Newsletter April 2024

Two Decades of TLK-Thermo GmbH 

20 Years of Innovative Solutions for Measurement, Software and Simulation

For over 20 years, we at TLK-Thermo have been developing innovative solutions for measurements, software and simulation for thermal systems and their components.


TLK-Thermo GmbH, founded in May 2003, has now grown into a company with more than 80 experts in the field of measurement, software development and simulation of thermal systems.


We measure components and systems on numerous specialized test benches in our four test halls totaling 1,500 m2 of floor area. We are currently expanding our measurement and testing capabilities by putting another high-performance system test bench into operation that will allow us to perform detailed analyses of complete systems for the complex thermal management of electrified vehicles.


Since our founding, we have developed nine software products for modelling, simulation, visualization and automation, which we are continuously adapting to new and changing requirements. The development of our software solutions benefits not only from the constructive feedback of own colleagues, who use our products for a broad range of testing and simulation projects, but also from the close and trusting cooperation of our customers and technical expertise from our ties to the TU Braunschweig. We would like to take this opportunity to express our gratitude for this. In this newsletter, we present the new features in TIL, DaVE and the TLK Simulator as examples of the continuous further development of our products.


In our anniversary year 2023, we worked intensively on new content and a redesign of the TLK homepage. Feel free to take a look! The many changes delayed the release of our new - and in this form final - newsletter. In the future, we will be publishing innovative articles from specialists on a regular basis on our website. The newsletter will then only inform you about new content on our website. You can also learn of current developments by following us on LinkedIn.


Many thanks to all those who have made the joint successes of the last two decades possible through the many professional and personal encounters.


Willi Tegethoff and Niko Lemke

Analysis of Direct Air Capture Processes

Exemplary Analysis of a DAC Process Based on the Adsorption Principle

Direct air capture (DAC) refers to technical processes that remove carbon dioxide (CO2) from the atmosphere. The CO2 extracted this way can either be used for chemical processes or underground storage. With software developed by TLK-Thermo, we are able to model different CO2 capture processes.


Capturing CO2 from the atmosphere is beneficial for several reasons. The aims of the Paris Climate Agreement cannot be achieved without the capture of CO2 and subsequent storage in the geological underground, as the IPCC World Climate Report 2023 shows. Furthermore, atmospheric CO2 can be used as raw material in the chemical industry to avoid the consumption of fossil carbon. Different capture processes can be used to remove CO2 from air – depending on the extraction point, either at high concentrations at the emission source (so-called point source) or at low concentrations directly from the atmosphere.


As a starting point, the TIL library in combination with other software solutions is suitable for analyzing and evaluating such processes and thus providing a basis for decision-making. Specific processes based on the adsorption principle can be modeled with the Add-On Adsorption from TLK Energy GmbH. Figure 1 shows a simulation model for an exemplary DAC process.

Figure 1: Simulation model of an exemplary DAC process modeled with the TIL library and the Add-On Adsorption

During the adsorption phase of the DAC process shown in Figure 1, a fan draws ambient air over the adsorbent. This co-adsorbs CO2 and steam from the air. When the adsorber material is almost completely saturated with CO2, the adsorption chamber is closed. A vacuum pump is used to evacuate the chamber in order to remove the remaining oxygen from the volume. This is necessary to prevent the adsorber material from experiencing oxidative degradation at high temperatures.


The CO2 is then desorbed by injecting steam at approximately 110°C and at a slight vacuum. The CO2/H2O mixture is extracted using a vacuum pump. After leaving the adsorber chamber, the mixture is cooled, causing the water to condense, thereby obtaining CO2 with a high degree of purity. At the end of the desorption phase, the steam supply is closed and the pressure in the adsorber chamber is significantly reduced again. The temperature of the adsorber material drops, primarily due to desorbing water, and a new adsorption process can be started. The separated CO2 can be permanently stored in geological formations or used as feedstock for the chemical industry.

Figure 2: Pressure and temperature development inside the adsorber material during the desorption phase

Figure 3: Loading of the adsorber material during an adsorption and desorption phase

Simulated results of this process are illustrated in Figures 2 and 3. Figure 2 shows the pressure and temperature in the adsorber material during desorption. The loading of the adsorber material with CO2 and H2O during a complete adsorption-desorption cycle is shown in Figure 3. The model can also be used to simulate desorption under vacuum conditions with internal adsorber heating and cooling.


Using our model, we are able to analyze the energy demand and performance of DAC systems under varying environmental conditions and system parameters in order to address related issues.


Please contact us for more information on DAC processes or the capture of CO2 from point sources. Contact for DAC processes:

Model Library TIL – New Features of the Software Releases 

New Functionalities and Models for Simulating Thermal Systems

TIL Suite is a comprehensive Modelica-based model library for steady-state and transient simulations of thermodynamic components and systems. In this article we present the improvements as well as the new functionalities and models (e.g. for valves, heat exchangers including frosting and heat transfer) of the current and the upcoming release.


The current release TIL Suite 3.15.1 (November 2023) includes the following improvements and models:


  • Improved provision of function derivatives

In TIL and TILMedia, function derivatives have been added or improved, especially for the TIL HD variant. The derivatives can be used by Modelica solvers to create the analytical Jacobian matrix, which can increase the simulation speed.


  • Four-way reversing valves for refrigerants

The new release contains an exemplary system model of a reversible air/water heat pump with propane as refrigerant and a four-way reversing valve for directing refrigerant flow (see Figure 1). Customers can use this example as a basis for their own system models.


  • Improved frosting models

Air-side ice formation at the evaporator has a significant influence on the performance and efficiency of a heat pump with air as the heat source (Figure 1).

The new TIL release includes improved frosting models, which are characterized by a clear structure and comprehensive documentation. Furthermore, an additional model has been added that provides detailed approaches with flexible and user-specific settings for ice formation.

Figure 1: TIL system model of an air/water heat pump with propane as refrigerant. The model can be used to analyze ice formation and periodic defrosting of the evaporator

The upcoming release of TIL Suite 3.16.0 (expected April 2024) will include the following new functionalities and models:


  • Offset-Strip-Fin heat exchanger 

The geometry of this type of heat exchanger is characterized by offset strip fins. In practice, this heat exchanger offers an alternative to plate heat exchangers. In TIL, this heat exchanger model can be used with both refrigerants (VLEFluids) and incompressible fluids (Liquids).


  • Modeling of check valves

Valve models for gases and orifice valve models for Liquids and VLEFluids can represent check valves with corresponding parameterization ensuring that only one flow direction is permitted.


  • Extension and new component model for thermal resistances

The extension enables users to simulate heat transfer of heat conduction and convection by specifying different geometries.


Further information on the TIL Suite can be found on here.


Contact for TIL Suite:

SiC Power Semiconductors for Tomorrow's Passenger Transportation

Reduction of Energy Requirements Based on Simulative Analyses

Last year, we successfully completed a research project called e-Tractiv. In addition to modeling air-cooled heat sinks with heat pipes, we also tested a pool boiling  cooling system for a module with IGBTs (Insulated-Gate Bipolar Transistor).


Within the e-Tractiv research project, we investigated the potential of silicon carbide (SiC) power semiconductors for high-performance application in the traction system of (sub-)urban trains. The objective was to reduce the energy requirements of a typical train by approximately 15 %. These savings should be achieved through innovations both in the traction system (~12 % savings anticipated) and in the auxiliary systems required for cooling (~3 % savings anticipated). This contributed directly to increasing efficiency in rail transport and reducing CO2 emissions. In cooperation with the project partners (Siemens Mobility, Infineon, University of Bayreuth), TLK-Thermo designed new cooling concepts and evaluated them using high-resolution field calculations.


Airstream cooler with embedded heat pipes

During the first phase of the project, different concepts for the passive cooling of SiC power semiconductors using an airstream cooler were tested. In addition to simple aluminum bodies, we investigated a system with embedded heat pipes (Figure 1). The main advantage of this system is the closer proximity of the individual temperature maxima of the semiconductor modules mounted on the heat sink. As a result, the temperature differences in the average temperatures of the modules could be halved (Figure 2). Overall, the project findings showed potential savings of 11.7 % (auxiliary systems 2.8 %, traction system 8.9 %) in the overall energy demand.

Figure 1, left: Heat sink (gray) with embedded heat pipes (red) under a solder layer (orange); Center: Exemplary arrangement of the IGBT modules; Right: Temperature field in a sectional view

Figure 2: Average temperatures at the semiconductor modules for different heat sink designs

Pool boiling cooling system

During the second phase of the project, a cooling system using pool boiling was investigated. The project partner, the University of Bayreuth, performed experimental studies on direct liquid cooling in a module with IGBTs. We simulated these experiments by creating a model for multiphase flow with a highly simplified representation of the geometry. We achieved good agreement in terms of the temperatures at the IGBTs for both the reference investigation without liquid and the investigation with demineralized water.


In addition to the advances made related to the energy efficiency of the trains, this project enabled us to improve our CFD competencies in the field of multiphase flow.


Contact for field calculation:

DaVE and Simulator Suite – New Software Releases

Extension of the Functionality of DaVE and the Simulator Suite

DaVE: Import of TIL graphics and export of presentations; Simulator Suite: Setting the FMU state, control via VBA and improved simulation kernel.


DaVE 2024.1

DaVE is a visualization environment that enables post-processing, the online display of dynamic data and the creation of P&I flow diagrams. The software supports various data sources, including files in different formats and online connections to simulations and measurements. Various instruments are available for visualization, which you can freely arrange and configure.

The following functionalities, among others, have been added to the current release of DaVE:


  • Import of TIL graphics

This new capability allows you to import your Modelica simulation graphics created with the TIL library directly into DaVE. In this way, your system does not have to be rebuilt in DaVE. 


  • Export of presentations

DaVE can create and export comprehensive reports and elegant presentations. In addition to the option already available in version 2023.2 to specify the content and a target file format when exporting, the current update adds the option to select the size and layout of the workspace. For each time mark, for example, three pages can be output either as a multi-page PDF in A4 format or as a PowerPoint presentation in 16:9.

Figure 1: The new layout of the toolbar with a horizontal action toolbar and a vertical instrument toolbar.

  • Controls in the toolbar

New controls have been added that enable you to set the position, width and height of your instruments. In order to ensure the proper display on smaller screens, we offer a vertical toolbar for the instruments and a previously introduced horizontal toolbar on which all the control options of the instrument layout can be found.



Simulator Suite 2024.2

The Simulator Suite enables you to efficiently evaluate models based on the Functional Mock-up Interface standard (FMI 1.0, FMI 2.0, FMI 3.0) or compiled Dymola code. With our software package, models can be simulated in familiar applications such as Excel or LabVIEW as well as used via SDKs in C/C++ and Python. Extensive configuration options and specialized solver technology allow the high-performance evaluation of complex thermodynamic systems. With the support of dedicated System Structure and Parameterization (SSP) features, the Simulator Suite also enables the calculation of interconnected systems.

The following functionalities, among others, have been added to the current release of the Simulator Suite:


  • Setting the FMU state

A new feature is the implementation of complete retrieval, serialization and setting of the FMU state. This means, for example, that iterations of optimization calculations can always be performed starting from a stationary state.


  • Control via VBA

The integration of Visual Basic for Applications (VBA) for controlling the TLK Simulator for Excel means that simulations can now be fully controlled using VBA. This in turn enables the creation of even more customized automated evaluation routines.


  • Simulation kernel

The current release includes a comprehensively revised simulation core with even more efficient memory utilization. This enables us to meet the increasing demands on scalability for carrying out extensive simulation studies and optimization calculations.


We also want to highlight the TLK Simulator for Python, which is ideal for the automated testing and validation of your individual models and systems. The simulator supports concurrent simulations in multiple threads as well as in separate processes. It is suitable for Python versions 3.7, 3.8, 3.9, 3.10 and 3.11 for both Windows and Linux operating systems.


As the Simulator Suite can also be integrated into various workflows via our MoBA Automation software, this combination offers you a tool that adapts to your individual needs. It enables the definition of complete optimization and validation workflows including extended GUI-guided interactions. 



Call for Papers – Users’ Meeting ThermoSim 2024

Simulation of Thermal Systems with Modelica and FMI

Our partner company LTX Simulation GmbH is pleased to invite you to the third Modelica and FMI Users' Meeting "ThermoSim 2024 - Simulation of thermal systems with Modelica and FMI" on September 9 and 10, 2024 in Munich. We are looking forward to receiving abstracts for a presentation or a poster. The deadline for submissions is June 15, 2024.

TLK-Thermo, XRG Simulation and LTX Simulation are jointly organizing the user meeting "ThermoSim 2024 - Simulation of thermal systems with Modelica and FMI".


Date: September 9 and 10, 2024

Location: Munich

Deadline for submission of abstracts: June 15, 2024


Im Fokus des Meetings stehen gleichungsbasierte Modellierungen und Simulationen thermischer Systeme, insbesondere in Verbindung mit der Programmiersprache Modelica, sowie FMI-basierte Methoden. 


The meeting will focus on equation-based modeling and simulation of thermal systems, especially in conjunction with the Modelica programming language, as well as FMI-based methods. 


Further information can be found here.