Question -7 . A horizontal steel pipe having inner and outer diameter as 150 and 180 mm respectively is lagged with 50 mm thickness of 85% magnesia insulation inside ,which has flue gas flowing at 260^oc

Find out
A - the heat loss per hour per meter run of pipe.
B - the external surface temperature of lagging

Data given-
Thermal conductivity of pipe and lagging = 44.64 &0.0576 w/m .^oc respectively.
Ambient air temperature =20^oc
Combined radiation and conductive external heat transfer co- efficient from outside surface to air =19.8 w/m2.^oc
The inside heat transfer film co- efficient = 22.7 w/m2.^oc