COLD TANK 



The refrigerated water supply is held in a 20- 

 gallon tank insulated with a 1-inch layer of cork. The 

 dimensions of the cold tank, 28 by 9 by 22 inches, were 

 determined by the size of the refrigeration coils mounted 

 inside. The cold tank is situated next to the hot tank with 

 which it shares a common return line from the main 

 calibration tank. It is cooled by use of a compressor of 

 sealed-unit construction mounted outside the building to 

 provide proper air circulation as well as noise suppression. 

 The compressor is rated at a 3-ton capacity and replaces 

 the original reciprocating-type unit which was unreliable 

 and rated at only 1. 2 tons. A manually adjustable thermo- 

 stat (fig. 5) maintains the temperature of the contents of 

 the cold tank to within ±2°C of any desired temperature 

 between -12°C and +10°C. 



HOT TANK 



The capacity of the hot tank is 10 gallons, and 

 the tank is insulated all over with 1-inch thick cork board. 

 It is located between the cold tank and the calibration tank 

 and is connected to the latter in a closed system, the water 

 pumped out from the bottom being replaced at the top by a 

 return line. A bourdon tube thermostat (hot tank) regulating 

 two 2000-watt, 230-volt heating elements connected in 

 series holds the temperature of the water to within ±2 C of 

 any desired value between 20°C and 90°C. The temperature 

 of the main tank rises about 5°C when 10 gallons of water 

 at 80 °C is pumped rapidly into it. 



TEMPERATURE CONTROLLER 



A constant temperature is achieved in the 

 calibration tank by the injection of hot or cold water to 

 counteract any drift away from the desired temperature. 

 Electrically controlled solenoid valves and manually 

 adjustable needle valves (fig. 5) regulate timing and quantity 



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