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Laser welding is a joining process, which is comparatively new to industrial production and especially to heat exchanger manufacturing. Due to the high energy density of the laser beam, the process is characterized by faster welding speeds with deep penetration as compared to the conventional welding processes. Therefore laser welding technology is widely used in the automotive industry on a variety of different applications. This paper describes the application of laser welding as possible joining technology for exhaust gas heat exchangers made of stainless steel. The cooled exhaust gas recirculation (EGR) technology shows good potential for meeting the actual and future emission targets of diesel engines combined with acceptable fuel consumption. It will be shown that the selection of the base metal and the joining technology are extremely important for the durability of the product because of the severe operating environment the EGR cooler must endure.

In the USA truckers often spend the night in the driver's cab and use the engine during these rest periods to heat or cool the cab. This practice leads to environmentally detrimental pollutant and noise emissions as well as high fuel consumption. This prompted Behr GmbH & Co. to develop a device which eliminates these negative side-effects. Under normal driving conditions energy is extracted from the exhaust gas and stored in a zeolite reactor. When the vehicle is stationary for longer periods of time this stored energy can be used for cooling or heating the cab. In a variation of this system the exhaust gas heat exchanger is replaced by a fuel burner which is used to charge the zeolite reactor for the cooling process and which also serves as a direct source of heat for the cabin. Moreover, the materials used in the device are non-poisonous, ecologically compatible and recyclable.

Due to the introduction of new, more stringent exhaust gas emission regulations for diesel engines, expected to be enforced in Europe and the USA in 1999 and 2004, respectively, new emission-reducing technologies are becoming the focus of attention. One such technology is the cooled exhaust gas recirculation method (cooled EGR) which permits a reduction in emissions with only a small increase in fuel consumption. The heat exchanger used in such a system must be capable of meeting high demands in terms of compact design, performance, resistance to high temperatures, corrosion and fouling. The paper describes the development of an EGR cooler designed by Behr which meets these demands and, in particular, has a high performance density. This was achieved by using a new kind of heat exchanger core.

Next to air temperature, humidity, and air quality, it is sound emission that exerts a significant impact on the driver's and passenger's comfort. Major progress in vehicle acoustics has motivated vehicle manufacturers and systems suppliers to evaluate HVAC systems no longer by their air conditioning performance alone. Sound emissions and sound quality have become additional important criteria for the development of new HVAC systems. In the initial conception phase, where systems and packaging considerations are made, acoustic optimization must begin with preliminary system studies and feasibility studies. In this phase acoustics should be based on fairly general systems specifications which describe the desired degree of acoustic comfort. In the subsequent design phase follows the specification of the acoustic goals and the optimization of the HVAC unit. Detailed analysis and optimization of air flow and blower are the common targets for improvement at this time.