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Principle of Calorimetry

A four stroke...

Question

A four stroke petrol engine has a compression ratio of 10.5, takes air at 90 kPa and $40^{\circ} C$ and is repeated 2500 times per minute. Using constant specific heats
( $c_{p} = 1.005 k J / k g K, c_{v} = 0.718 k J / k g K$ . and $γ = 1.4$ ) at room temperature, then the rate of heat input is _____ kW. if the cycle is to produce 900J/cycle.
61.515

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Solution

The correct option is A 61.515

The definition of cycle thermal efficiency reduces to

$η_{t h} = 1 - \frac{1}{r^{γ - 1}} = 1 - \frac{1}{{10.5}^{1.4 - 1}} = 0.6096 = 61.0 %$

$W_{n e t} = \frac{900 \times 2500}{1000 \times 60} = 37.5 k W$

The ratio of heat addition is then

$Q_{i n} = \frac{W_{n e t}}{η_{t h}} = \frac{37.5 k W}{0.6096} = 61.515 k W$

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30^{\circ} C

γ = 1.4 a n d C_{p} = 1.005 k J / k g K

1.005 k J / k g K

0.718 k J / k g K

c_{p} / c_{v} = 1.4

= 1.005 k J / k g K

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27^{o} C

γ = 1.4, c - v = 0.718 k J / k g K

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C_{p} of gas = 1.005 k J / k g K, C_{v} = 0.718 k J / k g K,

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