image Cooldt cool-down time calculator

Cooldt calculate the cooling duration of a multi-layers pipe in a cold environment. The duration to reach the “Final fluid temperature” or cool-down time (CDT) is calculated by solving the heat equation in cylindrical coordinates with a flux conservative formulation.

Example of a multi-layers pipe

↓↓ DOWNLOAD Cooldt 2 for Windows 32 / 64 bits ↓↓
↓↓ DOWNLOAD Cooldt 2 for Linux 64 bits ↓↓
↓↓ DOWNLOAD Cooldt 2 sources ↓↓



Spreadsheet Input

Spreadsheet Output

Initial, final temperature profiles and temperature decay at the fluid / solid interface


Install Cooldt

Download Gnu/Linux 64 bits or Windows 32/64 bits binaries version and extract the archive.

To install the Excel Add-in, follow these instructions. For the 32 bits version of Excel select cooldt.xll and for the 64 bits version of Excel select cooldt-w64.xll. No administrative privilege are required to install it.

Run Cooldt

LibreOffice or Excel

Open CooldtSheet.xls or CooldtSheet.ods, enter your data then click the Launch cooldt button.

The cooldt executable and the spreadsheet must be in the same folder and the decimal separator must be the point (.)

On Windows, Cooldt can not run on an UNC path (i.e. a path starting with \\). Map your UNC path, or run Cooldt from a local drive to solve this problem

Excel Add-in

The Excel Add-in provides a native Excel function to calculate cool-down time. It is very useful to calculate an insulation thickness for a given cool-down time with the Excel solver. Avoid goal seek, it does not work very well with non-linear functions. To use the CoolDownTime function, click on the fx button on the formula bar, select the Cooldt 2 category, select the CoolDownTime function then enter your data. Examples of usage are presented on the CooldtSheet.xls spreadsheet.

Command line interface

Type cooldt example.dat to calculate the cool-down time of the example.dat data file. Results will be saved to the example.txt file.

Command line interface

Replace cooldt by cooldt-w64 if you are using the 64 bits version of Windows.

The data file is a text file with numbers separated by spaces or tabs. The file format is presented in the table below:

InitialTemp.(°C) AmbientTemp.(°C) FinalTargetTemp.(°C) AmbientHeatTransfer(W/m2/K)
Pipe.ID(m) FluidConductivity.(W/m/K) FluidDensity(kg/m3) FluidHeatCapacity(J/kg/K)
Layer.1.OD(m) Layer.1.Conductivity.(W/m/K) Layer.1.Density(kg/m3) Layer.1.HeatCapacity(J/kg/K)
Layer.n.OD(m) Layer.n.Conductivity.(W/m/K) Layer.n.Density(kg/m3) Layer.n.HeatCapacity(J/kg/K)

Several files can be processed in one command, e.g. type cooldt file-1.dat file-2.dat file-3.dat to process three files.


To generate png and svg plots from a Cooldt output file, use the script file with the Gnuplot command:

gnuplot -e "OutputFile='example.txt';"

Excel Visual Basic Interface

Cooldt can be called from Visual Basic. The declaration of the cooldt function and two examples of usage are given in the CooldtVB file.

Build Cooldt from Source

Download the source code, extract the archive and follow these instructions.


Cooldt includes XLW – A Wrapper for the Excel API


Is it free ?

Yes. Cooldt is a free software. Read the license for details.

Why Cooldt does not work ?

On Windows, Cooldt can not run on an UNC path (i.e. a path starting with \\). Map your UNC path, or run Cooldt from a local drive to solve this problem.

What is the default Excel Add-in folder ?

Since Windows Vista and Excel 2007, it is %APPDATA%\Microsoft\AddIns. The following command should open this folder:

explorer.exe %APPDATA%\Microsoft\AddIns

How to update the Excel Add-in ?

Replace the old .xll file with new one in the add-in folder.