Document qdMRqN2VNavZQ8KjK09GG6q7x

American Society of Heating and Ventilating Engineers Guide, 1932 represents the difference between the dry-bulb temperature arid the dew point temperature for the conditions involved. (See discussion of con densation in Chapter 3). Insulation to Prevent Freezing of Water in Pipes Insulation will retard the freezing of water in pipes. With a certain amount of circulation, or even without circulation, if the air remains at a Chapter 12--Pipe Insulation jected to severe conditioris of temperature are insulated with insulations such as hair felt or cork. The insulation is applied in layers of approxi mately 1-in. thickriess, securely bound in place on the pipe and finished 6n the outside with a waterproof jacket. Fig. 2. Thickness of Pipe Insulation to Prevent Sweating1 "Solve problems by drawing lines as indicated by dotted line, entering chart at lower left hand scale. low temperature for only a short period, freezing may be prevented. Still water in pipes may be prevented from freezing by inserting a heating medium inside the insulation surrounding the pipe. No arnount of insulation, however, will prevent water in pipes from freezing where there is no circulation or where there is only a small amount of circulation in the pipe, if the outside temperature remains below the freezing point for a sufficient length.of time. Pipes carrying water and which may be sub- 200 Fig. 3. TEMPERATURE DIFFERENCE DEC. FAHR. (L. B. McMillan, Iron and Steel Engineer, July 1926.) Heat Losses from Surfaces Exposed to Various Air Velocities EFFECT OF AIR VELOCITY ON SURFACE LOSSES The rate of heat loss from a surface maintained at constant temperature is greatly increased by air circulation over the surface. Fig. 3 is based bn Larigmuir's equations (Trans. Am. Electro-Chem. Soc., Vol. 23). Other investigators have shown even greater increases in rates of heat loss from bare surfaces due to air velocity. 201.!' ,'. : ^