Finding the number of shell passes

[jpe1]

Hi guys, i need a code that calculates the number of shell passes in a heat exchanger. This can be done if given the inlet and outlet temps of the hot and cold streams. Equations of the lines can then be formed. To find the number of shell passes follow the outlet temp of the hot stream along the x axis until you intersect the cold stream line equation then follow this along the y axis until you hit the hot stream equation again. This process then repeats until the line across the x axis no longer intersects the cold stream line. I want the code to tell me how many imaginary lines along the x axis are needed. I have attached a picture to make this clearer.

[Pepe Le Mokko]

Attach a sample workbook (not a picture or pasted copy). Make sure there is just enough data to demonstrate your need. Include a BEFORE sheet and an AFTER sheet in the workbook if needed to show the process you're trying to complete or automate. Make sure your desired results are shown, mock them up manually if necessary.

Remember to desensitize the data.

Click on GO ADVANCED and then scroll down to Manage Attachments to open the upload window.

[jpe1]

Hi, i dont know how to make the code. This picture I attached explains what I need. I want to be able to state the inlet and outlet temps of the hot and cold streams and the code to tell me the number of passes needed.

[Pepe Le Mokko]

You just need to post a sheet with your data as described in my previous post. How can help be provided without eve seeing the data. Our members are all great at Excel, as to heat exchangers...

[AliGW]

Just to clarify - there must be data on which you have based your graph. If any member is going to be able to help you solve this, then they will need that dataset. YOu will also need to tell us exactly what your expected outcomes would be for the sample supplied and give some explanation of what the equations on the graph mean (they are actually too small to read).

[jpe1]

Hi ive attached some data and an explanation to the steps involved

[AliGW]

Thanks. What equation would you use to work this out manually?

[jpe1]

Hi, I dont think there is an equation, i normally just draw those graphs and do that by hand. I was just curious if someone could develop a code that would do it automatically.

[AliGW]

Maybe one of our maths-savvy experts will be able to help. It's more a maths/algebra question than an Excel one, really, but there are people like MrShorty who understand these things better than I. Just hang on in there - bear in mind it's a Sunday, so you may get no luck today. If that happens, just bump the thread tomorrow.

[jpe1]

Thank you, will do

[AliGW]

I've put out a call for help - let's see what happens.

[jpe1]

Bump Thread

[MrShorty]

It seems like there ought to be a closed form, algebraic solution to something like this, but I was too lazy to figure it out. Instead, I opted to simply implement the procedure you describe.

1) I need the slope and intercept for each line, so I enter these in the spreadsheet. In R8=-150, R9=450, S8=-160, S9=370. If I wanted to bypass creating the chart, I would use the LINEST() function or the SLOPE() and INTERCEPT() functions to get these.
2) In R11, I enter =C4 to bring the H(outlet) temperature into this table.
3) In S11, I calculate the "x" value from the C curve that would correspond to this H. =(R11-$S$9)/$S$8
4) In R12, I calculate H(x) at this new x value =$R$9+$R$8*S11.
5) Copy S11 into S12, then Copy R12:S12 down as far as I think I will ever need.
6) Now, it is a simple matter to calculate how many values in the H column are less than the C(inlet) temperature and add one to it. In some convenient cell, enter a COUNTIFS() function =COUNTIFS(R11:R21,"<"&$F$3)

Will an algorithm like that work for you?

[jpe1]

Thank you, That works.