(57) An ultra low temperature heat pump system with secondary refrigerant injection mechanism
is disclosed which comprising a compressor, a condenser, a reservoir tank, a thermal
expansion valve, a vaporizer and a separator, sequentially connected to form a circulation
loop, an air refill device I provided between the compressor and the reservoir tank,
which is constructed of an injection valve, an economizer, a first solenoid valve
and a second solenoid valve. The two solenoid valves are arranged in parallel with
the first solenoid valve connected directly to the compressor and the second solenoid
valve connects sequentially to the injection valve and the economizer. The economizer
is then connected to the compressor.
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