Practical Computational Fluid Dynamics: Thermal Management of Battery and Inverter Cabinet/Enclosure

Any Electrical/Electronic system requires an enclosure, without which the system is incomplete. Enclosure helps in systematic arrangement of electronic/electrical components, protects components causing harm from environmental effects and systematic provision of cooling mechanism. There is always a complexity in designing big enclosures consisting high heat generating components in choosing design of the system, cooling mechanisms and add-on features (Eco-friendly, easy access, aesthetic, compactness etc.) lead to high cost.

Thermal management in high heat generating components and thus enclosure is highly challenging, as heat transfer is multi-dimensional. Research has shown the life of electronic components will be cut in half on every 10 degree Celsius rise above normal temperature (22-24 degree Celsius). Therefore cooling becomes necessary and cooling mechanisms chosen plays a important role in reliability of electrical/electronic components.

Cooling mechanisms chosen always depends on amount of heat generated in an enclosure. Fig(a), shows simple graph on how the device temperature increases with time on cooling.

Fig (a): Device temperature increase with time on cooling

When the system is ON, the device absorbs heat and causing its temperature rise. At some point of time as the heat generated and heat absorbed by cooling becomes equal the temperature is said to be stabilized and the state is called as steady state operation condition and the temperature rise from the ambient is called as transient state operation condition as shown in Fig(a).

A typical electrical/electronic enclosure problem was studied comparing analytical and Computational Fluid Dynamics (CFD) software analysis result. Problem was modeled symmetrically using commercial CFD software defining its dimensions and components position. The electrical/electronic enclosure consisting Battery and Inverter as a major heat generating components. The total heat generated in an enclosure was above 1000W and to dissipate that exhaust fan was chosen through analytical approach based on CFM requirement. Fig (b), shows the result obtained from the analysis highlighting hot-spot zones and air flow streamlines and also contours are plotted for velocity and temperature. Relied results are obtained from the meshed model undergone mesh independence test.

Fig (b): Heat generating enclosure with Battery and Inverter

Interesting part of the problem was the optimization study by positioning exhaust fan at different locations, positioning inlet and provision to baffles with and without perforations to direct air to hot-spots. Optimization study makes important sense because over cooling and under cooling creates problem again and hence for effective cooling (optimized flow of air), it is necessary. Pressure drop in an enclosure is also a concern, as it is directly proportional to the pumping power cost of an enclosure.

Overall it was an interesting journey in my experience, solving this problem.

Conclusion:

Cooling of an heat generating enclosure becomes important to keep the components in optimized operating temperature range. Optimization study helps in providing effective cooling for a system. Any system should be tried for symmetric design for simplicity and ease in the system design, with this aspect choosing cooling mechanism creates real challenge for design and thermal engineers. Hence, from start of the design to deployment of the system, if all the important influencing parameters is considered then the system results in excellent reliability.

Interesting practical videos on Electrical/Electronics cooling are shown below.