The pipe in Problem 2 56 is covered with a layer of asbestos k 0 18 W m C while still surrounded by a convection environment with h 12W m2 C Calculate the critical insulation radius Will the heat transfer be increased or decreased by adding an insulation thickness of (a) 0 5 mm, (b) 10 mm Problem 2...

The pipe in Problem 2-56 is covered with a layer of asbestos [k = 0.18 W/m

Question:

The pipe in Problem 2-56 is covered with a layer of asbestos [k = 0.18 W/m · ºC] while still surrounded by a convection environment with h = 12W/m2 · ºC. Calculate the critical insulation radius. Will the heat transfer be increased or decreased by adding an insulation thickness of
(a) 0.5 mm,
(b) 10 mm?
Problem 2-56
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 · ºC. The convection coefficient on the outside is 12 W/m2 · ºC. Calculate the overall heat-transfer coefficient. What is the main determining factor for U?