Isobaric Expansion Engines Powered by Low-Grade Heat-Working Fluid Performance and Selection Database for Power and Thermomechanical Refrigeration

Abstract

A database is developed for the most suitable working fluids for Worthington-type and Bush-type isobaric engines based on their performances for a wide range of heat source temperature, from 40 to 300 °C, and operating pressures from 1 to 100 bar. Thermodynamics models are developed and simulated to study the effects of different operating temperatures and pressures on the efficiency and back work ratio of both engines. Results show that in temperature range from 40 to 60 °C, the achieved efficiency is less than 4% for most cases, suggesting that practical applications in this range are very limited. Ammonia and R32 show the highest efficiencies (≈11%) at high pressure of 50 bar for the temperature range of 100–300 °C. The refrigerant R161 has high performance for pressures between 10 and 50 bar for the full range of temperatures from 80 to 300 °C, which makes R161 the choice fluid for a wide range of applications. Novel applications are introduced, which integrate these isobaric engines with vapor compression refrigeration systems. The thermodynamic cycles of the heat driven compressor with the selected working fluids as in the current study and the simplified technological solutions are crucial components of the study novelty.