Liquid level detector and air conditioning apparatus including the liquid level detector

A liquid level detector, comprising:

• a vertically-mounted accumulator provided on a suction side of a compressor and configured to store refrigerant;
• a heater configured to heat the accumulator;
• a temperature detector configured to detect a surface temperature of the accumulator;
• a pressure detector configured to detect a pressure of the refrigerant in the accumulator;
• and
• a controller configured to detect a position of the liquid surface of the refrigerant in the accumulator based on a surface temperature of the accumulator detected by the temperature detector when the accumulator is heated by the heater, and a pressure of the refrigerant in the accumulator detected by the pressure detector,
• wherein the controller calculates a saturation temperature of the refrigerant from a pressure of the refrigerant detected by the pressure detector, and adds the preset threshold value to the calculated saturation temperature to thereby calculate a temperature sum,
• determines the position of the liquid surface of the refrigerant in the accumulator based on a result of comparison of the calculated temperature sum and the surface temperature detected by the temperature detector, and
• determines a frequency of the compressor based on the determined position of the liquid surface of the refrigerant in the accumulator.