hello fellow engineers! i just started work at a marine company and was assigned to investigate on this formula. it is from ISO 8861 and used to caculate the airflow needed for heat evacuation in a engine room. this is the formula, airflow needed = (heat emitted from engine and all other sources)/(air density X specific heat capicity of air X change in temp) - 0.4(air needed for combustion in engine) - air needed for combustion in boiler. i don't understand the second half of the equation. i was told that this is a empirical formula and the value of 0.4 can change under special arrangement in the engine room. my role is to investigate on the factor of 0.4 and find out the variable affecting it. has anyone came across this equation before or anyone has any idea how should i approach this problem?