6 replies to this topic

[amirali1572]

Hi every one

In shell and tube heat exchanger why Tube side inlet is from up of exchanger and shell side inlet is from down of exchanger?

THANKS

[markymaark]

The log-mean temperature difference is better when you have the feed inlets on opposite sides.

[Raj Mehta]

markymaark, 

 

can you elaborate a bit, because I am unable to correlate LMTD with the inlet position. LMTD talks about only the inlet & outlet tempertures

 

I thought that it has something to do with the ease of maintencance.

 

Best Regards.

[neel_avi]

LMTD is higher in a countercurrent flow than in a cocurrent flow.

 

However, Amirali1572 has a different query about the positioning of the nozzles w.r.t the tube and shell side. I believe the position of inlets is determined on the basis of the fluid conditions in each side. It differs from case to case and its generally - the inlet of hot fluid (lower density after getting cooled) is from top and inlet of cold fluid (higher density after getting heated) is from the bottom nozzle (irrespective of the shell or tube side).

 

Tube side fluid and shell side fluids however, are selected on other factors like corrosivity, cleanliness or fouling tendency, viscosity, ease of maintenance etc.

 

Please rectify me if I was wrong.

 

Regards

Avijit

[fallah]

Dear amirali,

 

I am agreed with above statement from neel_avi about your query other than his/her viewpoint on density change. The point is the hot fluid would have higher density after getting cooled and the cold fluid would have lower density after getting heated...

 

In fact, the incoming hot fluid would normally enters from the top and the cold fluid from the bottome irrespective of the shell or tube side..because for example if the hot fluid enters from the bottom when it gradually get cold and more dense, tends to fall toward bottom and might retard the flow which is going from the bottom to the top...

[neel_avi]

Mr. Fallah,

 

thanks for correcting me. It should be as you mentioned. Apologise for the silly mistake.

 

Regards

 

avijit 

[mkhairdi]

  Dear Mr. Fallah,

 

I have Diesel Feed/Diesel Product Exchanger. Its a six shell made in two stacks of 3 shells each.

The arrangement of the six shells is as follows:

Shell 3 C               D   Shell 4

Shell 2 B               E    Shell 5

Shell 1 A               F    Shell 6

 

Hot Product Diesel enters at the bottom of Shell F and Cold Feed Enters at the bottom of Shell A(tube side) . This is Pre-heat service without phase change.

The shell side fluid comes out from Shell D and enters the shell C at the top and Cold tube side exits the Shell C at the top and enters the Shell D at the top.

As you quoted about effects of denser fluid retarding the flow profile, I am not sure if it will impact installation in my plant

I am unable upload any sketch, but the description is sufficient I guess.

 

Regards,

Mudassar