Question

Difference between net calorific value and gross calorific value

Answer 1

Net calorific value:
It is actually amount of heat which is produced when the water is converted into gaseous with the help of combustion while the water remains at the state of gas.
it is sometimes also known as "Lower heating value" 

Gross calorific value:
It is also the amount of heat produced due to the process of combustion but in this amount of heat calculated includes when the water convert in to gaseous state  and then allowed to return to liquid state.
It's other name is  "High heating value'' because its value is higher than net calorific value.

Answer 2

Gross calorific value or GCV refers to the quantity of heat produced by combustion when the water produced by combustion is permitted to return to the liquid state.

While the net calorific value or NCV refers to the quantity of heat produced by combustion when the water produced by combustion continues to be in a gaseous state.

Water releases heat when it condenses. In net calorific value the water produced by combustion remains gaseous. So gross calorific value is bigger than net calorific value.

Gross calorific value is also known as higher heating value while net calorific value is also referred to as lower heating value.