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- 7.43 Liquid sodium is to be heated from 500 K to 600 K by passing it at a flow rate of 5.0 kg/s through a 5-cmID tube whose surface is maintained at 620 K. What length of tube is required?arrow_forwardDetermine 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_forward3.10 A spherical shell satellite (3-m-OD, 1.25-cm-thick stainless steel walls) re-enters the atmosphere from outer space. If its original temperature is 38°C, the effective average temperature of the atmosphere is 1093°C, and the effective heat transfer coefficient is , estimate the temperature of the shell after reentry, assuming the time of reentry is 10 min and the interior of the shell is evacuated.arrow_forward
- 2.42 A circumferential fin of rectangular cross section, 3.7-cm OD and 0.3 cm thick, surrounds a 2.5-cm- diameter tube as shown below. The fin is constructed of mild steel. Air blowing over the fin produces a heat transfer coefficient of K. If the temperatures of the base of the fin and the air are and , respectively, calculate the heat transfer rate from the fin.arrow_forward2.38 The addition of aluminum fins has been suggested to increase the rate of heat dissipation from one side of an electronic device 1 m wide and 1 m tall. The fins are to be rectangular in cross section, 2.5 cm long and 0.25 cm thick, as shown in the figure. There are to be 100 fins per meter. The convection heat transfer coefficient, both for the wall and the fins, is estimated to be K. With this information determine the percent increase in the rate of heat transfer of the finned wall compared to the bare wall.arrow_forwardThe cylinders that come out of the heat treatment furnace are cooled in a stagnant air environment in a horizontal position. The cylinders have a diameter of 100 mm and a length of 0.1 m. The temperature of the cylinders is 440 ° C and the ambient temperature is 20 ° C. Calculate the heat transfer from 10 cylinders to the environment. a) 3125 W b) 2350 W C) 1848 W d) 1354 W e) 2750 Warrow_forward
- The wall of a refrigerator is made of fiberglass insulation (k = 0.035 W/mK) glued between two 1 mm thick layers of metal plate (k = 15.1 W/mK). The refrigerated space is kept at 2°C, and the average heat transfer coefficients on the inner and outer wall surfaces are 4 W/m²K and 9 W/m²K, respectively. The average temperature in the kitchen is 24°C. It is observed that condensation occurs on the external surface of the refrigerator when the temperature of the external surface drops to 20°C. Determine the minimum thickness of fiberglass insulation that should be used on the wall to prevent condensation on the outside surface.arrow_forwardWater is to be heated from 35 °C to 65 °C in a rough tube with a relative roughness of 0.001. The tube has an electric heater provides a constant heat flux such that the tube average wall temperature is 20 °C above the average water bulk temperature. The Reynolds number used for calculating the heat-transfer coefficient is 100,000. Calculate the length of tube required for heating, expressed in meters, if the tube has a diameter of 1 cm.arrow_forwardWhat is heat transfer coefficient?arrow_forward
- STEAM FLOW IN AN INSULATE PIPE AT ATEMPERATURE 130 C. THE INSIDE HEAT TRANSFER COEFFICIENT IS 79 W/M-K AND THE OUTSIDE COEFFICIENT IS 15 W/M-K. THE PIPE IS MILD STEEEL (K=57 WLM-K) AND HAS AN INSIDE RADIUS OF 50 MM AND AN OUTSIDE RADIUS 57 MM. THE PIPE IS COVERD WITH A 25.4 MM LAYER ( K=0.09 W/M-K). DETERMINE THE OVERALL HEAT TRANSFER COEFFICIENTIF THE SURROUNDING AIR TEMPERATURE IS 21.1 C.arrow_forwardA transformer that is L=20cm long, 6.2 cm wide, and 5 cm high is to becooled by attaching a 10 cm × 6.2 cm wide polished aluminum heatsink (emissivity =0.03) to its top surface. The heat sink has seven fins,which are 5 mm high, 2 mm thick, and 10 cm long. A fan blows air at25°C parallel to the passages between the fins. The heat sink is todissipate 20 W of heat and the base temperature of the heat sink is notto exceed 60°C. Assuming the fins and the base plate to be nearlyisothermal and the radiation heat transfer to be negligible, determinethe minimum free-stream velocity the fan needs to supply to avoidoverheating. (k=0.02681W/m˚C, Pr=0.7248, V= 1.726×10-5 m2/s, )arrow_forwardA 50-cm diameter pipeline in the Arctic carries hot oil where the outer surface is maintained at 30 °C and is exposed to a surrounding temperature of -17 °C. The convection heat-transfer coefficient on the outside of the pipe is 9 W/m2 °C. Estimate the energy loss from the pipe per meter of length.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning