Simulation and Optimization of Heat Pump Water Heater with Wrapped-Tank Mini-Channel Condenser

Abstract

The application of mini-channel condenser in the field of heat pump water heater (HPWH) introduces new challenges for design and modeling tools, as the two-phase flow mechanisms and flow regime transitions in mini-channel is considerably different from those found in the more conventional larger diameter tubes in the condensing process. Based on the latest research of mini-channel research, this study develops a coupled model that integrates a vapor-compression heat pump model with a water tank heat transfer model, linked through a bidirectional coupling algorithm. In this framework, the heat pump model supplies the tank model with heat flux boundary conditions, while the tank model returns water side parameters to the system model. This coupled approach enables the prediction of both system level performance and the transient hydrodynamics and heat transfer behavior within the water tank, thereby enhancing overall design and analysis capability. Model accuracy is evaluated experimentally using system efficiency, compressor suction and exhaust pressures, condenser inlet and outlet temperatures, evaporating temperature, and water tank temperature measurements. Furthermore, a variable-pitch mini-channel condenser is proposed, and HPWH configurations featuring constant and variable-pitch condensers are simulated. The results demonstrate that the variable-pitch design leads to a more uniform temperature distribution in the tank and yields superior performance in terms of both system efficiency and heat-transfer enhancement.