You are supposed to design a shell and tube heat exchanger that can fulfill the

Question

You are supposed to design a shell and tube heat exchanger that can fulfill the following heat duty: A kerosene stream with a flow rate of 5.67 kg (45,000 lb/h) is to be cooled from 198.9 °C to 121.1 °C (390 °F to 250 °F) by heat exchange with 18.90 kg /s (150,000 lb/h) of crude oil at 37.78 °C (100 °F). A maximum pressure drop of 103.42 Kpa (15 psi) has been specified for each stream. Prior experience with this particular oil indicates that it exhibits significant fouling tendencies, and a fouling factor of 0.00057 m2 °C/W (0.003 hft2 °F/Btu) is recommended.

Explanation / Answer

You don't necessarily need to change the type of heat exchanger. That would actually be much more difficult and counterproductive. You just simply need to change a specification, or a couple, of the heat exchanger. For example, you could change the cooling medium, the mass flow rate of the cooling medium, the number of passes in the heat exchanger, the thickness of the shell/tube, the number of baffles to alter the flow patterns in the exchanger, the material used in the heat exchanger, etc.

I would look further into a shell-in-tube heat exchanger and just modify a spec or 2 to get your desired result. 10 tubes is certainly feasible, hell so is 3 or 4. Overall, the more contact the 2 fluids come in contact with each other (the duration the gas is in the heat exchanger or the amount of turbulence involved) the more effective your design will be.

Just remember one little modification can go a long way. Hope all this helps! good luck!


Edit: Different industries use different heat exchangers dependent on their operation. Some shell-in-tube heat exchangers are HUGE, while others are small. Its not uncommon for a heat exchanger to have a small amount of tubes, as long as it can perform what you want of it. Like I said, there are many ways to modify them, especially in a constrained area, to perform what you want out of the design. You can try looking at a plate heat exchanger or a spiral heat exchanger (spiral HE are cool, check out these neat heat exchangers at a company called Spinworks located in Erie, Pennsylvania: http://www.spin-works.com/SpyroCor.html)… I honestly think a simply designed shell-in-tube heat exchanger will do the trick (don't know your size constraint, etc.). Even try modifying some variables in your calculation to get the number of tubes down.

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