How to Calculate Engine Heat Loads
- 1). Determine the power produced from a standard six-cylinder engine. One horsepower is equivalent to 0.75 kilowatts of power. If an engine is rated for 150 horsepower, then the power produced is 112 kilowatts (150 x 0.75).
- 2). Determine the total cylinder volume of the engine. A typical automotive engine cylinder has a volume of 300 cubic inches. One cubic inch is equivalent to 0.000016 cubic meters so a 300-cubic-inch cylinder is 0.005 m3. Six cylinders have a total volume of 0.03 m3.
- 3). Determine the power density of the engine by dividing the power produced by the cylinder volume. This is 112 kilowatts / 0.03 m3 or 3,733 kilowatts/m3.
- 4). Determine the heat produced from the engine using the formula Q/A = h (Ts - Tf) where Q/A is the power density, h is the heat transfer coefficient, Ts is the temperature of the engine's surface and Tf is the ambient temperature. If the heat transfer is taking place through a gas such as air, the value of h will be 10. Assume ambient temperature to be 75 degrees Fahrenheit. Solving for the engine surface temperature gives Ts = Q/A / h + Tf which is 3,733/10 + 75 = 448 degrees.
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