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Heat Dissipation in Custom Enclosure Design

By 8th May 2019 No Comments

With electronic products becoming ever smaller in size, there is a growing need to design custom enclosures which facilitate adequate heat dissipation. It is an important consideration that must be factored into the design process from the onset. Designers, therefore, have to quickly evaluate options and find the optimal solution for the product. An ever more powerful tool for this process is Computational Fluid Dynamic (CFD) software which allows the thermal flow characteristics of a system to be quickly assessed and tweaked to move towards an optimal solution.

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The Importance of Simulation

Every day, designers and engineers are challenged to develop products that are extremely compact, whilst delivering high levels of functionality. Historically, when designers made changes to the design, each change needed to be physically prototyped and tested in a repeating cycle until the specifications for the product were met.

Design simulation software does not eliminate the need for physical testing from the design process. However, if used correctly, it should result in fewer physical prototypes being required, which reduces the cost and time scale of your project.  Many important design questions regarding the product’s ability to dissipate heat can be answered using this type of software. For instance, it can reveal the effectiveness of cooling systems and the thermal effect on the materials.

Improving Heat Dissipation

When it comes to designing custom enclosures for electronic products, thermal management is often a key challenge. Electronic products can produce a large amount of heat, which accumulates within the enclosure. As key electronic components become hot, the processor is forced to reduce the processing power which either leads to a reduction in the performance of the system or may cause it to shut down altogether. Moreover, for consumer electronic products, hot enclosures can become hazardous to the user.

Heat dissipation is a key area for all designers and, therefore, must be considered from the start.

Introducing simulations into your design process can expedite the discovery of any thermal issues your product encounters before the manufacturing stage.

Heat Dissipation Approaches

Heat Sinks

A heatsink is a component which is designed to transfer heat away from a specific component or surface. They are commonly used to dissipate heat away from microprocessors as the performance of these components can be dramatically affected by a build-up of heat. While heatsinks are produced in a wide variety of shapes and sizes, their general principle of operation is largely the same. One side of the heatsink is flat and is designed to be placed in contact with the source of the heat. Sometimes it can be difficult to place the heatsink in contact with processors due to the position of other components and so a conductive putty material is used to fill the gap. This large flat side of the heatsink is designed to use thermal conduction as the primary form of heat transfer from the heat source. On the other side of the heatsink, there are usually a number of thin fins. These fins are designed to dissipate the heat to the surroundings through thermal convection. As such, to maximise the level of convection achieved, a large surface area is required, hence the tall fins. Variations of the shape and style of the fins can be used depending on the enclosure size/shape.

Forced Air Cooling

Fans are often used to pass ambient air over hot components allowing them to cool by dissipating their heat via thermal convection. Fans are also often used in conjunction with heatsinks whereby the fan is positioned to induce a flow of cool air over the heatsink fins. This enables heat convection to occur at a faster rate. This is because the rate of thermal convection is driven by the differential between the temperature of the surface and the surrounding air. Without a fan, the air surrounding the heatsink fins rises which causes the rate at which the heatsink can dissipate heat to decrease. Fans represent a commonly used approach, but they do have some drawbacks for some situations. Fans can fail, they add more cost to the end product as well as taking up valuable space, and they can make unwanted noise.  Moreover, the product needs inlet and outlet vents ideally to supply fresh cool air and get rid of the heated air, otherwise, the air just circulates within a closed space. This adds challenges if the product needs to be IP rated to withstand ingress of dust/water.

Passive Air Cooling

Similar to forced air cooling in many ways, but the fan is removed. The design relies on air flow being created by warm air rising and pulling in cooler air from below. Mechanically much simpler than forced air cooling, and silent in operation. The downside is that less energy can be dissipated as air flow will be slower than when using a fan.

Peltier Cooling

Peltier coolers are widely available and can be added to a product to increase heat dissipation or cooling of a gas or liquid. They require an electrical feed and can add bulk and cost to a product, but are worth considering in certain applications. They will create temperatures lower than the ambient air temperature, so can be used to chill things, such as food and drink in a small fridge.

Water Cooling

Very common on vehicles, water can transport a lot of heat energy away from one place to be dissipated in another. Anyone who has built their own PC or is an avid gamer will know that water cooling is used on higher specification computers too. This approach is not used on most other electronic items as it is expensive, can be bulky, and can leak if damaged or not well engineered.

Software

Refinement of the operating software on a product can be a key consideration. If the management of a processor is improved so that it doesn’t run constantly at full speed, it will generate less unwanted heat.