HTRI learning - Question and Answers

[suresh750]

Air cooled HX uses "cool air" which is at ambient temperature to cool th process fluid. Obiviously the outlet temp which is less than the air temperature cannot b chieved . For this anothe shell & tube HX at the tail end will be required osing cold water

[suresh750]

Thermal resistance calcultions are the same used for calculating over-all heat transfer coefficient using the fluid property and conductivity etc.
% under design mans that the total heat transfer calculated by the programme is less than the design ' desired heat transfer .
For achieving over design u have to change the parameters of the HX, like number of passes, lengt of tubes, number of tubes etc.

[gipi]

can anyone gives me following ( related to HTRI)

what is thermal resistance calculations ?
% underdesign , how to make it overdesign

Thermal Resistance means the resistance offered by various elements to heat flow.
In case of exchanger, the elements are metal wall of tube, fouling layer and geometric & transport parameters of the shell side and tube side.
Under design means the amount by which the exchanger is falling short of its desired performance/capacity.
A exchanger with an under design parameters can be overdesigned either by changing the geometric parameters like tube thk, tube od, shell id, baffle spacing, etc. or in some case by increasing the mass flowrates of shell side and tube side fluids

[henj]

what is thermal resistance calculations ?
% underdesign , how to make it overdesign

The thermal resistance in the output summery is percent of the total thermal resistance.

Overdesign: This value is based on specified duty if input, on calculated duty if duty not input. Overdesign is calculated as follows:
% Over design = 100(Uo /Ureq –1)

If you make the size (area) bigger or higher velocity will help to get overdesign, or you may need to optimize say the baffles.
You may start to play with one of the examples.

[biswjeet]

Thanks everybody for the help foe my querries

can anyone gives me following

is over surface % = over design % in HTRI

PLS SPECIFY N DETAIL

[biswjeet]

HTRI- VMG Thermo Property error

hi everybody

in HTRI , i cannot able to create VMG Thermo property .

ERROR- VMG Thermo Package Authorization failed

is their requirement of cr*a*ck file of VMG Thermo property , like other .dll files
can anyone give me solution please

if any other problem , please give solution

[henj]

in HTRI , i cannot able to create VMG Thermo property .

ERROR- VMG Thermo Package Authorization failed

is their requirement of cr*a*ck file of VMG Thermo property , like other .dll files
can anyone give me solution please

if any other problem , please give solution

I just try the VMG property, and I got no error. I am not using VMG normally.
So it seems not always to be problems on authorization, and from the text on this page it should be include in the normal pack.

[link Point to another website Only the registered members can access]
Could you up-load the HTRI case file you are working on - or more detail needed.

[biswjeet]

Can anyone tel me

how to start with HTRI rating, i mean from start to finish

if requirement is of over design , then go for increasing tube s or shell id ? or any other parameter

where to stop rating ( satisfactorily calculations )

at which stage to start design

please explain with example --- if possible

[sniperel]

Hello!
Dear frends, can someone guide me with a dilema: Is the face velocity for an aircooler too low( 1 m/s) ? What is the lowest limit to consider?
Thanks a lot for your help!
Best regards!

[vne]

All,

I'm new to HTRI and have faced a warning message: "Setting plan error: Convergence problem during baffle check. Calculations terminated in routine BXPASS". It's a warning message so HTRI still runs to give the final output. I understand that there may be something wrong with the baffle spacing and/or baffle cut that leads to the warning message but don't understand why. I also searched for the word "BXPASS" in HTRI help but it returned no match. For detail (TEMA type, baffle info ...) please refer to the file attached. Please help explain the message and advise if it makes the design result unreliable.

Thank you.

[henj]

"Setting plan error: Convergence problem during baffle check. Calculations terminated in routine BXPASS". It's a warning message so HTRI still runs to give the final output. I understand that there may be something wrong with the baffle spacing and/or baffle cut that leads to the warning message but don't understand why. I also searched for the word "BXPASS" in HTRI help but it returned no match. For detail (TEMA type, baffle info ...) please refer to the file attached. Please help explain the message and advise if it makes the design result unreliable.

Out from the drawing in the sheet I can't see how your baffles could work - they are only in the center? Please upload the HTRI-file.

[aseptman]

Can anyone tel me

how to start with HTRI rating, i mean from start to finish

if requirement is of over design , then go for increasing tube s or shell id ? or any other parameter

where to stop rating ( satisfactorily calculations )

at which stage to start design

please explain with example --- if possible

Biswajeet,
In rating mode,
User shall specify most of the geometry and program shall then Rate the geometry and describe the expected performance.
To stop : One will check for
Pressure drops on tube and shell side are within desired limits
and area provided vs area required
If provided is more than required it is overdesign.
Now how much more. If one has experience with given exchagner and if he is sure that whaever streams he is handling are not going to change and that the fouling is adequately considered then even 1-2 % OD is also ok. If not then one has to ocer design by more if felt necessary for process