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Q7. A steam pipe with a bore of 200 mm and a wall thickness of 10 mm is 15 m long. It is covered with two layers of insulation, an inner layer 20 mm thick and an outer layer 15 mm thick.

Dry saturated steam at a pressure of 26 bar enters the pipe at a rate of 648 kg/hour.

The atmospheric temperature is 25℃.

Calculate EACH of the following:

(a) The rate of heat loss from the steam; (6)

(b) The outer surface temperature; (2)

(c) The mass of steam condensed per hour. (8)

Note: inner heat transfer coefficient may be ignored

Thermal conductivity of steel = 52  W⁄(m K)

Thermal conductivity of inner insulation = 0.045  W⁄(m K)

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

Outer heat transfer coefficient=10  W⁄(m² K)