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A steel pipe of 20 mm inner diameter and 2 mm thickness is covered with 20 mm thick of fiber glass insulation (k = 0.05 W/m degree). If the inside and outside convective coefficients are 10 W/m2 degree and 5 W/m2 degree, calculate the overall heat transfer coefficient based on inside diameter of pipe. In the diagram, the diameter of small circle is 20 mm

Correct Answer: 2.789 W/m2 degree
Q = 2 π l (t i – t 0)/ .

A single pass shell and tube heat exchanger, consisting of a bundle of 100 tubes (inner diameter 25 mm and thickness 2 mm) is used for heating 28 kg/s of water from 25 degree Celsius to 75 degree Celsius with the help of a steam condensing at atmospheric pressure on the shell side with condensing heat transfer coefficient 5000 W/m2 degree. Make calculation for overall heat transfer coefficient based on the inner area. Take fouling factor on the water side to be 0.002 m2 degree/W per tube and neglect effect of fouling factor on the shell side and thermal resistance of the tube wall

In a counter flow heat exchanger, water flowing through a tube of 10 cm inner diameter is heated by steam condensing on the outside of the tube. The convective film coefficient on the water and steam side are estimated to be 12000 and 20000 k J/m2 hr degree. Neglecting tube thickness and its resistance to heat flow, workout the overall heat transfer coefficient for the heat exchanger

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

A steel strap is serving as a support for the steam pipe. The strap is welded to the pipe and bolted to the ceiling. The junction between the support strut and the ceiling is adiabatic, and the outside temperature of steam pipe is 105 degree Celsius. The strut AB is 60 cm high and AD = BC = 12.5 cm. It is 0.3 cm thick. Workout the rate at which heat is lost to the surrounding air by the support strut. It may be assumed that thermal conductivity for steel is 45 W/m degree, the total outside surface coefficient is 17 W/m2 degree and the surrounding air is at 32 degree Celsius

A heat exchanger shell of outside radius 15 cm is to be insulated with glass wool of thermal conductivity 0.0825 W/m degree. The temperature at the surface is 280 degree Celsius and it can be assumed to remain constant after the layer of insulation has been applied to the shell. The convective film coefficient between the outside surface of glass wool and the surrounding air is estimated to be 8 W/m2 degree. What is the value of a critical radius?

A copper pipe (k = 350 W/m K) having inner diameter of 1.75 cm and 2.0 cm outside diameter conveys water and the oil flows through the annular passage between this pipe and a steel pipe. On the water side, the film coefficient is 4600 W/m2 K and the fouling factor is 0.00034 m2 K/W. The corresponding values for the oil side are 1200 W/m2 K and 0.00086 m2 K/W. Estimate the overall heat transfer coefficient between the oil and water

A hot fluid is being conveyed through a long pipe of 4 cm outer diameter and covered with 2 cm thick insulation. It is proposed to reduce the conduction heat loss to the surroundings to one-third of the present rate by further covering with same insulation. Calculate the additional thickness of insulation

A pipe of outside diameter 20 mm is to be insulated with asbestos which has a mean thermal conductivity of 0.1 W/m degree. The local coefficient of convective heat to the surroundings is 5 W/square meter degree. Find the critical radius of insulation for optimum heat transfer from a pipe?

Consider we have a Double Pipe Heat Exchanger, with the inner tube of Outer diameter 20mm (thickness 2mm) and outer tube of inner diameter 30mm. We have two fluids A & B, we desire to have their flow rates as 15 Kg/s and 21 Kg/s respectively. Calculate the convective heat transfer coefficient from tube to annulus side. (Given Nusselt number on tube side = 496 and K = 15W/mK)

In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m2 hr degree. Find the number of transfer units of the heat exchanger. At the condensing pressure, stream has saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to water. Take specific heat of water as 4 k J/kg K