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Q7. A steam pipe with a bore of 120 mm and wall thickness of 10 mm is 100 m long. It is insulated with materials each of 500 mm thickness.

Dry saturated steam at a pressure of 14 bar enters the pipe at a rate of 576 kg/hour.

The atmospheric temperature is 15℃. Calculate EACH of the following:

(a) The heat loss from the steam per hour; (6)

(b) The dryness fraction of the steam leaving the pipe; (5)

(c) The insulation interface temperature. (2)

(d) The outer surface temperatures. (3)

Note: inner heat transfer coefficient may be ignored

thermal conductivity of steel = 55 W⁄(m K)

thermal conductivity of the inner insulation = 0.05 W⁄(m K)

thermal conductivity of the outer insulation = 0.15 W⁄(m K)

outer heat transfer coefficient = 15 W⁄(m²K).