An air heater may be fabricated by coiling Nichrome wire and passing air in cross flow over the wire. Consider a heater fabricated from wire of diameter D=1 mm, L= 2m, electrical resistivity rho=10^-6 ohms, thermal conductivity k=25W/mK, and emissivity =.20. The heater is designed to deliver air at a temp. of 50deg C under flow conditions that provide a convection coefficient of h=250 w/m2K for the wire. The temperature of the housing that enclosed the wire and through which the air flow is Tsur=50 deg C. The temperature of the wire is 1200 deg C.
1)Determine the heat transfer by radiation (ANS: 335W)
2) If the heat transfer by radiation is 600 W, determine power delivered by the heater (ANS: 2410 W)