Hardware in the Loop Tests for thermal systems

Testing on test benches take up a lot of resources, are tedious and expensive. We enable tests with virtual prototypes of heat pumps, refrigerators or energy technology plants. This increases your test coverage, improves the quality of your control software and avoids errors in the field.

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Test bench vs. hardware-in-the-loop testing

Modelling thermal systems such as refrigeration cycles in heat pumps is extremely complex. This is why control systems are often tested as they were 40 years ago: in elaborate experiments on test benches in the laboratory.

In contrast, hardware-in-the-loop (HiL) tests have long been established in the development of controllers for mechanical and electronic systems. Here, the controlled system is mapped virtually as a simulation model. In this way, the control unit can be tested in a closed control loop, even without a real prototype of the plant.

Tests on the test bench

Test benches always fully booked

Time pressure

Is everything really tested?

Long iteration loops

Limited reproducibility

Software problems only discovered by the customer

Risk of callbacks due to increasingly complex functions

Another compressor destroyed...

Hardware-in-the-loop tests

Parallel development of hardware and software

100% test coverage

Perfect reproducibility

Protection during software updates

Fewer complaints


Shorter development cycles

Closed loop tests from the beginning

We will be happy to discuss your use case.

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Test better, increase quality, develop faster

Easy testing even under extreme conditions

Faults often occur under extreme conditions. On the test bench in the laboratory, extreme conditions are associated with a great deal of effort.

In hardware-in-the-loop tests, extreme conditions can be simulated very easily. No matter whether 20 °C or -60 °C. That way you can find errors already during tests and not only in the field.

Test at any time, even without a test bench

Via HiL, you can test the current software status in a closed control loop at any time. Also automated over night.

Regression tests possible with software updates

Measurements on the test bench always contain uncertainties. Tests with simulation models are 100 % reproducible. This means that errors can be avoided in future software updates through regression tests.

Increase quality of control software, reduce complaint rate

HiL tests with a virtual prototype enable early and systematic testing. This allows you to detect problems and errors early in the development process. Not just on the test bench in the laboratory or in the field at the customer.

Reach the market faster

With the simulation models as virtual prototypes, regulations can be tested from the first idea to the final version, allowing software and engineering teams to work in parallel. This saves time and enables shorter development cycles.



Web-based simulator for hydrogen refueling stations

To support technical sales at NEUMAN & ESSER, we have developed a customized web-based application for the dynamic simulation of hydrogen refueling stations.

Customer requirements such as type and number of refueled vehicles can be selected. The filling station can be configured in detail and in a simulation the dynamic behavior of the overall system is calculated for a typical period of time.

With this tool, sales staff can configure the product "filling station" according to customer requirements without time-consuming detours via engineers. Interested parties receive direct and detailed feedback.

Hydrogen Refueling Station Simulation and Design Tool by NEUMAN & ESSER, Youtube video


Supermarket refrigeration CO2 cycle concepts

Emerson develops components and systems for supermarket refrigeration. Due to its environmental benefits CO2 as refrigerant is becoming more and more important in this sector. But compared to traditional refrigerants the thermodynamic properties of CO2 are totally different (high pressures and low critical temperature). Designing efficient CO2 cycles is challenging and there are many different cycle concepts proposed. Together with Emerson experts we have developed simulation models for a number of different concepts and run a simulation study to compare the seasonal efficiency of these cycles.

Eric Winandy et al.: Assessment of the seasonal efficiency of different CO2 booster architectures for different climates. DKV Jahrestagung, 2018


Heat pump modeling for HiL tests

In their development process of heat pump controllers Vaillant has established a comprehensive testing strategy. Before they connect developed controllers to real heat pumps in their lab, they are connected to virtual heat pumps running on special real time simulation hardware and software from dSPACE. Crucial ingredients for this so-called Hardware-in-the-Loop (HiL) tests are simulation models of the heat pumps, that are accurate, fast and robust. We developed these models for Vaillant using our Modelica library TIL Suite and set up a reliable tool chain to export these models to dSPACE platform. The models include a full dynamic physical model of the refrigeration cycle. It can handle switching of refrigerant flow direction caused by different modes for defrost, heating and cooling. Vaillant is now able to detect issues in control code much earlier and saves with this virtual testing a considerable amount of expensive lab experiments.

Manuel Gräber et al.: Physical Modeling of Heat Pumps for Hardware-in-the-Loop Testing. 13th International Modelica Conference, 2019


Battery thermal management

Together with Volkswagen we have developed simulation models for battery thermal management systems. Geometry of cooling plates and its flow patterns are taken into account by discretization with finite volumes. Compared to detailed CFD simulations the spatial resolution is much lower but still high enough to achieve confident results. This approach reduces the computation time dramatically enabling usage of numerical optimization algorithms or large-scale simulation studies. Cooling systems can be designed with less pressure loss and increased energy efficiency.

Robert Wendland et al.: Dynamic Optimization of Thermal Management and Cooling Plate Design for Battery Systems. 27th Aachen Colloquium Automobile and Engine Technology, 2018


Fast and robust models for thermodynamic systems

TIL Suite: Our special library for thermodynamic systems

We have co-developed the TIL Suite together with our partner company TLK Thermo over the last 15 years and established it worldwide. With the latest methods, we can also robustly calculate zero mass flow and flow reversal.

Modelica Training bei TLK Energy

Expertise in thermodynamics and numerics

In HiL tests, Euler solvers with a fixed step size are standard. For thermodynamic systems, this quickly reaches its limits. We use numerical differential equation solvers with variable step size. This way we can achieve 100 % robustness.

Modelica Training bei TLK Energy

FMI interface: Use the software of your choice

Thanks to the FMI interface, our models are compatible with HiL software from various suppliers such as dSPACE or Mathworks/Speedgoat. You can easily integrate our models into your existing in-house solutions.

Modelica Training bei TLK Energy


Hardware in the Loop Tests for Thermal Systems with TLK

TIL Suite - The library for thermodynamic systems

  • Create real-time models
  • Fast material data calculation
  • Models exportable as C code (FMI)
  • Robust even with flow reversal and zero mass flow

Support in setting up your internal processes

  • Selection of suitable HiL software and hardware
  • Development of a modelling process and training of your team
  • Analysis and solution of numerical problems
  • Sharing of experience and best practices

Creation of real-time capable and robust system models

  • Complete model creation
  • Evaluation of measurement data and data sheets of individual components
  • Parameter identification

Tested tool chains with established HiL solutions

  • dSPACE, Mathworks/Speedgoat
  • Frequent compatibility tests for software updates
  • Close contact to the technical developers

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