10 replies to this topic

[Wong]

Dear all industrial experts,

 

 

I am trying to simulate the performance of an existing integral condenser using HTRI. It is a TEMA BEM integral condenser with column.

 

The hot side consist of a vapour containing 72 wt% Ethylene glycol, 27.8 wt% water and the remainder 0.2% inerts.

 

HTRI returns an overdesign value of -22%. I am using HTRI build-in property generator and all the values inputted are taken from heat exchanger design spec sheet.

 

Did I do something wrong. For your info, I used Advanced Peng Robinson as my property package for both liquid and vapour. Using other package like NRTL or UNIQUAC I was not able to attain the weight fraction inlet of vapour

 

A complete TEMA Data Sheet is attached

 

 

Attached Files

•  TEMA sheet.xls   68KB   104 downloads

[AlertO]

hi wong

 

Can you attach the original datasheet of this exchanger for comparing with you input?

 

Only your given information, i have noticed few design points which should be not practical:

 1. the outlet temperature of hot side is too low, shell and tube has a limit of minimum temperature approach i.e. 10 degC. please check this point again.

 2. based on your simulation, the exchanger is at poor heat exchange due to B fraction is quite low i.e. normally it should be higher than 0.5 or 0.6.

 

Hope this may help you

Edited by AlertO, 08 July 2015 - 03:25 AM.

[Wong]

hi wong

 

Can you attach the original datasheet of this exchanger for comparing with you input?

 

Only your given information, i have noticed few design points which should be not practical:

 1. the outlet temperature of hot side is too low, shell and tube has a limit of minimum temperature approach i.e. 10 degC. please check this point again.

 2. based on your simulation, the exchanger is at poor heat exchange due to B fraction is quite low i.e. normally it should be higher than 0.5 or 0.6.

 

Hope this may help you

 

Dear AlertO,

 

             Thank you very much for taking your time to look into my simulation result. I would be more than happy to share with you the original heat exchanger datasheet. For your info, the heat exchanger was specified with a hot liquid outlet of 37 degree celsius based on design data.

 

Please see attached for a copy of the design datasheet

Attached Files

•  condenser datasheet 1.PNG   61.3KB   10 downloads
•  condenser datasheet 2.PNG   104.8KB   2 downloads

[AlertO]

Hi Wong

 

It seems your inputs about the exchanger configuration is fine, so the problem should be from your fluid. Many parameters calculated from HTRI present the inconsistency with the original data e.g. heat duty, velocity, calculated presssure drop.

 

i assumes that your composition is same as the original design right? if yes, what i recommend you to do is to simulate your process stream in other simulation engine e.g. HYSYS or others and squad check all properites with HTRI.

 

Have a good day.

[serra]

as noted by AlertO the differences (experimental vs. calculated) may depend from the different properties calculated by selected thermo package,

in HTRI you can enter properties from tables (H20 + Glycol) or estimated with internal generator or a external software,

if the selected advanced Peng Robinson package includes a free energy term (for example with Huron-Vidal mixing rules) make sure that BIPs are available, you may verify calculated values vs. experimental data (for example comparing with tables of values for water + glycol),

for water + glycol + inerts I have utilized the CPA-PR model (available in PRODE PROPERTIES) with good results but other simulators may offer different models.

[Wong]

Hi Wong

 

It seems your inputs about the exchanger configuration is fine, so the problem should be from your fluid. Many parameters calculated from HTRI present the inconsistency with the original data e.g. heat duty, velocity, calculated presssure drop.

 

i assumes that your composition is same as the original design right? if yes, what i recommend you to do is to simulate your process stream in other simulation engine e.g. HYSYS or others and squad check all properites with HTRI.

 

Have a good day.

 

 

Thank you Alert0 and serra for taking the time to help me out. I took your advice and went and dig up the generated property list from design report and put it into HTRI. Overdesign is now -37%

 

Please see attached for new TEMA sheet with user inputted properties 

Attached Files

•  TEMA sheet with properties .xls   104KB   58 downloads

[Acetone]

Hi Wong!

Your condenser have not fouling resistance! It is necessary?

[AlertO]

hi wong

 

i quite surprise the result you show the increase of insufficient size of the exchager. however, you can see your tube side is now at the original design already (see heat duty, velocity and pressure drop).

your shell side is still underperformed compared to the original one e.g. low velocity and pressure drop. This leads to low heat transfer coeff as well as minus % over design.

 

Note: As Acetone mentioned, fouling resistance is usually required for exchanger design.

 

Have a good day

[serra]

Wong,

once you have verified that process data (including any safety factor as fouling, number of zones to evaluate etc.) and the values for fluid properties (in both tube and shell sides) are accurate you can do little more,

may be some input is not correct or for some reason HTRI cannot evaluate accurately heat transfer and pressure drop...

[Wong]

Wong,

once you have verified that process data (including any safety factor as fouling, number of zones to evaluate etc.) and the values for fluid properties (in both tube and shell sides) are accurate you can do little more,

may be some input is not correct or for some reason HTRI cannot evaluate accurately heat transfer and pressure drop...

 

Dear Serra,

 

           Thank you for your kind advice. I would perform a field performance test on the said exchanger by using the cooling water inlet and outlet parameter since we cant directly measure the hot side vapour flowrate without a proper model.

 

Just a side question.If the condenser is indeed undersized and we are not getting the proper heat duty, I should expect the temperature of the condensate to be higher than design and accumulation of uncondensed vapour in column overhead

 

Possible drawback is hotter than design reflux to column and column pressure profile

 

What other consequence in terms of performance to column?

[AlertO]

hi wong

 

It depends on your control system.  Although your condensor is sometimes under-performance, it may shift your operating pressure up a little bit increasing the condensing performance which your column is probably OK now.

 

Note: current operating condition and design condition can be different by many parameters.

 

Have a good day.