New air-source heat pump system without defrosting operation in practical use

Recently, air-source heat pump systems have become important from a stand point of saving energy and utilizing equipment effectively. However, there are some problems in usual heat pump systems, e.g., (1) the mechanism is complicated, (2) they periodically need defrosting to prevent the efficiency from going down due to frosting on the outdoor coil during heating operation, and (3) liquid floodback to the compressor takes place in heating operation under low ambient temperature. A new heat pump system is proposed to solve the problems accompanied by traditional air-source heat pump systems as mentioned above, and its performance experimentally evaluated. The results of experimental study of the new system show: the new heat pump system has better performance for preventing frost formation on the outdoor coil than conventional ones and it can operate for a long time without defrosting operation provided that the relative humidity of the ambient air is kept below 90%; since it becomes easy for the frost to form under the ambient air temperature at 1 to 4/sup 0/C. when the room temperature falls, it is desirable to select the suitable capacity of the heat pump system to keep the room temperature at 21/sup 0/C under the ambientmore » air temperature at as low as O/sup 0/C; and the amount of heat exchanged between increases as the ambient air temperature falls; therefore, the heat effectively avoids the liquid floodback to the compressor under the low ambient air temperature.« less