A Regulator Of Pressure In The Evaporator
Evaporator pressure regulator (EPR) of low-limit device that prevents the evaporator pressure because of reduction below set value. It supports diis low-limit set point, regardless of how low pressure die suction line may fall due to the actions of the compressor. Evaporator pressure regulator is not designed to maintain constant pressure in the evaporator, as CPXV. Instead, it is intended to limit the minimum pressure in the evaporator and performs no action when the pressure drop exceeds this limit. Evaporator pressure regulators are used in installations in which die evaporator pressure or temperature must remain above the minimum value. They are widely used with coolers of water and brines to prevent the freezing periods of reduced load. They are also used for air cooling applications where appropriate humidity control requires a minimum limit temperature of the evaporator.
EPR is working pressure control in die evaporator. As approaches the low-limit set in paragraph EPR, its plug connector begins to modulate closed, reducing the weight of the refrigerant flow to the evaporator.
Because the rate of refrigerant flow to the evaporator from the metering device does not affect the EPR, the evaporator pressure starts to increase. When the evaporator pressure increases beyond the low-limit set point, EPR plug departs from the chair. EPR-port remains open until die pressure falls below the lower limit set point.
EPRs are available with two positions, or of the modulation frequency response. In two-position of regulatory bodies control, differential exists between the opening and closing action of the valve. It is equal to the sum of changes die pressure in the evaporator, which should happen before tne EPR can open or close. This control differential prevents two positions EPR from rapidly Cycling pressure in the evaporator is within a few units of its lower limit set point. When the evaporator pressure drops below the lower limit set point, valve closes the port. It remains closed until the evaporator pressure increases above the value of the set point plus control of the differential. If the evaporator load remains light, EPR will continuously cycle until the thermostat opens the compressor circuit. If the load increases, the EPR will remain fully open to reduce the pressure, it adds to the low side ofthe system.
Modulating a regulator of pressure in the evaporator. Unlike two-position valve port a modulating EPR never totally closed during operation of the compressor. As evaporator pressure drop in response to the reduced load, EPR modulates connect it to the seat. This action reduces die suction flow of steam leaving the evaporator, supporting the evaporator pressure above its low-limit set point. Conversely, evaporator load increases, the pressure rises and EPR modulates to the full open position. When the system is running at full capacity, die regulator is wide open position in order to reduce the pressure, it adds to the low side of the system.
Evaporator pressure regulating valves respond only to the difference in pressure at the inlet. Inlet pressure acts against the bottom of the plug connector into the saddle disk), opposing force generated by die adjustable setpoint spring. The net amount of these two forces posts plugin to limit low pressure die in the evaporator. Increasing the force of the spring increases the low-limit pressure setpoint. The socket or the suction line pressure does not influence die operations EPR. Outlet pressure simultaneously acting on the bottom of the bellows and on the top of the plug connector. Since the effective area of these two opposite sides are equal, the opposing forces will be lifted...
|
Industrial