Thermodynamics

Thermodynamics

1. Theorical Principles

   • First Law
     • At a given interaction, energy can be transformed from one way into another, but its total quantity remains the same.
       • Internal Energy (U): It's the sum of all the molecular energies of the system
       • Heat (Q): A form where energy is transferred between two systems due to a temperature difference
       • Work (W): It's the transfer of the energy associated to a force that acts through a distance
   • Second Law
     • Energy has quality, quantity and processes that occur in a direction that reduces energy's quality.
       • Enthropy (S): It's energy degradation and functions as a disorder measurement
   • Third Law
     • It's impossible to achieve an absolute zero in practice due to the entropy of the system itself.
       • Temperature (T): Physical property that determines if two objects are in thermical equilibrium

2. Concepts

   • System
     • It's a quantity of matter or region in a chosen space for a study, they either can be open or closed.
       • Closed system (control mass)
         • It's a system in which the mass is constant as there isn't a transfer of it, but an exchange of energy.
       • Open system (control volume)
         • It's a properly selected region in a space that encloses a device that involves mass flow.
   • Surroundings
     • It's the mass or region outside the system, such can be fixed or movable.
   • Properties
     • Intensive
       • Those that are independent of the mass of a system like temperature, pressure and density.
     • Extensive
       • Those whose values rely on the system's size like mass, volume, or energy.
   • Equilibrium
     • It's a state where there are not potential imbalances o directive forces within the system.
   • Process
     • It's any change that a system undergoes from one equilibrium state to another
       • Isothermal: Temperature is constant Isobaric: Pressure is constant Isometric: Specific volume is constant Isentropic: Entropy is constant Cyclical: Initial and final states are identical
         • Pressure (P): It's a force applied perpendicularly to a surface by a fluid per unit area.
   • Path
     • A certain succession of states through which a system passes during a process according to the role a device assumes

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