Liquid cooling

The cooling system of the future

The Rohde & Schwarz high frequency (HF) high-power transmitters have increased performance and required an innovative new cooling system to cope with the extra waste heat

The new R&S®SK4105 and R&S®SK4110 HF high-power transmitters for beyond line of sight (BLOS) communications from shore stations are the first transmitters in the 5-10 kW power range that use liquid-cooling instead of air cooling. Decades of experience and expertise in the broadcast and media markets have given Rohde & Schwarz an opportunity to use this innovation to open a new market.

Liquid cooling offers incredible performance and, in these systems, the liquid transfers warmth from the components for better heat management than with air cooling. Liquid cooling works much like a radiator in a car or home. In these systems, the liquid circulates through aluminum blocks for the stressed components that need cooling. The relatively cool fluid circulating through the block dissipates heat from the components and cools them. The heated fluid is pumped to the radiator, where fans discharge the heat into the cool air. The re-cooled fluid returns to the aluminum block to remove heat and the cycle repeats.

This results in more efficient cooling while protecting adjacent parts by preventing strain from waste heat. Less wear means less maintenance for components, giving transmitters a longer service life in general. The hoses, heat exchangers and pump units can be set up and put into service quickly and economically. Heat exchangers are usually installed outside buildings, with the pump unit placed near the transmitter. The heat exchangers can be used in any environment, such as coastal areas with corrosive sea air or in cool regions with snow and ice.

The HF high-power transmitter with liquid cooling technology: This video illustrades and explains the innovative cooling technology of the HF high-power transmitters R&S®SK4105/SK4110 from Rohde & Schwarz.

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The HF high-power transmitter with liquid cooling technology: This video illustrades and explains the innovative cooling technology of the HF high-power transmitters R&S®SK4105/SK4110 from Rohde & Schwarz.

Air cooling - a proven cooling system

Air cooling systems have proven effective over the years and are good enough for most applications.

They are cost-efficient and easy to install but not as efficient as liquid cooling.
In conventional air cooling, waste heat rises from the parts. A fan then pulls the warm air in the heat sink away from the components.
Surrounding components are warmed and exposed to stress, while the fan spins faster to improve cooling as needed.
To ensure constant cooling during power peaks, the increased fan speed can generate much more noise than liquid cooling systems.
Air cooling is also fairly bulky both for the transmitter and the building where it is installed, since the system requires the complicated ductwork through the building.

In short: Liquid cooling lets customers operate new high-power transmitters at their absolute performance limits while maintaining safe temperatures.

By combining years of liquid-cooling technology experience for the broadcasting and media market with decades of expertise in HF/BLOS communications, Rohde & Schwarz can combine the unprecedented power of 5-10 kW with absolute reliability.

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Liquid cooling: Deep-dive into the innovative HF high-power transmitter cooling system solution

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Benefits of self-sufficient liquid cooling

The innovative cooling system of the HF high-power transmitters offer multiple benefits for maximum availability.

Due to increased performance resulting in emergence of extra waste heat, an innovative cooling system solution is needed.

Liquid cooling absorbs waste heat directly at the point of origin and re-uses it or removes it from the transmitter building; this extends the transmitter life, reduces failure rates and reduces the carbon footprint.
Much lower air conditioning capacity is needed keep transmitter rooms at their specified temperatures.
Each transmitter features a closed cooling system, making additional equipment for forced, dry and desalinated air unnecessary.
The transmitters do not have to be exposed to harsh environments, such as those in coastal regions.
They have no single point of failure for the transmitter stations. Self-sufficient liquid cooling is also easier to install with 40 mm hoses, instead of huge customized air ducts, while also ensuring reduced noise levels in the transmitter rooms.

Not all liquid cooling is the same. Thousands of installations worldwide have given Rohde & Schwarz the necessary experience to further development and optimize liquid cooling systems. The company focuses on reliability and easy operation. A state-of-the-art, modern liquid cooling system should have the following: a closed loop, pressurized, oxygen-free system; the absence of non-ferrous metals, except for aluminum; defined coolants delivered with the transmitter and industrial grade hoses and clamps.

If these requirements are met, the system will be extremely reliable and durable, preventive maintenance can be kept to a minimum and will be free from galvanic corrosion. This means that scheduled coolant replacements will be unnecessary and reduce the need for preventative maintenance. Only leaves and pollen will need to be removed from the heat exchanger every year along with coolant pH value, antifreeze effectiveness, expansion tank pressure and operating pressure of the cooling circuit. Every four years the pumps and fans need to be checked and replaced as needed.

Applications/scenarios

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Heat dissipiation

Liquid cooling is ideal when a lot of power is lost as heat and has to be dissipated as efficiently as possible

Heat losses typically occur with very high transmission power and efficiency. TV broadcast transmitters have up to 75% power efficiency and transmission power of over 100 kilowatts. Such high-power heat losses also occur with medium transmission power and relatively low power efficiency, such as with HF transmitters with a power efficiency of approx. 30% and transmission power of 5 kW or 10 kilowatts.

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Exposed locations

Liquid cooling has both a reduced footprint and generates much less noise for TV transmitters

These transmitters typically have an exposed location in television towers or mountain stations, where floor space is expensive. In onshore stations for coastal radio broadcasts with harsh environmental conditions, such as damp, salty air, the focus is on protecting the transmitter from the harsh environment with liquid heat convection.

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Highest reliability

Liquid cooling enables unprecedented power with absolute reliability

Modern liquid cooling systems are highly reliable, low maintenance and have lower operating costs for huge benefits in any application scenario.

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