Experimental and numerical study on year-round heat and mass transfer performance of an open counterflow heat-source tower heat pump system in high-humidity climates

This study experimentally and numerically evaluated the year-round performance and energy-saving potential of an integrated, energy-efficient heat-source tower heat pump (HTHP) capable of heating and cooling in humid climates. The heat and mass transfer models for summer and winter were validated using measured data. Results show that increasing inlet air temperature in summer enhanced latent heat transfer by 25% but reduced sensible heat transfer by 31%. Raising the water temperature from 28 ℃ to 34 ℃, latent heat transfer rose by 20.7% and sensible heat transfer decreased by 16.7%, raising the latent heat ratio to 87.19%. In winter, increasing the inlet air temperature from -1 ℃ to 7 ℃ enhanced sensible but reduced latent heat transfer. Higher solution temperatures reduced total heat transfer, and the latent heat ratio dropped to 18.2%. The inlet air humidity ratio had a greater effect on sensible heat transfer in summer, and the opposite in winter. Increasing the inlet solution mass flow rate enhanced the total heat transfer in both seasons, while the latent heat ratio slightly rose. Operational tests demonstrated that the system achieved COP ranging from 2.43 to 3.23 under typical January conditions and 3.8 to 5.0 under typical June conditions. The performance evaluation yielded a Heating Seasonal Performance Factor (HSPF) of 3.06, a Seasonal Energy Efficiency Ratio (SEER) of 4.3, and an Annual Performance Factor (APF) of 3.62. These results confirm the system's favorable year-round performance and offer guidance for HTHP applications in Guizhou and similar high-humidity regions.