9 replies to this topic

[PRkumar]

What is the difference in betwwen EMTD(Effective mean temprature difference) & LMTD (loag mean temprature difference) in heat exchanger?

Regards
PRANAV

[Nirav]

Effective mean temperature difference is nothing but the corrected LMTD after applying "LMTD correction factor".

[PRkumar]

dear ,
up to my knowledge EMTD & LMTD not same. WE are use EMTD only for the air cooled heat exchanger not for the shell & tube heat exchanger.

[Raj Mehta]

EMTD = LMTD * F 

 

F = correction factor. 

[Dipankarc84]

EMTD is typically a term used by HTRI and it is different from LMTD. It not only includes the Ft correction factor. Let me mention that an LMTD with an Ft correction factor only is not EMTD. It is called "corrected LMTD".
EMTD also includes an additional correction factor which is called a "temperature distortion". In effect, this factor may not affect the overall thermal design to a great extent in most cases. This temperature distortion is a factor used to account for the thermal ineffectiveness due to leakage bypass streams (fractions of shell side fluid that so not take part in direct heat transfer). In case you have access to HTRI software, you may want to read their help topic for better understanding of this.

Thanks
Dipankar

[PRkumar]

dear Dipankar,


Thanks.
pls solve my another doubt, EMTD used only for air cooler heat exchanger or both (sell & tube heat exchanger).
In HTFS softwear this guidelines available.Any another source available for this guidelines.

regards
pranav

Edited by PRkumar, 09 May 2013 - 04:36 AM.

[Dipankarc84]

Hi Pranav,

 

It is used for both. However, I will not be able to talk much on Air Coolers as my knowledge is limited in the same.

 

Thanks

Dipankar

[PRkumar]

DEAR DIPANKAR ,
As u say in post 5. IS THERE ANY OTHER SOURCE AVAILABLE FOR "TEMPRATURE DISTORTION".because i do not have HTRI SOFTWEAR .
REGARDS
PRANAV

[Dipankarc84]

Hi Pranav

You may read a book called "Practical Thermal Design of Shell and Tube Heat Exchangers" by Rajiv Mukherjee. This concept is beautifully explained.

 

Regards

Dipankar

[eko.saputro]

Hi Pranav,

Do you have "Practical Thermal Design of Air-Cooled Heat Exchanger" written by Rajiv Mukherjee also?