Comparative thermal and hydraulic performance of Type-22 panel radiators under continuous and pulsating flow

Pulsating water-side flow has been proposed as a radiator control strategy to enhance heat emission at low supply temperatures, yet device-level studies rarely quantify thermal gains together with hydraulic costs under matched baselines. This study experimentally investigates the coupled thermal and hydraulic response of a PCCP Type-22 panel radiator operated under continuous and on–off pulsating flow regimes. A dedicated test loop was developed using a temperature-controlled hot-water tank (50 °C setpoint) and an Arduino-based driver to impose repeatable pulsation, while measuring inlet/outlet temperatures, instantaneous flow rate, pump electrical energy, and spatiotemporal surface temperatures via infrared thermography. The results show that increasing the continuous flow rate provides the highest absolute heat output, but at the cost of increased pumping energy. In contrast, pulsating operation improves the thermal–hydraulic balance by increasing heat delivery relative to the reference case while reducing pump energy consumption. Among the tested pulsating cases, short-period pulsation produced the most favorable behavior by maintaining a warmer and more spatially stable radiator surface. Longer off-periods promoted deeper surface cooling, reduced the effective emitting area, and weakened the thermal benefit of pulsation. Infrared thermography confirmed that the pulsation period strongly affects surface-temperature uniformity and temporal stability. Overall, short-period on–off pulsation emerges as the most favorable operating mode when the objective is to increase heat delivery while lowering pumping energy in PCCP-type radiators.