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Introduction to Heat Transfer
- Quiescent means that you will be using natural convection (so buoyancy type of convection) (not forced convection) show a detailed solution to the problem. the solution is correct (use to double check) A horizontal cylindrical rod with a length of 2 m and a diameter of 0.2 m is used for the top of a swing set. On a sunny summer day, the temperature of the rod is 40°C and the temperature of the quiescent air is 30°C. What is the convective heat transfer rate from the rod? | 416 warrow_forwardSUPPOSE THE AMBIENT TEMPERATURE IS 20degrees CELSIUS, AND THE HOT RESERVOIR CONSISTS OF A SPHERICAL TANK WITH A RADIUS OF 4.00 m, THAT ACTS AS AN IDEAL EMITTER OF RADIATION. IF ALL THE RADIANT ENERGY EMITTED BY THE TANK COULD BE CAPTURED, WHAT IS THE AVERAGE AMOUNT OF WORK THAT COULD BE DONE EACH SECOND? ( please only answer if your 100% correct) (show work)arrow_forward4. The surface temperature of a planet is T, and the measured temperature is Tm (i.e. the temper- ature measured at the top-of-atmosphere based on the upwards flux Ft there). Assume radiative equilibrium. (a) Show that the infrared optical depth of the planet's surface 7 is related to the surface temperature T, and the measured temperature Tm by Calculate the infrared optical depth at the surfaces of (a) Earth, where T, = 300 K and Tm = 250 K. (b) Venus, where T, = 750 K and Tm = 230 K. (c) Mars, where T, = 240 K and T, = 220 K.arrow_forward
- An electric immersion heater, 10 mm in diameter and 300 mm long, is rated at 550 W. If the heater is horizontally positioned in a large tank of water at 20 °C, estimate its surface temperatures. Estimate the surface temperature if the heater is accidentally operated in air at 20 °C.arrow_forwardA concrete ball of radius 2.32 m and emissivity 0.620 is heated to 123°C. (a) Convert the given temperature to Kelvin. (Enter your answer to at least three significant figures.) ?K (b) What is the surface area (in m2) of the ball? ?m2 (c) If the ambient temperature is 26.0°C, what net power (in W) does the ball radiate? ?Warrow_forwardVacuum furnaces are used in manufacturing for metal heating in brazing and sintering processes, as well as for heat treatment of steel alloys. The vacuum, and absence of air/oxygen, facilitates a low contamination process and prevents detrimental surface oxidisation. Heat is often provided in these furnaces by electrical heating elements, and their thermal design is critical to the effective operation of the furnace. In one such case, this element is modelled as a long, cylindrical electrically heated rod, 20 mm in diameter installed in a vacuum furnace as shown. The surface of the heating rod has an emissivity of 0.9 and is maintained at 1000 K, while the interior walls of the furnace are black and are at 800 K. Calculate the net rate at which heat is lost from the rod per unit length.arrow_forward
- A solid sphere made of polished copper has a diameter of 2 cm and is at 100 C. We now expose the solid sphere to are at 50 C and 1 atm. Use the lumped capacitance method to plot the temperature of the solid sphere versus time after five minutes of exposure. The air is quiescent.arrow_forwardExample 7.9 The filament of a 75 W light bulb may be considered a black body radiating into a black enclosure at 70°C.The filament diameter is 0.10 mm and length is 50 mm. Considering the radiation, determine the filament temperature.arrow_forwardA 3-in-diameter cylindrical wire is coated in 3 inches of polyethylene insulation. The wire can be modeled as a grey body with an emissivity of .85. Due to the electrical resistance, the wire is at a temperature of 300 degrees Celsius. The insulation is also a great body with an emissivity of .95, at a temperature of 40 degrees Celsius. (Assume F12=1). What is the heat flux (W/m^2) of the energy going from the wire to the insulation?arrow_forward
- Compute the heat gain for a window facing southeast at 32° north latitude at 10 A.M. central daylight time on August 21. The window is regular double glass with a 13-mm air space. The glass and inside draperies have a combined shading coefficient of 0.45. The indoor design temperature is 25° C, and the outdoor tempera ture is 37°C. Window dimensions are 2 m wide and 1.5m high.arrow_forwardA pipe still uses 7110 lb per hour of a cracked gas (Net Heating Value (NHV) 20560 Btu per lb). The radiant section contains 1500 sq ft of projected area, and the tube (5 in. outside diameter) are spaced at a center-to-center distance of 10 in. there is only one row of radiant tubes, and they are 40 ft long. The ratio of air to fuel is (21 (30 percent excess air). a) What percentage of the heat liberation is absorbed in the radiant section? b) How many Btu are absorbed per hour through each square foot of projected area?arrow_forward7) Given a window of 20 ft facing east at 40° north latitude, estimate the cooling load due to solar radiation at 4:00 pm for a day in June. Assume the window does not have any interior shading and the shading coefficient is 0.2 (in Btu/hr) (a) 105 (d) 276 (b) 430 (c) 314 (c) 225arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning