# Specific heat in for the Otto cycle

• dinoclaro
In summary, the conversation discusses the process of modeling the Otto cycle using ideal gas properties for a class project. The speaker shares their approach of finding the specific calorific value of petrol and using it to approximate the value of qin. They mention using Excel solver to optimize the process and explain that their initial approximation does not affect the final optimized value. However, they express concern about not fully understanding the process of introducing heat in the Otto cycle and ask for alternative approaches to the problem.

#### dinoclaro

Thread moved from the technical forums to the schoolwork forums
A class project requires us to model the Otto cycle using ideal gas properties. We are not given the value for qin (specific heat in) and are told to make an intelligent approximation. My approach to this has been to find the calorific value of petrol, multiplying this by the density of petrol in which I then get the specific calorific value. I then proceed to multiply this by the volume of fuel in the cylinder (Volume at BDC divided by the air to fuel ratio). At the end of this process I get a value of around 980.35 J and cannot think of any way of converting this to specific heat as dividing by the mass obviously just returns the initial calorific value.

We are required to optimize the process using excel solver where the compression ratio and qin are the variables. Therefore this initial approximation has no bearing on the final optimized value (qin = 400Kj/Kg) . Although we are required to give an explanation of our initial value.

I fear that I am not understanding the Otto cycle process of where heat is introduced. Is there another way I should approach this problem?