The diameter and surface emissivity of an electricallyheated plate are
(a) Estimate the power needed to maintain a surfacetemperature of 200°C in a room [or which the airand the walls are at 25°C. The coefficient characterizing heat transfer by natural convection depends on the surface temperature and, in units of
(b) Assess the effect of surface temperature on thepower requirement, as well as on the relative contributions of convection and radiation to heat transfer from the surface.
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Fundamentals of Heat and Mass Transfer
- A spherical communications satellite, 2 m in diameter, is placed in orbit around the earth. The satellite generates 1000 W of internal power from a small nuclear generator. If the surface of the satellite has an emittance of 0.3, and is shaded from solar radiation by the earth, estimate its surface temperature.arrow_forwardAn electrical transmission line of 1.2-cm diameter carries a current of 200 amps and has a resistance of 310-4 ohm per meter of length. If the air around this line is at v, determine the surface temperature on a windy day, assuming a wind blows across the line at 33 km/h.arrow_forwardThe heat transfer rate from hot air by convection at 100C flowing over one side of a flat plate with dimensions 0.1m0.5m is determined to be 125 W when the surface of the plate is kept at 30C. What is the average convection heat transfer coefficient between the plate and the air?arrow_forward
- 1.76 Explain a fundamental characteristic that differentiates conduction from convection and radiation.arrow_forwardDetermine the power requirement of a soldering iron in which the tip is maintained at 400C. The tip is a cylinder 3 mm in diameter and 10 mm long. The surrounding air temperature is 20C, and the average convection heat transfer coefficient over the tip is 20W/m2K. The tip is highly polished initially, giving it a very low emittance.arrow_forwardQuestion:- A cylindrical steel tank with a diameter of 3 m and height of 4.4 m is used to store chilled water (at 9.3 °C) as part of an air conditioning system for a building. The heat transfer (convection) co-efficient for the surface of the tank in contact with the water in this application is 15 W/(m2.K). Given the surface temperature of the metal tank is 40 °C. At what rate must heat energy be removed from the water just to maintain its temperature constant at 9.3 °C ? Assume the tank is an enclosed cylinder and that the tank is always full. Note - the thickness of the tank is not relevant to this problem. Work in base SI units.arrow_forward
- You are cooling the door to a large heat-treating oven, which is 3.50 m tall by 1.30 m wide, with a large fan blowing air at 25.0°C over the outside of the door. The convection coefficient associated with this cooling process is h = 57.0 W/(m2-K). The outside surface temperature of the door is 58.0°C. Find the heat transfer rate q, in units of Watts, associated with this cooling process.arrow_forwardPROBLEM 1Consider an adult human standing in the centre of a closed room. The air and room’swalls, ceiling and floor surrounding the being are at a temperature of 25oC. Assume forthe adult body a temperature of 37oC, a surface area of 1.7m2, an emissivity of 0.95 andthe heat transfer coefficient of 6 W/m2K for natural convection between the air and thebody. Question:(a) Describe the modes of heat transfer between the adult human and theirsurroundings. What are some assumptions that must be made before calculatingthe heat transfer rates?(b) Determine the total rate of heat transfer from the adult into their surroundings.arrow_forwardSteam is being transported in a pipe at a chemical production facility in Gebze, Kocaeli. Theouter diameter of the pipe is 8 cm, and the surrounding air temperature is 20 °C. On the surface of thepipe, the combined heat transfer coefficient is 35 W/m2*K. The surface temperature of the pipe is 150 °C.Steady-state conditions exist.(a) What is the rate of heat loss from the pipe to the surroundings?(b) The power used to generate the steam is obtained from natural gas. Perform an online search forapproximate values of the calorific value of natural gas, as well as the cost of natural gas per cubicmeter, and estimate the financial loss due to heat loss from this steam pipe within a period of oneyear. Indicate your sources clearly in your answer.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning