Calorimeter

Calorimetry is a branch of science that measures a body’s condition in terms of thermal features in order to evaluate its chemical changes such as burning, acid-base neutralisation, and physical changes such as melting and evaporation.So,

• A calorimeter is used to measure a body’s thermal changes.

• Thermochemistry often uses calorimetry to calculate enthalpy, stability, heat capacity, and other properties.

What is a calorimeter?

The first calorimeter was created by Antoine Lavoisier and Pierre Simon de La Place. It essentially consists of a metallic vessel made of various materials such as aluminium and copper that are strong conductors of electricity. There is also a feature that allows you to stir the contents of the calorimeter. To reduce the heat dissipation to the environment, the stirrer and the vessel is housed in an insulating jacket. Only one opening can be used to put the thermometer to analyse the change in thermal characteristics within. 

Heat measurements with a calorimeter

Let us have a look at how heat measurements are made.

Assume a set quantity of fuel is burned in a calorimeter. The vessel is filled with water, and the fuel is burned, causing the water to heat up. The heat obtained by the water is equivalent to the heat lost by the fuel. Such measurements are simple to take with the calorimeter. This also shows us why it is critical to isolate the calorimeter from the environment in order to increase experiment accuracy. This difference in temperature may be monitored using a thermometer. We can determine the heat capacity of water as well as the energy contained in fuel using such a measurement.

Principle of calorimetry

According to the calorimeter’s operating principle, the heat energy emitted by a hot body in an insulated system is equal to the heat energy received by the cold body. Finally, heat is transferred until both bodies are at the same temperature (t). Although the components of the calorimeter should theoretically absorb no heat, they always absorb some energy from the system.

Types of calorimeter

Adiabatic calorimeters

This is a type of calorimeter used to check the runaway process. In an adiabatic environment, any heat created by the cloth sample that is being tested causes the temperature of the sample to rise, fuelling the reaction. The sample loses a tiny amount of heat typically to the sample holder. Phi-factor, also known as a mathematical correction factor, is frequently used to alter the calorimetric result to account for these heat losses.

Reaction calorimeters

A reaction calorimeter is a calorimeter in which a reaction takes place inside a sealed, insulated container. As a result of measuring reaction heat, the heat content is calculated by integrating time versus heat flow. Because industrial processes are designed to run at consistent temperatures, this instrument is used to measure the current temperatures.

In a reaction calorimeter, there are four fundamental sorts of techniques for measuring the warmth:

1. Heat Balance Calorimeter – The heating/cooling jacket controls the method’s temperature. The temperature received or lost by the warmth transfer fluid is monitored to determine how much heat is transferred.

2. Constant Flux Calorimeter – COFLUX or Constant flux calorimetry is a type of calorimeter that employs sophisticated control mechanisms to maintain a continuous flux or heat flow over the vessel wall.

3. Heat Flow Calorimeter – The jacket’s temperature should be managed by the heating or the cooling jacket. The temperature differential between the process and heat transfer fluid is monitored to calculate the heat.

4. Power Compensation – In order to maintain a constant temperature, a heater is inserted within the vessel. The energy provided to the current heater is frequently changed to accommodate reactions and hence the calorimetry signal is only obtained from this electric power. 

Bomb calorimeters

A bomb is a type of constant-volume calorimeter that is used to measure the temperature of a reaction’s combustion. The fuel is ignited using electrical energy. When the fuel burns, it warms the surrounding air, which expands and exits the calorimeter through a tube. When air escapes through the copper pipe, it also heats the water outside the tube as well. The temperature differential in the water allows the calorie content of the fuel to be calculated.

Here, a bomb is made up of a small cup to hold an ignition circuit linked to the bomb, an insulating container to prevent heat from the calorimeter from escaping into the environment, a chrome steel bomb, water, oxygen, a stirrer, a thermometer, and the sample. The reaction will occur with no volume change if the explosive is made of chromium steel.

Calvet-type calorimeters

A three-dimensional fluxmeter sensor is used to make the detection. The fluxmeter element is made up of a hoop with serial thermocouples. An alternate thermopile surrounds the experimental space within the calorimetric block with a high heat conductivity. The radially placed thermopiles ensure that the warmth is almost completely integrated. The calibration of the calorimetric detectors is a critical parameter that must be done meticulously. A specific calibration, known as the electrical calibration or Joule effect, has been created for Calvet-type calorimeters and is used to overcome a variety of difficulties.

Conclusion

Calorimetry is the study of measuring changes in a body’s state variable to determine the heat transfer rate that occurs simultaneously with the state transition. For instance, determining the state variable change during phase transformations or other types of physical changes. The calorimeter is a device that is used to research calorimetry.