Significance of Thermodynamics in Engineering

 Why study Thermodynamics?

Essential study of the internal motions of many-body systems is Thermodynamics. Substances that we encounter in everyday life are the body system of solid, liquid, gaseous, and light. Therefore, thermodynamics has a wide range of applicability in the field of physics. Thermodynamics is governed by four laws:

1.      Zeroth law of thermodynamics

2. The First law of thermodynamics

3.The Second law of thermodynamics

4.      Third law of thermodynamics

Zeroth  law

The Zeroth Law is the basis for the measurement of temperature. It states that two bodies that are in thermal equilibrium with a third body are in thermal equilibrium with each other.

Eg: Thermometer

In the Thermometer, there are few things,

1) a glass bulb

2) a glass column

3) liquid, normally Mercury

4) temperature scale on the glass tube

 Explanation

Normally mercury is stored in the glass bulb and this glass tube is connected to the glass tube at normal temperature mercury is in the bulb only. when the thermometer comes in contact with the hot body mercury in the bulb takes that heat. Mercury has the property to expand rapidly with a slight temperature difference. the area of the tube is constant and the Mercury starts to expand within the tube. based on the mark on the tube we can understand the temperature here, Mercury takes the temperature from the body and makes the thermal equilibrium. then get the temperature of the thermal equilibrium this is simply as per the zeroth law of thermodynamics. there are various thermometers used in various Thermal Properties such as digital thermometer constant volume Gas thermometer, Pacifier thermometer, electrical resistance thermometer.

First Law 

The First Law of Thermodynamics formally states that "while energy assumes many forms, the total quantity of energy is constant. When energy disappears in one form it appears simultaneously in other forms.

ΔU = Q-W

Eg: Heat Engine

The most common practical application of the First Law is the heat engine. Heat engines convert thermal energy into mechanical energy and vice versa. Most heat engines fall into the category of open systems. The basic principle of a heat engine exploits the relationships among heat, volume, and pressure of a working fluid. This fluid is typically a gas, but in some cases, it may undergo phase changes from gas to liquid and back to gas during a cycle. When gas is heated, it expands; however, when that gas is confined, it increases in pressure. If the bottom wall of the confinement chamber is the top of a movable piston, this pressure exerts a force on the surface of the piston causing it to move downward. This movement can then be harnessed to do work equal to the total force applied to the top of the piston times the distance that the piston moves. 

Second Law

It states that the entropy of any isolated system always increases. Entropy is a state variable whose change is defined as a reversible process at T where Q is the heat absorbed.

Third Law

The third law of thermodynamics states that the entropy of a system at absolute zero is a well-defined constant. This is because a system at zero temperature exists in its ground state so that its entropy is determined only by the degeneracy of the ground state.

Applications of thermodynamics in the field of energy Engineering.

Thermal Engineering has a wide range of applications in the field of Thermodynamics. All the aspects like industries, agriculture, transport, commercial and domestic activities use thermal engineering for its assistance But energy technology and power sector are fully dependent on the laws of thermodynamics.
For example

(i) Central thermal power plants, captive power plants based on coal.

(ii) Nuclear power plants.

(iii) Gas turbine power plants.

(iv) Engines for automobiles, ships, airways, spacecraft.

(v) Direct energy conversion devices: Fuel cells, thermionic, thermoelectric engines.

(vi) Air conditioning, heating, cooling, ventilation plants.

(vii) Domestic, commercial and industrial lighting.

(viii) Agricultural, transport, and industrial machines.

All the above engines and power-consuming plants are designed using the laws of thermodynamics.

How Thermodynamics is applied in the electrical field of Engineering?   Thermodynamics is a part of physics in which different types of energies are there. Various energy conversions take place in this branch of Science like Electrical to mechanical energy, heat to electrical, wind to electrical, chemical to mechanical, etc. It basically deals with the variables like Pressure, Temperature, and Volume which is also called Macroscopic Variables. If we talk about the application of thermodynamics in the electrical sector of engineering we will come across its uses in engines, phase transitions, chemical reactions, transport phenomena.The laws of thermodynamics are the initial point of thermodynamic consideration. It postulates that energy can be exchanged between physical systems as heat or work. They also postulate the existence of a quantity named entropy, which can be defined for any isolated system that is in thermodynamic equilibrium. It is used in Temperature measurement using NTC thermistors. NTC thermistors come in a picture if we talk about the equipment where the temperature has its major role. They are the most used type of Temperature sensor where it has a negative electrical resistance versus temperature (R/T) relationship. NTC thermistors are basically made up of Ceramics or Polymers. Depending on the Different materials used to make NTC, Various temperature Responses are obtained i.e. the typical values of temperature sensitivities range from -3% to -6% per °C. −55°C and 200°C are the suitable range for most of the NTC thermistors to obtain a precise and accurate reading.  For absolute Zero which is (-273.15°C), there are special types of NTC thermistors. The percentage change per degree Celsius is known as the temperature sensitivity of the NTC sensor. It is also used in Thermal considerations in using semiconductors and Use heat sinks. One of its significant applications is the Use of LM339 temperature-sensitive diode, design of gain and offset circuitry to interface with analog to digital converter spanning the range of 0.0 to 5.0 Volts, use of 4051 analog multiplexers under control of printer port to make up to eight measurements.It also plays a prominent role in Running NTC thermistors in self-heat mode to detect air movement and as a fluid detector.

 

Application of Thermodynamics in Mechanical Engineering

No process is executed within the industries, where there are no transfers and energy transformations, as mentioned at the beginning of the article with the three questions of analysis that was made, the transformation of electrical energy needs a science such as thermodynamics to be able to understand all those thermal and heat transfer processes. The thermoelectric converts the heat generated by diesel fuel into electricity, in all this process, is of vital importance to the fundamental principles of the laws of thermodynamics, especially to understand what there must be a balance in energy transfers.

Conclusion

Transcend in the study of thermodynamics to bring industrial processes in the best way, more optimized, especially in the industrial field where there are boilers, turbines, evaporators, condensers, cooling towers, large-scale combustion processes. Knowing how to handle and apply the laws of thermodynamics we will improve these processes, which in turn infer in the improvement of production systems.

The mechanical engineer as a designer, supervisor, and evaluator of various projects that involve being a maintainer, must have clear knowledge and application in thermodynamics, especially taking into account that already in the workplace is much lost academic sense and many processes are they let vital by the habit to solve the problems, and the academic thing is left of the hand, and in this particular case the thermodynamics like fundamental axis within the Engineering in general and still more in mechanical engineering.