Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 4th Semester (Fourth Semester) 2015-16 NBT 402 Heat Mass Transfer Question Paper
(Following Paper ID and Roll No. to be ?lled in your
Answer Books)
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B. TECH.
Theory Examination (Semester-IV) 2015-16
HEAT & MASS TRANSFER
Time : 3 Hours Max. Marks : 100
Section-A
1. Attempt all parts, all parts carry equal marks. Write
answer of each part in short. (2><10 = 20)
(a) What are various modes of heat transfer?
(b) What is the fourier's law of heat conduction?
(c) What is the difference between the 'natural' and 'forced'
convection.
(d) Differentiate between a black body and a gray body.
What is kichoff?s law?
(e) De?ne the term absorptivity, re?ectivity and trans-
missivity of radiation.
(f) Give mathematical statement of ?ck's law of diffu-
sion and give the meaning of each terms involved in
equation.
(1) P.T.O.
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(g)
(h)
(i)
(i)
Explain in brief rate of drying curve.
State various methods of generating super saturation.
De?ne gas absorption what for it is carried out indus-
trially? Give suitable Examples.
What is langmuir's isotherm. Define types of
adsorbents used.
Section-B
Attempt any ?ve questions. (SXIO = 50)
(a)
(b)
(e)
(d)
(e)
What are the various materials used for insulation
purposes? Distinguish between critical and optimum
insulation thickness.
De?ne the Reynolds numbers, prandtl number, Nusselt
number and Stanton number and ?nd the relation
between them.
Air at 27? C and 1 bar ?ow over plate at a speed of
2m/s. Calculate the boundary layer thickness at 400
mm from the leading edge of the plate. Find the mass
?ow rate per unit width of the plate. (For Air p=
19.8><10'6 kg/ms at 27?C)
Give governing differential equation for one ? di-
mensional transient heat ?ow?
A Wet solid of 28% moisture is to be dried to 0.5 %
moisture in tray dryer. A laboratory test shows that it
(2)
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requires 8 hours to reduce the moisture content of the
same solid to 2% . The critical moisture content is
6% and then equilibrium moisture is 0.2%. The Fall-
ing rate of drying is linear in the free moisture con-
tent. Calculate the drying time of the solid if the drying
conditions similar to those in the laboratory test are
maintained. A11 moistures are expressed as percent of
bone dry mass of solid.
(0 Give the sieder? tate equation for calculation of ?lm
coefficient in case of laminar ?ow.
(g) Explain in brief forced circulation evaporator With
external horizontal heating surface with reference to
its construction and working.
(h) How are Heat Exchangers are classi?ed? Discuss
brie?y different types of heat exchangers. What is
overall heat transfer coefficient? Give its signi?cance.
Section-C
Attempt any two question from this section. (2X15=30)
3. (Non-equimolar counter difmsion in distillation of a binary
? mixture)
An aqueous solution of methanol is being separated by dis-
tillation in a column. Methanol (A), which is the more vola-
tile component moves from the liquid phase to the vapor
phase while water(B), the less volatile component, gets trans-
(3) P.T.O.
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ported in the opposite direction . At a section of the column,
the vapor phase contains 0.76 mol fraction methanol and the
liquid has 0.6 mol fraction of it. The temperature is 712?C
and the total pressure is essentially atmOSphere. The diffu-
sional resistance offered is equivalent to that of a stagnant
vapour ?lm of 1.0mm thickness if the latant heat of vapor-
ization of methanol is 274.6 Kcal/kg and that of water is
557.7 Kcal/kg at the given temperature. Calculate the ?ux of
methanol and that of water vapour.
Given if the mole fraction of methanol in the solution is 0.6, it's
mole fraction in the equilibrium vapour would be 0.825. The
vapour phase mutual diffusivity DAB= 1.816 ><10'5
mZ/s.
4. What is the physical signi?cance of HTU and NTU ?
Calculate the height 0 equivalent of a theoretical plate.
5. (Calculation of the minimum solvent rate) In a petrochemi-
cal plant,a gas containing 4% cyclo-hexane and 96% inerts
has to be treated with a non- volatile absorption oil in a
packed tower. It is required to remove 98% of the cyclohex-
ane of the feed gas. The feed solvent is free from cyclo-
hexane. If the feed gas rate is 80 kmol per hour, calculate the
minimum solvent rate. The equilibrium reaction is given as
Y = (O.2x)/(1+O.8x)
(4)
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This post was last modified on 29 January 2020