In its annual report, 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. Matthew Beecham talked with Dr Thomas Heckenberger, director, technology centre, Behr Group and Dr Simon Edwards, director of advanced engineering, Engine Cooling, Behr Group, to find out more.

just-auto: Could you sum-up the factors driving the automotive engine cooling sector?

Behr: The automotive engine cooling sector is driven by the same factors affecting the rest of the first tier of the industry. In particular from the product perspective, the drivers can be seen as: emissions legislation, fuel economy improvements, pedestrian protection legislation, vehicle driveability improvement, cost reduction and lifetime reliability.

just-auto: Demands on engine cooling product performance, packaging and cost are continually increasing. In addition, automakers expect economical solutions that help reduce emissions from cars and trucks. With these demands in mind, how have you responded?

Behr: The response has been to try and meet these increasing demands. That means increasing specific performance, i.e. heat rejection per unit volume or weight or adding functionality. For example, Behr is 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. 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.

just-auto: It is commonly recognised that the key trends in the engine cooling sector are turbocharging and exhaust gas recirculation (EGR). In what ways has BHTC addressed the trend for supercharged diesel engines?

Behr: Behr does not see a trend to supercharged diesel engines. However, the ubiquitous turbocharging for the diesel engine is developing further with, for example, the trend for increasing numbers of two stage turbocharging applications. To address this trend, Behr has introduced products for indirect charge air cooling, in particular indirect intercooling: this is especially relevant for future truck engines where the need for full load EGR application means that high boost pressure levels and highly effective charge cooling are beneficial.

just-auto: In what ways does the EGR impact on the engine cooling system?

Behr: EGR in itself has little impact upon the engine cooling system. However, the need to realize cooling of the EGR, either for emissions benefits on a diesel engine or fuel economy improvement in a gasoline engine, has a significant impact upon the cooling system. In the first place EGR coolers need to be integrated into the EGR and cooling circuits: this can either be done with indirect, coolant cooled EGR coolers — as is most common — or with direct EGR coolers as first developed by Behr and now in production with Scania. The indirect EGR coolers do add heat load to the cooling circuit, which needs to be dissipated through the radiator: for passenger car diesel engines, this additional heat load does not normally occur at the same engine operating points as the maximum engine heat rejection, thus the impact is not so great; for passenger car gasoline engines full load EGR can be beneficial but since these are also the conditions for maximum engine heat rejection, the cooling system capacity must be increased accordingly; for commercial vehicle diesel engines the EGR rates at full load are also high (and increasing with each emissions level) which means that the cooling system must be sized to cope with this additional heat rejection. The direct EGR coolers add heat load directly to the cooling air, as such the radiator does not need to be resized, but the cooling module at the front of the vehicle has to be laid our such that space for the EGR cooler is available.

just-auto: What are the design implications on the engine cooling pack as engines become down-sized?

Behr: 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 hybridization of the powertrain; this has implications on the cooling pack design as noted below.

just-auto: Although hybrids have not really created a substantial change in the heat transfer philosophy of the engine, has this technology created the need for additional product on the electronic side of things?

Behr: Yes, there are additional cooling requirements for battery cooling and power electronics/converter cooling. 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.

just-auto: Generally speaking, in respect of fuel economy, is there a trend toward more use of electronics to try to more closely monitor engine temperature for maximum efficiency? i.e. perhaps using electronic thermostats and electronic water pumps to completely take control of the heat rejection itself. Does this mean there is always a trade-off the carmaker must make between adding weight and cost (through electronics) and saving fuel?

Behr: Yes and possibly. To exemplify, the use of map controlled thermostats (where the wax element of the thermostat can be electrically heated to in order to control the thermostat opening point depend upon the operating point on the engine map) has enabled engine fuel economy improvements to be achieved. These map controlled thermostats can be supplemented with additional coolant standstill functionality, which can achieve the same engine warm up improvements as a electrical or mechanically switchable coolant pump, in order to further reduce engine fuel consumption. The use of switchable or controllable coolant pumps brings further advantages when coupled with indirect charge air cooling. This enables demand orientated charge air cooling, which can be beneficial for emissions control (on both passenger cars and truck) and brings some additional fuel economy benefits.

Whilst there is usually a trade-off between adding extra functionality and additional weight, it has been seen that basic thermo management measures, such as map controlled thermostat, bring measurable fuel economy improvements at an almost indiscernible weight increase and with a very good cost to benefit ratio.

just-auto: To what extent is the shift from using R134a refrigerant to R744 impacting on the engine cooling system?

Behr: There is no impact from R744 air conditioning to the coolant loop in case of cabin cooling. In case of R7744 based heat pumps there is an impact because the coolant plays the role of the low temperature heat source.

just-auto: With pedestrian safety laws swinging into force in Europe, how does that impact on engine cooling system design? i.e. Does this mean manufacturers must design smaller modules and systems with no deterioration in performance and quality? As radiators become thinner, is the key challenge is to achieve the same amount of heat rejection from thinner radiators? What other components are affected by these regulations?

Behr: In several ways, possibly, yes and many, although not all are known to Behr. To elucidate in relation to the cooling system: detailed attention to the design of the cooling module and its integration into the front end of the vehicle must be paid in order to successfully achieve the new pedestrian safety laws. This does not mean that, in all cases, the modules must be smaller, yet no loss in performance nor quality can be accepted. The use of thinner radiators, i.e. increased specific heat rejection is a trend in itself not necessarily related to pedestrian safety laws: a thinner radiator has knock-on benefits for the performance of the rest of the cooling module and the better packaging gives more styling freedom.

Headquartered in Stuttgart, Germany, Behr GmbH & Co KG is a major developer and manufacturer of automotive air conditioning and engine cooling systems. Its engine cooling division generated sales of €1,640 million in 2007, equivalent to 48.8% of the group’s turnover. Behr’s current product portfolio covers mechanically fitted products such as radiators and heater cores, brazed products including aluminium-brazed radiators, charge-air coolers, oil coolers, condensers, evaporators and heater cores, and cooling modules, HVAC units, plastic parts, electric/electronic parts, blower units and control panels. Behr employs 19,500 people at 17 development sites, 30 production sites and 13 joint venture companies worldwide.

See also: RESEARCH ANALYSIS: Hot topics in the engine cooling sector