Abstract
The simultaneous need for energy efficiency and indoor comfort may not be met by existing air source heat pump (ASHP) technology. The novelty of this study lies in the use of a new gravity-driven radiator as the indoor heating terminal of ASHPs, aiming to provide an acceptable indoor comfort with improved energy efficiency. To confirm and quantify the performance improvement due to the proposed system retrofit, a field test was conducted to examine the system performance under real conditions. In the tests, measurements were made on the refrigerant- and air-side of the system to characterize its operational characteristics. Results showed that the proposed radiator has a rapid thermal response, which ensures a fast heat output from the system. The proposed system can create a stable and uniform indoor environment with a measured air diffusion performance index of 80%. The energy efficiency of the proposed system was also assessed based on the test data. It was found that the system’s first law efficiency is 42.5% higher than the hydraulic-based ASHP system. In terms of the second law efficiency, the compressor contributes the most to the overall system exergy loss. The exergy efficiency of the proposed system increases with the outdoor temperature and varies between 35.02 and 38.93% in the test period. The research results and the analysis methodology reported in this study will be useful for promoting the technology in search of energy efficiency improvement in residential and commercial buildings.
Highlights
Air source heat pump (ASHP) is widely recognized as an energy efficient and cost effective means to provide space heating in buildings (Dai et al, 2020; Yang et al, 2020)
As an ASHP operates based on vapor compression cycle, its heat output is constantly higher than the electricity input to provide an energy efficiency ratio always greater than unity (Chen et al, 2021; Zendehboudi et al, 2021)
This study contributes to the literature by proposing a novel gravity-driven radiator for use as the indoor heating terminal of ASHPs
Summary
Air source heat pump (ASHP) is widely recognized as an energy efficient and cost effective means to provide space heating in buildings (Dai et al, 2020; Yang et al, 2020). It functions to transfer heat from outdoors to an indoor space with the aid of electrical work. Traditional ASHP system uses indoor air as heat carrier medium (referred to as the air-based system) In this system, indoor air is re-circulated and heated by the heat pump to compensate the space heat losses in winter (Zhang et al, 2017).
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