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Heat Transfer - Engineering

Q1:

Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by
 This is valid for the value of NRe equal to

A < 2100

B 2100-4000

C > 4000

D > 10000

ANS:D - > 10000

The heat transfer coefficient (ℎh) for a fluid flowing inside a clean pipe is typically given by the Dittus-Boelter equation: ℎ=4(0.023⋅)0.8h=4k⋅D​(0.023⋅DNRe⋅Pr​)0.8 Where:

  • ℎh is the heat transfer coefficient (W/m²·K),
  • k is the thermal conductivity of the fluid (W/m·K),
  • D is the diameter of the pipe (m),
  • NRe is the Reynolds number of the flow (dimensionless),
  • Pr is the Prandtl number of the fluid (dimensionless).
This equation is valid for turbulent flow inside a clean pipe, where the Reynolds number (NRe) is typically greater than 4000. So, the correct answer is: >4000NRe>4000.