Calorific Value: Fuels, Definitions, Measurement, Formula, Importance, Efficiency, Applications, and Sample Questions

Calorific Value Overview

The quantity of heat produced by a unit volume of a substance upon full combustion is referred to as its calorific value. It is measured in kilojoules per kilogram. Calorific Power is another name for it. The heat contained in fuels or food is determined by the full combustion of specified quantities at constant pressure and normal circumstances.

Calorific Value Definition

"Calorific value refers to the amount of heat produced by a substance per unit volume by complete combustion."

What is Calorific Value?

The calorific value of a substance specifies its energy content; it is the quantity of heat produced following full combustion. It is also known as the gross calorific value (GCV) or high heating value. In addition, a substance's calorific value (usually, solid biofuel or food) is the specific energy of burning per unit mass. KJ/kg is the SI unit for calorific value.

Importance of Calorific Value

The following are some of the importance of calorific value-

1. Gas shippers and suppliers require this information to bill gas consumers. 
2. It also helps to determine the transportation charges of gas shippers and suppliers.
3. It is critical to understand the calorific value of fuel in order to carry out our daily activities. 
4. People would live a healthy life if they only consumed a certain number of calories per day. 
5. The human body requires calories to carry out daily activities. 
6. This information allows us to calculate the amount of energy we transport. 
7. Too much or too low-calorie consumption eventually leads to health problems.
8. When compared to carbohydrates, protein, alcohols, roughage, and other biomolecules involved in the maintenance and metabolic processes, fats have a higher calorific value.
9. Without calories, the body would stop working, and the cells in the body would die. 

Measurement and Formula for Calorific Value

Calorific value is the amount of heat produced per unit volume of a material when completely burned. Kilojoules per kilogram, or kJ/kg, is the unit of measurement.

For Example: If we state that kerosene has a calorific value of 45000 kJ/kg, it indicates that if 1 kilogram of kerosene is totally combusted, it would create 45000 kilojoules of heat energy.

The following is the formula for determining calorific value-

Calorie Value = (Heat produced in Kilojoules) / (Amount of fuel consumed in kg)

There are two sorts of Calorific value, and their relationship is as follows-

Gross Calorific Value = Net calorific value + Latent heat of water vapor

The heat created by burning 1 kg of the material and then cooling it to room temperature is referred to as the Gross Calorific Value, as the water vapor formed during the combustion process also produces heat that should be recovered. The more heat recovered from water vapor, the higher the Gross Calorific Value.

Calorific Values of Fuels

Calorific Value is mostly used to determine fuel economy. The higher the calorific value, the more efficient the gasoline and the better the fuel. The quantity of heat created by various types of fuels varies based on the element's nature and the percentage of elements contained in them. When fuels are burned, they have the potential to generate energy in thermal power plants. The optimum fuel for generating power is mostly determined by its calorific value. The following fuels and their calorific values are listed-

LPG has a higher calorific value than diesel, petrol, and kerosene.

Calorific Value of Food

The heat energy produced in the human body during metabolism is referred to as the Calorific Value of food. When food is digested, the energy in the meal breaks down to provide fuel for the body to carry out everyday operations. It is usually expressed in Kilocalories. It is the amount of energy needed to raise the temperature of one liter of water by one degree Celsius. The following table lists numerous food products and their calorie counts-

The widely held assumption that fat should be avoided while dieting stems from the fact that fat has the highest calorific value when compared to other macronutrients.

Efficiency and the Calorific Value

The calorific value of a food fuel determines its efficiency; the higher the value, the higher the efficiency, and vice versa. Hydrogen fuel, for example, has the highest calorific value, 150 KJ/kg. Therefore, it is easy to realize that the efficiency of the substance is related to the calorific value. Furthermore, water vapor formed during the combustion process includes heat, and if it is recovered using various procedures, the substance will have a greater calorific value (GCV), and vice versa if it results in a lower or net calorific value (NCV). NCV is the consequence of allowing the products of combustion to escape.

Read more about the Variety of Food and Adulterated Food.

Applications of Calorific Value 

The following are some of the applications of calorific value-

1. Calorie consumption, whether low or high, might cause health problems.
2. Calorific value is used by gasoline shippers and suppliers to charge consumers.
3. Humans' calorie intake through eating allows them to stay healthy. 
4. It is necessary to consume calories on a regular basis in order to carry out everyday tasks.

Points to Remember

1. Calorie intake must be adequate for the human body to be healthy.
2. Calorific levels are commonly expressed in kilojoules/kilogram for fuels and kilocalories/gram for food.
3. Calorific values are an excellent indicator for determining a substance's commercial worth; the greater the value, the more efficient the material.
4. Fat is a high-energy macronutrient.
5. Good fuel is defined as having a higher calorific value.
6. The higher the calorific value of the fuel, the greater its efficiency.

Sample Questions for Calorific Values

Sample Question 1: What factors influence a fuel's Calorific Value?

Solution: The calorific value of a fuel is determined by its composition and the relative quantities of the components present. It rises as the quantity of hydrogen in the fuel grows and falls as the moisture content drops.

Sample Question 2: The calorific value is stated in what unit?

Solution: Kilojoules per kilogram (kJ/kg) is the calorific value.

Sample Question 3: Which of the following fuels has the highest calorific value?

Solution: Hydrogen, as it contains 150000 kJ/kg of calorific value. The energy contained in a fuel or food is estimated by measuring the heat produced by the full combustion of a particular quantity of it. This is currently commonly represented in terms of joules per kilogram. As a result, hydrogen has the greatest calorific value.