PRINCIPLES OF NAVAL ENGINEERING 



CHARGING 

 CONNECTION 



TO EXPANSION 

 VALVE 



FROM CONDENSER 



DRAIN - 



Figure 19-8.— Receiver for R-12 

 refrigeration system. 



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improper setting of the high pressure cutout 

 switch. If the relief valve opens, it discharges 

 high pressure vapor to the suction side of the 

 compressor. 



A water regulating valve, as shown in figure 

 19-11, is usually installed to control the quantity 

 of circulating water flowing to the refrigerant 

 condenser. The valve is located either at the 

 inlet to the condenser or at the outlet from the 

 condenser. The valve is actuated by the refrig- 

 erant pressure in the compressor discharge line; 

 this pressure acts upon a diaphragm or a bel- 

 lows arrangement which transmits motion to the 

 valve stem. As the temperature of the circu- 

 lating water increases, the temperature of the 

 refrigerant vapor increases; this causes the 

 pressure of the refrigerant to increase, and 

 thereby raises the condensation point . When this 

 occurs, the increased pressure of the refrig- 

 erant causes the water regulating valve to open 

 wider, thus automatically permitting more cir- 

 culating water to flow through the condenser. 

 When the condenser is cooler than necessary, 

 the water regulating valve allows less water to 

 flow through the condenser. Thus the flow of 

 cooling water through the condenser is auto- 

 matically maintained at the rate actually re- 

 quired to condense the refrigerant under vary- 

 ing conditions of load and temperature. 



A water failure switch is provided to stop 

 the compressor in the event of failure of the 

 circulating water supply. This is a pressure- 



actuated switch, generally similar to the low 

 pressure cutout switch and the high pressure 

 cutout switch previously described. If the water 

 failure switch should fail to function, the re- 

 frigerant pressure in the condenser would 

 quickly build up to the point where the high 

 pressure cutout switch would function. 



Because of the solvent action of R-12, any 

 particles of grit, scale, dirt, and metal that 

 the system may contain are very readily circu- 

 lated through the refrigerant lines. To avoid 

 damage to the compressor from such foreign 

 matter, a strainer is installed in the compressor 

 suction connection. In addition, a liquid strainer 

 is installed in the liquid line leading to each 

 evaporator; these strainers serve to protect 

 the solenoid valves and the thermostatic ex- 

 pansion valves. 



A number of pressure gages and thermom- 

 eters are used In refrigeration systems. A 

 compound refrigerant gage is shown in figure 

 9-12. The temperature markings on this gage 

 show the boiling point (or condensing point) of 

 the refrigerant at each pressure; the gage can- 

 not measure temperature directly. The dark 

 pointer (which is actually red in color) is a 

 stationary pointer that can be set manually to 

 indicate the maximum working pressure. Other 

 pressure gages and thermometers include a 

 water pressure gage, installed in the circulating 

 water line to the condenser, and standard ther- 

 mometers of appropriate range, installed in the 

 refrigerant lines. 



Refrigerant piping is normally made of 

 copper. Copper is particularly good for this 

 purpose because it does not become corroded 

 by the refrigerant, the internal surface is smooth 

 enough to minimize friction, and the tubing is 

 easily shaped to meet installation requirements. 



AIR CONDITIONING 



Air conditioning is a field that deals with 

 the design, construction, and operation of equip- 

 ment used in establishing and maintaining de- 

 sirable indoor air conditions. It is the science 

 of maintaining the atmosphere of an enclosure 

 at any required temperature, humidity, and pur- 

 ity. As such, air conditioning involves the 

 cooling, heating, dehumidifying, ventilating, and 

 purifying of air. 



Aboard ship, air conditioning serves to keep 

 the ship's crew comfortable, alert, and physi- 

 cally fit. The temperature, humidity, cleanli- 

 ness, quantity, and distribution of the condi- 

 tioned air supply is a matter of vital concern. 



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