US 4,282,718 A · Evaporator inlet water temperature control system

Abstract

An evaporator inlet water temperature control system for controlling the inlet water temperature of an evaporator utilized in an inverter driven centrifugal chiller. The system creates the proper chilled water set point at the evaporator outlet needed to maintain the inlet water at its set point for greater efficiency of operation. Control is accomplished by generating an electrical error signal which is a function of an inlet water set point voltage and the actual inlet water temperature. A logic signal is produced as a function of the error signal detected by the circuit and establishes a dead zone band representing a range in which the error signal is acceptable. Output of the control system is passed to the capacity control circuit of an inverter driven centrifugal compressor chiller. When the inlet water temperature reaches its set point during pull-down, the logic output of the circuit sets a flip-flop which enables transmission gates to control changes in the outlet water set point as needed to balance the load of the cooling system.

Claims16

Dependent claims

An evaporator inlet water temperature control system for a refrigeration system including a compressor having an adjustable capacity control means, a condenser and an evaporator having an inlet receiving fluid from a load and an outlet discharging chilled fluid to be returned to said load comprising:

means for sensing the temperature of said fluid at the evaporator inlet,
means for sensing the temperature of said fluid at the evaporator outlet,
a first control circuit means coupled to said outlet fluid temperature sensing means to regulate said adjustable capacity control means in response to the temperature of said outlet fluid, said control circuit having a variable set point,
means for establishing a set point temperature for the fluid at the evaporator inlet, and
a second control circuit means coupled to said inlet fluid temperature sensing means and said set point temperature means to generate a differential electrical signal as a function of the difference between the sensed temperature and the set point temperature of the fluid,
said second control circuit means having an output coupled to said first control circuit and dependent on said electrical signal for adjusting the variable setpoint and regulate the adjustable capacity control means to maintain the inlet set point temperature.

3 more elements

Dependencies are inferred from the claim text.

Evaporator inlet water temperature control system

Life of this patent

Evaporator inlet water temperature control system

Life of this patent

Abstract

Claims16