Methods to Measure Calorific Value Explained | WhatsApp20Image202023 09 2720at2015.24.44

Introduction

The estimation of calorific value is an important operation in the area of energy exploration which reveals the bound of potential energy in various fuels. One of the most essential parameters in understanding the efficiency and energy content in fuels is the calorific value, or heat of combustion. The main subject of this blog is the process by which we calculate the calorific values in all cases the energy generated through the combustion of fuels is quantified.

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Before knowing about different methods to measure Calorific Value,it is necessary to know about what is a calorific value?

Defining Calorific Value

The calorific value, also known as the heating value, represents the amount of heat a fuel produces per unit mass or volume when it burns completely under specified conditions. For solids and liquids, it expresses energy per unit mass in MJ/kg or kcal/kg. For gases, it expresses energy per normal cubic meter or per standard cubic meter (MJ/Nm³).

Engineers use calorific value to size boilers and furnaces. They estimate fuel costs per unit of useful heat using this parameter. They also model emissions and evaluate thermal efficiencies based on it. Utilities and fuel traders treat calorific value as a commodity parameter. Environmental teams calculate CO₂ emissions per unit of energy released using calorific value.

Calorific Value of particular substance and it's reaction with particular matters

Constituent	Higher calorific value
C	8080 kcal/kg
H	34500 kcal/kg
S	2240 kcal/kg

If oxygen is also present, it combines with hydrogen to form `H_2O`.Thus, the hydrogen in combined form is not available for combustion and is called fixed hydrogen.Amount of hydrogen available for combustion = Total mass of hydrogen–hydrogen combined with oxygen.

`[H_2+½left(O_2right)=H_2O]`

1 8 9

that is 8 parts of oxygen combines with 1 part of hydrogen to form water or for every 8 parts of oxygen, 1 part of hydrogen gets fixed.If the fuel contains x mass of oxygen then

Fixed hydrogen = 18×X=Mass of oxygen in fuel8

Amount of hydrogen available for combustion = (H-`frac{o}{8}`)

Dulong's formula for calculating calorific value is given as

Gross calorific value (HCV) = `frac{1}{100}`[8080C + 34500(H-`frac{o}{8}`) + 2240S] kcal/kg

Here C, H, O and S are percentages of carbon, hydrogen, oxygen and sulphur in fuel.

Net calorific value (LCV) = (HCV-`frac{9H}{100}times587`) kcal/kg

(HCV – 0.09 H × 587) kcal/kg

(Latent heat of steam = 587 kcal/kg).

Units of calorific value and heat

Unit of calorific value

The units of calorific value for solid, liquid and gaseous fuels are given below.

System	Solid / Liquid fuels	Gaseous fuels
CGS	calories/g	cm3
MKS	kcal/kg	m3
BTU	BTU/lb	Btu/ft3

These units can be interconverted as follows:

1 cal/g =1 kcal/kg = 1.8 BTU/lb

1 kcal = 0.1077 BTU/

f t^{3}

1 BTU/

f t^{3}

= 9.3 kcal/

m^{3}

Units of heat

1.Calorie:The amount of heat required to raise the temperature of 1 g of water by 1 °C (from 15 °C to 16 °C) is defined as one calorie.

1 calorie = 4.185 Joules =

4.185 \times 10^{7}

ergs.

2.Kilocalorie: The amount of heat required to raise the temperature of 1 kg of water by 1 °C (from 15 °C to 16 °C) is defined as one kilocalorie. It is stated that 1 kilocalorie is equal to 1000 calories.

3.British Thermal Unit (BTU): The amount of heat required to raise the temperature of 1 pound (lb) of water by 1 °F (from 60 °F to 61 °F) is defined as one British Thermal Unit (BTU).

1 BTU = 252 cal = 0.252 kcal = 1054.6 Joule =

1054.6 \times 10^{7}

ergs.

4.Centigrade Heat Unit (CHU):It is defined as the amount of heat required to raise the temperature of one pound of water by 1 °C (from 15 °C to 16 °C).

1 kcal = 3.968 BTU = 2.2 CHU

Gross and Net Calorific Value

Gross Calorific Value (GCV): It also refers to higher calorific value (HCV) and defines it as the total amount of heat produced when a unit quantity (mass/volume) of fuel burns completely, and the products of combustion cool to room temperature.

Usually all fuels contain hydrogen. During combustion, the combustion process converts the hydrogen present in the fuel into steam. When the combustion products cool to room temperature, they condense the steam into water and evolve heat that equals the latent heat of condensation of steam. The measured heat includes this heat; therefore, the total value becomes higher. For this reason, experts refer to it as the higher calorific value.

Low Calorific Value (LCV):It also refers to net calorific value (NCV) and defines the heat produced when a unit quantity (mass/volume) of a fuel burns completely and allows the hot combustion products to escape.

In actual practice, when someone burns a fuel, they cause water vapor to escape along with the hot combustion gases; hence, the available heat becomes lesser than the gross calorific value.The process incorporates this heat into the measured heat, which ultimately elevates its value; hence, experts commonly refer to it as the higher calorific value.

Thus LCV = HCV – Latent heat of water vapour formed.

As 1 part by weight of hydrogen gives 9 parts by weight of water,

H2+ ½ O2 → H2o

LCV = HCV – Weight of hydrogen in unit mass/volume of fuel × 9 × latent heat of steam.

Basically there are two ways to measure the Calorific Value.

Bomb calorimeter
Boy's Gas calorimeter

We will discuss about it in next article in detail.

Applications and Important of Calorific Value

1. Fuel Quality Assessment

The calorific value further determination is especially important in the evaluation of the quality of different fuels. It gives the opportunity to compare energy content and efficiency enabling the choice of the best fuel for particular purposes.

2. Energy Production

Industries largely depend on correct calorific value assessments to precisely optimize combustion processes that are vital in energy generation. This guarantees maximum energy harvest and efficiency in power generation.

3. Environmental Impact

To evaluate the environmental impact of different fuels one has to familiarize with their calorific value. Higher calorific value fuels normally provide a higher energy output with lower emissions per unit of energy produced and this way promote cleaner and greener energy production.

4. Research and Development

Estimation of calorific value is one of the basic stages of a new fuel and energy products researches and developments. It offers an understanding of possible deployments, and how operate about emerging technologies.

Challenges and Considerations for calorific value

Firstly, calorific value determination is valuable; indeed, it aids energy analysis. Furthermore, it supports fuel assessment, consequently providing data. Therefore, accurate measurements matter, additionally aiding design. Moreover, it boosts efficiency, thus helping industries. Meanwhile, consider impurities, since they affect accuracy, hence requiring checks. Similarly, combustion completeness matters, besides influencing results, ultimately impacting outcomes. Nevertheless, fuel variability exists; however, methods adjust. Likewise, calibration helps, accordingly ensuring precision. Otherwise, errors occur. In fact, consistent testing is vital, next, analysis proceeds, finally, measurements guide optimization.

Conclusion

The assessment of calorific value is a voyage into the place of energy potential, giving essential information about the productivity and the appropriateness of various fuels for a horde of undertakings. Firstly, scientists and engineers use bomb calorimetry and adiabatic flame calorimetry; indeed, these tools are vital. Furthermore, they enable precision, consequently improving analysis. Therefore, data guides research, additionally aiding design. Moreover, methods optimize systems, thus enhancing efficiency. Meanwhile, industries apply findings, since energy demands grow, hence requiring solutions. Similarly, technology advances, besides ensuring sustainability, ultimately producing the key for a future of efficient, green energy use.

What is Calorific Value? Application and types of it