The concrete slab of a basement is 11 m long, 8 m wide, and 0.20 m thick. During the winter, temperatures are nominally
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Introduction to Heat Transfer
- Consider the process of baking potatoes in a conventional oven. Can the hot air in the oven be treated as a thermal energy reservoir? Explain.arrow_forwardWhat is the approximate temperature difference between a hot plate and the surrounding air if the heat flux from the plate is 800 W/m2? Assume that the air is flowing past the surface with a velocity of 5 m/s giving a heat transfer coefficient of 20 W/(m2K).arrow_forwardCalculate the thermal resistance due to convection for the following situations:a. w arm water with h = 200 W⁄m2 .Kb. warm air with h = 10 W⁄m2 .Kc. warm moving air (windy situation) h = 30 W⁄m2 .Karrow_forward
- Convective heat transfer coefficient is 15 W/(m*K), surface area of the fin is 2 m^2, the temperature at the base is 70 C and the ambient temperature is 20 C. Determine the fin efficiency if the actual heat transfer rate from the fin is 500 W?arrow_forwardA Gasoline engine operating on an air standard condition has a clearance volume of 15cm3and a displacement volume of 100cm3. Determine the theoretical thermal efficiency of the engine.a. 55.7253% b. 55.7250% c. 55.7251% d. 55.7254%arrow_forward....A journal bearing is to be used for a centrifugal pump where the shaft diameter is 50 mm and the bearing length is 80 mm. The ambient and bearing surface temperatures are 20°C and 45°C, respectively. Which of the following is the heat dissipated by the bearing if the heat dissipation coefficient is 280 W/m2-°C? Group of answer choices 56 W 14 W 73 W 28 Warrow_forward
- In a thermal power plant, a horizontal copper pipe of "D" diameter, "L" length and thickness 0.6 cm enters into the boiler that has the thermal conductivity as 0.33 W/mK. The boiler is maintained at 105C and temperature of the water that flows inside the pipe is at 28C. If the energy transfer (Q) is 118922 kJ in 6 hours. Determine the Heat transfer rate, Surface area of the pipe and Diameter & Length of the pipe, if D = 0.016 L. Change in Temperature (in K) = Heat Transfer Rate (in W) = Surface Area of the Pipe (m2) =arrow_forwardA cylindrical fuel rod (k = 30 W/m•K) of 2 cm in diameter is encased in a concentric tube and cooled by water. The fuel rod generates heat uniformly at a rate of 100 MW/m3, and the average temperature of the cooling water is 115°C with a convection heat transfer coefficient of 2500 W/m2.k. The operating pressure of the cooling water is such that the surface temperature of the fuel rod must be kept below 200°C to avoid the cooling water from reaching the critical heat flux (CHF). The critical heat flux is a thermal limit at which a boiling crisis can occur Determine the temperature at the surface of the rod. What can you do to lower the temperature aty the surface?arrow_forwardOver the outside part of the room window, the wind is blowing with a speed of 10 m/sec. Due to this wind motion, the temperature on the outer surface of the window is 5 degrees lower than the room temperature. Determine the convective heat flux if the wind temperature is 10 C with a heat transfer coefficient of 10 W/(mK). Accept the temperature inside the room as 25 C. A) 200 W B) 100 W C) 200 W/(m^2) D) 100 W/(m^2) E) Not sufficient informationarrow_forward
- The 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_forwardSteam at 235°C is flowing inside a steel pipe (k = 61 W/m ∙ °C) whose inner and outer diameters are 10 cm and 12 cm, respectively, in an environment at 20°C. The heat transfer coefficients inside and outside the pipe are 105 W/m2 ∙ °C and 14 W/m2 ∙ °C, respectively. Determine (a) the thickness of the insulation (k = 0.038 W/m ∙ °C) needed to reduce the heat loss by 95 percent and (b) the thickness of the insulation needed to reduce the exposed surface temperature of insulated pipe to 40°C for safety reasons.arrow_forwardA 12-m-long and 5-m-high wall is constructed of two layers of 1-cm-thick sheetrock (k = 0.17 W/m·K) spaced 16 cm by wood studs (k = 0.11 W/m·K) whose cross section is 16 cm * 5 cm. The studs are placed vertically 60 cm apart, and the space between them is filled with fiberglass insulation (k = 0.034 W/m·K). The house is maintained at 20°C and the ambient temperature outside is 29°C. Taking the heat transfer coefficients at the inner and outer surfaces of the house to be 8.3 and 34 W/m2·K, respectively, determine (a) the thermal resistance of the wall considering a representative section of it and (b) the rate of heat transfer through the wall.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning