The refrigeration unit is protected against overpressure and compressor overload.
with insufficient ventilation of the condenser (e.g. dirt deposits) the equipment is
switched off.
This cooling process is a self-refrigerating cascade type.
A mixture of non-flammable and safe refrigerants is compressed and circulated by a
compressor. In a simplified version, the cycle comprises:
(a) compressing a mixture of refrigerants,
(b) partially condesning the higher boiling fractions in an air-cooled condenser,
(c) withdrawling and throttling the condensate to produce cooling which condenses
the remaining vapors in a special heat exchanger,
(d) throttling and evaporating this latter condensate in a coil to produce cooling at
very low temperatures,
(e) passing the refrigerant leaving the cooling coil back through the heat exchanger
to the compressor.
Basic Auto-Cascade Refrigeration Cycle
Operating pressures and compressor temperatures are similar to those in
air-conditioning systems. The compressor lubricating oil circulated with the discharge
vapors is promptly returned to the compressor without reaching the very low
temperature portions of the system. This eliminates the common problems of oil
plugging in evaporators and expansion devices too frequently experienced in low
temperature systems. The mixed refrigerant charge is hermetically sealed into the
system; normally neither it nor the compressor lubricating oil requires replacement or
recharging.