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- Consider a long, insulated cable supplying power to a community. It is elevated in the air by using poles. The ambient air temperature is 20oC and the convective heat transfer coefficient is h = 20 W/m2.K. Radiation exchange between the cable surface and the environment can be neglected. Make your calculations considering per meter-length. The wire carries 500 Amp current and has a resistance of 0.0001 Ohm/m. The diameter of the solid core wire is 1.0 cm and has a thermal conductivity of k = 20 W/m.K The electrically insulating material covering the wire-core has a thickness of 0.5 cm with a thermal conductivity of k = 0.01 W/m.K a) What is the rate of heat loss from the cable to the environment in kW/meter? b) What is the outside surface (exposed to air) temperature of the cable? c) What is the temperature of the interface between the insulation sleeve and the core-wire carrying the electric power? If the sleeve material has to remain below 100 oC for the long term, would this…arrow_forwardPlease I want the correct answer DONT't copy the previous answers here they are wrong 922 W is wrong answer pleasearrow_forwardA steam pipe 50 mm diameter and 2.5 m long has been placed horizontally and exposed to still air at 25 degree Celsius. If the pipe wall temperature is 295 degree Celsius, determine the rate of heat loss. At the mean temperature difference of 160 degree Celsius, the thermo-physical properties of air are k =3.64 * 10 -2 W/m v =30.09 * 10 -6 m2/ P r =0.68 Β =1/160 + 273 = 2.31 * 10^-3/Karrow_forward
- The rectangular wall of a furnace consists of 3in. fire clay brick surrounded by 0.25in. of steel on the outside. There are six 0.25in.diameter mild steel bolts per square foot connecting the steel and the brick. The furnace is surrounded by 70°F air (with a film coefficient of 1.65 Btu/hr-ft²-°F), while the inner surface of the brick is maintained at a constant 1000°F. Determine the heat flux per square foot through this wall?arrow_forward- Ground cherry seeds need to be planted at a depth of 1-cm below the surface and will only germinate if their surrounding soil is at a temperature of 24-30°C. Farmer Joe wants to know whether adding straw mulch (Amulch = 0.05 W/m K, Lmulch = 10 cm) on top of his soil will increase the odds of germination. The topsoil in Deleware is sandy loam (soil = 0.5 W/m K), with a thickness of 1 m. Immediately beneath the topsoil is the subsoil, which is at a constant temperature of Tsubsoil = 10°C. You can assume that the air in Deleware is fairly calm, with a heat transfer coefficient of h = 10 W/m².K. deleware (a) Sketch the system (with and without mulch), labeling all temperatures, dimensions, and proportionality constants. You may assume that the subsoil, topsoil, mulch, and air are at steady state. You should have two sketches.arrow_forwardQuiz: A double-pane window consists of two 3 mm thick layers of glass separated by a 12 mm wide stagnant air space. For specified indoors and outdoors temperatures. 1. Determined rate of heat loss through the window and 2. The inner surface temperature of the window. kalass = 0.78 W/m-°C and k stagnant space = 0.026, The area of the window and the individual resistances are A=(1.2 m)x (2 m) = 2.4 m² Glass Glass Stagnant space Toi= 24 h = 10 w/m?.c To2- -5 c h2 25 w/m2.c 12 mm 3 mm mmarrow_forward
- Determine the heat-transfer rate from an electronic chip whose surface temperature is 40°C and has an exposed surface area of 3 cm². The temperature of the surrounding air is 22°C. The heat-transfer coefficient for this situation is h = 25 in both SI units (in W) and U.S. Customary units (in Btu/h). rate in W W Btu/h rate in Btu/h What is the R-factor (film resistance, in K. m²/W) for this situation? K. m²/w W m². K Express your answerarrow_forwardTo maximize production and minimize pumping costs, crude oil is heated to reduce its viscosity during transportation from a production field. (1) Consider a pipe-in-pipe configuration consisting of concentric steel tubes with an intervening insulating material. The inner tube is used to transport warm crude oil through cold ocean water. The inner steel pipe ( ks = 40 W/m·K) has an inside diameter of Di,1 = 150 mm and wall thickness ti = 20 mm while the outer steel pipe has an inside diameter of Di,1 = 250 mm and wall thickness . Determine the maximum allowable crude oil temperature to ensure the polyurethane foam insulation ( kp = 0.0425 W/m·K) provides an external convection heat transfer coefficient of ho = 500 W/m2·K. The convection coefficient associated with the flowing crude oil is hi = 450 W/m2·K. (2) It is proposed to enhance the performance of the pipe-in-pipe device by replacing a thin ( ta =10 mm) section of polyurethane located at the outside of the inner pipe with an…arrow_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_forward
- To maximize production and minimize pumping costs, crude oil is heated to reduce its viscosity during transportation from a production field. (1) Consider a pipe-in-pipe configuration consisting of concentric steel tubes with an intervening insulating material. The inner tube is used to transport warm crude oil through cold ocean water. The inner steel pipe (ks= 40 W/m·K) has an inside diameter of Di, 1= 150 mm and wall thickness ti= 20 mm while the outer steel pipe has an inside diameter of Di, 2= 250 mm and wall thickness to=ti. Determine the maximum allowable crude oil temperature to ensure the polyurethane foam insulation (kp= 0.0675 W/m·K) between the two pipes does not exceed its maximum service temperature of Tp, max= 70°C. The ocean water is at ∞ T∞, o= -5°C and provides an external convection heat transfer coefficient of ho= 500 W/m2·K. The convection coefficient associated with the flowing crude oil is hi= 450 W/m2·K. (2) It is proposed to enhance the performance of the…arrow_forwardTo maximize production and minimize pumping costs, crude oil is heated to reduce its viscosity during transportation from a production field. (1) Consider a pipe-in-pipe configuration consisting of concentric steel tubes with an intervening insulating material. The inner tube is used to transport warm crude oil through cold ocean water. The inner steel pipe (ks= 40 W/m·K) has an inside diameter of Di, 1= 150 mm and wall thickness ti= 20 mm while the outer steel pipe has an inside diameter of Di, 2= 250 mm and wall thickness to=ti. Determine the maximum allowable crude oil temperature to ensure the polyurethane foam insulation (kp= 0.0675 W/m·K) between the two pipes does not exceed its maximum service temperature of Tp, max= 70°C. The ocean water is at ∞ T∞, o= -5°C and provides an external convection heat transfer coefficient of ho= 500 W/m2·K. The convection coefficient associated with the flowing crude oil is hi= 450 W/m2·K. (2) It is proposed to enhance the performance of the…arrow_forward2. A steam line is covered with two successive layers of insulation. The 1.6 in thick layer in contact with the pipe is asbestos which is covered with a 1.4 inch thickness of magnesia insulation. The internal pipe diameter is 3 in, the pipewall thickness is 0.40 in made from common brick. The steam temperature is 850ºF, and the internal surface film coefficient is 50 Btu/hr.ft².F, while the ambient outer temperature is 105°F and the outer surface film coefficient is 3.0 Btu/hr.ft².F. Calculate the following: a. value of U based upon the external area of the magnesia covering, Btu/hr.ft2.F b. heat loss from the steam for a length of 190 feet of pipe, Btu/hrarrow_forward
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