Experimental investigation of the effect of preheating on the performance of a novel thermally driven pumping system

This paper presents the attempt made to develop a new configuration of a thermally driven pumping system. A vertical narrow evaporation channel and displacer unit concepts were introduced to implement the TPP cycle in a liquid piston configuration. An experimental setup was developed to investigate the performance and characteristics of the system. For a heat source temperature of 60 ºC, it was possible to attain the delivery pressures up to 174kPa using isopentane as a working fluid. The corresponding thermal efficiency of the system was in the range of 0.5 - 0.7%, which is found to be higher than the literature. The effect of introduction of preheating times (PHT) on the system performance was investigated and it was found that for a short critical PHT, the efficiency of the system improves by the order of 2%. However, longer periods were observed to deteriorate the system performance. The results seem to suggest that the boiling process in the evaporation channel may be in the subcooled pool boiling regime when the system is operating without the preheating periods, as the thermal demand of the system is lower, and it operates at a higher frequency in such conditions.