A
Want to see the full answer?
Check out a sample textbook solutionChapter 1 Solutions
Introduction to Heat Transfer 6th Edition (Wiley Editor's Choice Edition)
- An electronic box that consumes 200 W of power is cooled by a fan blowing air into the box enclosure. The dimensions of the electronic box are 15 cm * 50 cm * 50 cm, and all surfaces of the box are exposed to the ambient except the base surface. Temperature measurements indicate that the box is at an average temperature of 32°C when the ambient temperature and the temperature of the surrounding walls are 25°C. If the emissivity of the outer surface of the box is 0.75, determine the fraction of the heat lost from the outer surfaces of the electronic box.arrow_forwardThe temperature of a tank in the form of liquid nitrogen is -10 ° C. Tank diameter is 16 cm. The amount of heat lost by convection and radiation from the tank to the environment is 65.5 W / m. Calculate the temperature of the environment where the tank is located .h = 4.35 W / m2K, e= 1.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. Not sufficient information 100 W 200 W/(m^2) 100 W/(m^2) 200 Warrow_forward
- The temperature of a cylindrical tank containing liquid nitrogen is -10 ° C. Tank diameter is 16 cm. The amount of heat lost by convection and radiation from the tank to the environment is 65.5 W / m. Calculate the temperature of the environment where the tank is located: h = 4.35 W / m2K, ∈ = 1.arrow_forwardThe inner surface temperature of a 23 cm thick wall of an oven is 820°C, and the outer surface temperature is 170°C. When kept constant, the heat loss of the furnace is measured as 2450 W/m2 from m2 of the wall. heat of the wall Calculate the transmission coefficient.arrow_forward2.A person stands in front of a fire at 650°C in a room where air is at 5°C. Assuming the body temperature to be 37°C and a connection coefficient of 6 W/m²K, the area exposed to convection as 0.6m2, determine the net heat flow from the body. The fraction of radiation from the fire of 1m² are reaching the person is 0.01arrow_forward
- A cylindrical tube has an inner diameter of 2 cm and a wall thickness of 1 cm. The tube is evacuated. In the center, there is a radiation source along its axis that sends 1e^5 W/m^2 to the inner surface of the tube. K for the tube wall is 2 W/m K. If the outer surface of the tube is cooled with water at 298 K with a convective heat transfer coefficient of 100 W/m^2 K, determine the minimum temperature rating for the tube material for safe operation.arrow_forwardThe case-to-ambient thermal resistance of a power transistor that has a maximum power rating of 15 W is given to be 25°C/W. If the case temperature of the transistor is not to exceed 80°C, mark the power at which this transistor can be operated safely in an environment at 40°C.. a)Between 1.0 to 1.5 W b)Between 1.5 to 2.0 W c)Between 2.0 to 2.5 Warrow_forwardA 2 m X 1.5 m section of wall of an industrial furnace burning gas is not insulated, and the temperature at the outer surface of this section is measured to be 80oC. The temperature of the furnace room is 30oC, and the combined convection and radiation heat transfer coefficient at the surface of the outer furnace is 10 w/oC. It is proposed to insulate this section of the furnace wall with glass wool insulation (K=0.038 W/moC) in order to reduce the heat loss by 90 percent. Assuming the outer surface temperature of the section remains at about 80oC, determine i) the thickness of the insulation that is needed and ii) the outer surface temperature of the insulation after installation.arrow_forward
- Consider a black spherical ball, with a diameter of 25 cm, is being suspended in air. Determine the surface temperature of the ball that should be maintained in order to heat 11.7 kg of air from 20°C to 30°C in the duration of 5 minutes.Given: cv = 718 J/kg∙K Stefan-Boltzmann constant (σ) = 5.67 × 10–8 W/m2∙K The surface temperature of the ball is Ts = _____ °C.arrow_forwardBecause you forgot to let the pipes drip during a freezing night, a section of an outdoor pipe is now frozen. The frozen section is L = 1 m long and the inner pipe diameter is D = 1.8 cm. During the day, the pipe is exposed to the cold air, the Sun, and the radiating surroundings. The cold air temperature is T∞ = -10°C, and has convection heat transfer coefficient h = 20 W/m2·K. The Sun provides solar irradiance of Gsun = 1350 W/m2. The steel pipe surface has absorptivity α = 0.6 and emissivity ε= 0.1. The surroundings, such as vegetation, houses, ground, etc. can be assumed to be blackbody held at Tsur = 280 K. A) Using the energy conservation system illustrated below, establish an equation that describes the stored energy in the section of frozen water (Est). B) Determine the amount of time needed to melt the ice in the pipe. Ice has density ρ= 920 kg/m3, and latent heat of fusion hsf = 334 kJ/kg. The ice is Tw = 0°C. Ignore conduction through the pipe walls – assume the pipe…arrow_forwardExplain, motorcycle engine is either considered as free or forced convection. Justify your answerarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning