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Heat Transfer Operation - 2 - May 2016
MU Chemical Engineering (Semester 6)
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary
1(a) How do noncondensables affects condenser operation?
5 marks
1(b) List gasket materials used in plate heat exchanger with their respective applications 5 marks
1(c) What , if fouling is not considered while exchanger design? 5 marks
1(d) Explain the working of kettle type reboiler with neat sketch. 5 marks
2 There is a requirement to cool 160,000 Kg/hr of a ethanol from 70°C to 30°C. Cooling water will be used for cooling, with inlet and outlet temperature of 20°C and 60°C. Design a gasketed-plate heat exchanger for this duty with stainless steel(k=15 W/mK) Plates of 0.5mm thick. Maximum operating pressure and allowable pressure for both fluids is 2 bar and 0.6 bar respectively and maximum permissible velocity is 3 m/s. Show one iteration of design calculation including thermal and hydrodynamic and if design is not satisfactory in lirst iteration then comment on the calculations?
Data:
Property | Cooling water | Ethanol |
Specific heat, KJ/Kg.k | 4.179 | 2.46 |
Viscosity, cP | 0.705 | 0.67 |
Thermal conductivity, /m.k | 0.62 | 0.171 |
Density, Kg/m3 | 995 | 772 |
3(a) Explain working of horizontal reboiler with schematic sketch. 5 marks
3(b) Explain operation of barometric condenser. 5 marks
4(a) What are the factors to be considered for allocation of fluid in shell or tube? 5 marks
4(b) Explain use of sealing strips in shell and tube exchanger. 5 marks
4(c) How do overdesign influence operation of heat exchanger like condenser, reboiler and coolers? 5 marks
5 A shell and tube heat exchanger has the following configration:
The shell side fluid is a hot water (mass flow = 7500 kg/hr) with the following properties:
Specific heat, kcal/Kg.K | 4.3706 |
Thermal conductivity, W/m.K | 0.5787 |
Viscosity, cP | 0.3307 |
Specific gravity | 0.9673 |
Using Bell-Delaware method, calculate the shell side heat transfer coefficient for following data.
Number of tubes | 34 |
Shell Inner Diameter | 279.401 mm |
Bundle diameter | 254.88 mm |
Tube outer diameter | 25.4 mm |
Sealine strips | None |
Pitch 1.25Δ | 31.75 mm |
No. of baffles | 35 |
Baffle spacing (centre to centre) | 75 mm |
Baffle cut | 24.48% |
6(a) 9150 kg/hr of saturated cyclohexane vapour will be condensed at 83.33°C and 1.1.0 bar using a tube bundle containing 147 tubes arranged for single pass. The tubes are 1 inch. Outer diameter 14 B WG thickness with a length of 6096 mm. Calculate the condensing side coefficient for the tube bundle is condense with condensation over tube, and comment on result.
Data:
Density of condensate, kg/m3 | 791.0 |
Viscosity, cP | 0.3311 |
thermal conductivity, W/m.K | 0.1512 |
Specific heat, KJ/kg.K | 2.1562 |
6(b) Explain operation of reflux condenser. 5 marks