A hot plate of 15 cm2 area maintained at a temperature of 200 0C is exposed to still air at 30 0C temperature. When the smaller side of the plate is held vertical, convective heat transfer rate is 14% higher than when the bigger side of the plate is held vertical. Determine the dimensions of the plate. Neglect internal temperature gradient of the plate thickness. Also determine the heat transfer in both the cases. 30
Use the following relations :
Nu = 0.59 (Gr. Pr)0.25
Take the following properties of air:
|
Temperature (0C)
|
r
(kg/m3)
|
Cr
(kJ/kg-K)
|
m
(N-s/m2)
|
K
(W/m-K)
|
|
30
115
200
|
1.165
0.910
0.746
|
1.005
1.009
1.026
|
18.6 ´ 10–6
22.65 ´ 10–6
26 ´ 10–6
|
0.0267
0.331
0.0393
|