3 replies to this topic

Could someone please help determine/confirm how to answer the following question:

A 1:1 shell & tube heat exchanger is required to cool 10,000 kg/h of light oil from 105°C to 20°C using cooling water which is available at 15°C and leaves at 30°C. The light oil flows inside the tubes and the water is on the shell side.

(i) Based on the stated temperatures, show whether the flow configuration is concurrent or countercurrent.

I asked my lecturer the following;

"by 'SHOW whether the flow configuration is countercurrent' do you mean; draw the T-L curve, or give reasons for why it's countercurrent, or other?"

To which he replied;

There is a distinct reason for the choice of the flow configuration. I'll leave it up to you to discover that reason.

My textbook states that;

Parallel flow is rarely used in a single pass exchanger because it is not possible with this method of flow to bring the exit temperature of one fluid nearly to the entrance temperature of the other, and that the heat that can be transferred is less than that possible in countercurrent flow.

Is the above an adequate reason for selecting the countercurrent configuration, & could someone suggest how the answer can be 'shown'?

Thanks in advance!

[breizh]

Kelly,

Let you draw the temperature profile of both liquid (shell and tube), Temp versus length. You should vizualize and undestand the reason. All along the length of the HX heat transfert must take place.

Regards
Breizh

[breizh]

Think so !
Breizh

[AlertO]

Basically,temperature cross will not occur with co-flow HX.
Temp cross can occur with counter current flow, but HX will require extra area and high fluid velocities.

Lucky