When you move from fundamental principles (in physics) to calculating something ‘useful’ (in engineering), you seem to move from energy to enthalpy. Enthalpy is measured in Joule, as well as energy. It is assigned to a ‘system’, a part of the physical world separated from other parts by interfaces. The canonical example is a vessel…

# Tag: Thermodynamics

## Statistical Independence and Logarithms

In classical mechanics you want to understand the motion of all constituents of a system in detail. The trajectory of each ‘particle’ can be calculated from the forces between them and initial positions and velocities. In statistical mechanics you try to work out what can still be said about a system even though – or…

## Heat Conduction Cheat Sheet

I am dumping some equations here I need now and then! The sections about 3-dimensional temperature waves summarize what is described at length in the second part of this post. Temperature waves are interesting for simulating yearly and daily oscillations in the temperature below the surface of the earth or near wall/floor of our ice/water…

## Can the Efficiency Be Greater Than One?

This is one of the perennial top search terms for this blog. Anticlimactic answer: Yes, because input and output are determined also by economics, not only by physics. Often readers search for the efficiency of a refrigerator. Its efficiency, the ratio of output and input energies, is greater than 1 because the ambient energy is…

## Consequences of the Second Law of Thermodynamics

Why a Carnot process using a Van der Waals gas – or other fluid with uncommon equation of state – also runs at Carnot’s efficiency. Textbooks often refer to an ideal gas when introducing Carnot’s cycle – it’s easy to calculate heat energies and work in this case. Perhaps this might imply that not only must the…

## Simulating Life-Forms (2): Cooling Energy

I found an incredibly detailed research report by the Australian government – about energy use in private homes, by appliance and purpose. It confirms my reluctance to ‘predict’ cooling energy as usage of air conditioning depends strongly on life-style choices.

## Entropy and Dimensions (Following Landau and Lifshitz)

Some time ago I wrote about volumes of spheres in multi-dimensional phase space – as needed in integrals in statistical mechanics. The post was primarily about the curious fact that the ‘bulk of the volume’ of such spheres is contained in a thin shell beneath their hyperspherical surfaces. The trick to calculate something reasonable is…

## Spheres in a Space with Trillions of Dimensions

I don’t venture into speculative science writing – this is just about classical statistical mechanics; actually about a special mathematical aspect. It was one of the things I found particularly intriguing in my first encounters with statistical mechanics and thermodynamics a long time ago – a curious feature of volumes. I was mulling upon how…

## And Now for Something Completely Different: Rotation Heat Pump!

Heat pumps for space heating are all very similar: Refrigerant evaporates, pressure is increased by a scroll compressor, refrigerant condenses, pressure is reduced in an expansion value. *yawn* The question is: Can a compression heat pump be built in a completely different way? Austrian start-up ECOP did it: They invented the so-called Rotation Heat Pump….

## Re-Visiting Carnot’s Theorem

The proof by contradiction used in physics textbooks is one of those arguments that appear surprising, then self-evident, then deceptive in its simplicity. You – or maybe only: I – cannot resist turning it over and over in your head again, viewing it from different angles. tl;dr: I just wanted to introduce the time-honored tradition…

## An Efficiency Greater Than 1?

No, my next project is not building a Perpetuum Mobile. Sometimes I mull upon definitions of performance indicators. It seems straight-forward that the efficiency of a wood log or oil burner is smaller than 1 – if combustion is not perfect you will never be able to turn the caloric value into heat, due to…

## A Sublime Transition

Don’t expect anything philosophical or career-change-related. I am talking about water and its phase transition to ice because … …the fact that a process so common and important as water freezing is not fully resolved and understood, is astonishing. (Source) There are more spectacular ways of triggering this transition than just letting a tank of water…

## Pumped Heat from the Tunnel

The idea to use a reservoir of water as a heat pump’s heat source is not new. But now and then somebody dares to do it again in a more spectacular way. Provided governmental agencies give you permit, lakes or underground aquifers could be used. Today a (German) press release about a European research project called Sinfonia…

## Mastering Geometry is a Lost Art

I am trying to learn Quantum Field Theory the hard way: Alone and from textbooks. But there is something harder than the abstract math of advanced quantum physics: You can aim at comprehending ancient texts on physics. If you are an accomplished physicist, chemist or engineer – try to understand Sadi Carnot’s reasoning that was…

## On the Relation of Jurassic Park and Alien Jelly Flowing through Hyperspace

Yes, this is a serious physics post – no. 3 in my series on Quantum Field Theory. I promised to explain what Quantization is. I will also argue – again – that classical mechanics is unjustly associated with steampunk pictures of clocks and trains. It looks more like representations of time-lines in Back to the…

## Random Thoughts on Temperature and Intuition in Thermodynamics

Recent we felt a disturbance of the force: It has been demonstrated that the absolute temperature of a real system can be pushed to negative values. The interesting underlying question is: What is temperature really? Temperature seems to be an intuitive everyday concept, yet the explanations of ‘negative temperatures’ prove that it is not. Actually, atoms have…

## Joule, Thomson, and the birth of big science

Originally posted on carnotcycle:

William Thomson, later Lord Kelvin (left), James Joule and the famous hand-operated pump. The Joule-Thomson effect is named after them, as are the SI units of thermodynamic temperature (kelvin) and energy (joule). Historical background In early May 1852, in the cellar of a house in Acton Square, Salford, Manchester (England), two…

## The First Heat Pump Ever Was Built in Austria

I have confessed recently that I am from Austria. So the patriot in me wants to entertain her readers with the story of a milestone in the history of engineering thermodynamics – set by an Austrian! The development of the first heat pump is attributed to Peter von Rittinger [1]. (Note that [1] is by a Swiss author,…

## Einstein and His Patents

No, this is not about Einstein’s achievements as a moonlighting scientific paradigm shifter, while working as a patent examiner in his day job. Einstein is famous for the theories of special and general relativity, and for the correct explanation of the photoelectric effect that has been rewarded with the Nobel prize. It is not so common knowledge that he contributed…

## Why Do Heat Pumps Pump Energy so Easily?

I know my posts are usually walls of text, but I am trying to improve! In his landmark physics course, the Feynman Lectures on Physics, Richard Feynman tries to explain what an explanation in physics actually is. You can always understand “the math” and follow a proof step-by-step. But deep, yet intuitive, understanding becomes harder and…