Water flows on the inside of a steel pipe with an id of 2.5 cm. the wall thickness is 2 mm, and the convection coefficient on the inside is 500 w/m2 · ◦c. the convection coefficient on the outside is 12 w/m2 · ◦c. calculate the overall heat-transfer coefficient. what is the main determining factor for u

U = 11.67 W/m² °C

Explanation:

Inner diameter, d = 2.5 cm = 0.025 m

Thickness of the wall, t = 2 mm = 0.002 m

thus, the outer diameter, D = d + 2t = 0.025 + 2 x 0.002 = 0.029 m

Now, based on outside convection heat transfer

we have

on rearranging, we get

where, are the perimeter respective to inner and and outer diameter

on substituting the values, we get

or

U = 11.67 W/m² °C

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