Answer/Explanation:
From the properties of stainless steel AISI 302.
At temperature 100°C, Thermal coefficient Ks = 16.2W/m.K.
Water at 40°C, Kf = 0.62W/m.K.
Using the rate equation, applying energy balance at x = 0,
Ks (T1 - T2)L = h(T1 - T[infinity])
h = (Ks/L) * (T1 - T2)/(T - T[infinity])
h is water flow convention coefficient, T1, T2, Ks, and L have their usual notations.
T1 = 100°C, T2 = 40°C,
T[infinity] = 25°C, L = 0.2m
h = (16.2W/m.K/0.2m) * (60/15)
h = 324W/m².K
Temperature gradient in the wall (dT/dx) = -(T1 - T2)/L = -60°C/0.2m = -300°C/m
In water at x = 0, the definition of h gives
(dT/dx)x=0 = -h/Kf(40°C - 25°C)
= (324W/m².K x 15°C)/0.62W/m.K = 7838.7°C/m
