Tag Archives: thermodynamics

Heat

Heat is energy transferred due to temperature differences only.

  1. Heat transfer can alter system states;
  2. Bodies don’t “contain” heat; heat is identified as it comes across system boundaries;
  3. The amount of heat needed to go from one state to another is path dependent;
  4. Adiabatic processes are ones in which no heat is transferred.

The overall heat loss from a building can be calculated as

H = Ht + Hv + Hi (1)

where

H = overall heat loss (W)

Ht = heat loss due to transmission through walls, windows, doors, floors and more (W)

Hv = heat loss caused by ventilation (W)

Hi = heat loss caused by infiltration (W)

Insulation Thickness, Thermal Conductivity & Performance Criteria

Insulation – Terms, Definitions & Formula

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the evolution of globally aggregated economic wealth

Thermodynamics of long-run economic innovation and growth

This article derives prognostic expressions for the evolution of globally aggregated economic wealth, productivity, inflation, technological change, innovation and growth. The approach is to treat civilization as an open, non-equilibrium thermodynamic system that dissipates energy and diffuses matter in order to sustain existing circulations and to further its material growth. Appealing to a prior result that established a fixed relationship between a very general representation of global economic wealth and rates of global primary energy consumption, physically derived expressions for economic quantities follow. The analysis suggests that wealth can be expressed in terms of the length density of civilization’s networks and the availability of energy resources. Rates of return on wealth are accelerated by energy reserve discovery, improvements to human and infrastructure longevity, and a more common culture, or a lowering of the amount of energy required to diffuse raw materials into civilization’s bulk. According to a logistic equation, rates of return are slowed by past growth, and if rates of return approach zero, such “slowing down” makes civilization fragile with respect to externally imposed network decay. If past technological change has been especially rapid, then civilization is particularly vulnerable to newly unfavorable conditions that might force a switch into a mode of accelerating collapse.

Can we predict long-run economic growth?

For those concerned with the long-term value of their accounts, it can be a challenge to plan in the present for inflation-adjusted economic growth over coming decades. Here, I argue that there exists an economic constant that carries through time, and that this can help us to anticipate the more distant future: global economic wealth has a fixed link to civilization’s overall rate of energy consumption from all sources; the ratio of these two quantities has not changed over the past 40 years that statistics are available. Power production and wealth rise equally quickly because civilization, like any other system in the universe, must consume and dissipate its energy reserves in order to sustain its current size. One perspective might be that financial wealth must ultimately collapse as we deplete our energy reserves. However, we can also expect that highly aggregated quantities like global wealth have inertia, and that growth rates must persist. Exceptionally rapid innovation in the two decades following 1950 allowed for unprecedented acceleration of inflation-adjusted rates of return. But today, real innovation rates are more stagnant. This means that, over the coming decade or so, global GDP and wealth should rise fairly steadily at an inflation-adjusted rate of about 2.2% per year.

No way out? The double-bind in seeking global prosperity alongside mitigated climate change

In a prior study, I introduced a simple economic growth model designed to be consistent with general thermodynamic laws. Unlike traditional economic models, civilization is viewed only as a well-mixed global whole with no distinction made between individual nations, economic sectors, labor, or capital investments. At the model core is an observationally supported hypothesis that the global economy’s current rate of primary energy consumption is tied through a constant to a very general representation of its historically accumulated wealth. Here, this growth model is coupled to a linear formulation for the evolution of globally well-mixed atmospheric CO2 concentrations. While very simple, the coupled model provides faithful multi-decadal hindcasts of trajectories in gross world product (GWP) and CO2. Extending the model to the future, the model suggests that the well-known IPCC SRES scenarios substantially underestimate how much CO2 levels will rise for a given level of future economic prosperity. For one, global CO2 emission rates cannot be decoupled from wealth through efficiency gains. For another, like a long-term natural disaster, future greenhouse warming can be expected to act as an inflationary drag on the real growth of global wealth. For atmospheric CO2 concentrations to remain below a “dangerous” level of 450 ppmv, model forecasts suggest that there will have to be some combination of an unrealistically rapid rate of energy decarbonization and nearly immediate reductions in global civilization wealth. Effectively, it appears that civilization may be in a double-bind. If civilization does not collapse quickly this century, then CO2 levels will likely end up exceeding 1000 ppmv; but, if CO2 levels rise by this much, then the risk is that civilization will gradually tend towards collapse.

Are there basic physical constraints on future anthropogenic emissions of carbon dioxide?

Global Climate Models (GCMs) provide forecasts of future climate warming using a wide variety of highly sophisticated anthropogenic CO2 emissions models as input, each based on the evolution of four emissions “drivers”: population p, standard of living g, energy productivity (or efficiency) f and energy carbonization c. The range of scenarios considered is extremely broad, however, and this is a primary source of forecast uncertainty. Here, it is shown both theoretically and observationally how the evolution of the human system can be considered from a surprisingly simple thermodynamic perspective in which it is unnecessary to explicitly model two of the emissions drivers: population and standard of living. Specifically, the human system grows through a self-perpetuating feedback loop in which the consumption rate of primary energy resources stays tied to the historical accumulation of global economic production – or p times g – through a time-independent factor of 9.7 +/- 0.3 milliwatts per inflation-adjusted 1990 US dollar. This important constraint, and the fact that f and c have historically varied rather slowly, points towards substantially narrowed visions of future emissions scenarios for implementation in GCMs.

Comments: 18 pages including 5 figures, 1 table, and appendices Accepted on 27 August 2009 to Climatic Change
Subjects: Atmospheric and Oceanic Physics (physics.ao-ph); Physics and Society (physics.soc-ph)
DOI: 10.1007/s10584-009-9717-9
Cite as: arXiv:0811.1855 [physics.ao-ph]
(or arXiv:0811.1855v2 [physics.ao-ph] for this version)
Subjects: Atmospheric and Oceanic Physics (physics.ao-ph); Physics and Society (physics.soc-ph)
Journal reference: Earth System Dynamics 3, 1-17, 2012 http://www.earth-syst-dynam.net/3/1/2012/esd-3-1-2012.html
DOI: 10.5194/esd-3-1-2012
Cite as: arXiv:1010.0428 [physics.ao-ph]
(or arXiv:1010.0428v3 [physics.ao-ph] for this version)
Subjects: General Finance (q-fin.GN); Physics and Society (physics.soc-ph)
Journal reference: Garrett, T. J., 2012: Can we predict long-run economic growth?, Retirement Management Journal 2(2) 53-61
Cite as: arXiv:1211.3102 [q-fin.GN]
(or arXiv:1211.3102v1 [q-fin.GN] for this version)
Comments: 31 pages, 6 figures
Subjects: General Finance (q-fin.GN); Physics and Society (physics.soc-ph)
DOI: 10.1002/2013EF000171
Cite as: arXiv:1306.3554 [q-fin.GN]
(or arXiv:1306.3554v1 [q-fin.GN] for this version)

Zeroth Law of thermodynamics

Like the other laws of thermodynamics we will see, the Zeroth Law is based on observation. We start with two such observations:

  1. If two bodies are in contact through a thermally-conducting boundary for a sufficiently long time, no further observable changes take place; thermal equilibrium is said to prevail.
  2. Two systems which are individually in thermal equilibrium with a third are in thermal equilibrium with each other; all three systems have the same value of the property called temperature.

These closely connected ideas of temperature and thermal equilibrium are expressed formally in the “Zeroth Law of Thermodynamics:”

Zeroth Law: There exists for every thermodynamic system in equilibrium a property called temperature. Equality of temperature is a necessary and sufficient condition for thermal equilibrium.

The Zeroth Law thus defines a property (temperature) and describes its behavior1.3.

Note that this law is true regardless of how we measure the property temperature. (Other relationships we work with will typically require an absolute scale, so in these notes we use either the Kelvin $ K = 273.15+ ^\circ C$ or Rankine $ R = 459.9 + ^\circ F$ scales. Temperature scales will be discussed further in Section 6.2.) The zeroth law is depicted schematically in Figure 1.8.

 

Figure 1.8: The zeroth law schematically
Image fig2ThermometerEquilibrium_web

thermodynamic state

http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node11.html

The thermodynamic state of a system is defined by specifying values of a set of measurable properties sufficient to determine all other properties. For fluid systems, typical properties are pressure, volume and temperature. More complex systems may require the specification of more unusual properties. As an example, the state of an electric battery requires the specification of the amount of electric charge it contains.

Properties may be extensive or intensive. Extensive properties are additive. Thus, if the system is divided into a number of sub-systems, the value of the property for the whole system is equal to the sum of the values for the parts. Volume is an extensive property. Intensive properties do not depend on the quantity of matter present. Temperature and pressure are intensive properties.

Specific properties are extensive properties per unit mass and are denoted by lower case letters. For example:

$\displaystyle \textrm{specific volume} = V/m = v.$

Specific properties are intensive because they do not depend on the mass of the system.

The properties of a simple system are uniform throughout. In general, however, the properties of a system can vary from point to point. We can usually analyze a general system by sub-dividing it (either conceptually or in practice) into a number of simple systems in each of which the properties are assumed to be uniform.

It is important to note that properties describe states only when the system is in equilibrium.

thermodynamic system

A thermodynamic system is a quantity of matter of fixed identity, around which we can draw a boundary. The boundaries may be fixed or moveable. Work or heat can be transferred across the system boundary. Everything outside the boundary is the surroundings.

When working with devices such as engines it is often useful to define the system to be an identifiable volume with flow in and out. This is termed a control volume.

A closed system is a special class of system with boundaries that matter cannot cross. Hence the principle of the conservation of mass is automatically satisfied whenever we employ a closed system analysis. This type of system is sometimes termed a control mass.

 

Figure 1.3: Piston (boundary) and gas (system)
Image fig0PistonAndSystemBoundary_web