MHD Full Form
What is the full form of MHD?
MHD stands for Magneto Hydrodynamics. This word is derived from magneto - meaning magnetic field, hydro - meaning water and dynamics meaning movement. Magneto Hydrodynamics is the study of the magnetic properties and behaviour of electrically conducting fluids. The key concept behind Magneto Hydrodynamics is that magnetic fields can induce currents in a moving conductive field, which in turn polarises the fluid and reciprocally changes the magnetic field itself. Magneto Hydrodynamics is a direct energy conversion process in which thermal energy is used to convert to electrical energy. MHD plays an important role in the power industry.
History of MHD
The field of study of MHD was initiated by Mr. Hannes Alfven (1908-1995). In 1970, Mr. Alfven was conferred the honour of the Nobel Prize for his research in this field. Mr. Alfven who worked towards these fundamental discoveries in MHD, was able to put various important applications of Physics to use in different parts of plasma physics.
Study of MHD
Magneto Hydrodynamics is a macroscopic theory. Few examples of magnetic fluids are saltwater, electrolytes, plasma and liquid metals. Magneto Hydrodynamics is a mathematical-physical concept which is mainly related to the dynamics of different magnetic fields which flow within electrically conducting fluids. The study of MHD expressed that magnetic fields could be supported by the conductive fields which is the main key point of Magneto Hydrodynamics. Magnetism is mainly throughout the earth’s ecosystem, interstellar medium etc. These types of magnetic fields are generated and maintained by MHD.
The MHD system is a non-conventional source of energy which is based upon Faraday’s law of electromagnetic induction. This law says that when an electrical conductor moves relative to a magnetic field, EMF is induced in the conductor which results in flow of current across the terminals.
Applications of MHD
Following are the various applications of MHD:
MHD can be used as a backup system in power plants
Driving submarines, aircraft uses MHD generator
Used to generate electric power
Used in defense also
Advantages of MHD
Here is the list of few advantages of MHD:
Vibration and noise are eliminated
This system produces the power without pollution
The maintenance cost is low
Low operational cost and better fuel utilisation
There are no moving parts. So, it is more reliable.
Less cost of power generation
Less fuel consumption
This is high efficient than conventional power plant
MHD generators have high power density, rapid start and low specific weight
Disadvantages of MHD
Here is the list of few disadvantages of MHD:
High amount of losses due to fluid friction
Need large magnets to create high magnetic field and this is a major expense
Need high temperature and due to high temperature stresses, parts of MHD generator have shorter life
Choice of material is very less
There are some technical limitations on enhancing the fluid conductivity and the strength of magnetic field
Frequently Asked Questions (FAQs)
In an open cycle MHD system, working fluid after generating electrical energy is discharged to the atmosphere through a stack while in closed cycle MHD system, working fluid is recycled to the heat sources and we can use it again.
Coal as a fuel may create a problem of molten ash which may short circuit the electrodes. Therefore, coal as a fuel is not a better option for MHDs. Oil or natural gas are always much better fuels for MHDs.
The extensions of MHD are collisionless, Electron MHD and Hall MHD.
Liquid metals such as Sodium (Na), Potassium (K) and Lithium (Li) can be used in a liquid metal MHD system. These liquid metals are good electrical conductors in the liquid state. Therefore, they can be used in the working fluid in the liquid state only.
In the MHD generator, the seeding materials such as potassium and cesium are used to reduce the ionisation temperature and these seeds are mixed with fuel material such as natural gas.