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Unformatted text preview: PTFE 3210 QUIZ #4
Spring 2009
Problem Maximum Score Score 7
1 10
2 20
3 20
4 50 Total 100 Name @g, 2% S“
FIFE 3210
Spring 2989
KEY
Quiz #4 1. Write the fate equation (Fiek’s law) for molar diffusion of species A in a binary mixture of A
and B measured relative to coordinates that move With the average velocity of the mixture
and deﬁne all terms used in your expression. (10 points) ‘ .7), * (kmelfs ' m2) is the difﬁlsive molar ﬂux of species A measured relative to coordinates that
move with the exterage velocity of the mixture. C is the total 131013? concentratien.
' 124333 the binary diﬁusion coefﬁcient or mass eifﬁxsivity.
V is the del operator, xA is the molar ﬁaetion of species A. Gradino
5 points for the equation 1 point each for deﬁning; symbols 2. Darcy’s equation describing ﬂow through a porous medium is given below: dp/dx =  (iifk) (Jim (4 points) (1 points each for total 01'4 points) dpde = presSure gradient in the ﬂuid in the direction of ﬂow H
k = viscosity of the Newtonian ﬂuid
= permeability of the solid matrix :3 = apparent velocity A. Develop a relationship for the mass ﬂow rate, m , in terms the known quantities. 12 Points 3. By deﬁnition, heat exchanger effectiveness, E, is deﬁned as i

it: : Clactual I Qmax A heat exchanger is used to heat a cold stream. The following information concerning the
hot and cold streams is known: The heat capacitance rate for the hot stream, Cg, equals 1000 BTU/'(hr—“B.
The heat capacitance rate for the cold stream, Cc, equals 625 BTUf(hr°F).
The input temperature of the hot stream is 250°F. The exit temperature of the hot stream is 200°F. The exit temperame of the cold stream is 80°F. Calculate 5.. and gum for the conditions given above: (20 points) ‘ Clam; r' a; 2: Vow {gm/mo?“ Hot oil is used in a singlepass cross ﬂow heat exchanger to heat dye solution in a carpet mill. ' The mixedﬂow dye solution (Cp = 1.12 BTU/ lb°F) enters a 100°]? at a ﬂow rate of 2250
lb/hr. The unmixedﬂow oil (Cp = 0.46 BTU/ lb°F) enters at a temperature of 500°F and a
ﬂow rate of 1370'1b/hr. The ﬂow system produces an overall heattransfer coefﬁcient of 5 0
BTU] hrﬁ2°F. The exchanger surface area is 63 ftz. Determine: A. The exiting temperature of the oil. (‘16 points) B. The exiting temperature of the dye solution. (16 points)
C. The rate of heat transfer. (18 points) Clearly indicate which equations and ﬁgures that you are using. Do not simply write answers. If
you do not Show you work, you will not get partial creditl! 5/,Vng1— P2455 cwm CW g 51% C.
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 Spring '11
 Dr.Carr

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