A horizontal, opaque surface at a steady-state temperature of 77 ∘ C is exposed to an airflow having a free stream temperature of 27 ∘ C with a convection heat transfer coefficient of 28 W / m 2 ⋅ K . The emissive power of the surface is 628 W / m 2 , the irradiation is 1380 W / m 2 , and the reflectivity is 0.40. Determine the absorptivity of the surface. Determine the net radiation heat transfer rate for this surface. Is this heat transfer to the surface or from the surface? Determine the combined heat transfer rate for the surface. Is this heat transfer to the surface or from the surface?
A horizontal, opaque surface at a steady-state temperature of 77 ∘ C is exposed to an airflow having a free stream temperature of 27 ∘ C with a convection heat transfer coefficient of 28 W / m 2 ⋅ K . The emissive power of the surface is 628 W / m 2 , the irradiation is 1380 W / m 2 , and the reflectivity is 0.40. Determine the absorptivity of the surface. Determine the net radiation heat transfer rate for this surface. Is this heat transfer to the surface or from the surface? Determine the combined heat transfer rate for the surface. Is this heat transfer to the surface or from the surface?
Solution Summary: The author calculates the energy balance equation as per the incident radiation on a surface.
A horizontal, opaque surface at a steady-state temperature of
77
∘
C
is exposed to an airflow having a free stream temperature of
27
∘
C
with a convection heat transfer coefficient of
28
W
/
m
2
⋅
K
. The emissive power of the surface is
628
W
/
m
2
, the irradiation is
1380
W
/
m
2
, and the reflectivity is 0.40. Determine the absorptivity of the surface. Determine the net radiation heat transfer rate for this surface. Is this heat transfer to the surface or from the surface? Determine the combined heat transfer rate for the surface. Is this heat transfer to the surface or from the surface?
A piston–cylinder device contains 50 kg of water at 250 kPa and 25°C. The cross-sectional area of the piston is 0.1 m2. Heat is now transferred to the water, causing part of it to evaporate and expand. When the volume reaches 0.26 m3, the piston reaches a linear spring whose spring constant is 100 kN/m. More heat is transferred to the water until the piston rises 20 cm more.
NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part.
Determine the work done during this process.
The work done during this process is kJ.
A 4-m × 5-m × 7-m room is heated by the radiator of a steam-heating system. The steam radiator transfers heat at a rate of 10,000 kJ/h, and a 100-W fan is used to distribute the warm air in the room. The rate of heat loss from the room is estimated to be about 5000 kJ/h. If the initial temperature of the room air is 10°C, determine how long it will take for the air temperature to rise to 25°C. Assume constant specific heats at room temperature. The gas constant of air is R = 0.287 kPa·m3/kg·K (Table A-1). Also, cv = 0.718 kJ/kg·K for air at room temperature (Table A-2).
Steam enters the radiator system through an inlet outside the room and leaves the system through an outlet on the same side of the room. The fan is labeled as W sub p w. The heat is given off by the whole system consisting of room, radiator and fan at the rate of 5000 kilojoules per hour.
It will take 831 Numeric ResponseEdit Unavailable. 831 incorrect.s for the air temperature to rise to 25°C.
A piston–cylinder device contains 50 kg of water at 250 kPa and 25°C. The cross-sectional area of the piston is 0.1 m2. Heat is now transferred to the water, causing part of it to evaporate and expand. When the volume reaches 0.26 m3, the piston reaches a linear spring whose spring constant is 100 kN/m. More heat is transferred to the water until the piston rises 20 cm more.
NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part.
Determine the final pressure and temperature.
The final pressure is kPa.
The final temperature is ºC.
Find the work done during the process
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