An experimental study on the operating performances of a novel bed-based air source heat pump (B-ASHP) system.

• A novel bed-based air source heat pump (B-ASHP) system was proposed. • A prototype experimental B-ASHP system was established and tested. • The B-ASHP system can be operated at both nighttime and daytime modes. • Better thermal comfort and bed surface temperature distribution can be achieved. • A number of issues requiring further considerations were identified. Air source heat pumps (ASHPs) have been increasingly used for space heating due to their high energy efficiency and installation flexibility. On the other hand, in many rural areas in northern Chinese provinces, Kangs, a kind of traditional heating systems based on burning biofuels, are still being used for space heating in winter. Based on the pros and cons of both ASHPs and Kang-based heating systems, a novel bed-based ASHP (B-ASHP) system has been proposed to combine the advantages from both an ASHP and a Kang heating system. In this paper, a prototype experimental B-ASHP system was designed and established, and its dynamic and steady-state operating performances tested in four test cases. The test results from the four test cases demonstrated that the prototype experimental B-ASHP system can achieve quicker increases in indoor air temperatures and bed-surface temperatures than Kang-based heating systems. The use of experimental B-ASHP system can lead to a more uniformed vertical indoor air temperature gradient, thus a better occupants' thermal comfort, than the use of a conventional convection-based ASHP system. Furthermore, compared to using a Kang-based heating system, a more uniformed bed surface temperature may be obtained when using a B-ASHP system. Nonetheless, although currently the prototype experimental B-ASHP system can be satisfactorily operated, a number of issues related to the designs of a B-ASHP system such as choices of refrigerant, refrigerant tube layout optimizations, and the use of variable speed compressors for capacity control, should be carefully considered to further improve its operational safety and energy efficiency. [ABSTRACT FROM AUTHOR]