| Abstract: | ![]()
Steady-state performance data have been obtained on a domestic sized engine-driven water-to-water heat pump. The optimum working fluid suction superheat for the system was found to be 12°C. Over a range of heat sink conditions, increasing the engine speed linearly increased the total heat prouduced by the unit. Similarly, over a range of heat source conditions, increasing the engine speed linearly increased the working fluid evaporation rate. To produce water at 80°C, the heat pump was designed to operate with a heat sink temperature of 70°C, but its efficiency was improved by operating with the heat sink at 55°C. With a heat sink temperature of 55°C the primary energy ratio of the unit was observed to vary from 0–85 to 1–16, over a range of heat source temperatures. Algorithms developed from the steady-state experiments were incorporated as control function subroutines in a microcomputer program. Using this program, the microcomputer was employed to control the heat pump outlet water temperature and the working fluid suction superheat. The control system was tested in a series of dynamic experiments and was found to operate effectively and achieved its control requirements. In certain tests, the transient time period was extended because the electrically-controlled expansion valve was too large for the system and created instability in the suction superheat. |
