Thermodynamic cycle of a liquid piston pump

This paper presents a contribution to the solution of the irrigation problems of rural areas in developing regions, where conventional energy solutions are often too expensive. The work presents the operational principles, the theoretical analysis and experimental results of a pumping device, for irrigation use, that works based on a cyclical variation of pressure exerted on the water by a confined mass of gas. The gas alternately contacts a hot or a cold plate, by the movement of an insulating displacer, presenting therefore an oscillation in temperature. The movement of the displacer is connected by a buoy to the movement of the liquid surface. Presented here is a description of the experimental prototype and of the mechanical pumping cycle with its connection to the thermodynamic cycle experienced by the gas inside the device. A classical thermodynamics analysis of the idealized cycle is made, shown on equilibrium diagrams. Experiments were conducted with a prototype and the results are presented and discussed. The presented experimental data confirm the initial hypothesis, and suggest the technical feasibility of the device. The final comments discuss some technological drawbacks that need yet to be removed in order to arrive at a practical prototype.