Aheat engine uses fuel of energy content 43.1 mj/kg and produces 17.4 kw of useful power. the heat rejection rate (through the exhaust and cooling systems) is 44.8 kw. determine: (a) the efficiency of the engine (b) the usage rate of fuel in kg/h.

a)27.9%

b)

Explanation:

Given that

Fuel energy content = 73.1 MJ/kg

Useful power = 17.4 KW

Heat rejection rate = 44.8 KW

From first law of thermodynamics

Heat addition rate =Heat rejection rate + Power out put

Now by putting the values in the above formula

Heat addition rate = 44.8 + 17.4

Heat addition rate =62.2 KW

We know that efficiency is given as follows

So

So the efficiency is 27.9%.

Now to find usage rate of fuel

Lets take usage rate is

Fuel energy content  x  usage rate of fuel = Heat addition rate

Now by putting the values