A device that recovers heat from high-temperature combustion products involves passing the combustion gas between parallel plates, each of which is maintained at 35 0 K by water flow on the opposite surface. The plate separation is 4 0 mm , and the gas flow is fully developed. The gas may be assumed to have the properties of atmospheric air, and its mean temperature and velocity are 1 000 K and 6 0 m / s . respectively. (a) What is the heat flux at the plate surface? (b) If a third plate, 2 0 mm thick, is suspended midway between the original plates, what is the surface heat flux for the original plates? Assume the temperature and flow rate of the gas w be unchanged and radiation effects to be negligible.
A device that recovers heat from high-temperature combustion products involves passing the combustion gas between parallel plates, each of which is maintained at 35 0 K by water flow on the opposite surface. The plate separation is 4 0 mm , and the gas flow is fully developed. The gas may be assumed to have the properties of atmospheric air, and its mean temperature and velocity are 1 000 K and 6 0 m / s . respectively. (a) What is the heat flux at the plate surface? (b) If a third plate, 2 0 mm thick, is suspended midway between the original plates, what is the surface heat flux for the original plates? Assume the temperature and flow rate of the gas w be unchanged and radiation effects to be negligible.
Solution Summary: The author explains the heat flux at plate surface. The mean temperature of the air is 1000 K, and the dynamic viscosity is 424.2.
A device that recovers heat from high-temperature combustion products involves passing the combustion gas between parallel plates, each of which is maintained at
35
0
K
by water flow on the opposite surface. The plate separation is
4
0
mm
, and the gas flow is fully developed. The gas may be assumed to have the properties of atmospheric air, and its mean temperature and velocity are
1
000
K
and
6
0
m
/
s
. respectively.
(a) What is the heat flux at the plate surface?
(b) If a third plate,
2
0
mm
thick, is suspended midway between the original plates, what is the surface heat flux for the original plates? Assume the temperature and flow rate of the gas w be unchanged and radiation effects to be negligible.
How does an increase in gas temperature affect pressure drop in a haghouse, assuming the mass flow rate of particles and the molar flow rate of gas are constant?
Air at 1 atm and 27 C enters a rectangular duct that is 1 m long with a cross-sectional area that measures 4 mm x 16 mm as shown below. The mass flow rate of the air is 3 x 10* kg/s. A uniform heat flux of 600 W/m2 is imposed on all four sides of the duct surface. Evaluate air properties at the inlet temperature since the outlet temperature must be determined. 4 mm a. b. What is the outlet temperature of the air (K)? Ans. 379.8 K What is the temperature of the duct surface at the outlet (K)?
(Hint:By taking advantage of the heat flux given the average temperature of the flow you can find)
What is the ratio of total convective heat transfer rate to laminar convective heat transfer rate for the flow over 2 m length flat plate if 10 m/s air velocity is observed?
For air: ν = 20x10-6 m2/s
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