Intermittent heating performance of convective-radiant terminal based on flat heat pipes focusing on human behavior and human scale

Building energy saving plays a crucial role in global sustainability efforts, with heating systems accounting for a significant portion of energy consumption in office buildings. This study investigates the intermittent heating performance of convective-radiant terminals in office environments, with a specific focus on human behavior and human-scale thermal comfort through combined experimental and field measurements. The terminals employ flat heat pipes to enhance thermal response while balancing convective and radiant heating. Field tests in four offices revealed occupancy durations of only 14.5 %–18.3 % of testing time, demonstrating the system's adaptive capability through user-driven mode switching - maximum heating capacity for rapid warm-up followed by radiation-dominant steady operation (20.5–21.0 % radiation ratio). Human-scale temperature response matching coefficient showed 4.7–26.8 % improvement over whole-room values, confirming occupant-focused performance. The intermittent operation strategy achieved 19.1 % energy savings compared to continuous operation, as brief high-capacity start-ups (9.5–14.6 % of runtime) were offset by extended low-power periods and unoccupied phase savings. The study provides practical guidelines for intermittent heating implementation, terminal optimization, and control strategies in office buildings. • Field tests of convective-radiant terminals under real occupancy patterns. • Human-scale TRMC method for localized comfort evaluation under field tests. • Revealed operational patterns of heating capacity and radiation ratio adjustments. • Verified 19.1 % energy savings via intermittent operation.