2 replies to this topic

[jatinder]

Dear All,

 

I have a question regarding shell and tube heat exchanger. I did a case using Aspentech Shell and Tube Heat Exchanger software. please find attached result datasheet for your consideration.

 

I can't understand few things from the datasheet. They are as follow:

 

1 - Transfer rate, serivce - 185,7 W/(m2K)

2 - Dirty - 143.3 W/(m2K)

3 - Clean - 143.3 W/(m2K)

 

The area is fixed and Heat exchanged  = 180 kW

 

What does three three different values represent i.e. transfer rate serivce, dirty and clean?

 

Does Transfer rate, service (185.7 W/(m2K)) MEANS the required transfer for this particular process?

 

At clean service (no fouling), Total U = 143.3 W/(m2K)

 

So Required rate for this process = clean / transfer rate service = 143.3 / 185.7  = 77%

 

(100% - 77%) = 23%

 

So does that means my heat exchangers are 23% under designed?

 

Any suggestions?

 

Thank you very much to all,

 

Regards

 

Jatinder

 

 

 

Attached Files

•  Heat Exchanger datasheet.pdf   511.22KB   2088 downloads

[PingPong]

Yes, it means that you would need a U of 185.7 whereas even clean you only have a U of 143.3

 

When you specify a proper fouling resistance for shell and tube side the exchanger is even more under designed than 23 %.

All assuming that Aspen is correct, of course.

 

Note also that a tube side velocity of only 0.08 m/s indicates a terrible design.

[jatinder]

PingPong,

 

Thank you very much for your reply.

 

Well I do understand that it is underdesigned. My clean value must be larger than the rate transfer value.

 

But the funny thing is that HTRI and Aspen gives different results for these values.

 

Cheers