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Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
- Determine the rate of heat transfer per meter length to a light oil flowing through a 2.5-cm-ID, 60-cm-long copper tube at a velocity of 0.03 m/s. The oil enters the tube at 16C, and the tube is heated by steam condensing on its outer surface at atmospheric pressure with a heat transfer coefficient of 11.3 kW/m K. The properties of the oil at various temperatures are listed in the following table: Temperature, T(C) 15 30 40 65 100 (kg/m3) 912 912 896 880 864 c(kJ/kgK) 1.80 1.84 1.925 2.0 2.135 k(W/mK) 0.133 0.133 0.131 0.129 0.128 (kg/ms) 0.089 0.0414 0.023 0.00786 0.0033 Pr 1204 573 338 122 55arrow_forwardA spherical fuel element has a center temperature of 3600 F. The fuel element is covered by two layers of coating. The fuel ball is cooled by helium. Find the rate of heat transfer. Data: rfuel = 0.5 in, r1 = 0.7 in, r2 = 0.9 in. kfuel = 2 Btu/ft·h·F, kcoating = 7 Btu/ft·h·F, Tf = 700 F and h = 5000 Btu/ft·h·F. [Ans.: 4100 Btu/h].arrow_forwardThe resistance wire of a heater is composed of nichrome (a nickel-chromium alloy), completely surrounded by a 1/8 in (k = 0.15 BTU / h ftºF) layer of asbestos, and this in turn, surrounded by another layer of 1/8 in.thick stainless steel (k = 10 BTU / h ftºF). If the core temperature of the wire is kept constant at 1000 F, the convective heat transfer coefficient is 3 BTU / h ft ºF, and the ambient temperature is 70ºF. Calculate: a) The heat flux delivered to the wire in BTU / h ft^2 b) The outside temperature of the wire in ºFarrow_forward
- A 30 m long pipe with an external diameter of 75 mm is being used to convey steam at a rate of 1000 kg/h. The steam pressure is 198.53 kPa. The steam enters the pipe with a dryness fraction of 0.98 and must leave the other end of the pipe with a minimum dryness fraction of 0.95. Insulation with a thermal conductivity of 0.2 W/(m K) is available. Determine the minimum thickness of insulation necessary. * Indicates an advanced level of difficulty in solving. 400 CHAPTER 4 Heat Transfer in Food Processing The outside surface temperature of insulation is assumed to be 258C. Neglect the conductive resistance of the pipe material and assume no pressure drop across the pipearrow_forwardThe resistance wire of a heater is composed of nichrome (a nickel-chromium alloy), completely surrounded by a 1/8 in (k = 0.15 BTU / h ft ºF) layer of asbestos, and this in turn, surrounded by another layer of 1/8 in.thick stainless steel (k = 10 BTU / h ft ºF). If the core temperature of the wire is kept constant at 1000 F, the convective heat transfer coefficient is 3 BTU / hft ºF, and the ambient temperature is 70 ºF. Calculate: a) The heat flux delivered to the wire in BTU / h ft^2 b) The outside temperature of the wire in ºFarrow_forwardC heat and mass transfer problemarrow_forward
- Steam condenses at 100°C on the outer surface of a pipe with a thermal conductivity of 180 J/ms°C. The surface heat transfer coefficient of the water flowing in the pipe is 4000 J/m²s°C, and the heat transfer coefficient created by the steam condensing outside is 10000 J/m²s°C. The length of the pipe is 5 m and the thread diameter is 25 mm. Since the pipe thickness is 1 mm, calculate the total heat transfer coefficient and the rate of heat transfer from the condensed steam to the water at 15 °Carrow_forwardThe both sides of a sheet of paper, 0.1 mm (or 104 m) thick, initially at 20.4°C, are suddenly exposed to combustion products for which T. 412°C and h=68 w/m K. Determine the time of exposure in (second) required for the surtace to reach the ignition temperature of 233"C. The properties of the paper are as follows • density - 545 kalm • thermal conductivity = 0.17 w/m "C • heat diffusivity = 1.31 x 107 m/s (The tolerance of your answer is 2%) Answer: Checkarrow_forwardA welding heat source is capable of transferring 160 kJ/min to the surface of a metal part. The heated area is approximately circular, and the heat intensity decreases with increasing radius as follows: 50% of the power is transferred within a circle of diameter = 0.25 cm and 75% is transferred within a concentric circle of diameter = 0.625 cm. What are the power densities in (a) the 0.25 cm diameter inner circle and (b) the 0.625 cm diameter ring that lies around the inner circle? (c) Are these power densities sufficient for melting metal?arrow_forward
- Task mechanical engineeringarrow_forwardRequired information Heat dissipated from an engine in operation can cause hot spots on its surface. If the outer surface of an engine is situated in a place where oil leakage is possible, then when leaked oil comes in contact with hot spots above the oil's autoignition temperature, it can ignite spontaneously. Consider an engine cover that is made of a stainless-steel plate with a thickness of 1 cm and a thermal conductivity of 14 W/m.K. The stainless-steel plate is covered with a 5-mm-thick insulation (k=0.5 W/m.K). The inner surface of the engine cover is exposed to hot air at 350°C with a convection heat transfer coefficient of 5 W/m².K as shown in the figure. The 2-m-long engine outer surface is cooled by air blowing in parallel over it at 7 m/s in an environment where the ambient air is at 60°C. To prevent fire hazard in the event of oil leak on the engine cover, the engine cover surface should be kept below 180°C. It has been determined that the 5- mm-thick insulation layer is…arrow_forwardA pipe 30 m long with an outer diameter of 75 mm is used to deliver steam at a rate of 1500 kg / hour. The steam pressure is 198.53 kPa entering the pipe with a quality of 98%. The pipe that needs to be insulated with a thermal conductivity of 0.2 W / (m K) so that the quality of the steam only decreases slightly to 95%. The temperature of the outer surface of the insulation is assumed to be 25 ° C. The conductive of the pipe material and the situation of no pressure drop in the pipe. A. Determine the enthalpy of incoming vapor = Answer kJ / kg. b. Determine the enthalpy of steam that comes out = Answer kJ / kg. c. Determine the change / loss of steam heat along the flow = Answer watt. d. Determine the minimum required insulation thickness = Answer cm.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning