essentialsdaa.blogg.se - Second law of thermodynamics

Combined heat and power (CHP) attempts to make use of this heat in industry for for heating. To maximize the value we get from our fuel requires finding a place for this heat. The Second Law means that heat is a necessary by-product of electricity generation. electricity) will always generate lower quality forms of energy, such as heat or sound. We always end up losing exergy and generating entropy when we convert energy.Ĭonverting heat (i.e. It restricts us even more than the First Law - the Second Law makes it explicit that we can never convert all of the energy in fuel into useful work.

The Second Law limits the amount of useful work we can do with energy. The Second Law further limits the fraction of fuel we can convert to power. In reality, it’s not possible to generate power at 100 % efficiency. The First Law puts no limit on the efficiency of power generation - the First Law limits the amount of power generation at 10. In this example, our efficiency of power generation is 40%.

an energy balance allows us to calculate the heat generation at 6 units.

Unknowns such as flow rates of water or temperatures of gases can be solved for using balances.Ī common energy transformation is converting fuel into power and heat. The practical implication of the First Law for energy engineers is the ability to draw mass & energy balances. The First Law applies to both mass & energy, and allows for conversion between the two. The First Law is a law of conservation - energy cannot be created or destroyed, only only converted from one form to another. The insights I have chosen to highlight are how they relate to practical energy engineering.

The Second Law says we can never break even, and will always lose.īoth of these Laws have alternative definitions and interpretations.

The First Law limits us to only ever breaking even,.

Let’s start at the end - here are two simple definitions of the First & Second Law of Thermodynamics: