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03000ME302052001

PART B

Answer any three full questions, each carries 10 marks.
An aluminium sphere weighing 6kg and initially at temperature of 350°C is
suddenly immersed in a fluid at 30°C with h = 60 W/m? C. Estimate the time
required to cool the sphere to 100°C.
Define fin efficiency and effectiveness
Explain the features of pool boiling process with the curve
Derive an expression for heat flow from a fin with tip insulated (derivation may
start from solution of general fin differential equation, ദവാ with
clear statement of boundary conditions)
Classify heat exchangers based on flow direction .Explain why a counter flow is
superior arrangement. When do we use specifically use parallel flow heat
exchangers?
Derive the expression for LMTD of a parallel flow heat exchanger
The following are the details of a parallel flow heat exchanger - Heat capacity of
cold flow entering at 40°C = 20000 W/K, Heat capacity of hot flow entering at
150°C = 10000 W/K, A=30 m? , U=500 W/mK. Determine heat transfer rate
and exit temperatures

PART C

Answer any four full questions, each carries 10 marks.
State and prove Kirchhoff’s law of radiation
Two black discs of diameter 50 cm each are placed parallel to each other
concentrically at a distance of 1൩. Disc temperatures are 727°C and 227°C .
Calculate the heat transfer between discs if no other surface is present in
between.
What are radiation shields? Mention some of their applications
Two concentric cylinders have inner and outer radius with Scm and 10cm and
length 20cm. Calculate the view factors
Determine the heat lost by radiation per meter length of 80mm diameter pipe at
300°C, if (i)Located in a large room with red brick walls at temperature of 27°C
(ii)Enclosed in a 160 mm diameter red brick conduit at a temperature of 27°C.
Emisssivities of pipe material and brick 0.79 and 0.93 respectively
State ficks law of mass diffusion, explaining all the terms

Air at atm temperature 25°C, 18% RH flows through a pipe of 25mm inside dia

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