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Investigation of a Multi-functional Heat Pump System with Air Source and Gray Water Source

Xiaoyu Liu, University of Nebraska - Lincoln


A multi-functional heat pump system is proposed to efficiently utilize the gray water as heat source and sink for heating and cooling of residential buildings, respectively and reclaim condenser heat to supply domestic hot water for residential use. Based on this idea, a simulation program is developed to study the feasibility of the innovative system in 15 typical cities across U.S. To study the performance of this innovative system, laboratory testing is performed with a prototype of the multi-functional heat pump system. This prototype is set in two environmental chambers that they represent: the outdoor and indoor environments, respectively. This prototype is designed to realize five functions: (1) space heating, (2) space heating plus hot water supply, (3) space cooling, (4) space cooling plus hot water supply, (5) hot water supply only. The system is designed to allow four combinations of two heat sources/sinks that they are a water-source heat exchanger and an air-source heat exchanger. Initial prototype is developed from an air-source heat pump system and is tested. Due to the drawbacks of the initial prototype, an optimization for the prototype is needed. Optimized prototype shows that the drawbacks of initial one are solved and can be more practical and provide significant energy savings in space heating and hot water supply., compared with initial prototype. The main idea of this multi-functional heat pump is to utilize the condenser heat. However, condenser heat recovery may not necessary bring the positive effect on improving the system performance in cooling mode. This study investigates the effect of the condenser heat recovery on the system performance with capillary tube and thermal expansion valve (TXV). Two remedy ways are proposed and analyzed. Based on the optimized prototype and measured data, a new regression model of the multi-functional heat pump system is developed. An annual energy analysis and a life cycle cost analysis are made via the updated simulation program. Significant energy savings and cost savings are shown in this study.

Subject Area


Recommended Citation

Liu, Xiaoyu, "Investigation of a Multi-functional Heat Pump System with Air Source and Gray Water Source" (2013). ETD collection for University of Nebraska - Lincoln. AAI3590982.