# Gas Cooler design

1. Nov 3, 2013

### ApolloEngineer

Hello, I'm a senior ME student and for part of my project I'm designing a gas cooler, and I need help understanding the heat transfer process going on (I have yet to taken heat transfer).

So basically my design is a a metal pipe (AISI 302 Steel k=15.1 W/m-k) carrying the gas (which for simplification purposes can be assumed to be pure Carbon Monoxide gas with a volumetric flow rate of 0.00549 m^3/s) which is surrounded by water at room temperature. What I am trying to achieve is lowering the temperature of the gas from 700K to 400K.

The main dimension I am focused on finding is how long this section of tube submerged in water must be to provide sufficient heat transfer for what I want. I know this will be a function of the inner and outer diameter of the pipe, but I am ok including those variables in some kind of final expression.

As I understand it, convection will occur on both surfaces of the pipe and conduction through the pipe wall. I have no idea how to calculate the convection coefficients, or how to take in to account how this system will operate through time (this gas cooler can be expected to be run with the above conditions for up to ~6 hours), or how to model the cylindrical pipe.

Any help is much appreciated! Thanks!

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2. Nov 15, 2013

### Baluncore

Water boils at 100°C which is 373K. You want 400K.
So, split the gas into many metal tubes that pass through a boiler.
That will guarantee the air cools to the temp of the water. The boiling water can be utilised as a source of energy. The pressure in the boiler can be higher than atmospheric so you can operate the boiler at a pressure that sets the temperature to 400K.

Alternatively if excess cold water is available you could pass some gas through tubes in water, then mix the remainder of the gas back in to restore the temp to 400K. A temp sensitive mixer valve would regulate the proportions.

3. Nov 16, 2013

### rollingstein

Use standard correlations for heat transfer coefficents. Look up any heat transfer text.

It'd lead to a better design if you provide forced circulation outside the tubes too rather than depend on free convection. Have you chosen a pipe dia / thickness yet?

Since CO is substantially insoluble in water another option is direct heat transfer. Just bubble your gas through a large bath of water.