A copper wire has a diameter "d" is heated by a short circuit to "T_0" before a slow-blow fuse burns out. If the still air temperature is "T_a", how long will it take for the wire to drop to temperature "T", if the variable τ (tau) is found to be 0.02 hr ?
The following material properties are given:
k = 224 (BTU-ft/hr-ft2 -o R)
h = 1.65 (BTU/hr-ft2 -o R)
cp = 0.091 (BTU/lbm-o R)
rho = 558 (lbm/ft3 )
T_a = 99F
T = 139F
T_0 = 296F

Ahot wire operates at a temperature of 200°c while the air temperature is 20°c. the hot wire element is a tungsten wire of 5 um diameter and 2 mm in length. plot using excel current, heat transfer and heat generated by the wire for air velocity varying from 1-10 m/s in steps of lm/s? matlab the sensor voltage output, resistance, or assume nu 0.989 re033pr13 take air properties at tr (200°c20°c)/2 = 110°c properties of tungsten: c 0.13 kj/kg. k 3 p 19250 kg/m k (thermal conductivity) = 174 w/m. k