Experimental study of a new solar-assisted air-conditioner for performance prediction and energy saving

This paper aims to analyse the performance of a new solar-assisted direct expansion air-conditioner and to demonstrate its capability of energy savings and ecological conservation. Here, an integrated flat collector storage system as well as an immersed piped coil is equipped with the direct expansion evaporator to raise the superheat temperature entering the variable speed compressor, causing a smaller duty cycle of the compressor and a slight increase in its suction pressure, and hence, reduce its energy consumption. Water in the flat solar collector is in contact with the collector's absorbing surface and therefore, heat is transferred to the water and then to the refrigerant in the immersed heat exchanger. Once the room has achieved its desired temperature, the compressor turns off while room cooling will continue until the refrigerant pressure within the circulation loop fails to maintain the desired temperature. The system advantage is that heat can be imparted into the refrigerant via the flat plate collector, so the compressor can remain off longer. This process justifies up to 40% energy savings. Mathematical models will be derived for the system components. These models are then validated against by using experimental data. For this, the system is equipped with several sensors and data-loggers. The models are coded into a transient simulation tool using FORTRAN. Predictions from the model are obtained over a very wide range of operating conditions and exhibit a good coincidence with experimental results. They serve to determine the principal parameters that remain most effective in performance enhancement in terms of reduction of energy consumption and greenhouse gas emission.