Refrigeration systems

A method of operating a vehicle air-conditioner comprising:

• condensing compressed gaseous difluorodichloromethane refrigerant to a liquid in a condenser cooled by ambient air,
• evaporating said liquified refrigerant in an evaporator at a temperature between about -5.degree.C and 10.degree.C to form gaseous refrigerant,
• compressing said gaseous refrigerant in a helical screw compressor having a male rotor with a diameter between 40 and 55 mm operated at between 1,200 and 14,000 rpm while admixing oil containing dissolved refrigerant with said gaseous refrigerant to form a mixture of compressed gaseous refrigerant and oil containing dissolved refrigerant at a discharge pressure of at least 10 kg/cm.sup.2,
• separating said compressed gaseous refrigerant from said oil containing dissolved refrigerant and feeding said compressed gaseous refrigerant to said condenser to be liquified, and
• recycling said oil containing dissolved refrigerant from said oil separator to said compressor,
• said oil having a dielectric constant at 50.degree.C of between 4.9 and 8 and a kinematic viscosity at 50.degree.C of between about 270 and 660 cSt.

A method of operating small refrigeration systems comprising:

• condensing compressed gaseous halocarbon refrigerant to a liquid in a condenser,
• evaporating said liquified refrigerant in an evaporator to form gaseous refrigerant,
• compressing said gaseous refrigerant in a helical screw compressor having a male rotor with a diameter between 30 and 105 mm operated at between about 2,900 and 3,600 rpm while admixing oil containing dissolved refrigerant with said gaseous refrigerant to form a mixture of compressed gaseous refrigerant and oil containing dissolved refrigerant at a discharge pressure of between about 30 and 10 kg/cm.sup.2,
• separating said compressed gaseous refrigerant from said oil containing dissolved refrigerant and feeding said compressed gaseous refrigerant to said condenser to be liquified,
• recycling said oil containing dissolved refrigerant from said oil separator to said compressor,
• the dielectric constants of said oil and liquified refrigerant, and the viscosity of the oil, satisfying the following relationships
• .vertline. 1n .epsilon..sub.r - 1n .epsilon..sub.r .vertline. = x
• and when x .gtoreq. 1
• v = Y .sup.. e .sup..sup.[(c . P.sbsp.1 ) /u.sup.]
• and when x <
• 1 ##EQU5## wherein Y is a value between 25 and 200, 1n is the natural logarithm, .epsilon..sub.r is the dielectric constant at 50.degree. C, v is the kinematic viscosity of the pure oil in centistokes at 50.degree. C,
• p.sub. 1 is the discharge pressure of the compressor, u is the tip speed of the male rotor, e is the base of the natural system of logarithms, and c is a constant equal to ##EQU6## when P.sub.1 is measured in kp/cm.sup.2 and u is measured in m/sec.

Refrigeration apparatus comprising in combination:

• an oil injected helical screw compressor for compressing gaseous halocarbon refrigerant, an oil separator connected to said compressor to receive a mixture of compressed gaseous refrigerant and oil containing dissolved refrigerant for separating said compressed gaseous refrigerant from said oil containing dissolved refrigerant, a condenser connected to said oil separator to receive said compressed gaseous refrigerant for liquifying said refrigerant, an evaporator connected to said condenser by a conduit means containing an expansion valve for evaporating said liquified refrigerant to the gaseous state, means for returning said evaporated gaseous refrigerant to the suction end of said compressor, and means for recycling said oil containing dissolved refrigerant to said compressor,
• said compressor having a male rotor and a female rotor, said male rotor having a diameter of between about 105 and 300 mm and means for being rotated to provide a male rotor tip speed of between about 15 and 50 m/sec, said compressor having a discharge pressure of between about 10 and 30 kp/cm.sup.2,
• the dielectric constants of said oil and liquified refrigerant, and the viscosity of the oil, satisfying the following relationships
• .vertline. 1n .epsilon..sub.r .varies. - 1n .epsilon..sub.r .vertline. = x
• and when x .gtoreq. 1
• v = Y .sup.. e.sup[sup.(c . P.sbsp.1) /u.sup.]
• and when x <
• 1 ##EQU7## wherein Y is a value between 30 and 200, 1n is the natural logarithm, .epsilon..sub.r is the dielectric constant at 50.degree.C, v is the kinematic viscosity of the pure oil in centistokes at 50.degree.C, P.sub.1 is the discharge pressure of the compressor, u is the tip speed of the male rotor, e is the base of the natural system of logarithms, and c is a constant equal to ##EQU8## when P.sub.1 is measured in kp/cm.sup.2 and u is measured in m/sec.

A method of operating refrigeration systems comprising:

• condensing compressed gaseous halocarbon refrigerant to a liquid in a condenser cooled by ambient air,
• evaporating said liquified refrigerant in an evaporator to form gaseous refrigerant,
• compressing said gaseous refrigerant in a helical screw compressor having a male rotor with a diameter between 105 and 300 mm operated at between about 2,900 and 3,600 rpm while admixing oil containing dissolved refrigerant with said gaseous refrigerant to form a mixture of compressed gaseous refrigerant and oil containing dissolved refrigerant at a discharge pressure of between about 10 and 30 kg/cm.sup.2,
• separating said compressed gaseous refrigerant from said oil containing dissolved refrigerant and feeding said compressed gaseous refrigerant to said condenser to be liquified,
• recycling said oil containing dissolved refrigerant from said oil separator to said compressor,
• the dielectric constants of said oil and liquified refrigerant, and the viscosity of the oil, satisfying the following relationships
• .vertline. 1n .epsilon..sub.r - 1n .epsilon..sub.r .vertline. = x
• and when x .gtoreq. 1
• v = Y .sup.. e .sup..sup.[(c . P.sbsp.1 ) /u.sup.]
• and when x <
• 1 ##EQU9## wherein Y is a value between 25 and 200, 1n is the natural logarithm, .epsilon..sub.r is the dielectric constant at 50.degree.C, v is the kinematic viscosity of the pure oil in centistokes at 50.degree.C, P.sub.1 is the discharge pressure of the compressor, u is the tip speed of the male rotor, e is the base of the natural system of logarithms, and c is a constant equal to ##EQU10## when P.sub.1 is measured in kp/cm.sup.2 and u is measured in m/sec.