A gear motor can develop 2 hp when it turns at 450rpm. If the motor turns a solid shaft with a diameter of 1 in., determine the
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Answer:
(a) The amount of heat transferred to the air, is 215.5077 kJ/kg
(b) The net work output, , is 308.07 kJ/kg
(c) The thermal efficiency is 58.8%
(d) The Mean Effective Pressure, MEP, is 393.209 kPa
Explanation:
(a) The assumptions made are;
= 1.005 kJ/(kg·K),
= 0.718 kJ/(kg·K), R = 0.287 kJ/(kg·K),
Process 1 to 2 is isentropic compression, therefore;
From;
We have;
Process 2 to 3 is reversible constant volume heating, therefore;
p₃ = 2 × p₂ = 2 × 2190.43 = 4380.86 kPa
Process 3 to 4 is isentropic expansion, therefore;
The amount of heat transferred to the air, = 215.5077 kJ/kg
(b) The net work output, , is found as follows;
(c) The thermal efficiency is given by the relation;
(d) From the general gas equation, we have;
The Mean Effective Pressure, MEP, is given as follows;
The Mean Effective Pressure, MEP = 393.209 kPa.