View Feed
Coffee Room
Discuss anything here - everything that you wish to discuss with fellow engineers.
12893 Members
Join this group to post and comment.

What is the difference between efficiency and gain?

can anyone explain the difference between efficiency and gain with detail?

please give me technical answer ..    

Input -> System -> Output

Output/Input x 100 = %Efficiency

1 kg diesel put into an engine say gives an output of 4.6 KWHr. ! kg diesel gives 10000 KCal energy. 4.6 KWHr is equal to 4000 KCals. 

So, Efficiency = 100x(4000/10000)= 40%

Gain = Input-Output

There is 5 litres water at 50 deg C in an open vessel on a stove. It is losing 5 KCal/min by radiation and evaporation. If 10 KCal/min is given to the vessel by the stove, then       the net heat input into the water is 10-5=5KCal/min.

Gain = 10-5 =5 Kcal/min. The water will heat up at the rate of 5 deg C/minute.

These are rather quick and dirty examples.

Take the water example 10 KCal/ Min was put in. What was the output? Not the 5 Kcal lost by radiation and evaporation but the % KCal gained by the water. So efficiency is 100x(5/10)=50%.

Unfortunately, the loss = gain so the % was the midpoint in this case. The important thing is to know what the actual output is.

I apologise for an arithmetic error in my first post. 5 Kcal/min added to 5 litres of water will increase the temperature by 5/5=10C/min and not 50C.

Share this content on your social channels -