A single-cylinder air-cooled lawn mower engine operates under steady conditions. The cylinder temperature cannot exceed 300 ⁰C. To cool the engine, annular fins are placed around the cylinder. The fins are 0.3 cm thick and are 2 cm long from base to tip. The fins are made of cast iron (k = 52 W/mK). The outside diameter of the engine cylinder at the base of the fin is 0.3 m. Assume that the engine operates in 30 ⁰C air and that the heat transfer coefficient on the sides and tip of the fin is 12 Wm^-2K^-1. Determine the number of fins needed to cool a 3 kW engine to the given temperature if the engine has an efficiency of 30 % and 50 % of the total heat given off by the engine actually is dissipated through the fins ?
A single-cylinder air-cooled lawn mower engine operates under steady conditions. The
cylinder temperature cannot exceed 300 ⁰C. To cool the engine, annular fins are placed
around the cylinder. The fins are 0.3 cm thick and are 2 cm long from base to tip. The fins
are made of cast iron (k = 52 W/mK). The outside diameter of the engine cylinder at the
base of the fin is 0.3 m. Assume that the engine operates in 30 ⁰C air and that the heat
transfer coefficient on the sides and tip of the fin is 12 Wm^-2K^-1. Determine the number of
fins needed to cool a 3 kW engine to the given temperature if the engine has an efficiency of
30 % and 50 % of the total heat given off by the engine actually is dissipated through the
fins ?
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