Impact of operation strategies on performance of integrated kang-floor heating system in severe cold areas

Abstract

Efficiently and cost-effectively meeting the heating requirements of residents in severely cold regions by utilizing solar energy is currently a pressing need. Therefore, a solar heating system that integrated Kang-floor heating was established and tested for a passive solar house in Gan-nan Tibetan. This study reveals the effects of adjusting the flow/intermittent time periods and implementing variable flow rate operations on performance of system, to improve energy efficiency and optimize sleeping comfort. Findings indicated decreasing flow/intermittent time to 15/15 min had strengthened the average heat transfer from the water side, and mitigated the influence of returning water on internal water temperature of the tank, ultimately enhancing heat supply. The heating period was divided into three stage (18–24, 0–4, 4–8 o'clock), with a specific flow rate assigned to each stage. Under five flow rate configurations(A-E) with identical initial conditions: during constant flow rate, the greater the initial supply water temperature of the system, the more heat was transferred to room, and the higher heating efficiency was achieved, however, under variable flow rate, the effect of the water temperature on heating efficiency was significantly less evident. Mode B (low-to-high flow rate) had the highest heating efficiency and heat supply. The heating rate and cooling rate of Kang surface, temperature variations were notably less compared to the other four modes. Shortening the flow/intermittent periods and implementing variable flow method could improve the system's heat supply and sleep comfort with limited capital and resource investment.