Project ForgeHeat Transfer
Heat Exchangers
GATE 2017
Medium
A heat exchanger tube has inner diameter 25mm, outer diameter 30mm. The overall heat transfer coefficient based on the inner area is 360 W/m²·°C. The overall heat transfer coefficient based on the outer area, rounded to nearest integer, is
300 W/m^2.C(± 3 accepted)
Explanation
UoAo=UiAi (same duty per unit ΔT), and for the same tube length, A∝D. Uo=Ui×(Di/Do)=360×(25/30)=300 W/m²·°C.
Source: GATE CH 2017 (2017)
This question is part of a 15-day revision cycle — sign in and Project Forge will bring it back the day before you'd forget it.