This system produces the cooling by the rapid evaporation of water in a very high vacuum. This results in cooling of the unevaporated water which is circulated through the cooling coil.
The equipment is essentially composed of the cold water or cooling circuit and the condensing circuit.
The cooling circuit consists of the evaporator, cold water pump, cooling coil and connecting piping. This circuit is maintained under a vacuum by the steam ejector as described below. The relatively warm water from the cooling coil is sprayed into the evaporator when a portion of it is evaporated due to the low pressure. This lowers the temperature of the remaining water which falls to the bottom of the evaporator where it is picked up by the pump and sent through the cooling coil.
The vapor formed by evaporation is removed from the evaporator by the steam ejector and in order to maintain the required amount of water in the circuit arrangements are made to add water as it is needed.
The ejector consists of a converging tube (a tube that becomes smaller toward the end) with its large end attached to the evaporator and its small end connected to the small end of a diverging tube (a tube that becomes larger toward the end). The other end of the latter is connected to the condenser. A nozzle is located in the evaporator end of the ejector.
When steam under proper pressure is supplied to the nozzle it expands in the flared end of it and leaves the nozzle with a very high velocity and at very low pressure. The ejector action of this jet draws water vapor from the evaporator and maintains the vacuum necessary for operation. The steam ejector may be considered as the equivalent of an ordinary vacuum pump.
The condensing circuit consists of the condenser, purge ejector, spray water pump, sprays and fans.
The mixture of steam from the ejector nozzle and the water vapor from the evaporator pass from the ejector into the condenser, where it is condensed. The condenser is cooled by the combined effect of spraying it with water and blowing large volumes of air over it.
The condensed water which is formed in the condenser is removed by the purge ejector. This acts in the same manner as the steam ejector except that water is used. Some of the condensed water is fed to the evaporator to make up for the water evaporated there and the remainder is added to the spray water supply.
The loss of water by evaporation from the condenser spray is more than the condensed water obtained from the condenser, so it is necessary to provide a supply of water.
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