The rate of heat transfer through a pipe wall is given by, q = 2π k (Ti- T0)/ln (ri /r0). For cylinder of very thin wall, q can be approximated by

Related MCQs

• A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2 .°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be
• Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the
• The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2 .°C-1 . The rate of heat loss from the outer surface in W.m-2 is
• The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8 , where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as
• The rate of heat loss through a furnace wall is 1000 kcal per hour when inside temperature is 1000?C and outside wall temperature is 500?C. What should be the wall thickness in case the thermal conductivity of wall material is 0.5 kcal/m-hr?C
• A dimensionless heat transfer coefficient which gives a measure of the ratio of the heat transfer rate to the rate at which heat would be conducted within the fluid under a temperature gradient is known as
• In case of heat transfer by conduction in a hollow cylinder, __________ mean area is used to calculate the heat transfer rate.
• The average heat transfer co-efficient over the entire length of the plate (ha) and the local heat transfer co-efficient (hL), in case of heat transfer over a flat plate in laminar zone is related as
• The face temperatures of a flat wall are 650?C and 450?C respectively and the thermal conductivity of wall material is 0.30 kcal/m-hr-?C. For a wall thickness of 20 cm, the rate of heat conduction per square meter of wall area will be
• Which of the following situations can be approximated to a steady state heat transfer system?