This download link is referred from the post: JNTUA M.Tech 1st Sem last 10 year 2010-2020 Previous Question Papers (JNTU Anantapur)
M.Tech I Semester Supplementary Examinations August/September 2018
CONDUCTION & RADIATION HEAT TRANSFER
(Refrigeration & Air Conditioning)
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(For students admitted in 2013, 2014, 2015 & 2016 only)Time: 3 hours
Answer any FIVE questions
All questions carry equal marks
Max. Marks: 60
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Note: Standard heat & mass transfer data book and steam tables are permitted.*****
- (a) Differentiate between steady and transient heat conduction.
(b) Calculate the rate of heat loss for a red brick wall of length 5 m, height 4 m and thickness 0.25 m. The temperature of the inner surface is 110°C and that of the outer surface is 40°C. The thermal conductivity of the red brick, k = 0.70 W/mK. Calculate also the temperature at an interior point of the wall at a distance of 20 cm from the inner wall. - (a) Drive an expression for heat transfer through a plane and composite walls.
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(b) A 40 x 40 cm copper slab 5 mm thick at a uniform temperature of 250°C suddenly has its surface temperature lowered at 30°C. Find the time at which the slab temperature becomes 90°C. Take p = 9000 kg/m³, C = 0.38 kJ/kg K, K = 370 W/mK and h = 90 W/m² K. - (a) What is meant by lumped heat analysis?
(b) Aluminum sphere weighing 5.5 kg and initially at a temperature of 290°C is suddenly immersed in a fluid at 15°C. The convective heat transfer coefficient is 58 W/m²K. Estimate the time required to cool the aluminum to 95°C, using lumped capacity method of analysis. - (a) What is Heisler chart?
(b) A surface wall consists of 23 cm of fire brick and 11.5 cm of insulating brick having thermal conductivities of 0.72 W/mK and 0.27 W/mK respectively. Calculate the rate of heat lost per square meter when the temperature difference between inner and outer surface is 650 K. - (a) What are Biot and Fourier numbers? Explain their physical significance.
(b) The inner surface temperature of an annealing oven varies according to a sine function from 800°C to 200°C. Each complete cycle requires 12 hours, compute:
(i) Time lag of the temperature wave at a depth of 10 cm from the inner surface.
(ii) The heat flow through a surface located at a distance of 10 cm from the surface during the first six hours interval while the temperature is above the mean value. Assumea = 0.02 m²/h; K = 1.8 W/mK. - (a) Derive the expression for radiation exchange between small gray bodies.
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(b) Emissivities of two large parallel planes maintained at 800°C and 300°C are 0.3 and 0.5 respectively. Find the net radiant heat exchange per square meter for these plates. - (a) Distinguish between the black body and grey body.
(b) Two parallel plates of size 0.5 m x 1 m are placed parallel to each other at a distance of 0.5 m. One plate is maintained at a temperature of 1000°C and other at 500°C and the emissivities are 0.2 and 0.5 respectively. The plates are located in a large room whose walls are at 27°C. If the plates exchange heat with each other and with the room, but only plate surface facing each other are to be consider in the analysis. Calculate: (i) Heat lost by the plates. (ii) Heat gain by the room. - (a) Determine the radiation heat transfer per unit length between two long concentric cylinders of radius 0.5 m and 0.6 m with emissivity values of 0.6 and 0.4 respectively. The inner cylinder is at 600°C while the outer is at 300°C.
(b) Derive the radiation heat transfer coefficient
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This download link is referred from the post: JNTUA M.Tech 1st Sem last 10 year 2010-2020 Previous Question Papers (JNTU Anantapur)
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