Analytical Study of Liquid-Piston Heat Pump Technology

摘要

While the evaluation of the feasibility of the liquid-piston heat pump concept is not yet complete, several preliminary conclusions may be stated based upon the initial results: (1) Simulation of an isothermal LPHP using the second order computer model indicates that the LPHP can self-start and achieve stable oscillations. (2) Examination of the principal loss mechanisms has identified no losses that are peculiar to the LHPH, and indicates that the magnitudes of the losses are similar to those of conventional Stirling engines and heat pumps. (3) The cooling COP of an LPHP operated from a 400 exp 0 C heat source is estimated to lie between 0.3 for an adiabatic high pressure-ratio heat pump, up to about 1.2 for an isothermal heat pump or an adiabatic, low pressure-ratio heat pump. (4) Examination of liquid piston frictional effects and other practical considerations suggest that it will not be feasible to achieve isothermal expansion/compression in practice. Therefore, prediction of LPHP performance should be based on upon an adiabatic model. (5) Although a true optimization has not yet been performed, preliminary indications are that the favorable operating frequency of an LPHP will be in the range of 1 to 10 Hz. In order to achieve high specific power (e.g., of the order of 10 kW/liter of displacement), a mean pressure of the order of 7 MPa (1000 psia) is required. (6) Taylor instability of the liquid piston interface will occur at all frequencies of interest unless some means of stabilizing the interface is employed. Loose fitting floats should provide an acceptable solution. 8 refs., 16 figs., 3 tabs. (ERA citation 11:013440)