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Q4. Dry saturated steam at 10 bar enters a steam pipe 50 m in length with an inner diameter of 100 mm and wall thickness of 3 mm.

The pipe insulation limits the condensation of the steam to 6%, when the mass flow rate of steam in the pipe is 7200 kg/hr and the air temperature surrounding the pipe is 20℃.

Calculate EACH of the following:

(a) the thickness of the insulation surrounding the pipe; (8)

(b) the percentage reduction in condensation when the thickness of the insulation is doubled. (8)

Note: inner heat transfer coefficient of the pipe = 545 W/m² K

thermal conductivity of steel = 50 W/mK

thermal conductivity of the insulation = 0.5 W/mK

the outer heat transfer coefficient of the pipe may be ignored