Adequate cooling of the power-intensive components is usually one of the key challenges for particularly high-performance PC systems. While classic servers are operated in optimally air-conditioned and clean rooms, PCs in industrial environments often have to cope with high temperatures and increased exposure to dust. In order to be able to provide the necessary cooling performance in both cases, powerful fans are required, which operate under high load when subjected to appropriate stress. This results in two fundamental problems: the faster a fan rotates, the higher the noise level inside the computer - the rotation of the fan generates some of the noise and the movement of the air flows, as soon as they cannot run unhindered, causes hissing and whistling. In addition, a fan operating under high load transports proportionally more dust into the housing, which in the long term leads to increased maintenance costs or cooling deterioration of the system.

Increase performance, minimize noise

Munich-based industrial PC manufacturer Inonet was confronted with these challenges for a customer in the image processing sector: For the new generation of a customized 19-inch system, the customer required a significant increase in both CPU and graphics performance. At the same time, the new system needed to be quieter for better integration into the working environment.

The 'thermal tunnel' is an open passageway through the PC. All power-intensive components are docked to the tunnel via heat pipes.

© Inonet

It was clear that the customer's requirements could not be met with a conventional approach: In order to cool the system at the specified output, active ventilation would be necessary, which would generate too much noise on the one hand and be impossible to manage in terms of EMC on the other. The engineers first began to develop a virtual prototype and looked at alternative approaches. Passively cooled embedded systems, whose power-intensive components are connected to a heat sink with heat pipes for heat dissipation, were decisive for the new concept. If SSDs are also installed in such systems, the computers operate completely silently.

In order to utilize this effect in a high-performance rackmount PC, the engineers developed the thermal tunnel - a new type of cooling concept in which power-intensive components such as CPU and graphics card are connected to a tunnel running through the housing with heat pipes in order to conduct the heat generated there directly out of the chassis. "Essentially, we wanted to insulate the components that generate a lot of heat in order to prevent excessive heat build-up in the housing. We tested a wide variety of approaches and confirmed that the separate dissipation of heat with heat pipes was by far the best way to achieve the desired effect," says Zied Saadi, Systems Engineer at Inonet.

Thermal tunnel as heat exchanger

The housing of a computer equipped with the thermal tunnel principle: In the center is the 'entrance' to the thermal tunnel, to the right is the conventional fan.

© Inonet

The thermal tunnel, with a fan in the middle, is an air passage (tunnel) that runs through the enclosure and thus functions as a heat exchanger between the interior of the enclosure and the air flowing through from outside. The air flowing through can be conveyed unhindered and unfiltered through the air conditioning tunnel, enabling an extremely high air flow rate with minimal noise development. All power-intensive components can be docked to the tunnel via heat pipes. As the thermal tunnel is air-impermeable to the interior of the housing, no dust can enter the interior of the housing through the tunnel, which significantly reduces the maintenance effort for the entire system.

Systems with a thermal tunnel have an additional conventional fan in the chassis, which transports cool air from the outside into the housing. As the CPU and GPU 'hot spots' are already cooled by the thermal tunnel, the conventional fan can run at low power and thus ventilate the other, less power-intensive components, such as hard disks. There is no longer any heat exchange between the hot spots in the chassis and the other components, as the heat is already dissipated directly from there via the heat pipes.

10 decibels quieter

The first prototype, which Inonet presented at SPS IPC Drives 2015, already achieved impressive measured values. The system, which is equipped with either one or two powerful Intel Xeon E5s and a high-end multiport graphics card, ran 10 dB quieter than an equivalent computer with conventional cooling. The cooling performance of the thermal tunnel on the CPU and GPU is also impressive: Under full load, the heat development there at half the sound pressure was 15 °C lower than in a conventionally cooled system with the same performance. The combined cooling capacity of around 600 W (500 W from the air conditioning tunnel, 100 W from the conventional fan) is still sufficient to cool an additional high-end graphics card with the same results. Such a system is ideal for computing-intensive applications such as industrial image processing.

For the Thermal Tunnel, which is now ready for series production, the engineers at Inonet worked on shortening the tunnel. This means that the cooling solution can now also be configured for more compact systems. Inonet is currently developing an embedded computer with server performance for the automotive industry, which is used for data acquisition and evaluation in test vehicles. By using a thermal tunnel in the system, the compact computer is sufficiently cooled even at high temperatures in the vehicle. The production-ready generation of the climate tunnel has also been fitted with additional fins. This allows a greater heat load to be dissipated from the existing components or additional components can be connected to the thermal tunnel with heat pipes.

Author:
Ulli Uffhausen is Public Relations Manager at Inonet.