3 replies to this topic

[Wong]

Hi everyone, my name is Chris and I am seeking help for a heat exchanger study work given by my senior colleague. For your info, I have no prior HTRI training however with some help from the inbuild tutorials I was able to at least use the software.

 

We are trying to come up with design data of the existing heat exchanger to create a TEMA database. This database will then be compared to real world data at the plant.

 

The condenser is an integral column TEMA BXU condenser.

 

The tubeside cold fluid is cooling water and the hot shellside is exposed to vapour rising up the column comprising of 99.1% Diethylene glycol and 0.9% ethylene glycol. The hotside fluid inlet and outlet temperature is 289 ^oF 

 

The hotside vapour is simulated using VMGThermo UNIFAC/ideal/chemical for both liquid and vapour

 

Because the condenser is integral with the column, the U-tube bundles are exposed directly to the rising vapour with no shell. However, there is no option in HTRI to simulate the situation.

 

I tried specifying a single big nozzle about the same length as the u-tubes. I am getting an overdesign of 52.3%. Am I going the correct way because no one in my department seems to be able to give me a concrete answer.

 

Here is the TEMA Specsheet for the integral column

Attached Files

•  E6853 integral column.xls   26.64KB   36 downloads
•  E6853 integral column.xls   27KB   30 downloads

[PingPong]

Why do you say there is no shell?

 

There is a horizontal shell. You see it on the sketch, and the datasheet gives its inside diameter as 1270 mm.

[Wong]

Why do you say there is no shell?

 

There is a horizontal shell. You see it on the sketch, and the datasheet gives its inside diameter as 1270 mm.

 

Hi, that is the Shell ID of the column. The condenser is mounted on top of the column with the U-tube exposed directly to the vapour. HTRI does not allow me to continue if I do not specify the shell ID so I inputted the column inside diameter

 

Here is a picture to illustrate it

Attached Files

•  internal condenser.PNG   12.47KB   11 downloads

Edited by Wong, 03 December 2014 - 07:39 PM.

[PingPong]

The sketch on the exchanger datasheet shows a horizontal shell on top of the column, but now you say that the tubebundle simply sticks into the column shell?

How do you know that the rest of the data on the datasheet does correspond with the actual tubebundle that now is installed in the column? In any case there seems to be a mismatch between the bundle area and the number of tubes and tubelength on the datasheet.

 

Such arrangement will give a very poor U-value, as the tubebundle is only a small part of the column crossectional area. A lot of vapour molecules can flow directly to the outlet nozzle without even noticing that there is a tube bundle on which they are supposed to condense, even though the datasheet implies that 98 % of the vapour must condense.

 

I would say: don't waste your time on this particular exchanger. Just leave it out of your TEMA database.