Learning Forum

[Danielgkh]

Hi,nI am running a CFD simulation on the exhaust gas system for Micro CHP. The design I am working on functions mainly as the muffler for the exhaust gas, but also as a secondary heat exchanger. It consists of a double pipe, with exhaust gas flowing in the inner pipe and coolant-water-mixture flowing in the cavity between the inner pipe and outer pipe.nFrom the datasheet of motor, i have calculated the mass flow rate, which is why I am currently using mass flow inlet with conatnt mass flow rate. However the mass flow is actually not constant, it varies with the strokes of engine. From my result, I am suspecting that by using a constant mass flow, it creates less turbulane which in turn reduce the heat exchange rate with the coolant-water-misture.nThe question now is, which type of inlet should i actually choose as my inlet? How do i set it up that it varies with the **** of engine? Does using a constant mass flow rate affects the result?n

[Amine Ben Hadj Ali]

You can make a function of the crank angle or of time. Either you read it as profile file (time dependent) or you create an expression based on the cranck angle which you can make it variying over time.n