Experimental Study on Heat Transfer of Supercritical CO_2 in a Tri-Partite Brazed Plate Gas Cooler

摘要

A transcritical carbon dioxide (CO_2) heat pump test facility is developed to study the heat transfer performance of supercritical CO_2 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 CO_2 inlet pressure, CO_2 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 CO_2 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 CO_2 is in a high-temperature state.