
               High speed 
             
             
                 
                 
               Process 
               Process 
               Outdoor-air-flow 
               Process 
               Cross-Defrosting 
             
             
               223 
               First defrost-condenser 
               Disabled 
               Disabled 
               Disabled 
               Condensation 
               Disabled 
             
             
                 
                 
                 
                 
                 
               Process 
             
             
               224 
               Second defrost-condenser 
               Disabled 
               Disabled 
               Disabled 
               Disabled 
               Condensation 
             
             
                 
                 
                 
                 
                 
                 
               Process 
             
             
               251 
               First defrost-flow valve 
               Closed 
               Closed 
               Closed 
               Open 
               Closed 
             
             
               252 
               Second defrost-flow valve 
               Closed 
               Closed 
               Closed 
               Closed 
               Open 
             
             
               231 
               First upper-flow valve 
               Open 
               Closed 
               Open 
               Closed 
               Open 
             
             
               232 
               Second upper-flow valve 
               Open 
               Open 
               Closed 
               Open 
               Closed 
             
             
               291 
               First venting fan 
               Full speed 
               Full speed 
               Full speed 
               Decreasing speed 
               Full speed 
             
             
               292 
               Second venting fan 
               Full speed 
               Full speed 
               Full speed 
               Full speed 
               Decreasing speed 
             
             
               283 
               First indoor-air-intake fan 
               Disabled 
               Disabled 
               Disabled 
               Operating at a 
               Disabled 
             
             
                 
                 
                 
                 
                 
               controlled speed 
             
             
               284 
               Second indoor-air-intake fan 
               Disabled 
               Disabled 
               Disabled 
               Disabled 
               Operating at a 
             
             
                 
                 
                 
                 
                 
                 
               controlled speed