Fundamental experiment of pumpless Rankine-type cycle for low-temperature heat recovery

This paper proposes a new pumpless Rankine-type cycle for power generation from low-temperature heat sources. The new cycle mainly consists of an expander, two heat exchangers, and switching valves for the expander and heat exchangers. Instead of using a working fluid pump, the switching valves method (SVM) is employed to control the cycle. The SVM makes each heat exchanger switch between functioning as an evaporator and functioning as a condenser. In this arrangement, the working fluid flows back and forth between the two heat exchangers without a working fluid pump. Therefore, the new cycle does not involve problems caused by a pump. In the first basic experiment carried out to clarify the feasibility of the proposed cycle, the function of the expander was emulated by using an expansion nozzle. HFC245fa was used as the working fluid. The experimental results confirm that the proposed cycle works and that it has the potential to produce power. Fundamental time-varying characteristics of the proposed cycle are also shown and discussed. ► “Pumpless” Rankine-type cycle for low-temperature heat recovery is proposed. ► Switching valves method (SVM) drives the cycle without working fluid pump. ► This new cycle does not involve problems caused by the working fluid pump. ► First experimental results confirm that the cycle works to produce power.