HTRI learning - Question and Answers

[aseptman]

Hi!
How to design the Air Cooled Heat Excahnger when Tube side outlet temp. is less than the Air inlet temp. ? As per HTRI help menu, i have tried with Economiser mode but found the same error msg. : Process out temp. is less than the air in temp. and run failed.

Kindly advise.

Nilam,
You can not use economiser it is something else.
It is Air Cooler. You are supposed to have a Hot stream inside tubes.
If your Air inlet temp is 30 deg C and out is 35 deg C.
Tube in what(u have not specified) but if tube out is less than 33 deg C. Then how can it be Air Cooler which is supposed to be used for cooling the other stream.
You can use A Cooler for:
say Cooling the Hot stream in tubes ( Say water from 90 to 50 deg C) or
Condensing a hot stream ( say ethanol at 78 deg C to 78 deg C no subcooling)
but you can not use it for say glycol ( 0 deg in to 20 deg C ) means heating using air

[dhproeng]

Hi can anybody tell me how HTRI calculates Mean Temperature Differnece. I have consulted HTRI design manual but still unclear to me.

[henj]

Hi can anybody tell me how HTRI calculates Mean Temperature Differnece. I have consulted HTRI design manual but still unclear to me.

Please note that the EMTD (Effective Overall Temperature Difference) is not the same as the usually LMTD. As far as I know it is done by calculations with increments.

The Help in Vers. 5 under Fundamentals of Exchanger Design / under "Calculation of Overall Coefficients in Xace and Xist": gives the method, and Search for "Overall Performance Data" gives some more info.

I hope this could be of some help, but to me one has to accept that the EMTD is not the same as LMTD even after correction by the curves.

[dhproeng]

Can anybody tell me how HTRI calculates MTD. I have consulted HTRI design manual but I am not clear about it. What is the difference between True Temperature Diference and MTD. I have calculated True Temperature Difference myself but it shows some difference from MTD.

[sniperel]

Hy guys! I have some questions related to column condensers:
1. Which is the most common type: horizontal or vertical?
2. What is the direction of vapors entering the condeser : upward or downward?
Thanks a lot!

[muzaffar84]

Can anybody tell me how HTRI calculates MTD. I have consulted HTRI design manual but I am not clear about it. What is the difference between True Temperature Diference and MTD. I have calculated True Temperature Difference myself but it shows some difference from MTD.

HTRI divides the length of HE into number of increments. Then it calculates MTD for all increments and adds to calculate the effective MTD. The reason why your MTD and HTRI's MTD don’t match is that the flow in a S&T heat exchanger with baffles is not truly cocurrent/countercurrent. flow direction varies at every point. lets suppose F type shell with single pass tube side. If flow is cocurrent at top of baffle, it will be cross in center of two baffles and the countercurrent at bottom of the next baffle. So, fortunately, HTRI's approach is correct to divide the geometry into different increments and then to calculate MTD.

[muzaffar84]

Hy guys! I have some questions related to column condensers:
1. Which is the most common type: horizontal or vertical?
2. What is the direction of vapors entering the condeser : upward or downward?
Thanks a lot!

1. Word Column itself is defining the orientation of your condenser i.e. Vertical
2. Vapors should be entered from bottom

[poliloco]

you can simulate the mixed stream on PRO II and use the HTRI-PROII interface to load the stream properties, install PRO II and go to edit>program settings>properties and select PROII then setup package and specify the location of PROII.INI file.

[kirtisha]

I want to size top (Column) mounted condenser . Please send guideline.

[anuragsharma23]

HI Guys

Does anybody have experience in Thermosiphon reboiler rating in HTRI 5 . it is giving me some problem like not changing tube count when i change manually. I am totally new to this software. A detail document of HTRI use would be most welcomed.Also i am trying to USe HTRI 6 but it seems i do not have proper files. can anybody share??

[viswanathankasi2]

i too required the worked out samples. if any one have pl. upload

[sniperel]

Hola!
Who can tell me between HTRI and TASC gives the more accurate results regarding shell and tube heat exchangers. Thanks!