To all the mechanical engineering students out there! Thermodynamics and Heat Transfer are one of the major subjects of interests and govern the dynamics of many everyday mechanical systems working. Today, I started exploring Thermodynamics and its history when I figured out some of the simple to understand differences between Thermodynamics and Heat transfer.
So basically, if we cover Thermodynamics, it is more of a phenomena which studies the spontaneity of a thermodynamic process, the process parameters at certain state points etc. whereas heat transfer deals with so many other parameters, like flow behaviour, material properties, temperature gradient.
In thermodynamics, time of reaction doesn’t play any role, whereas heat transfer can help us determine the exact time and quantity based parameters involving in the process. How the heat flows from body to body, where it looses uniformity etc.
If you look at the laws involved in computation of thermodynamics, they can be listed as follows:
- Zeroth Law of Thermodynamics (defines temperature)
- First law of Thermodynamics (defines internal energy)
- Second Law of Thermodynamics (defines entropy)
- Third Law of Thermodynamics (limits the lowest temperature attainable)
Observe the process parameters which are given importance in this kind of process, whereas, heat transfer has following laws for its process variable computation:
- Fourier’s Law (Heat conduction)
- Newtons Law of Cooling (Heat convection)
- Planck’s Law (Thermal Radiation)
- Stephan Boltzman’s Law (Thermal Radiation)
- Wein’s Law (Thermal Radiation)
- Kirchoff’s Law (Thermal Radiation)
- Lambart’s Law (Thermal Radiation)
Heat transfer is slightly more broader than Thermodynamics, and goes a bit more specific into a process as a whole. Considering the type of material, its geometry, the fluid flow, the temperature gradient and many other parameters are taken into account while obtaining or analyzing the variables that involve heat transfer problems in real life.
Though, heat transfer won’t consider the computation of process end points, but it won’t be wrong if we formalize the equation which says:
Heat transfer=Thermodynamics+Material Science+Fluid Mechanics
Though, it’s not like going into hundred percent depth of these topics which will be involved in computing heat transfer problems in real life, but some segments of all these subjects are somewhere involved when it comes to compute those problems which involve heat transfer.
In conclusion we can say that:
Thermodynamics is process descriptor and tells us about the amount of heat, energy, work, dissipations etc. as total and doesn’t involve individual states (until and unless properly defined by the process parameters) whereas heat transfer is the study of computation of non equilibrium states and the entire process at various steps, looking for uniformity, material properties, distortions, thermal stresses etc. Heat transfer is actually a study of rate of transfer of these physical variables like energy and material properties.
Hope this helps you distinguish between the two more precisely and clearly 🙂