Passenger cars consist of 3 to 9 heat exchangers, which guarantee a proper thermal management of the engine and the transmission, comfort in the driver cabin and low NOx emissions. This paper gives an overview about the design principles of the different types of heat exchangers used in passenger cars. A compact cooling system is presented. A thin module is attained by using a compact counterflow plate heat exchanger for cooling and heating of the automatic transmission fluid instead of a conventional air-cooled heat exchanger. The replacement of the conventional automatic transmission heat exchanger results in a tower air-side pressure drop and thus in a higher air flow rate. A second pass in the radiator provides coolant at a low temperature level (about 13 K lower than that of the main coolant flow) for the cooling of the automatic transmission fluid. In the future, this principle provides an excellent temperature level for the cooling of power control units of crank shaft starter generator systems. The heat management with this module allows for accurate control of the automatic transmission fluid temperature during cold start as well as for other driving conditions. Control of the transmission fluid temperature was achieved by varying the coolant inlet temperature to the plate heat exchanger. This is accomplished by using two actuators, which control both the flow rate and the mixing of hot coolant from the expansion bottle and cold coolant from the low temperature section of the radiator. Test data ware presented that show the fluid heat up characteristics during cold start. It was also shown that for 95 % of the driving time, the coolant inlet temperature of the transmission heat exchanger varied by only +- 4 K from the desired value of 80 degree C for a wide range of engine coolant outlet temperatures. Transmission temperature control leads to a prolonged life for the transmission and reduced fuel consumption.
Compact heat exchangers for passengers cars
Kompakte Wärmeaustauscher für Personenkraftwagen
2002
13 Seiten, 15 Bilder, 1 Tabelle, 3 Quellen
Conference paper
English
Compact heat exchangers for passenger cars
Automotive engineering | 2002
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