It was covered since the inception of the Dutch constitution. It was simply not explicitely stated until now.

It's 100% efficient, that is all electricity is converted into heat, eventually. So a 1 kW oven running at maximum capacity will consume some 1 kW of electricity to produce the same amount of heat. So it generates heat from electricity. A heat pump on the other hand merely 'pumps heat' using electricity. This means at certain operating conditions (this is dependent on e.g. the outside and inside temperatures) it will use 1 kW of electricity to move 3 kW of heat from the cold outside into your warm home. This gives it a Coefficient Of Performance (COP) of 3 kW/1 kW = 3 at those operating conditions.

Instead of 'randomness' it's probably clearer to think of entropy as the amount energy unavailable to perform useful work. So pressure losses and frictional losses for instance consist of energy we cannot use to generate electricity. This is also why entropy must always remain equal or increase.

>(which, if you Google and read a bit, will confirm that calling desublimation, fusion is an old phrase that is being replaced).

>if you suddenly called desublimation, fusion. We've not used fusion to refer to desublimation since the 70s.

Now I know for sure you don't know what you're talking about because desublimation is the phase transition from a vapour directly to a solid, not from a solid to a liquid. I was listing several types of latent heats earlier, not synonyms as you must've erroneously assumed.

>Again, widely used where?

Internationally. The exact same term is used for instance by Y. Cengel in his textbook Thermodynamics: An Engineering Approach, which is a very popular book on engineering thermodynamics for university-level courses on this topic. This terminology continues to be used to this day by a plethora of researchers. If you don't believe me, again, just search for the term 'latent heat of fusion' on Google Scholar. This is an odd hill to want to die on.

'Latent' comes from latin 'lying hidden', i.e. heat which does not result in a change in temperature, as opposed to sensible heat. 'Latent heat of fusion/(de)sublimation/melting/vaporisation' etc. are widely used terms. Just type in 'latent heat of fusion' in Google scholar to see for yourself.

The person you responded to made a mistake in the type of latent heat relevant here, but not in their use of 'fusion' to refer to a specific type of latent heat.

>Mmm, not fusion. Fusion is a specific physical process that only occurs in stars and H bombs (so far). And not freezing. That's liquid to solid.

The latent heat of fusion is the amount of energy required for a substance to transition between its solid and its liquid state. Their terminology is correct.

Phase changes occur at fixed temperatures. When you introduce a saturated liquid in a heat exchanger and extract a saturated vapour from it, your temperature difference between the exchanger and your heat source has remained constant (assuming a sufficiently large source). Same goes for a saturated vapour entering a heat exchanger and leaving as a saturated liquid. This is more efficient than heating a vapour, as its temperature will increase, causing a smaller temperature difference between itself and its heat source/sink and with that a reduced heat flux. The latent heat of vaporisation for e.g. water is quite high, which means you can absorb or reject a lot of heat at a constant temperature.

This is readily apparent from the heat capacity of water vapour and the latent heat of vaporisation of water. The c_p of water vapour is roughly 1.8 or 1.9 kJ/(kg K) at 0 degrees Celsius. This means that adding 1.8 kJ to one kilogram of water vapour will raise its temperature one Kelvin. The latent heat of vaporisation for water at 0 degrees Celsius is about 2500 kJ/kg. Meaning one kilogram of saturated liquid water will absorb 2500 kJ before its temperature will start to rise.

So to answer your question more directly, yes, you can use a heat engine with only a gas as a working fluid, but phase transitions are an excellent way of absorbing or rejecting large amounts of heat quickly. An example of a real-world gas-only heat engine is the Stirling engine, which runs on the Stirling cycle.

It's not so much extracting energy as it is transforming heat into useful electricity through performing work. If your goal was to heat homes and businesses directly, you'd use a heat exchanger and a fluid with a high heat capacity to distribute the heat. But because you want energy in a different form, you're pretty much left to the Rankine cycle if you want high efficiencies between your conversion from heat to electricity. The reason water is typically used as the working fluid in most Rankine cycles is because it is non-toxic, cheap/abundant and has a high heat of vaporisation amongst other thermodynamically favourable properties. There are other working fluids, for instance for an Organic Rankine Cycle (ORC), such as toluene, but an ORC is better suited for lower-temperature waste heat and the like, and toluene for instance is nasty stuff you'd prefer not to use.

u/philosopherssage:

>The vast majority of lift comes from near the tips of the blades. The transition from subsonic to supersonic is where the pressure from the moving object is greater than the fluid pressure (air). When this happens vacuum bubbles form and contact with the fluid is lost preventing the transfer of force. This is why lift is lost when the portion of the prop/rotor goes supersonic. The little bubbles also cause many shockwaves and can damage the surface, underwater this is called cavitation. The bubbles also disturb the flow of air and causes turbulence which even further reduces lift.

Cavitation flow is distinctly different from compressible flow in gases, as it involves a local phase change from the bulk liquid into its gaseous state. No 'vacuum bubbles' are formed in either case. In the case of wings, normal shocks on top of the wing cause flow separation, this is called wave drag which leads to loss of lift or in case of rotors or propellers, loss of thrust.

It does, which is why fighter jets for instance have very flat airfoils which are not very efficient for generating lift in subsonic flight. The cross-section of the wings of the famous SR-72 Blackbird reveals a simple ellipse. They require a tremendous amount of thrust to generate enough lift when flying at supersonic speeds, hence why their jet engines have afterburners. When flying at supersonic speeds, airfoil shape is of lesser importance to generating lift.

Aircraft designers are very keen to prevent (local) shockwaves forming on their wings. If you look at a passenger jet, you will notice it has swept wings. These swept wings delay the formation of shockwaves on the wing when flying at transonic speeds, thus increasing efficiency whilst still enabling the aircraft to fly at these speeds.

Regular, subsonic propellers or rotors going supersonic are incredibly inefficient, with efficiencies close to zero, or the propellers/rotors even producing a net drag. It's not a question of material strength. The book 'Introduction to Flight' by Anderson has a nice exercise (6.24 for edition 5) in which it is shown that claims by WWII fighter pilots of breaking the sound barrier in vertical, power-on dives are theoretically impossible. Rotors naturally suffer from the same problems as propellers.

The only propeller aircraft I know of which broke the speed of sound is the modified McDonnell XF-88B fitted with a turboshaft engine. It did not use the propeller as a primary source of thrust, but it did achieve a supersonic dive using only the propeller. I assume this was using basically flat, angled plates as propellers, which would be better suited for generating lift (which in this case would be thrust) in a supersonic airflow than regular, subsonic propellers.