A tube 13 mm in diameter (OD) and 1.5 m long is used to condense steam at 40 kPa (Tsat=76 ˚C). Calculate the heat transfer coefficient for this tube in Twall=52˚C

A thermocouple is used to measure a hot gas flowing in a tube maintained at 180 ˚C. The thermocouple indicates a temperature of 50˚C. If the emissivity of the thermocouple junction is 0.5 and the convective heat transfer coefficient is 250 W/m²-K, determine the actual temperature of the gas

A central heating radiator has a surface temp of 70˚C and heats a room maintained at 20˚C. Calculate the contribution of convection and radiation to heat transfer from

the radiator. Use Nul=0.118 (GrPr)1 /3 for convection. Mean film temp. properties are:

k=0.026 W/m-K, µ=1.8x10^-5 Pa.s, p=1.2 kg/m3, Pr=0.71

A thin walled concentric tube Heat exchanger is used to cool engine oil at 160˚C to 60˚C with water that is available at 25˚C acting as coolant. The oil and water flowrates are each 2 kg/s and the diameter of the inner tube is 0.50 m and the corresponding value of Ui=250 W/m²-K. How long must the heat exchanger be to accomplish the desired cooling?

Determine the surface area required in a counter flow heat exchanger in which steam enters at 180˚C in a dry saturated state and leaves at 250˚C with an increase of enthalpy of 159 kJ/kg. The hot combustion gases (Cp=1.05 kJ/kg=K) enter when the super heater at 510 ˚C. The steam flow rate is 1000 kg/hr, and the U=26 W/m²-K.

A cross flow heat exchanger with both fluids unmixed is used to heat water flowing at a rate of 20 kg/s, from 25˚C to 75˚C using gases available at 300˚C to be cooled at 180˚C. The U=95W/m²-K. Determine the area requirement. Cp gas=1005 J/kg-K.

Engine oil is to be cooled from 120 ˚C to 70˚C in a double pipe heat exchanger having an area of 1.4 m². The specific heat of oil is 2100 J/kg-K. Water at 30˚C is used to cool the oil and the maximum temperature of water is limited to 90˚C. The flow rate of water is available at 215.311 kg/hr. The overall heat exchanger coefficient is 300 W/m²-K. Determine the maximum possible flow rate of oil.

The wall of a furnace is conducted from a 15 cm thick fire brick having a constant thermal conductivity of 1.7 W/m-K. The two sides of the wall are maintained at 1400 K and 1150 K, respectively. What is the rate of loss through the wall that is 50 cmx 3m on a side?

The roof of an electrically heated home is 6m long, 8m wide and 0.25 m thick, and is made of a flat layer of concrete whose thermal conductivity is K=0.80 W/m-K. The temperatures of the inner and outer surfaces of the roof one night are measured to be 15˚C and 4˚C respectively for a period of 10 hrs. Determine:

(a) The rate of heat loss;(b) Cost of heat loss to the home owner is cost of electricity if 0.08/kwH.

A large glass window, of 0.50 cm thick (K=0.75 w/m-K) is exposed to warm air at 25˚C over its inner surface with convection coefficient of 15 W/m²-K. The outer air is at -15˚C with convection coefficient of 50 W/m²-K. Determine the heat transfer rate and inner and outer surface temperatures of the glass.

Consider a 0.80 m high and 1.5 m wide double pane window consisting of 4-mm thick layers of glass (K=0.78 w/m-K) separated by 10-mm wide stagnant air space (K=0.026 w/m-K). Determine the rate of heat transfer through the window and temperature of its inner surface for a day during which the room is maintained at 20˚C while the temperature of the outdoors is -10˚C. Take the convection coefficients on inner and outer surfaces to be hi=10 w/m²-K and ho=40 w/m²-K.

A 3-m high 5-m wide wall consists of long 16 cm x 22 cm cross section horizontal bricks (K=0.72 W/m-K) separated by 3-cm thick plaster layers (k=0.22 w/m-K). There are also 2 cm thick plaster layers on each side of the brick and a 3-cm thick rigid foam (k=0.026 w/m-K) on the inner side of the wall. The indoor and outdoor temperatures are 20˚C and -10˚C respectively, and the convection heat transfer coefficients on the inner and outer sides are hi=10 w/m²-K and ho=25 w/²m-K. Assuming one dimensional heat transfer and disregarding radiation, determine the rate of heat transfer through the wall.

A stainless steel pipe with a length of 35 ft has an inner diameter of 0.92 ft and an outer diameter of 1.08 ft. The temperature of the inner surface of the pipe is 122˚F and the outer temperature of the surface is 118˚F. The thermal conductivity of the stainless steel pipe is 108 Btu/hr-ft-˚F. Calculate the heat transfer (q) and heat flux (q/A) of the pipe.

A steel pipe (k=50 w/m-K) of 100 mm ID and 110 mm OD is to be covered with two layers of insulation each having a thickness of 50 mm. The thermal conductivity of the first insulation material is 0.06 w/m-K, and that of the second is 0.12 W/m-K. Estimate the heat loss per 1m length of pipe when the temperature of the inside tube surface is 523 K and that of the outer surface of insulation is 323 K. If the order of insulation were reversed, calculate the change in heat loss with all other conditions kept unchanged.

A steel tube (k=45 w/m-K) of outside diameter is 7.6 cm and thickness of 1.3 cm is covered with an insulation material, (K=0.20 W/m-K) of thickness 2cm. A hot gas at 330˚C with a convection coefficient of 200 w/m-K is flowing inside the tube. The outer surface of the insulation is exposed to ambient air at 30˚C with a convection coeff of 50 w/m²-K. Calculate:

(a) Heat loss to air from the 5 m long tubes(b) Temperature drop due to thermal resistance of hot gases, steel tube insulation layer

and altitude air.