Our students perform a laboratory experiment to determine mass transfer from a wet paper towel experiencing forced convection and irradiation from radiant lamps. For the values of T ∞ and T w b prescribed on the sketch, the towel temperature was found to be T s = 310 K . In addition, flat-plate correlations yielded average heat and mass transfer convection coefficients of h ¯ = 28.7 W/m 2 ⋅ K and h ¯ m = 0.027 m/s , respectively. The towel has dimensions of 92.5 mm x 92 .5mm and is diffuse and gray with an emissivity of 0.96. (a From the foregoing results, determine the vapor densities, ρ A , s and ρ A , ∞ , the evaporation rate, n A ( k g / s ) , and the net rate of radiation transfer to the towel, q r a d ( W ) . (b) Using results from part (a) and assuming that the irradiation G is uniform over the towel, deter- mine the emissive power E , the irradiation G , and the radiosity J .
Our students perform a laboratory experiment to determine mass transfer from a wet paper towel experiencing forced convection and irradiation from radiant lamps. For the values of T ∞ and T w b prescribed on the sketch, the towel temperature was found to be T s = 310 K . In addition, flat-plate correlations yielded average heat and mass transfer convection coefficients of h ¯ = 28.7 W/m 2 ⋅ K and h ¯ m = 0.027 m/s , respectively. The towel has dimensions of 92.5 mm x 92 .5mm and is diffuse and gray with an emissivity of 0.96. (a From the foregoing results, determine the vapor densities, ρ A , s and ρ A , ∞ , the evaporation rate, n A ( k g / s ) , and the net rate of radiation transfer to the towel, q r a d ( W ) . (b) Using results from part (a) and assuming that the irradiation G is uniform over the towel, deter- mine the emissive power E , the irradiation G , and the radiosity J .
Solution Summary: The author explains how the mass transfer convection rate equation can be used to get water evaporation rate from the towel.
Our students perform a laboratory experiment to determine mass transfer from a wet paper towel experiencing forced convection and irradiation from radiant lamps. For the values of
T
∞
and
T
w
b
prescribed on the sketch, the towel temperature was found to be
T
s
=
310
K
. In addition, flat-plate correlations yielded average heat and mass transfer convection coefficients of
h
¯
=
28.7
W/m
2
⋅
K
and
h
¯
m
=
0.027
m/s
, respectively. The towel has dimensions of
92.5
mm x 92
.5mm
and is diffuse and gray with an emissivity of 0.96.
(a From the foregoing results, determine the vapor densities,
ρ
A
,
s
and
ρ
A
,
∞
, the evaporation rate,
n
A
(
k
g
/
s
)
, and the net rate of radiation transfer to the towel,
q
r
a
d
(
W
)
.
(b) Using results from part (a) and assuming that the irradiation
G
is uniform over the towel, deter- mine the emissive power
E
, the irradiation
G
, and the radiosity
J
.
Net movement of mass from one location, usually meaning stream, phase, fraction, or component, to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtration, and distillation.
QI/The top surface of the passenger car of a train moving at a velocity of 70 km/h is 2.8 m wide
and 8 m long. The top surface is absorbing solar radiation at a rate of 200 W/m2, and the
temperature of the ambient air is 30°C. Assuming the roof of the car to be perfectly insulated and
the radiation heat exchange with the surroundings to be small relative to convection, determine the
equilibrium temperature of the top surface of the car.
Ans =35.1 c
Saturated steam at a temperature of 65°C condenses on a vertical plate surface at 55°C. At a location 0.2 m from the plate top, determine the following parameters on the basis of per unit width of the plate. The fluid property values are: ρl = 985 kg/m3; ρv = 0.1614 kg/m3; kl = 0.6513 W/m.K; cp = 4183 J/kg.K; μl = 4.7083×10^– 4 kg/m.s; hfg = 2346.2 kJ/kg (use this value of hfg, where needed, without modifying it).
a) find Thickness of the condensate film
b) find condensate heat flow rate
c) local convective heat transfer coefficient and condensate flow rate for (b=1)
The global average sensible heat flux is 17 W/m2. Use the following information to estimate the latent heat flux in units of W/m2. The annual global precipitation amount is about 520×1012 m3/yr. The latent heat of vaporization for water is 2.5×103 kJ/kg and the radius of the Earth is 6400 km. What is the global annual average latent heat flux?
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