Study on Running Performance of a Split-type Air Conditioning System Installed in the National University Campus in Japan

Abstract

Split-type air conditioning systems, or heat pump systems with multiple indoor and outdoor units, are becoming very popular for room cooling and heating of small or middle-sized non-residential buildings in Japan. However, their running performance is yet to become known due to the difficulty of measuring the actual amount of heat transferred by the system. Mixed irregular flow of vapor and liquid refrigerant prevents building engineers from obtaining accurate heat flow data between indoor and outdoor units. This study introduces an alternative method to calculate heat transferred by the system from air volume and enthalpy measured with simple sensors attached to the indoor units. Experimental results on a national university campus in suburban Tokyo showed unexpectedly low COP values both in summer and winter mainly due to the prevailing low partial load factors under 20-30% of the system capacity.