Category: Evaporators

Electric-compensating back-pressure regulator

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Electric-compensating back-pressure regulator

usually found at the top of the regulator. In an electrically compensated regulator, turning the stem to obtain different refrigerant pressures and temperatures in the evaporator is accomplished by a small electric motor. This motor rotates the adjusting stem in accordance with temperature variations in a thermostatic bulb placed in the medium being cooled as …

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Air-compensating back-pressure regulator

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Air-compensating back-pressure regulator

A standard regulator is reset by manually turning the adjusting stem, which increases the spring pressure on top of the diaphragm. In an air compensated regulator, a change of pressure on top of the diaphragm is accomplished by introducing air pressure into the airtight bonnet over the diaphragm. As this air pressure is increased, the …

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Refrigerant-powered compensating-type pilot valve

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Refrigerant-powered compensating-type pilot valve

The upper portion of the valve head is similar to a standard pressure regulating head. On the lower portion of the head another diaphragm is connected to the main diaphragm by a push rod. As the thermal bulb warms, the liquid in it expands, pushing up on the rod and opening the regulator. Because this …

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HVAC Back-Pressure Regulator Applications of Controls

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In a refrigeration system designed to maintain a predetermined temperature at full load, any decrease in load would tend to lower below fullload temperature the temperature of the medium being cooled. To maintain constant temperatures in applications having varying loads, means must be provided to change refrigerant temperature to meet varying-load requirements. Refrigerant temperature is …

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Valves and Controls for Hot-Gas Defrost of Ammonia-Type Evaporators

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The following valves and controls are used in the hot-gas defrost systems of ammonia-type evaporators: Hot-gas or pilot-solenoid valve. The valve is a 1/8 in. ported solenoid valve. It is a direct-operated valve suitable as a liquid, suction, hotgas, or pilot valve at pressures to 300 lb. Suction-, liquid-, or gas-solenoid valve. The suction-solenoid valve …

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HVAC Dual-Pressure Regulator

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HVAC Dual-Pressure Regulator

Adual-pressure regulator is shown in Fig. 10-24. It is used on a shell-andtube cooler. The dual-pressure regulator is particularly adaptable for the control of shell-and-tube brine or water coolers, which at intervals may be subjected to increased loads. Such an arrangement is shown in Fig. 10-24. The high-pressure diaphragm is set at a suction pressure …

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HVAC Year-Round-Automatic Constant Liquid Pressure Control System

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HVAC Year-Round-Automatic Constant Liquid Pressure Control System

The constant liquid control system is a means of increasing the efficiency of a refrigeration system that utilizes air-cooled, atmospheric, or evaporative condensers (see Fig. 10-23). This is accomplished by automatically maintaining a constant liquid pressure throughout the year to assure efficient operation. Constant liquid pressure on thermal expansion valves, float controls, and other expansion …

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Low-temperature ceiling blower

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Low-temperature ceiling blower

The low-temperature liquid recirculating system illustrated in Fig. 10-22 uses several controls. During the cooling cycle, Number 1 pilot valve is opened and Number 2 pilot valve is closed, holding the gas-powered solenoid valve wide open. This allows flow of liquid through the energized liquid-solenoid valve from the recirculator and then through the circuit of …

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HVAC Flooded recirculator

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HVAC Flooded recirculator

Bottom hot-gas feed The multiple system shown in Fig. 10-20 shows a check valve mounted in each of the liquid-refrigerant branch lines. A single solenoid valve is used in the main refrigerant line. The defrost gas is bottom fed. Top-gas feed The system illustrated in Fig. 10-21 shows a check valve mounted directly at the …

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HVAC Liquid-Recirculating Systems

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HVAC Liquid-Recirculating Systems

Liquid refrigerant recirculating systems are frequently fed by upward liquid flow through their evaporators. These systems are called bottomfed. This is accomplished by either mechanical or gas-displacement recirculators during the refrigerant cycle (see Fig. 10-20). In some systems, more than a single evaporator is fed from the same recirculator, as shown in Fig. 10-20. Then, …

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