Experimental assessment of two-phase bubble pump for solar water heating

Abstract

The research goal is to develop a new solar water heater system (SWHS) that uses a solar bubble pump instead of an electric pump. The pump is powered by the steam produced from an evacuated tube collector. Therefore, heat could be transferred downward from the collector to a hot water storage tank. The designed system consists of two sets of heat-pipe evacuated tube collectors, a solar bubble pump installed at an upper level and a water storage tank with a heat exchanger at a lower level. Discharge heads of 1 and 5 m were tested. The bubble pump could operate at the collector temperature of about 90-100 degrees C and vapor gage pressure of 80-90 kPa. It is found that water circulation within the SWHS depends on the incident solar intensity and system discharge head. Experimental investigations are conducted to obtain the system thermal efficiencies from the hourly, daily and long-term performance tests. The thermal performance of the proposed system is compared with conventional solar water heaters. The results show that the proposed system achieves system characteristic efficiency of 10% higher than that of the conventional systems using electric pump if taking the consumption of electric power into account. And the former is a zero carbon system.