Question

how much heat transfer coefficient should be given in heat transfer

Answer 1

I think may more than threshold frequency

Answer 2

As mentioned earlier in the article the convection heat transfer coefficient for each stream depends on the type of fluid, flow properties and temperature properties. Some typical heat transfer coefficients include: Air - h = 10 to 100 W/(m²K) Water - h = 500 to 10,000 W/(m²K).