Performance of Multiple Variable Refrigerant Flow Air-Conditioning System with Heat Recovery

Some multi-system air conditioners have been applied in residential and light commercial buildings. However, their operation is limited to a single mode--heating or cooling—at one time. Some rooms in a building should be cooled even in winter because of computers and other electronic machinery, and in that case, concurrent heating and cooling is necessary, which cannot be achieved with a conventional multi-system air conditioner. A multiple variable refrigerant flow (VRF) air conditioning system with heat recovery has been developed in this paper. This system consists of two indoor units and one outdoor unit. Its capacity responds to the load of each room by using a variable frequency compressor and electronic expansion valves (EEV) that can control the refrigerant volume for each indoor unit and changing the airflow rate of each heat exchanger. Thus, A suitable operating mode can be selected for each indoor unit independently in this system, hence, concurrent heating and cooing is possible. This paper describes the configuration, basic operating methods, and experimental results indicated a maximum one times higher coefficient of performance (COP) in the current heating and cooling mode compared to single-mode operations.