For a boiling process such as shown in Figure 1.5c, the ambient temperature
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Introduction to Heat Transfer
- Water is to be heated from 15°C to 65°C as it flows through a 3-cm-internaldiameter 5-m-long tube . The tube is equipped with an electric resistance heater that provides uniform heating throughout the surface of the tube. The outer surface of the heater is well insulated, so that in steady operation all the heat generated in the heater is transferred to the water in the tube. If the system is to provide hot water at a rate of 10 L/min, determine the power rating of the resistance heater. Also, estimate the inner surface temperature of the tube at the exit.arrow_forwardConsider hotdog being cooked in boiling water in a pan. Would the heat transfer be modeled as one-dimensional or two-dimensional? Would the heat transfer be steady or transient? Explain.arrow_forwardThe temperature in the room is 22 °C, and the energy transfer to the cylindrical electric heater is 350 W. The diameter of the heater is 20 cm. Determine the surface temperature of the heater. Will this temperature of the heater change over time? Why, or why not? If the temperature of the heater does not change over time, determine the value of this temperature. If the temperature of the heater changes over time, determine the final value of this temperature.arrow_forward
- Why is this equation fundamental in the analysis of heat transfer? Why is this a big deal for engineers?arrow_forwardThe heat transfer coefficient of oil flowing through a pipe is 300 W/m2 K. Determine the heat transfer coefficient in BTU/h ft2 oF.arrow_forwardConsider a wall heated by convection on one side and cooled by convection on the other side. Show that the heat-transfer rate through the wall is q = (T1 - T2) / (1/h1A + x/kA + 1/h2A) where T1 and T2 are the fluid temperatures on each side of the wall and h1 and h2 are the corresponding heat-transfer coefficients.arrow_forward
- Consider steady heat transfer between two parallel plates at a constant temperaturearrow_forwardThe blades of a wind turbine turn a large shaft at a relatively slow speed. The rotational speed is increased by a gearbox that has an efficiency of 0.93. In turn, the gearbox output shaft drives an electric generator with an efficiency of 0.95. The cylindrical nacelle, which houses the gearbox, generator, and associated equipment, is of length L = 6 m and diameter D = 3 m. If the turbine produces P = 2.5 MW of electrical power, and the air and surroundings temperatures are T = 25 oC and Tsur = 20 oC, respectively, determine the minimum possible operating temperature inside the nacelle. The emissivity of the nacelle is 0.83, and the convective heat transfer coefficient is h = 35 W/m2 .K. The surface of the nacelle that is adjacent to the blade hub can be considered to be adiabatic, and solar irradiation may be neglected. Use Fin or N number of fins to reduce the Ts of the nacelle less than 143 oCarrow_forwardWater is to be heated from 15C to 65 C as it flows through a 3 cm internal diameter 5 m long tube. The tube is equipped with an electric resistance heater that provides uniform heating throughout the surface of the tube. The outer surface of the heater is well insulated, so that in steady operation all the heat generated in the heater is transferred to the water in the tube. If the system is to provide hot water at a rate of 10 L/min, determine the power rating of the resistance heater. Also, estimate the inner surface temperature of the tube at the exit. The water properties at the bulk mean temperature are: density=992.1 kg/m3, k = 0.631 W/m.K, v= 0.658 x 10* m^2/s, Cp = 4.179 kJ/kg. K, Pr = 4.32.arrow_forward
- An average man has a body surface area of 1.8 m2 and a skin temperature of 33°C. The convection heat transfer coefficient for a clothed person walking in still air is expressed as h = 8.6V 0.53 for 0.5 < V < 2 m/s, where V is the walking velocity in m/s. Assuming the average surface temperature of the clothed person to be 30°C, determine the rate of heat loss from an average man walking in still air at 10°C by convection at a walking velocity of (a) 0.5 m/s, (b) 1.0 m/s, (c) 1.5 m/s, and (d) 2.0 m/s.arrow_forwardIn a power plant, pipes transporting superheated vapor are very common. In a certain plant, superheated vapor is flowing at a rate of 0.3 kg/s inside a 5 cm diameter pipe of 10 m length. The air in the plant is maintained at 20oC while the surface temperature of the pipe is 100oC. If the temperature drop between the inlet and exit of the pipe is 30oC and the specific heat capacity of the vapor is 2190 kJ/kg.K, determine the convective heat transfer coefficient at the pipe surface. If necessary, how could this coefficient be increased?arrow_forwardThe net radiant-heat exchange between a 20-by-20 ft rough plaster panel-heated ceiling and a 20-by-10-ft side wall, which has an emissivity of 0.80, is 2400 Btu/hr. If the surface temperature of the ceiling is 120 deg. F, determine the average surface temperature of the side wall.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning