CALORIFIC VALUE OF FUEL IS THE QUANTITY OF HEAT PRODUCED BY IT’S COMBUSTION AT CONSTANT PRESSURE AND STANDARD CONDITION I.E AT 0°C AND UNDER A PRESSURE OF 1013 mbar.
HIGHER CALORIFIC VALUE IS THE AMOUNT OF HEAT EVOLVED WHEN A UNIT AMOUNT OF FUEL IS COMPLETELY BURNED AND THE PRODUCT OF COMBUSTION COOLED TO NORMAL CONDITION (WITH WATER VAPOUR CONDENSED AS A RESULT).
LOWER CALORIFIC VALUE IS THE AMOUNT OF HEATEVOLED WHEN A UNIT MASS OF FUEL IS COMPLETELY BURNED AND THE PRODUCT OF COMBUSTION AND WATER VAPOR LEAVES WITHOUT BEING CONDENSED.
LOWER CALORIFIC VALUE= HIGHER CALORIFIC VALUE- LATENT HEATOF VAPOURIZATION
HENCE THE DIFFERENCE BETWEEN THE TWO CALORIFIC VALUE GIVES THE HYDROGEN CONTENT OF THE FUEL. THE IMPORTANCE OF TWO CALORIFIC VALUE IS THAT IT SHOWS THE AMOUNT OF USEFUL HEAT PRODUCED. THIS IS BECAUSE WHEN THE FUEL IS BURNED, SOME OF THE ENERGY IS CONSUMED TO EVAPORATE THE WATER PRODUCED IN THE FUEL DUE TO COMBUSTION AND THE REST ENERGY IS USED TO PRODUCE POWER. HENCE TO FIND THE USEFUL POWER THAT CAN BE PRODUCED BY THE FUEL WE REQUIRE THE TWO VALUES OF THE CALORIFIC VALUE.