Cherry-red embers in a fireplace are at 875∘C and have an exposed area of 0.2 m2 and an emissivity of 1.0. The surrounding room has a temperature of 21∘C. If 50% of the radiant energy enters the room, what is the net rate of radiant heat transfer, into the room, in kilowatts?
given
T1 = 875 C = 875 + 273 = 1148 K
T2 = 21 C = 21 + 273 = 294 K
A = 0.2 m^2
using Stefan-Boltzman's law,
the rate of radiant energy enters the room = 0.5*A*sigma*(T1^4 -
T2^4) (here sigma is stefan's constant)
= 0.5*0.2*5.67*10^-8*(1148^4 - 294^4)
= 9806 W
= 9.806 kW <<<<<<<<---------------Answer
Cherry-red embers in a fireplace are at 875∘C and have an exposed area of 0.2 m2...
Cherry-red embers in a fireplace are at 875∘C and have an exposed area of 0.2 m2 and an emissivity of 1.0. The surrounding room has a temperature of 21∘C. If 50% of the radiant energy enters the room, what is the net rate of radiant heat transfer, into the room, in kilowatts?
Cherry-red embers in a fireplace are at 835°C and have an exposed area of 0.240 m2 and an emissivity of 0.980. The surrounding room has a temperature of 15.0°C. If 50% of the radiant energy enters the room, what is the net rate of radiant heat transfer in kilowatts? Radiation makes it impossible to stand close to a hot lava flow. Calculate the rate of heat transfer by radiation in kilowatts from 1.00 m2 of 1140°C fresh lava into 35.0°C...
A wall panel is insulated on the back and exposed to solar radiation on the front surface. The exposed surface of the plate has an absorptivity α = 0.8 for radiation (i.e. 80% of radiant energy is absorbed). Solar radiation arrives to the panel at a rate of 1 kW⁄m2. The panel emissivity ϵ = 1 and the surrounding air temperature is 25°C. a. If we assume radiation is the only mechanism of heat transfer, in this scenario determine the...
Consider a 295 m2 black roof on a night when the roof's temperature is 32°C and the surrounding temperature is 17.5°C. The emissivity of the roof is 0.900.At what net rate does heat radiate, in kilowatts, from the roof?
Consider a 270 m2 black roof on a night when the roof's temperature is 30.5°C and the surrounding temperature is 17.5°C. The emissivity of the roof is 0.900. At what net rate does heat radiate, in kilowatts, from the roof?
Homework 7 heat transfer 2018-20 1) A horizontal tube of 12.5-mm dimeter with an outer srface temperature of 240°C is placed in a room with an air temperature of 20°C. Estimate the heat transfer rate per unit length of the tube due to free convection. 2) Air at -10°C flows at 10 m/s over the roof plate of two 5m length rooms whose air is at Too-200C. The roof plate is 0.20-m thick concrete (k = 0.6 w/ m. K)....
The temperature distribution across a wall 0.2 m thick at a certain instant of time is T(x) = a + bx + cxº, where T is in degrees Celsius and x is in meters, a = 200°C, b = -190°c/m, and c = 30°C/m2. The wall has a thermal conductivity of 1 W/m.k. (a) On a unit surface area basis, determine the rate of heat transfer into and out of the wall and the rate of change of energy stored...
Radiation of Energy The rate of heat transfer by emitted radiation is determined by the Stefan-Boltzmann law of radiation: = aeAT4 where o 5.67x10-8 J/s - m2 K is the Stefan-Boltzmann constant, A is the surface area of the object, and T is its absolute temperature in kelvin. The symbol e stands for the emissivity of the object, which is a measure of how well it radiates An ideal jet-black (or black body) radiator has e 1,whereas a perfect reflector has...
10. (10pts) The surface area of an adult human being is 1,8 m2. Suppose a person with a skin tem omperature of 34°C is standing with bare skin in a room where the air is 22°C but the walls are 21°C. (ơ 5.67" 104 J / (sm"к"). There is a "dead ai lay ran around you next to your skin that acts as insulation. This dead-air layer is 5.0 mm thick. a) Draw b) What is the person's rate of...
The rate of heat transfer by emitted radiation is determined by the Stefan-Boltzmann law of radiation = ceAT4 t where a 5.67x108 J/(s m2. K4) is the Stefan-Boltzmann constant, A is the surface area of the object, and T is its absolute temperature in kelvin. The symbol e stands for the emissivity of the object, which is a measure of how well it radiates. An ideal jet-black (or black body) radiator has e 1, whereas a perfect reflector has e...