Patent ID: 6109047
Filing Date: 2000-08-29
Classification: B23Q,F25B,F25D

Abstract:
In a system for regulating the temperature of heat transfer fluid to maintain a selectable refrigerated temperature level at an apparatus in thermal interchange relation with a heat transfer fluid by boiling off a varying amount of a pressurized liquid refrigerant from a refrigeration unit, an arrangement for insuring that refrigerant is returned in gas phase to the refrigeration unit, comprising:means for dividing the pressurized refrigerant into at least first and second flows;reference evaporator means receiving the first flow, said reference evaporator means including means for expanding the liquid refrigerant to establish a minimum reference temperature level;means responsive to the temperature at the apparatus for providing a control signal to indicate the refrigeration rate needed for the apparatus;a device receiving the second flow and responsive to the control signal for controlling the refrigerant flow to boil off a selected proportion of the refrigerant in heat exchange relation with the thermal transfer fluid to establish a desired temperature therein;a circuit for determining the difference, in refrigerant outflow temperature, between the flow from the reference evaporator means and flow from the boil off device; anda compensator for reducing the refrigerant flow to the boil off device from that indicated by the control signal when the difference is less than a selected amount.