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(c) Considera diffuse circular disk ofdiameter D and areaA₂ and a piane diffuse surface of area A, (A, « A,). The surfaces are parallcl. and A, is located at a distance H from the centre of A₂. Obtain an expression for the view factor F_{| 2}.

5. Answerany two parts of the fol lowing:    (10*2=20)

(a)    Describe various modcs of condensation.

(b)    Saturated steam at 373 K condenses in a double pipę heat exchanger with a surface area of 0.5 m^: and an overall ( heat transfer coefficient of 2000 W/m\ K. Water enters

at 0.5 kg/s and 288 K. Determine the outlet temperaturę of the water and the ratę of steam condensation (Latcnt heat = 2257 kJ/kg).

(c)    Discuss Fick's law for steady State diffusion through stationary medium consisting of two species and derive an expression for spccies diffusion resistance.

Some Correlations :

1.    For Laminar flow over a fiat piąte :

www.mtuexam.blogspot.iii

Nu = 0.332 Re ^1,2 Pr^,/3 (0.6 < Pr)

2.    For Turbulent flow over a fiat piąte :

Nu_x = 0.0296 Re/'³ Pr^,/5 (0.6 < Pr < 60)

3.    For Mixed boundary layer flow over a fiat piąte :

Nu_x = (0.037 Re/'⁵ - 871) Pr'*

(0.6 < Pr < 60; Re, < Re, < 10*; Rc = 5 * 10³)

4.    For Double pipc heat exchanger:

e = 1 - exp (- NTU) ; for C /C =0 e = NTU/ (1 + NTU) ; for (T/(T = 1

5.    For Fully developed laminar flow through tubę:

Nu_d * 4.36 ; for uniform surface heat flux condition Nu_d= 3.66 ; for uniform surface temperaturę condition.

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EME504

|(Following Paper ID and Roli No. to be filled in your Answer Book)

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PAPER II) : 2104

Roli No.

B.Tech.

(SEM. V)THEORY EXAMnsJAT10N 2011-12 HEAT AND MASS TRANSFER

Time : 3 Hours    Total Marks : 100

Notę :— (I) Attempt all questions. Marks are indicated against each question/part.

(2)    You may usc the correlations provided at the end of the question paper.

(3)    Assume missing data suitably, if any.

(4)    Use of Heisler's Chart is permitted.

1. Answer any two parts of the following:    (10*2=20)

(a)    (i) Derive an expression for thermal resistance for

spherical wali.

(ii)    What do you understand by contact resistance ?

(iii)    What do you understand by overall heat transfer coefficient ?

(b)    A copper (k = 401 W/m. K) cablc of 30 mm diameter has an electrical resistance of 5 * 10"⁵ O/m and is used to carry an electrical current of 250 A. The cable is exposed to an ambient air at 20° C, and the associated convection coefficient is 25 W/m². K. What are the surface and centerline temperatures of the cable ?

(c)    A 10 mm diameter electric wire with a resistance per unit length of 2* 10 ⁴ O/m is coatcd with an insulation of thermal conductivity k = 0.20 W/m.K. The insulation iscxposed to ambient air at 30° C for which heat transfer coefficient is

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