HeatExchanger

Introduction

Purpose

The Heat Exchanger Library, or the HXL, is intended for the heat-exchanger design, dimensioning, and stacking. The library contains heat exchanger models supporting several flat-tube, louvered fin and plate designs. Users can simulate inhomogeneous airflow, temperature distribution and heat-exchanger stacking along the airflow path. The library is suitable for studying the effects of heat exchanger dimensioning and positioning on cooling performance. Heat Exchanger Library has native interfaces to Air Conditioning Library, Vapor Cycle Library, and Liquid Cooling Library for complete thermal management design. The models can be coupled to CFD-derived boundary conditions on the air side, bridging the gap between CFD and system simulations.

Key features involve:

• Geometry based heat exchanger models for system simulations,
• Friction and heat transfer models for louvered fin designs,
• Capture effects of inhomogenously distributed inlet air flow,
• Coupling to CFD data, and
• Modeling of heat exchanger stacks with different heat exchanger geometries, sizes and positioning.

Modeling and simulation

Many simulation tools are essentially user-interfaces for setting the parameters of fixed simulation models. This means that the actual equations that describe the model are impossible, or difficult, to modify by users. This Modelon modelica library offers a different approach and provides much more flexibility. In combination with a simulation tool this Modelon library is a complete modeling and simulation tool. This is important to understand, since it implies that the working procedure is slightly different and contains some additional steps:

• Build models that describe the phenomena of interest,
• Tune the model parameters,
• Use the models to set up an experiment that exposes the phenomena of interest,
• Simulate the experiment, and
• Analyze the results.

This Modelon library contains a large set of pre-defined models and templates that makes most modeling tasks straightforward. For many standard tasks it is possible to use the library in the same way as a pure simulation tool, i.e. it is sufficient to choose the right model, define all parameters and start the simulation.

Flexibility with prudence

It is possible for users to modify and extend most of the models in the library, and also to complement the library with custom models. It is also possible to mix with model components from other libraries. This is one of the major benefits of describing models using a high-level modeling language like Modelica. Customization of models and components can be done either from the graphical user interface and diagram view, or, for advanced users, by typing Modelica source code. There is also great flexibility in setting up experiments and analyzing results. The flexibility implies great freedom for users to define models and experiments, but may also require more attention to details and understanding.

Modelon libraries

All Modelon libraries are compatible and can be combined to solve specific engineering design tasks. Two libraries of Modelon are of particular interest for the Heat Exchanger library: the Vapor Cycle library and the Liquid Cooling library. The Vapor Cycle library is used to model vapor compression cycles. The Liquid Cooling library is designed for modeling of coolant circuits. Please note that both these libraries can also be used as a stand alone solution.