A 0.5 cm diameter copper wire is exposed to environment air in cross flow over the wire with uniform velocity of 0.5 m/s. The copper wire is insulated by a rubberized sheath with thermal conductivity of 0.13 W/m∙K. The outer surface of the wire has a temperature of 60˚C due to the electric current flowing through it. The thermo-physical properties of the environment are υ =15.89 × 10-6 m2 /s, Pr = 0.707, k = 26.3 x 10-3 W/m.K. The outer surface of the insulation must be kept at temperature of 45˚C or below. Design a suitable thickness of the insulation in order toallow the use of such insulated wire in a room temperature of 27˚C.

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Conduction and Convection

When energy travels from one object to another it is said to have undergone heat transfer. Heat transfer is nothing but the transfer of thermal energy or internal energy from one thing to another, like e.g., when a vessel with water, kept on top of a burner, heats up because of the flame underneath it.