Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
8th Edition
ISBN: 9781305387102
Author: Kreith, Frank; Manglik, Raj M.
Publisher: Cengage Learning
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2.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 0.01
Two surfaces make up an enclosure where surface 1 is flat and has area A1,temperature T1 and emissivity 1. Surface 2 is black and has temperature T2. Showthat the net power transfer rate (net heat flux) in W/m2 at surface 1 is given by
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.
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- According to an Atomic Energy Commissionreport, a hydrogen bomb can be approximated as a large fireball at a temperature of 7200 K. You are to assess theimpact if such a bomb exploded 5 km above a city. Assumethe diameter of the fireball to be 1 km, and the blast to last15 s. Investigate the level of radiation energy people, plants,and houses will be exposed to and how adversely they will beaffected by the blast.arrow_forwardQ#01:a) Define Radiation and give at least 3 examples.b) Define Stefan-Boltzmann Law and emissivity. Is there any surface whose emissivity valueis greater than 1? If no, explain the reason.arrow_forwardTwo concentric spheres of diameters D1 = 15 cm and D2 = 25 cm are separated by air at 1 atm pressure. The surface temperatures of the two spheres enclosing the air are T1 = 350 K and T2 = 275 K, respectively, and their emissivities are 0.75. Determine the rate of heat transfer from the inner sphere to the outer sphere by (a) natural convection and (b) radiation.arrow_forward
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