Air-conditioning apparatus

Abstract

An air-conditioning apparatus includes a controller that has: a first determination value obtained by multiplying by a first constant, a time constant which is a response value required until heating and cooling capacity in refrigeration circulation in a refrigeration cycle circuit is stabilized, and which is a value at a rise of a waveform representing the heating and cooling capacity calculated from a measured value; and a second determination value obtained by multiplying the time constant by a second constant smaller than the first constant. The controller increases the lowest frequency for a subsequent operation of the compressor, when in the intermittent operation, an intermittent operation time from the start to stop of the compressor is longer than the first determination value, and deceases the lowest frequency for the above subsequent operation, when in the intermittent operation, the intermittent operation time is shorter than the second determination value.

1 . An air-conditioning apparatus comprising:
 a compressor configured to compress refrigerant;   a condenser configured to condense the refrigerant discharged from the compressor;   a pressure-reducing device configured to reduce a pressure of the refrigerant which flows from the condenser;
 an evaporator configured to evaporate the refrigerant decompressed by the pressure-reducing device; 
 a temperature sensor configured to measure a temperature of the refrigerant in the evaporator; and 
 a controller configured to control the compressor and the pressure-reducing device to cause a heating operation or a cooling operation to be performed, configured to cause an intermittent operation to be performed, the intermittent operation being an operation in which an operation of the compressor is stopped when a cooling load or a heating load decreases and the operation of the compressor is started when the cooling load or the heating load increases, and configured to cause, when the operation of the compressor is performed in the intermittent operation, the intermittent operation to be performed at a lowest frequency set as a lower limit frequency in a frequency range that is set for the operation of the compressor, 
 wherein the controller has
 a first determination value obtained by multiplying by a first constant set in advance, a time constant which is a response value which is a value in a time period required until a heating and cooling capacity in circulation of the refrigerant in a refrigeration cycle circuit is stabilized, and which is a value at a rise of a waveform representing the heating and cooling capacity calculated from a value measured by the temperature sensor, and 
 a second determination value obtained by multiplying the time constant by a second constant set in advance that is smaller than the first constant, and 
 
 wherein the controller is configured to increase the lowest frequency for a subsequent operation of the compressor, when in the intermittent operation, an intermittent operation time from a start of the operation of the compressor to a stop of the operation of the compressor is longer than the first determination value, and configured to decrease the lowest frequency for the subsequent operation of the compressor, when in the intermittent operation, the intermittent operation time is shorter than the second determination value. 
   
     
     
         2 . The air-conditioning apparatus of  claim 1 , wherein the controller is configured to compare, when the lowest frequency is increased, the lowest frequency in the intermittent operation with a maximum frequency at which an energy consumption efficiency increases to a maximum, and configured to set, when the lowest frequency is higher than the maximum frequency, the lowest frequency to a same value as the maximum frequency. 
     
     
         3 . The air-conditioning apparatus of  claim 1 , wherein the controller is configured to compare, when the lowest frequency is decreased, the lowest frequency in the intermittent operation with a lower limit frequency that is a minimum frequency required for operating the compressor, and configured to set, when the lowest frequency is lower than the lower limit frequency, the lowest frequency to a same value as the lower limit frequency. 
     
     
         4 . The air-conditioning apparatus of  claim 1 , further comprising an indoor suction temperature sensor configured to measure an indoor temperature in an air-conditioning target space in which the condenser or the evaporator is located,
 wherein   the controller is configured to determine that the cooling load increases, start the operation of the compressor, and start measurement of the intermittent operation, when in the intermittent operation in the cooling operation, the indoor temperature measured by the indoor suction temperature sensor is higher than a temperature obtained by adding a set value, which is a predetermined set range, to a set temperature for an indoor space, and   the controller is configured to determine that the cooling load decreases, stop the operation of the compressor, and stop the measurement of the intermittent operation time, when the indoor temperature measured by the indoor suction temperature sensor is lower than a temperature obtained by subtracting the set value from the set temperature, after start of the measurement of the intermittent operation time.   
     
     
         5 . The air-conditioning apparatus of  claim 1 , further comprising an indoor suction temperature sensor configured to measure an indoor temperature in an air-conditioning target space in which the condenser or the evaporator is located,
 wherein   the controller is configured to determine that the heating load increases, start the operation of the compressor, and start measurement of the intermittent operation time, when in the intermittent operation in the heating operation, the indoor temperature measured by the indoor suction temperature sensor is lower than a temperature obtained by subtracting a set value, which is a predetermined set range, from a set temperature for an indoor space, and   the controller is configured to determine that the heating load decreases, stop the operation of the compressor, and stop the measurement of the intermittent operation time, when the indoor temperature measured by the indoor suction temperature sensor is higher than a temperature obtained by adding the set value to the set temperature, after the start of the measurement of the intermittent operation time.