Electrical-analogy network model of a modified two-phase thermofluidic oscillator with regenerator for low-grade heat recovery

Abstract

An electrical-analogy network model including a regenerator model based on wet thermoacoustic principle is proposed to predict the resonant frequency and the onset temperature difference of a modified two-phase thermofluidic oscillator, which is similar to a non-inertive-feedback thermofluidic engine reported in the literature. Besides, a screen-stacked regenerator is introduced to reduce the irreversible loss induced by heat transfer and a gas reservoir is inserted to tune the acoustic field. An electrical capacitance that accounts for the compressibility caused by thermal-relaxation effect and an electrical resistance that accounts for the heat loss due to viscous dissipation are included in the regenerator model, with all other components modeled based on lumped principle. The electrical-analogy network model can well predict the onset temperature difference in both trend and magnitude, with which the deviations from experimental results are only 0.8–5.8% for the present model, while they are 68.5–72.0% for the previous linear temperature profile heat exchanger model. In addition, the calculated and experimental resonant frequencies are also in reasonable agreement, since the present model overestimates the measured resonant frequencies by 1.5–12.5%, while the previous model overestimates by 5.2–16.5%. The effects of the liquid column length inside the load tube, the gas reservoir volume and the working fluid on the resonant frequency and the onset temperature difference are investigated. The results from this work can help to better understand and then optimize a two-phase thermofluidic oscillator.