9 replies to this topic

[Celopsin.Khan]

Thermo-physical properties, which are used in Design problems of many equipment are a function of Temperature. 

 

Now there is this one fact (I m not confirm about it) that while designing a Heat Exchanger if delta T is greater than 50 degrees then we cannot use arithmetic mean Temp of In and Out Temp and we have to use Caloric Temperature Correction. 

 

1. Now What exactly is Caloric Temperature? and how can we apply this correction.

2. Also if there is linear relation of any property say Cp with temperature at constant API gravity, can we use simple average T for extracting thermo-physical properties for delta T > 50 ?

3. Can anyone provide me a clear scanned Figure of "Page 827 | Fig 17 - Caloric Temperature Correction | D. Q. Kern' Process Heat Transfer"

[PingPong]

Caloric Temperature is supposed to be the "correct" average temperature between inlet and outlet of a stream.

 

When using the stream properties at that temperature one should, in theory, obtain those film coefficients (h_i and h_o) for tube and shell sides that would result in the correct U value of the exchanger.

 

 

Attached Thumbnails

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[Celopsin.Khan]

What range of assumed Overall Heat Transfer Co-efficient should be taken while designing a Crude / Kero Heat Exchanger ... Qern Page 840 states ranges for all types of fluids ... just dont know what range should I take.

 

Can you have a look at this Design. Assumed U = 260 W/m2 K, Although Linear Velocity is in Range 1 - 5 m/s and Pressure Drop is < 10 psi. But I have little experience designing Heat Exchanger.

 

Also the Thermo physical Properties have been calculated using Magdi Assaad' Computerized Heat Exchanger Design Procedure. calculation is in done in sheets using Interpolation.
 

Also is there any way (tables or equation) to calculate friction factor (shell and tube sides) without using graphs. ... would be a real peace.?

 

Is the Design O.K

Attached Files

•  Design of Shell & Tube HX.xlsx   5.24MB   7640 downloads

Edited by Celopsin.Khan, 17 May 2014 - 08:11 AM.

[breizh]

Hi,

 

for friction factor , use the search engine in this forum :

key words : friction factor and you will find correlations .

 

Breizh

[Celopsin.Khan]

Hi,

 

for friction factor , use the search engine in this forum :

key words : friction factor and you will find correlations .

 

Breizh

 

Thanks got it

[PingPong]

Also is there any way (tables or equation) to calculate friction factor (shell and tube sides) without using graphs.

It is very simple to turn every graph into a formula by using curve fitting software. You can find several freeware curve fitting programs on the internet, just google.

[srfish]

It appears that the shell is under-tubed. This could go in a size smaller. The 4 tube passes will probably give a tube side pressure drop higher than 10 Psi.

[frnz]

Hi .

 

Can any body help to find the K value for below mentioned conditions of fluid.

1) Kerosene heated from 75F to 120F for P.D of 10PSI.

1) GAsoline Cooled from 160F to 120F for P.D of 07PSI.

 

I have gone trough the graph shown in Kern Process heat transfer and i got k as .65,is correct or not?

 

pradeep

[srfish]

Those temperature ranges are too small to be using caloric temperature for physical properties. Fifty degrees is the lowest line shown.on the graph.

[frnz]

Than , what to do with such cases?

Is their any other way to go or not?