GIVEN ? A disk rotating in air ? Diameter (D) = 2 m ? Rotational speed (?) = 600 rev/min ? Air temperature (T?) = 20°C ? Surface temperature (Ts) = 50°C FIND ? The rate of heat transfer from one side (q) ASSUMPTIONS ? The heat transfer has reached steady state ? The disk is horizontal ? Air is still SKETCH
GIVEN
? A disk rotating in air
? Diameter (D) = 2 m
? Rotational speed (?) = 600 rev/min
? Air temperature (T?) = 20°C
? Surface temperature (Ts) = 50°C
FIND
? The rate of heat transfer from one side (q)
ASSUMPTIONS
? The heat transfer has reached steady state
? The disk is horizontal
? Air is still
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Table 28, for dry air at the mean temperature of 35°C
The rotational Reynolds number for the disk is
The critical Reynolds number is given in Section 8.4
The average heat transfer coefficient is given by Equation (8.47)
The rate of heat transfer is
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