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[mbogsl]

Hi,

I need a bit of guidnace for selecting the right kind of heat exchanger for an unusual application for us.

We have hydrocarbon liquid (oil) which needs heating. To get the right outlet temperature some of the oil will vapourise to the gas phase (7% by mass) but 70% by volume!

Heating medium is 50%teg/50%water

Normally for oil heating we would use simple shell and tube (oil shell side, heating medium tubes), but normally we dont have liquid vapourizing. I dont think a horizontal shell and tube is the right selection for this application.

We would like to keep the oil on the shell side as its easier to clean.

Q1 Should we be looking at a vertical or horizontal exchanger?

Also any other guidance as to what sort of exchanger would be appreciated, should I treat this as a thermosyphon reboiler?

Thanks

[Art Montemayor]

mbogsl;

Your heating application involves 2-phase flow as a product of the heat transfer and it is going to require one of two basic methods to bring it about in a controlled manner:

1) Produce the two phases in a vaporizer-type exchanger, which includes vapor disengagement space for separation of the two phases; once separated, the two phases are withdrawn separately and handled in their respective required manner.

2) Produce the two phases as a mixture in a one-pass heat exchanger on the process side; this requires carefull and experienced process and mechanical design of the heat exchanger and the required inlet and outlet piping. The product mixture is handled as a 2-phase mixture and transported downstream as such until it is separated into its two phases. I suspect you are probably right, it might call for a vertical, process in tube side, BEM-type exchanger. Handling and transporting the 2-phase mixture is tricky and very hardware dependent. You cannot afford to form vapor pockets in the system.

You haven't given us enough basic data to remark or comment further, so I'll close with the comment that I would prefer to handle this as a vaporizer application. I suspect you are going to have to ultimately confront the separation of the product vapor /liquid mixture; therefore, I would design the vaporizer around the employment of a BKU-type vaporizer and carry out both the heating and the vapor separation in one vessel, at one time.