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An animal's body has a skin temperature of 33 °C and is the room temperature where...
How much power (power is the energy per second) is radiated by the person
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...
The rate of heat transfer by emitted radiation is determined by the Stefan-Boltzmann law of radiation...
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...
In this problem you will consider the balance of thermal energy radiated and absorbed by a...
In this problem you will consider the balance of thermal energy radiated and absorbed by a person in a room. The rate of heat transfer from radiation is: ΔQΔt=eσA(T42−T41)=eσAT42−eσAT41. This equation has two terms which represent the rate of absorption from the room (a gain) and the rate of radiation into the room (a loss). In this problem, we will consider these two terms separately. Assume that the area of a human body may be considered to be that of...
A stainless steel block (H 0.1 m and k 16 W/(m K)) that is perfectly insulated...
A stainless steel block (H 0.1 m and k 16 W/(m K)) that is perfectly insulated on 5 of its 6 sides is floating in space (no convection heat transfer). It is exposed to irradiation, G, of 2500 W/m2. The block is generating heat uniformly where 4x 104 W/m2. The Stefan- Boltzmann constant, o, is 5.67 x 108 W/(m2-K4)·The emissivity of the exposed surface is 0.8. (25 Points) A) What is the exposed surface's temperature? B) What is the maximum...
The emissivity of the human skin is 97.0 percent. Use 35.0 °C for the skin temperature...
The emissivity of the human skin is 97.0 percent. Use 35.0 °C for the skin temperature and approximate the human body by a rectangular block with a height of 1.81 m, a width of 40.5 cm and a length of 32.0 cm. Calculate the power emitted by the human body. 1.430x103 w You are correct. Your receipt no. is 158-4715 Previous Tries Fortunately our environment radiates too. The human body absorbs this radiation with an absorbance of 97.0 percent, so...
3. Two gray-diffuse spheres have properties and temperatures shown below. R and R2 are 0.1 m and 0.3 m respectively. (i...
3. Two gray-diffuse spheres have properties and temperatures shown below. R and R2 are 0.1 m and 0.3 m respectively. (i) Compute heat transfer rate of sphere 1, q W]. Also, to minimize the heat loss, you decide to put a radiation shield in between the two spheres. (ii) Where do you prefer to place the radiation shield, i.e., close to sphere 1 or sphere 2 or right in the middle? (iii Somehow you place the radiation shield with R3...
A room has dimensions of 5m (W), 5m (D), by 2.4m (H). It includes an open...
A room has dimensions of 5m (W), 5m (D), by 2.4m (H). It
includes an open door 1m(W) by 2m(H), and a window 2m(W) by 1m(H).
The window is 1m above ground and is within 2m of a 1.2m high
timber fence.
The room is fully engulfed in fire which has reach flashover and
is fully developed at approx 500 degree celsius.
Calculate the maximum radiation received at the timber fence.
Ans in kW/m2
Where:
= configuration factor, show working...
The surface area of an average naked human adult is 2.2 m^2 and the average skin...
The surface area of an average naked human adult is 2.2 m^2 and the average skin temperature is 33 degrees C. The emissivity of human skin is 0.95. Determine the radiation heat transfer rate from the human to the walls of a room if they are at 22 degrees C. This is why naked person feels chilly at room temperature.
In this problem you will consider the balance of thermal energy radiated and absorbed by a...
In this problem you will consider the balance of thermal energy radiated and absorbed by a person. Assume that the person is wearing only a skimpy bathing suit of negligible area. As a rough approximation, the area of a human body may be considered to be that of the sides of a cylinder of length L=2.0m and circumference C=0.8m. For the Stefan-Boltzmann constant use σ=5.67×10−8W/m2/K4. Part A If the surface temperature of the skin is taken to be T_body=30∘C, how...
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed...
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed to cooling airflow at 27 "C resulting in the convective coefficient, h = 114 W/m' K. The relevant properties of mild steel are given as follows: Density p= 7850 kg/m . Specific heat c = 475 J/kg K and thermal diffusivity a = 0.043 m/hr Determine: (i) Time required to cool the sphere (lumped parameter system) from 540 °C to 95°C. [7 marks] (ii)...
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...
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...
A stainless steel block (H 0.1 m and k 16 W/(m K)) that is perfectly insulated on 5 of its 6 sides is floating in space (no convection heat transfer). It is exposed to irradiation, G, of 2500 W/m2. The block is generating heat uniformly where 4x 104 W/m2. The Stefan- Boltzmann constant, o, is 5.67 x 108 W/(m2-K4)·The emissivity of the exposed surface is 0.8. (25 Points) A) What is the exposed surface's temperature? B) What is the maximum...
The emissivity of the human skin is 97.0 percent. Use 35.0 °C for the skin temperature and approximate the human body by a rectangular block with a height of 1.81 m, a width of 40.5 cm and a length of 32.0 cm. Calculate the power emitted by the human body. 1.430x103 w You are correct. Your receipt no. is 158-4715 Previous Tries Fortunately our environment radiates too. The human body absorbs this radiation with an absorbance of 97.0 percent, so...
3. Two gray-diffuse spheres have properties and temperatures shown below. R and R2 are 0.1 m and 0.3 m respectively. (i) Compute heat transfer rate of sphere 1, q W]. Also, to minimize the heat loss, you decide to put a radiation shield in between the two spheres. (ii) Where do you prefer to place the radiation shield, i.e., close to sphere 1 or sphere 2 or right in the middle? (iii Somehow you place the radiation shield with R3...
A room has dimensions of 5m (W), 5m (D), by 2.4m (H). It
includes an open door 1m(W) by 2m(H), and a window 2m(W) by 1m(H).
The window is 1m above ground and is within 2m of a 1.2m high
timber fence.
The room is fully engulfed in fire which has reach flashover and
is fully developed at approx 500 degree celsius.
Calculate the maximum radiation received at the timber fence.
Ans in kW/m2
Where:
= configuration factor, show working...
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed to cooling airflow at 27 "C resulting in the convective coefficient, h = 114 W/m' K. The relevant properties of mild steel are given as follows: Density p= 7850 kg/m . Specific heat c = 475 J/kg K and thermal diffusivity a = 0.043 m/hr Determine: (i) Time required to cool the sphere (lumped parameter system) from 540 °C to 95°C. [7 marks] (ii)...
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