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Mechanical Properties Of Fluids

Question
CBSEENPH11019823

An engine consumes 30 kg of coal per hour and does the work at the rate of 45H.P. Find the efficiency of heat engine. The heat of combustion of coal is 2 x l06cal per kg.

Solution

Power developed = 45 HP = 33570 J/s 
Coal consumed per hour = 30kg 
Heat produced per hour = 30 cross times 2 cross times 10 to the power of 6 space cal divided by hr 
Heat produced per sec = space 30 cross times 2 cross times 10 to the power of 6 fraction numerator 4.2 over denominator 3600 end fraction straight J divided by straight s 
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Efficiency,   space space space straight eta equals 33570 over 70000 cross times 100 almost equal to 48 %