Experimental and numerical study on the heat transfer performance of the radiant floor heating condenser with composite phase change material

Abstract

Traditional hot-water ASHP systems have disadvantage of low energy efficiency due to the requirement of secondary heat exchange. To maintain the stability of indoor air temperature during defrosting, the existing ASHP systems adopt heat exchanger to store heat, which increases the system complexity. To overcome these obstacles, a novel ASHP system integrated with radiant floor heating condenser (RFHC) is proposed, which uses refrigerant as working fluid to exchange heat with indoor environment directly. In addition, the composite phase change material (CPCM) is added in the RFHC for heat storage. Experiments are conducted and results show that compared with traditional ASHP systems, the proposed system has higher energy efficiency and can reduce indoor air temperature fluctuation under defrosting condition. A detailed numerical model of the RFHC is established and validated with the experimental data, and then the impacts of the operating and structural parameters on the heat transfer performance of the RFHC system are investigated. Results show that under the indoor air temperature of test room keeps at 18.0 oC, the optimal operating condition of this system is the condensing temperature with 38.0 oC and the refrigerant mass flow rate with 3.8 kg· h-1. The optimal structural scheme of the RFHC is the copper pipe spacing with 0.25 m and the length of copper pipe with 12.0 m