Abstract
The effect of particulate build up on the cooling performances and overall heat transfer coefficient of a shell-and-tube EGR cooler has been studied experimentally.
The heat rejection and the heat transfer coefficient were measured on a special stationary test bench. A heavy-duty diesel engine was used as a generator of exhaust gas. A valve system was used to regulate the flow through the exchanger. The cooler had a dedicated cooling system. Particulate mass could be measured at different locations in the cooler using eleven removable tubes.
This study is based on three testing loads selected out of the 13-mode European test cycle. Two of them are under full load at different rotation speed, and the third one was low idling. Particulate were accumulated during 5 hours stationary tests and a one hour cycle test. The cycle test was repeated during thirteen hours.
The tests have shown a maximum reduction in heat rejection and heat transfer coefficient by respectively 25% and 37% under stationary test. The pressure drop increased by 11% at most during these tests. The most important result was a stabilization of the particulate build up mass after the second hour of all stationary tests.
The cycle test has shown a cleaning process under transient conditions. The heat transfer coefficient decreased by 20% during a loading cycle, but it was restored to its initial value due to particulate removal during transient phases, and condensation under idle conditions.