Preliminary Modeling of a Heat Pump Based on the Vuilleumier Thermodynamic Cycle
Thermally-driven heat pumps are becoming increasingly attractive choices for residential and commercial heating and hot water applications as fuel costs continue to rise. They can have overall heat-delivered to heat-consumption ratios of 160%−180% or more. Heat pumps based on the Vuilleumier thermodynamic cycle are a particularly attractive class of devices for such applications. The mechanical motion of such a heat pump can be driven by a traditional mechanical crankshaft-connecting rod assembly, but alternative approaches are also available. This work reviews the Vuilleumier thermodynamic cycle and its benefits for heat pump applications, and then discusses the development and validation of a force-based motion model of a two-displacer Vuilleumier heat pump based on a classic damped harmonic oscillator. The model also incorporates sliding friction and the driving forces to maintain operation of the heat pump to overcome friction and viscous losses. Model results are compared to experimental data for a prototype heat pump design. The data allow parameter estimation of the model parameters to provide a tool for future system designs.