Question

Which of the following statement regarding overall heat transfer coefficient is Wrong? Select one: O a. It cannot be applied to heat transfer involving convection O b. It is the reciprocate of Rtotal A O c. It is related to total thermal resistance O d. It takes into account all of the individual thermal resistance

Answer 1

Answer: Option (a) is the correct answer.

Explanation:

Heat transfer in terms of convection means that heat is transferring due to the   motion of mass of an object or substance.

As convection is related to fluids, that is, only liquids and gases.

Now, relation between heat transfer and $R_{total}$ is as follows.

              q = $\frac{(T_{1} - T_{2}}{R_{total}}$ ........ (1)

Also,        q = $U \times A \times (T_{1} - T_{2})$ ......... (2)

where,     U = overall coefficient

                A = surface area of substance

Hence, equating both equations (1) and (2) we get the following.

                U = $\frac{1}{R_{total} \times A}$

So, it means that overall heat transfer coefficient is the reciprocate of  $R_{total}$ and also it is related to thermal resistance.

Thus, we can conclude that out of the given options, the statement it cannot be applied to heat transfer involving convection, is wrong.