Patent ID: 7356998

Claim:
A flash tank of a two-stage compression heat pump system for cooling and heating in a single unit, and in which an intercooler increases cooling effect by increasing a degree of sub-cooling of refrigerant sent to the flash tank and a separately-allocated evaporator, and in which the two-stage compression heat pump system performs a single-stage compression cooling operation in summertime using only a low-stage compressor, and both the low-stage compressor and a high-stage compressor in wintertime, wherein the two-stage compression heat pump system comprises: a fluid-level detecting sensor mounted inside the flash tank for detecting a fluid-level of refrigerant; an alarm sensor for notifying a saturated state of refrigerant in the flash tank; an evaporator pressure sensor for measuring and notifying pressure of refrigerant flowing into the evaporator; a condenser pressure sensor for measuring and notifying pressure of refrigerant flowing out of the condenser; a flash tank fluid-level controller for receiving signals from the fluid-level detecting sensor, the alarm sensor, the evaporator pressure sensor, and the condenser pressure sensor and controlling intermediate pressure and the fluid-level of the flash tank; and a bypass valve controller for controlling a bypass valve that receives signals from the alarm sensor, the bypass valve controller allowing refrigerant to directly flow from the low-stage compressor to the high-stage compressor, the flash tank comprising: an intercooler outlet pipe coupled on one side of the flash tank; a low-stage compressor outlet pipe coupled on another side of the flash tank; a high-stage compressor inlet pipe installed inside the flash tank, the high-stage compressor inlet pipe having a U-shaped end portion at a bottom of the flash tank, wherein a refrigeration oil inlet is provided at a bottom side of the U-shaped end portion, and wherein the high-stage compressor inlet pipe also has another end portion connected to the high-stage compressor; and an orifice installed so as to correspond to the refrigeration oil inlet provided at the bottom side of the U-shaped end portion, the orifice being provided for filtering contaminations in refrigeration oil.