Air conditioner and control method thereof

Abstract

Disclosed herein is a water-source heat-pump type air conditioner in which a receiver is connected to a super-cooler or economizer, and a control method of the air conditioner to reduce the quantity of liquid refrigerant collected in the receiver during a cooling/heating overload operation. When a cooling/heating overload operation occurs, an electric expansion valve associated with the super-cooler or the economizer is opened by a predetermined opening degree, to bypass high-pressure liquid refrigerant collected in the receiver, thereby preventing a rapid pressure increase due to a great quantity of liquid refrigerant collected in the receiver.

1 . An air conditioner, comprising:
 a compressor to compress refrigerant;   an outdoor heat exchanger to undergo heat exchange between the refrigerant and water;   a receiver to store a part of the refrigerant that has undergone heat exchange with the water in the outdoor heat exchanger, and to divide the stored refrigerant into gas, refrigerant and liquid refrigerant;   a sub heat exchanger to perform super-cooling of the liquid refrigerant separated from the receiver;   an electric expansion valve to bypass the liquid refrigerant separated from the receiver;   a pressure sensor to sense a pressure of refrigerant discharged from a high-pressure side of the compressor;   a temperature sensor to sense a temperature of the outdoor heat exchanger; and   a control unit to determine whether a cooling/heating overload operation occurs based on an operation capacity of the compressor, the pressure of refrigerant at the high-pressure side and the temperature of the outdoor heat exchanger, and to control an opening degree of the electric expansion valve to reduce the quantity of liquid refrigerant collected in the receiver during the cooling/heating overload operation.   
     
     
         2 . The air conditioner according to  claim 1 , wherein the compressor is a Pulse Width Modulation (PWM) type compressor, an operation capacity of which is adjusted according to a loading time for which refrigerant is compressed and an unloading time for which compression of refrigerant stops. 
     
     
         3 . The air conditioner according to  claim 1 , wherein the sub heat exchanger includes an economizer or super-cooler. 
     
     
         4 . The air conditioner according to  claim 3 , wherein the electric expansion valve is an Electronic Expansion Valve (EEV) usable with the economizer or the super-cooler. 
     
     
         5 . The air conditioner according to  claim 1 , wherein the pressure sensor is installed to a discharge pipe of the compressor to sense a high pressure. 
     
     
         6 . The air conditioner according to  claim 5 , wherein the temperature sensor is installed to a pipe provided at one side of the outdoor heat exchanger to sense a temperature of a heat exchange location of the refrigerant and the water. 
     
     
         7 . The air conditioner according to  claim 6 , wherein the outdoor heat exchanger functions as a condenser upon a cooling operation, and the temperature sensor senses an exit temperature of the condenser to measure a temperature of the water. 
     
     
         8 . The air conditioner according to  claim 6 , wherein the outdoor heat exchanger functions as an evaporator upon a heating operation, and the temperature sensor senses an entrance temperature of the evaporator to measure a temperature of the water. 
     
     
         9 . The air conditioner according to  claim 7 , wherein the control unit determines occurrence of the cooling overload operation if the operation capacity of the compressor is a predetermined capacity or more upon a cooling operation, the high pressure sensed by the pressure sensor is a first predetermined pressure or more and the exit temperature of the condenser sensed by the temperature sensor is a first predetermined temperature or more, and increases the opening degree of the electric expansion valve to bypass the liquid refrigerant inside the receiver to a low-pressure side of the compressor. 
     
     
         10 . The air conditioner according to  claim 9 , wherein the first predetermined pressure is about 30 kg/cm 2 G. 
     
     
         11 . The air conditioner according to  claim 9 , wherein the first predetermined temperature is about 42° C. 
     
     
         12 . The air conditioner according to  claim 8 , wherein the control unit determines occurrence of the heating overload operation if the operation capacity of the compressor is a predetermined capacity or more upon a heating operation, the high pressure sensed by the pressure sensor is a second predetermined pressure or more and the entrance temperature of the evaporator sensed by the temperature sensor is a second predetermined temperature or more, and increases the opening degree of the electric expansion valve to bypass the liquid refrigerant inside the receiver to a low-pressure side of the compressor. 
     
     
         13 . The air conditioner according to  claim 12 , wherein the second predetermined pressure is about 35 kg/cm 2 G. 
     
     
         14 . The air conditioner according to  claim 12 , wherein the second predetermined temperature is about 30° C. 
     
     
         15 . The air conditioner according to  claim 9 , wherein the control unit counters a bypass operation time for which the liquid refrigerant inside the receiver is bypassed to the low-pressure side through the electric expansion valve having the increased opening degree, and keeps the electric expansion valve at an original opening degree if the bypass operation time exceeds a predetermined time. 
     
     
         16 . The air conditioner according to  claim 9 , wherein the pressure sensor senses variation of the high pressure caused by bypassing the liquid refrigerant inside the receiver to the low-pressure side through the electric expansion valve having the increased opening degree, and the control unit keeps the electric expansion valve at an original opening degree if the varied pressure is a predetermined pressure or less. 
     
     
         17 . The air conditioner according to  claim 12 , wherein the control unit counters a bypass operation time for which the liquid refrigerant inside the receiver is bypassed to the low-pressure side through the electric expansion valve having the increased opening degree, and keeps the electric expansion valve at an original opening degree if the bypass operation time exceeds a predetermined time. 
     
     
         18 . The air conditioner according to  claim 12 , wherein the pressure sensor senses variation of the high pressure caused by bypassing the liquid refrigerant inside the receiver to the low-pressure side through the electric expansion valve having the increased opening degree, and the control unit keeps the electric expansion valve at an original opening degree if the varied pressure is a predetermined pressure or less. 
     
     
         19 . The air conditioner according to  claim 3 , further comprising:
 a solenoid valve is connected to a low-pressure pipe between the economizer and the accumulator and is opened or closed to introduce the heat-exchanged refrigerant from the economizer in the accumulator or the medium-pressure suction hole of the compressor;   when the solenoid valve is opened, the refrigerant discharged from the economizer is introduced into the accumulator having a relatively low pressure;   when the solenoid valve is closed, the refrigerant discharged from the economizer is introduced into the injection pipe connected to the medium-pressure suction hole of the compressor having a relatively high pressure.   
     
     
         20 . A control method of an air conditioner comprising a compressor to compress refrigerant, an outdoor heat exchanger to perform heat exchange between the refrigerant and water, a receiver to store a part of the heat-exchanged refrigerant to divide the stored refrigerant into gas refrigerant and liquid refrigerant, a sub heat exchanger to perform super-cooling of the liquid refrigerant and an electric expansion valve to bypass the liquid refrigerant, the control method comprising:
 sensing a pressure of refrigerant discharged from a high-pressure side of the compressor;   sensing a temperature of the outdoor heat exchanger;   determining whether a cooling/heating overload operation occurs based on an operation capacity of the compressor, the pressure of refrigerant at the high-pressure side and the temperature of the outdoor heat exchanger; and   bypassing the liquid refrigerant of the receiver to reduce the quantity of liquid refrigerant collected in the receiver during the cooling/heating overload operation.   
     
     
         21 . The control method according to  claim 20 , wherein the occurrence of the cooling overload operation is determined if the operation capacity of the compressor is a predetermined capacity or more upon a cooling operation, the pressure of refrigerant at the high-pressure side of the compressor is a first predetermined pressure or more and the temperature of the outdoor heat exchanger is a first predetermined temperature or more. 
     
     
         22 . The control method according to  claim 20 , wherein the occurrence of the heating overload operation is determined if the operation capacity of the compressor is a predetermined capacity or more upon a heating operation, the pressure of refrigerant at the high-pressure side of the compressor is a second predetermined pressure or more and the temperature of the outdoor heat exchanger is a second predetermined temperature or more. 
     
     
         23 . The control method according to  claim 20 , wherein the bypass of the liquid refrigerant inside the receiver includes opening the electric expansion valve by a predetermined opening degree to allow the liquid refrigerant inside the receiver to be bypassed to a low-pressure side of the compressor. 
     
     
         24 . The control method according to  claim 23 , further comprising:
 checking a bypass operation time for which the liquid refrigerant inside the receiver is bypassed to the low-pressure side through the electric expansion valve having a predetermined opening degree; and   keeping the electric expansion valve at an original opening degree if the bypass operation time exceeds a predetermined time.   
     
     
         25 . The control method according to  claim 23 , further comprising:
 sensing pressure variation of refrigerant at the high-pressure side caused by bypassing the liquid refrigerant inside the receiver to the low-pressure side through the electric expansion valve having a predetermined opening degree; and   keeping the electric expansion valve at an original opening degree if the sensed pressure at the high-pressure side is a predetermined pressure or less.