Condenser pressure regulators
System, in General, satisfactory work a maximum ambient conditions, and the condenser will have the size of this. In cold weather, condensation temperature and pressure will drop, and, as a consequence, reducing the pressure difference across the thermostatic expansion valve; this may cause malfunction. Pressure drop, the difference in half the normal number can reduce the mass flow is lower than required, and it will be necessary to prevent condenser pressure drop too low.
Air-cooled condensers and cooling towers may reduce airflow, automatic valves for controlling the speed of the fan or fans off when two or more adapted. Monitoring should work with the pressure, but it may work on temperature.
Water-cooled condensers can be installed directly under the control of the water control valve is controlled condenser pressure, or you may have a three-way mixing valve in the water circuit. Condenser pressure regulator can be in the form of a pressure release valve creeps through the condenser to distract the hot gas to the receiver.
Valve diaphragm balanced set of spring and open the bypass, when the condensing pressure falls. A similar effect can be obtained by pressure controlled valve between the condenser and receiver to restrict the flow and allows fluid builds up in the condenser, reducing its effectiveness. For operating economy it is important that such valves are not set at too high a pressure.
Where evaporative condensers and cooling towers there is only one fan (or fan drive motor), coarse control can be done by switching off. Time delay depends on the mass of water in the circuit, and the sensing element must have a wide differential to prevent frequent starts the engine.
The tower should have thermostatic fan control for prevention of freezing of water on the packing in the winter. Integrated control circuit with electronic expansion valve can be arranged with the permission of the fall of the condensing pressure, providing valve can transfer the flow of refrigerant required to meet the load. This gives a much lower energy costs for the compressor.
All forms of control the pressure in the condenser, at least to maintain the pressure must be low, which will give the satisfactory operation, in the interests of economic management. Indication of the relative cost of 350 kW air conditioning plant are described in Table 9.1.
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