In this thesis I investigated the energy saving potential of a low temperature lift heat
pump (LTLHP) such as water source heat pump (WSHP), and studied the utilization of a
plate heat exchanger (PHE) as the LTLHP evaporator. Due to the facility limitation, I
only tested and studied the evaporator for LTLHP. Since the LTLHP requires a large
water flow rate, its heat source liquid-to-refrigerant PHE is operated at lower refrigerant
mass flux than typical applications. I varied the vapor quality, heat flux, evaporation
pressure, and refrigerant mass flux to provide unique heat transfer characteristics, and I
studied their effects on evaporation heat transfer. Based on the collected data, I concluded
that at a low mass flux range, evaporation heat transfer is dominated by nucleate boiling,
and convective boiling has mall influence. In addition, I carried out a simulation to
compare the performance of WSHP with air source heat pump (ASHP).