Design method for heating towers used in vapor-compression heat pump systems

Abstract

Given that they are highly efficient in summer and frost-free in winter, heating tower heat pumps are evolving rapidly. However, lack of an appropriate design method of heating towers is complicating the design process and causing a mismatch between cooling and heating conditions. To address this problem, this study develops a total heat transfer model taking enthalpy difference as the driving force, then experiments are carried out to test the volumetric enthalpy transfer coefficients. Based on the model and the coefficients, a novel design method is proposed based on curves of required and available transfer units, involving four steps, namely: 1) determination of design conditions, 2) calculating tower thermal performance, 3) sizing x-y section of packing, 4) determination of air flow rate and packing size. Finally, a performance comparison and matching degree analysis of the designed tower are presented. The results show that the proposed design method is simple and clear by avoiding trial-and-error. The designed tower saves considerable power consumption of the tower fans and pumps and achieves good matching degree between its heating and cooling capacities by setting reasonable approaches and ranges. The model, the coefficients and the design method can be used accurately by researchers/designers.