Study of the phase change phenomena on the liquid piston steam engine heating surface by unsteady-state temperature measurement

A novel liquid-piston steam engine which can achieve high efficiency at low temperature region of T < 300 °C as well as high reliability and low cost is developed. In this study unsteady- local inner wall temperature is measured to clarify the phase change phenomena in the heating section of the liquid piston steam engine to improve the accuracy of the design method. Thin Platinum film temperature sensor with 1 kHz response has been deposited by sputtering on the heating surface of the hollow plane type liquid piston steam engine. Nucleate boiling begins when the liquid piston enters the heating section, and it terminates when the vapor pressure approaches saturation pressure. The evaporation of the liquid film continues after the liquid piston leaves out from the heating section. Vaporization model using both the mechanism of liquid film evaporation and nucleate boiling is valid. On the other hand, fluctuations of pressure and heat flux are observed in the experiment when liquid piston enters the heating section. In order to predict these fluctuations, it is necessary to consider the effect of steam bubbles mixed inside the liquid piston.