Double Pipe Heat Exchanger

This Excel spreadsheet helps you design a double pipe heat exchanger (also known as a concentric tube heat exchanger). Double pipe heat exchangers are often used in the chemical, food processing and oil & gas industries. They have a particular advantage when close temperature approaches are needed or in high pressure applications.

The spreadsheet will give you important design parameters, such as the overall heat transfer area, the length required, pressure drops, fluid velocities and much more.  The spreadsheet uses the
• Gnielinski correlation for the heat transfer coefficient of the shell side and tube side fluids (hh and hc). The Gnielinski correlation is valid for 0.5 ≤ Pr ≤ 2000 and 2300 ≤ Re ≤ 56.It gives the heat transfer coefficient in terms of the friction factor, the Reynolds number and the Prandtl number.
• Filonenko correlation for the friction factor (valid for smooth pipes in turbulent flow with 104 ≤ Re ≤ 107).
The equations for the heat transfer coefficients, the friction factor, the length of the heat exchanger and the overall heat transfer coefficient are given below

 Double Pipe Heat Exchanger Equations

• Nu is the Nusselt Number
• Re is the Reynolds Number
• f is the friction factor
• Q is the rate of heat transfer (determined from a heat balance)
• dic is the internal diameter of the inner pipe
• doc is the external diameter of the inner pipe
• kp is the thermal conductivity of the pipe material
• hc is the heat transfer coefficient of the cold fluid (in the inner pipe)
• hh is the heat transfer coefficient of the hot fluid (in the outer pipe)
• ΔTLMTD is the log mean temperature difference
The Excel spreadsheet uses variable names in the formulas to help you better understand the equations. Generally, the suffixes h and c represents quantities defined for the hot and cold streams respectively (e.g. hh is the heat transfer coefficient for the hot stream, hc is the heat transfer coefficient for the cold stream)

 Named variables

INSTRUCTIONS

Step 1. Enter your parameters. The spreadsheet will calculate initial values of the heat transfer coefficients, the rate of heat transfer across both fluids, and the length of the heat exchanger. Provide an initial guess for the parameter (i.e. mass flowrate) you will change in Step 2.

Step 2. Equalize heat transfer across both streams. The rate of heat transfer across the shell side and tube side fluids must be the same. You must use Goal Seek to make the difference between the two rates of heat transfer equal to zero by changing a design parameter (e.g. mass flowrates)

 Goal Seek

You have now established important design parameters, such as the fluid velocities, the tube-side and shell-side pressure drops, Prandtl numbers, the length of the heat exchanger and so on.

 Intermediate Calculations and Results

Roddy Tyrrell said...

I am working on a process, where it is vitally important to accurtely size the double pipe heat exchangers. Too big and we create serious process control problems and too small and we limit plant capacity.

Your spreadsheet is very good and well thought out. I did find a couple of minor discrepancies, which were very easily corrected. The hydaulic diameter of the inner tube should be equal to the ID of the inner pipe and the flow area of the inner pipe shouild be based on the ID not the OD.

I have not previously come across your formulae for UA and total tube length before and I wonder where you sourced them. We calculated UA from Q/DTlm, and it was exactly the same as your UA.

My e-mail address is roddy.tyrrell@gmail.com and I would very much like to hear from you

Roddy Tyrrell,
Proncipal Engineer, Panorama Eng, Cork

xoxo said...

How to define the pressure loss coefficient in the input parameter box.

Kalluf said...

Hi Samir, I would like to know which is the reference source for your Nusselt Number calculation? Should not you use a different correlation when Re < 2000 (laminar flow)and 2000 < Re < 10000 (transient flow)? By using your formula, we will get several negative numbers when Re is < 1000.

BR, Kalluf.

Samir Khan said...

@Kalluf - the friction factor is the Filonenko correlation for smooth circular ducts in turbulent flow (google it). The Nusselt number correlation is valid for turbulent flow and is referenced at http://web2.clarkson.edu/projects/subramanian/ch302/notes/conv1.pdf

Miquel Artiol said...

Hi Samir,
I can't open the file. Could you please chek if it is corrupted. I'm really interested on it. Thanks in advanced

shahab said...

Does the calculation work if I change tube and sell side?
Cold fluid is on the shell side, hot fluid is on the tube side