Demands on engine cooling product performance, packaging and cost are continually increasing. As automakers expect economical solutions that help reduce emissions from cars and trucks, Matthew Beecham reports on how suppliers of engine cooling systems are responding.

Thermal energy flows are an important part of a vehicle’s energy balance. Even in the most advanced diesel engines, the vehicle drive uses barely one-third of the fuel energy. The task of engine cooling is to draw waste heat out of the engine in order to allow the engine to operate efficiently. Behr states that the key trends its engine cooling business faces are turbocharging and exhaust gas recirculation. The combination of the two will enable compliance with stricter emissions standards while offering minimum fuel consumption. Behr says it is accelerating the development of these systems with new components. For example, the company’s engineers have developed a module to control exhaust gas recirculation (EGR) in diesel engines. It combines mass flow and temperature control in one part. Production is due to commence this year. Behr has also accommodated the trend for supercharged diesel engines with an expanded product range for direct and indirect charge air cooling with low temperature radiators.

Spain’s Dytech ENSA (formerly known as Dayco ENSA) designs, develops and manufactures EGR systems for automotive and commercial vehicle applications, both off and on road. Stuart Kirby, commercial and business development director for Dytech ENSA SL, told us: “In order to meet the new regulations EGR rates have increased, the amount of gas recirculated, and more complex EGR systems are required. Extra space under the bonnet, even on a large truck, has never been exactly easy to find and packaging more complex systems and more components into the space available becomes an exercise in putting the famous square peg into the round hole. Early EGR system, late 90’s, comprised usually of a fairly small EGR cooler and EGR valve and tubing to connect it all together, a Euro VI system may well be dual loop systems with a high pressure and a low pressure EGR system, a much larger EGR cooler and perhaps a diesel oxidation catalyst too and of course tubing to connect it all together including the EGR valve. Dytech ENSA’s response to this has been from three fronts. Firstly, improved EGR cooler performance. Second, component integration and third, modular systems.”

Packaging the engine cooling system is indeed a major driver of innovation. Engine cooling systems must fit into ever smaller spaces under the bonnet. Given the pressure on supplier to squeeze higher performing products and systems into a smaller space under the bonnet, radiators have gradually become smaller in size. For example, a modern aluminium radiator is about two-thirds the size of a unit produced in the late 1970s. The high cost of fuel, particularly in Europe, means that designers are seeking ways of reducing the airflow in the car, which is leading towards the use of smaller heat exchangers. Late last year, Visteon revealed that it had developed an internal heat exchanger (IHX) that increases cooling power. It uses a novel coaxial tube design integrated in the refrigerant circuit for enhanced automotive air conditioning system performance. The new internal heat exchanger, which replaces a part of the suction and liquid refrigerant lines in a traditional R134a system, exchanges energy in a counter-flow arrangement. When combined with tuning of the expansion device settings, the IHX increases system cooling performance up to 14% and improve operating efficiency up to 12% – depending on the base system and thermal expansion valve settings. Applied to the new near drop-in refrigerant R1234yf, the technology delivers similar performance improvements. Visteon says it will launch its first commercial applications during the first quarter of this year.

Meanwhile, Webasto used last year’s Geneva motor show to reveal a new device that rapidly heats engine coolant in extreme cold conditions. The supplier says this new technology should be available on at least one North American vehicle by 2010. Webasto claims that its so-called Liquid Heat Generator will save fuel, cut emissions and improve driver comfort. The belt-driven device mounts to the front of the engine and quickly heats the coolant by rapidly swirling it in a rotor and a slator. The fast heating of the coolant means that the vehicle’s interior heater and windshield defroster can be fully operation in about three minutes, down from ten minutes in a vehicle without such a device.

Not only are auto engine cooling parts becoming smaller but there is a clear trend toward more component integration. For example, combining the condenser and radiator can save space and help cut costs. Modularity plays an important role in packaging engine cooling systems. This approach can, of course, help cut costs and simplify the entire installation on the assembly line.

Another challenge facing suppliers is the relentless push by automakers to downsize engines for diesel as well as gasoline engines. Upgraded engine cooling modules capable of handling more heat rejection in a smaller space are being introduced.

Dr Simon Edwards, director of advanced engineering, Engine Cooling, Behr Group, told us: “In the first instance the heat rejection from an engine, i.e. the cooling requirement, is proportional to the rated power of an engine rather than its swept volume. As such engine downsizing, which reduces the engine swept volume but usually through boosting retains the engine power, does not, in the first instance have an impact on the cooling pack in terms of the requirement radiator performance. Since most engine downsizing is enabled via boosting, and charge air boosting is more effective when charge air cooling (aftercooling and/or intercooling) is applied, then the cooling pack is affected by the trend of engine downsizing as it must then also include a direct charge air cooler or, as is often the case when indirect charge air cooling is applied, a secondary low temperature radiator. This effect is especially observed for gasoline engines in the American market, where the trend to downsized, direct injected and turbocharged engines [e.g. Ford EcoBoost] means an increasing market for charge air cooler technology. Consequently, the addition of a new cooling pack component in the cooling module also means that, in some instances, the engine cooling fan, cooling module layout, etc. have to be redesigned. Engine downsizing is also sometimes enabled via electric hybridisation of the powertrain; this has implications on the cooling pack design.”

Although hybrids have not really created a substantial change in the heat transfer philosophy of the engine, this technology has created the need for additional product on the electronic side of things. “There are additional cooling requirements for battery cooling and power electronics/converter cooling,” said Edwards. “Li-Ion batteries have an upper temperature limit of around 40ºC. High temperatures reduce lifetime of the battery. Under warm climate conditions the Li-Ion battery therefore has to be cooled with the aid of the air conditioning system. Converter cooling requires a coolant temperature of around 60ºC. Therefore so called low temperature radiators are required in addition to the normal power train radiator.”

As the pressure on suppliers to make engine cooling parts thinner and lighter without any loss of strength continues, OEMs must consider the need to recycle parts at the end of their useful life, too. Although North American radiator manufacturers talk of going back from a plastic tank to an all-metal product with an aluminium base, the pace of change has not been as fast as some in the industry expected.

Behr is currently developing a new range of radiators with thinner walled tubes and reduced tank sizes which leads to a reduced package size for the same performance and lower weight because of reduced material usage. Dr Thomas Heckenberger, director, technology centre, Behr Group, told us: “With regard to economic emissions reduction solutions Behr has worked closely with the engine development companies to evaluate new EGR technologies to achieve, for example, Euro 5 NOx emissions levels without the need for NOx aftertreatment technology.”

The increasingly use of eco-friendly materials in manufacture are becoming important, too. In January of this year, for example, Denso revealed that it has developed a plant-derived resin radiator tank using an organic compound derived from castor-oil tree. The company plans to start mass-producing this new product in April 2009 for vehicles sold worldwide. “In addition to increasing installations of the new radiator tank to more vehicles, Denso aims to incorporate the new resin into a wide range of products in an effort to reduce the use of limited oil resources, reduce CO2 emissions during a product’s life cycle and help prevent global warming,” said Akio Shikamura, managing officer responsible for Denso’s Thermal Systems Business Group.” The plant-derived resin, which Denso jointly developed with DuPont Kabushiki Kaisha, is produced by a chemical reaction between two organic compounds that are derived from castor-oil tree and petroleum. An additive, such as glass fibre, is then added to the substance to produce the resin. Plant-derived ingredient comprises about 40% of the resin.

We should expect to see further innovation in cooling systems and components due to the trends noted here. The challenge for suppliers will be to meet demands from automakers for improved engine efficiency and output, as well as respond to rising production of diesel vehicles and direct-injection and turbocharged gasoline vehicles. In terms of social trends and legal regulations, the supply sector will continue to face demands for improved fuel efficiency due to surging gasoline prices and stricter fuel consumption regulations, as well as for more compact and thinner radiators and other parts in response to the more stringent legislation designed to protect pedestrians.

Matthew Beecham


See also: Global market review of automotive engine-cooling systems – forecasts to 2016 (download)