A new thermodynamic cycle of heat pump relying on excess enthalpy changing

Abstract To improve the efficiency of absorption heat pump, a new thermodynamic cycle mainly dependent on excess enthalpy of the solution was proposed in this paper. CO 2 and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF 6 ]) were chosen as the working pair to verify it. The new system does not require high temperature heat resource, and can be driven by a solution pump. Due to the trans-critical cycle, the heat is produced not only isothermally but also at higher temperature, more than 120 °C. It has a prominent coefficient of performance, over 2, when the temperature of heat absorbing and generating set at 290 K and 400 K, respectively. Meanwhile, new system is more compact compared with the vapor compression heat pumps of R1234yf, R1234ze(E), R227ea or R245fa.