Refrigerating circuit apparatus with two stage compressor and heat storage tank

Claim 1

A refrigerating circuit apparatus comprising: two stage compressing means including a lower stage compressor element and an upper stage compressor element connected in series for compressing refrigerant, each compressor element respectively having an input port and output port, the output port of the lower stage compressor element being in communication with the input port of the upper stage compressor element, the two stage compressing means having an intermediate port communicating with the output port of the lower stage compressor element and the input port of the upper stage compressor element; liquid separation means for separating liquid and gaseous refrigerant, the liquid separation means including an inlet port, an outlet port and intermediate port; upper stage side variable opening valve means disposed in-line between the output port of the upper stage compressor element and the input of the liquid separation means for controlling the flow amount of refrigerant exiting the output port of the upper stage compressor element between a fully open position and a fully closed position; lower stage side variable opening valve means disposed in-line between the output port of the liquid separation means and the input port of the lower stage compressor element for controlling the flow amount of refrigerant into the input port of the lower stage compressor element between a fully open position and a fully closed position; heat storage means, disposed in-line between the intermediate port of the two stage compressor means and the intermediate port of the liquid separation means, for storing heat therein from the refrigerant or for discharging heat therefrom to the refrigerant; heat-exchange means, disposed in-line between the lower stage side variable opening means and the input port of the lower stage compressor element, for exchanging heat with refrigerant, the heat-exchange means including an external heat-exchanger subject to accumulation of frost thereon; bypass pipe means, disposed between the output port of the upper stage compressor element and the output port of the liquid separation means, for bypassing a selected amount of refrigerant from the output port of the upper stage compressor element to the external heat-exchanger; and means for controlling the bypass pipe means and for controlling the lower stage side variable opening valve means for carrying out a defrost operation wherein refrigerant flows from the upper stage side variable opening valve means to the intermediate port of the two stage compressing means through the heat storage means to absorb heat into the refrigerant from the heat storage means, and refrigerant flows from the output port of the upper stage compressor element to the external heat-exchanger through the bypass pipe means to discharge absorbed heat from the refrigerant to the external heat-exchanger thereby removing frost accumulated on the external heat-exchanger.