For a laminar flow of fluid in a circular tube, 'h1' is the convective heat transfer co-efficient at velocity 'V1'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is
A)1.26 h1
B)0.794 h1
C)0.574 h1
D)1.741 h1

Question

Quizplus · Accepted Answer

For laminar flow in a circular tube, the Nusselt number (Nu) is constant, and the convective heat transfer coefficient (h) is directly proportional to the velocity (V) to the power of 0.5. Therefore, if the velocity is halved (V2 = 0.5V1), the new heat transfer coefficient (h2) would be h1*(0.5)^0.5 = 0.707*h1. However, none of the options exactly match this calculation due to the approximation or potential specific conditions assumed in the question. The closest option provided is B) 0.794 h1, which suggests a slight deviation from the straightforward theoretical calculation, possibly due to rounding or specific empirical correlations used for laminar flow in the question's context.

For a Laminar Flow of Fluid in a Circular Tube