Closed cycle refrigeration system and mixed component refrigerant

A closed cycle refrigeration system to produce temperatures in the range of from about 70 to about 230° K comprising in combination:

• a refrigerant consisting of at least two components, with each component selected from any one of the groups consisting of atmospheric gases, normally gaseous and liquid fluorocarbons, normally gaseous and liquid hydrofluorocarbons, and normally gaseous and liquid hydrocarbons;
• an oil lubricated compressor to pressurize said refrigerant, an after cooler to receive and cool said pressure refrigerant, an oil separator to receive said refrigerant and remove oil from said refrigerant so as to produce a refrigerant containing less than 1% by weight lubricating oil in the refrigerant, a filter/dryer to receive said refrigerant from said oil separator and remove water from said refrigerant;
• a heat exchanger to receive said refrigerant from said filter/dryer and cool said refrigerant by heat exchange with a low pressure refrigerant return stream;
• a fixed orifice throttle device to receive said refrigerant stream from said heat exchanger and expand said high pressure refrigerant to produce a low pressure low temperature refrigerant stream, said throttle device so constructed and arranged to provide during cooldown of said refrigerant from normal ambient temperature more than about 60% of the maximum refrigeration capacity of said system available during desired steady state operation of said system, resulting in a low pressure low temperature refrigerant stream, means for utilizing said low pressure low temperature refrigerant stream to provide cooling and means for returning a warmed low pressure refrigerant stream to the oil lubricated compressor.