Thermal characteristics of an aluminum fanless radiant panel heat exchanger assisted heat pump: Experimental investigation across diverse operating regimes

This study experimentally investigates a novel air source heat pump (ASHP) system integrated with an aluminum fanless radiant panel heat exchanger (AHE) incorporating thermal storage for cold climate applications. The system’s thermal performance was evaluated under the normal (7°C), typical (–7°C), and ex¬treme (–12°C) winter conditions, with condensation temperatures varying from 34.1-60.7°C. Results demonstrate that the ASHP-AHE system maintains stable operation with consistent COP values of 2.19 ±0.03 at 7°C, 2.07 ±0.05 at –7°C, and 1.80 ±0.03 at –12°C, and with heat dissipation fluctuations remaining below ±1.8%. The integrated thermal storage effectively buffers temperature variations while maintaining a characteristic 15.8% radiant heat transfer proportion at the condensation temperature of 46.0°C. Comparative analysis reveals that the average COP is 4.1%-7.7% higher than conventional systems, particularly at medium temperatures below 40 °C. Pressure drop analysis shows minimal impact on heat dissipation. The flow resistance accounts for merely 3.1%-4.4% of the total pressure. The system exhibits superior performance stability at lower ambient temperatures, with heat flux remaining constant (2260.3 ±14.5 W/m2 at 46.0 ±0.3°C condensation temperature) regardless of outdoor conditions. These findings validate the technical feasibility of thermal storage-integrated radiant terminals for ASHP systems in cold climates, providing design guidelines for efficient heating solutions in severe winter regions. The study contributes empirical evidence for advancing low carbon heating technologies while addressing performance limitations under extreme cold conditions.