Calculating Mass of Octane Needed to Heat Aluminum Block

[ghostanime2001]

this question is still foggy to me

 

[lewdtenant]

So, you have an engine block, and octane is used to heat it from 15 to 85 C. You have a certain amount of fuel that is combusted, but only 20% of the heat from that combustion goes towards heating up the aluminum block. The rest of it is waste heat. Regardless of how much octane you have, you can assume (for this problem) that 20% of the heat goes towards heating the block and 80% is lost as waste heat. So, you need to find how much octane is needed to supply the right amount of heat to raise the temperature 70 C. But you want to determine the total amount of octane needed, including the excess waste heat.

Maybe a helpful analolgy: (Please realize that even though this analogy deals with fuels, it is totally unrelated to the above problem). The space shuttle is attached to a rocket to launch it into outerspace. The rocket is propelled by liquid hydrogen that is in a fuel tank. The shuttle and rocket have a combined weight, and engineers calculate how much hydrogen they will need to launch it. But they also have to account for the weight of the fuel tank and the weight of the fuel itself. So, they have to add additional hydrogen to launch this extra weight.

The engine block problem is the same concept. You want to know how much extra octane is needed to heat the block to 85 C.