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usagimiller
usagimiller
21.08.2019 • 
Chemistry

Ethyl alcohol (specific heat capacity = 3840 j kg k-') at a flow of 30,000 kg his to be cooled from 78°c to 44°c. a one shell pass, two tube pass heat exchanger is available, consisting of 35 tubes in each pass. the tubes are made of stainless steel (thermal conductivity = 19 w m-'-'), each of 33 mm external diameter, 26 mm internal diameter, with a total length over the two passes of 15 m. cooling water is available at 9°c and at a flow of 24665 kg h'. properties of water at 28°c: p = 996 kg mau = 834 x 10 kg m's, k = 0.615 w m! k and cp = 4179 j kg-k. (a) calculate the exit temperature of the cooling water. [3 marks] (b) the water is to flow through the 35 tubes of each pass of the heat exchanger. the cross sectional area of each tube is 5.309 x 104 m². evaluate the re number for the flow through the tubes. [2 marks] show that the convection heat transfer coefficient on the tube side is approximately 1900 w m 2k- [3 marks] the convection heat transfer coefficient on the shell side is 900 w m-k-, and fouling coefficients on both the inside and outside of the pipes are 5500 w m 2 k- calculate the overall heat transfer coefficient based on the outside area of the tubes. [4 marks] using either of the charts (on pages 5 and 6) for the correction factor or the effectiveness/ntu for a one shell pass, two tube pass shell and tube heat exchanger, calculate the total surface area required. [7 marks] is the available heat exchanger sufficiently large enough for this duty?

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