Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 4th Semester (Fourth Semester) 2016-17 CH401 Heat Transfer Question Paper
B. TECH.
THEORY EXAMINATION (SEM?IV) 2016-17
HEAT TRANSFER
Time : 3 Hours Max. Marks : 100
Note : Be precise in your answer. In case Ofnumerical problem assume data wherever not provided.
SECTION ? A
1. Attempt all parts of the following question: 10 x 2 = 20
(a) State Newton?s law of cooling.
(b) Define Fin efficiency and effectiveness.
(c) What is the physical significance of the Biot number?
(d) What is black body and gray body?
(e) What is natural convection? How does it differ from forced convection?
(f) What is meant by Boiling and condensation?
(g) What is meant by compact heat exchangers?
(h) What is meant by Fouling factor?
(i) Define emissive power and monochromatic emissive power.
(j) State Kirchhoff 3 law of radiation.
SECTION ? B
2. Attempt any five of the following questions: 5 x 10 = 50
(a) A furnace wall made up of 7.5 cm of fire plate and 0.65 cm of mild steel plate. Inside
surface exposed to hot gas at 650C and outside air temperature 270C. The convective
heat transfer co?efficient for inner side is 60 W/m2 K. The convective heat transfer co-
efficient for outer side is 8 W/mZK. Calculate the heat lost per square meter area of the
furnace wall and also find outside surface temperature.Thermal conductivity for fire
plateK1 = 1035 X 10'3 W/m K,Thermal conductivity for mild steel plateKz = 53.6W/m
K.
(b) A steel tube (K1 = 43.26 W/m K) of 5.08 cm inner diameter and 7.62 cm outer diameter
is covered with2.5 cm layer of insulation (K2 = 0.208 W/m K) the inside surface of the
tube receivers heat from a hotgas at the temperature of 316C with heat transfer co?
efficient 0f 28 W/mzK. While the outer surfaceexposed t0 the ambient air at 30C with
heat transfer co?efficient 0f 17W/m2K. Calculate heat loss for 3 m length of the tube.
(c) Oil at 120C is used to heat water at 30C in a 1?1 con-current shell and tube heat
exchanger. The available heat exchanger area is ALThe exit temperature of the oil and
the water streams are 90C and 60C respectively. The con?current heat exchanger is
replaced by 1?1 counter current heat exchanger having heat exchange area A2,If the exit
temperature and the overall heat transfer coefficient are same. What is the ratio of A1 to
A2?
(d) A double pipe heat exchanger is to be designed to heat 4 kg/s Of a cold feed from 20 to
40C using a hot stream available at 160C and a ?ow rate of 1 kg/s. The two streams
have equal specific heat capacities and the overall heat transfer coefficient of the heat
exchanger is 640 W/m2 k. What is the ratio of heat transfer area for con-current and
counter current modes of Operations?
(e) Define irradiation and emissive p0wer.Determine the net radiant interchange between
two parallel oxidized iron plates, placed at a distance of 25mm,having sides of 3m X
3m.The surface temperature of the two plates are 100C and 40C.Emissivities 0f the
plates are equal.
(f) Explain development of hydrodynamic and thermal boundary layers with suitable
figure. Differentiate Viscous sub layer and buffer layer.
(g) What is Optimum thickness of insulation? Derive the critical thickness of insulation of
Cylinder.
(h) Show by sketch, the various methods of feeding arrangement in triple effect
evaporators. Discuss their relative merits & demerits.
SECTION ? C
Attempt any two of the following questions: 2 x 15 = 30
What are the different regimes involved in pool boiling? In a concurrent heat exchanger, an oil
stream is cooled from 450K to 410K by water inlet & outlet temperature of 300K & 350K
respectively. The exchanger consists of a number of tubes of 1m length each. It is now desired
to cool the Oil to 390K (instead of 410K) while maintaining the ?ow rate of oil, ?ow rate of
water, inlet temps of Oil & water & number of tubes at the same values as before. Calculate the
length of each tube required for this purpose. Assume the physical properties remain
unchanged.
Derive an expression for the LMTD of a parallel ?ow heat exchanger. State clearly the
assumptions made. Why is counter ?ow heat exchanger better than parallel ?ow heat
exchanger?
Classify heat exchangers, draw temperature distribution in a condenser and evaporator and
derive the Expression for effectiveness of parallel ?ow heat exchanger by N TU method.
This post was last modified on 29 January 2020