## ANSYS and Da Vinci’s quest for perfection

**Prototyping for science and art has been around since medieval times. But unlike Da Vinci’s trials to find the perfect proportions for his Vitruvian man, today’s designers have software tools that help them analyse ideal specifications. When creating the liquid cooled resistor EV2, the team at Cressall didn’t use ink and paper to prototype it; instead they employed engineering simulation software called ANSYS.**

The EV2 is the most advanced version of our liquid cooled modular resistor and is used everywhere from hybrid and electric vehicles to winches and cranes. It can be deployed alone, or in banks, and in the latter case, an input manifold is required. The design of this manifold was critical to creating a resistor with suitable cooling for medium voltage industrial applications.

The right design was achieved by employing multi-physics engineering simulation software called ANSYS. The goal was an input manifold which presents the same mass flow rate to each connected EV2 resistor. This ensures that each one experiences the same cooling effect.

An initial manifold design was produced in Autodesk Inventor. This 3D CAD package is Cressall’s choice of design software, offering an easy-to-use set of tools for 3D mechanical design, documentation and product simulation. The Inventor model was then imported directly into ANSYS. Next, the design team used ANSYS Boolean capability to “invert” the model and obtain the manifold’s enclosed cavity shape.

ANSYS then generates a finite element mesh of this cavity, and once appropriate boundary conditions for the manifold wall and inputs/outputs are applied, the model is ready to be solved and the output flow rates calculated.

This requires the solution of tens of thousands of simultaneous equations. Solving these manually would take more than a lifetime! However, ANSYS uses mathematical algorithms to optimise this process and with a modern computer, the solution to a model of this complexity can be reduced to just a few minutes!

As expected, the first results showed that the manifold’s central outlets received more fluid flow than the ones situated at the extremities.

To correct this, some design modifications were necessary, so our engineers re-appraised the design. It was evident that reducing the diameter of the outlets nearer the middle would even up the flow. The question now was, which ones and by how much?

The ANSYS model could easily be adjusted to investigate the effect of various diameter combinations, and several options were quickly examined. A final design was chosen such that the maximum mass flow variation across all outlets was reduced to just 8%. This satisfies the requirement for each resistor in the bank to receive the same cooling effect.

Using the ANSYS analysis tool enables our engineers to examine a design modification proposal, verify its suitability and then refine it a number of times to achieve an optimal solution. Unlike poor Da Vinci who had to spend numerous hours drawing and re-drawing his sketches, the solution for improving the EV2 design came in just minutes thanks to ANSYS.

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