Applied thermodynamics Flashcards
What are the four laws of thermodynamics?
Zerowth: ‘if two systems are both in thermal equilibrium with a third system then they are in thermal equilibrium with each other’ how can we measure temperature?
First: law of energy conservation - energy can not be lost or produced, Only be transformed or conserved
Second: Law of irreversibility: with any eneryg transformation, exergy is lost and entropy is generated. anything ends up in chaos. There is effort to make order again.
Third: At an absolute zero point (0 Kelvin) a system must be in a state of minimum possible energy. Transfer of energy is impossible.
Name and explain the main arguments for the energy debate.
- Fossile fuels are finite stocks
- We are depending on a guaranteed flow of energy (dependent)
o Can’t handle a blackout
o Are dependent on Russia basically - Climate change (fighting air pollution on global scale)
- Improving air quality (fighting air pollution on local scale)
Out of which two components can energy exist?
Power and time
Name the trias energetica
- Limit demand for energy through rational use of energy
- Use renewable energy to fulfil remaining demand
- Use fossil fuels, if necessary. As efficiently and cleanly as possible.
Explain the steps of the REAP
- Reduce demand and emphasize on energy efficiency
- utilize waste flows
- Generate resources sustainability - use renewable energy sources.
Tell me the components of a ‘system’.
State-space representation oriented physical quantities: temperature, pressure p, volume.
Then you have heat that goes into the system. This is process oriented (time/fuel). Heat says something about activities.
Coffee heats the body: higher temperature than surrounding. Coffee does the work to the surrounding, since it goes from high to low temperatures. With beer, the person would ‘do the work’. since that goes from a lower temperature to a higher ambient one.
This is basically comparing a system with a reference system the whole time. –> same temperature and calibrating the whole time.
What is exergy?
The minimum amount of work a system can perform when it’s brought to thermodynamic equilibrium with it’s environment.
In more simple terms this is more or less the ‘quality of energy’. e.g. gas produces a lot of heat but is used to warm up houses. That is a low quality purpose. This is a low exergy way of using energy.
Explain examples of temperature with a beer in the dessert and in the south pole.
In the dessert the temperature is higher in surrounding than the beer. In that case, the environment is ‘doing the work’, since the environment warms up the colder beer.
With a pole it’s the other way around. The environment is colder, but the beer is warmer. The higher temperature is then heating the surrounding.
Explain the components and idea of REAP.
Energy cascading: Each spatial function gets the proper heat to keep doing the function (power plant needs more high quality heat than residential areas). Each spatial function needs less and less. First you have a power plant, then industry with high quality process heat
than green housewith high temp residual heat
then offices with medium temperature residual heat
then residential areas with low temperature residual heat.
What are three principles of exergy planning?
No place for waste, waste = source of remaining quality
Spatial functions, from mono to multi
Proximity or connectivity or both.
Energy in wind can only be measured by?
Speed of wind.
Why is wind energy difficult to use as an energy source for the whole country?
You need a lot of space. In practice 13.596 km2. This would mean the whole North Sea would be full with windturbines. If numbers are mentioned, it becomes clear why step 1 ‘limit demand for energy through a rational use of energy’ is first.
