Experimental Study on Heat Transfer of Supercritical CO₂ in a Tri-Partite Brazed Plate Gas Cooler

A transcritical carbon dioxide (CO2) heat pump test facility is developed to study the heat transfer performance of supercritical CO2 cooled in a tri-partite brazed plate gas cooler. The gas cooler is partitioned to separately serve the functions of domestic water preheating, space heating, and domestic water reheating. The effects of CO2 inlet pressure, CO2 and water mass flow rates, and water inlet temperature are investigated. As shown by the experimental results, the heat transfer coefficient increases with the increase of CO2 mass flow rate, and the operating pressure has a considerable impact on the heat transfer coefficients in the near-critical region. The maximum of heat transfer appears near the pseudo-critical point and the peak of the heat transfer coefficient shifts to the high-temperature state when the operating pressure increases. Furthermore, no significant and clear influence of the water inlet temperature is demonstrated when CO2 is in a high-temperature state.