The heat transfer conditions in automotive exhaust piping are only recently being studied in depth
because of their important role in the design and optimization phases of exhaust after-treatment
systems. The complex geometry of the exhaust line and the special ¯ow conditions complicate the
problem of accurately estimating several important heat transfer parameters. This paper initially
summarizes the current status of knowledge regarding heat transfer phenomena in automotive exhaust
systems. Experimental data from steady state and transient heat transfer measurements in automotive
exhaust systems are presented and analyzed by means of a comprehensive transient computer model
covering all exhaust piping con®gurations (single wall, double wall with air gap or insulation) already
presented elsewhere. Examples are presented, illustrating the application of the model in the comparative
assessment of dierent exhaust con®gurations. In conjunction with existing models which simulate the
operation of three-way catalytic converters and of other exhaust gas after-treatment devices, the model
is already integrated in a CAE package for the support of exhaust system design optimization. # 1999
Elsevier Science Ltd. All rights reserved.