Q1: 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

ANS:B - 0.794 h₁

When the velocity of laminar flow in a circular tube is reduced by half, the convective heat transfer coefficient (h) changes according to the Dittus-Boelter equation for laminar flow: ℎ2ℎ1=(21)0.8h1​h2​​=(V1​V2​​)0.8 Where:

• ℎ1h1​ is the convective heat transfer coefficient at velocity V1​.
• ℎ2h2​ is the convective heat transfer coefficient at velocity V2​.

Given that the velocity is reduced by half (V2​=2V1​​), we can substitute this into the equation: ℎ2ℎ1=(1)0.8h1​h2​​=(V1​2V1​​​)0.8 ℎ2ℎ1=(12)0.8h1​h2​​=(21​)0.8 ℎ2ℎ1=(0.5)0.8h1​h2​​=(0.5)0.8 ℎ2ℎ1=0.794h1​h2​​=0.794 So, the new convective heat transfer coefficient (ℎ2h2​) is approximately 0.794×ℎ10.794×h1​. Therefore, the correct answer is: 0.794 ℎ10.794h1​