Quality of the Joule

In this chapter, we make preparations for performing a thermodynamic analysis of a process. The principles of such an analysis are defined first. From the calculation of the minimum, also called the ideal amount of work to perform a certain task, the convenience, not the necessity, of defining the concept of exergy is made plausible. Exergy can have a physical and a chemical component. The quality of the Joule is another convenient concept for a clear analysis and for conclusions on process performance. 

At this point, it is useful to show how the second law can be related to the transformation of energy while making use of the "quality of the Joule" concept. Let us turn to Figure 6.7 in which the system is defined as contained within the rectangle and prevails in a steady state, that is, its properties do not change with time. Energy flows 1 and 2 enter the system, energy flows 3 and 4 leave the system and the first law requires that... 

In line with what was discussed in Chapter 6 with regard to the quality of the Joule, one can interpret Orwell [6], "All Joules are equal, but some Joules are more equal than others." This means that 1J of heat at 1000 K is more useful than, say, 1J of heat at 298 K. This is a direct consequence of the work available in these amounts of heat, as stated in Chapters 6 and 7, where precise definitions of physical and chemical exergy are given. A direct consequence of the second law of thermodynamics is that the available work (exergy) can never be utilized completely in real processes. Since all real processes are irreversible, every process step will produce a finite amount of lost work, thus diminishing the amount of useful work. 

The factor 1 - (T0/T) is often called the thermal efficiency, but we prefer to call it the Carnot factor For example, if heat is supplied at 600K and the temperature of the environment is 300 K, the Carnot factor is 1/2. We could also say that in this instance the quality q of every Joule of heat is 1/2 J/J, if we wish to express that at most half of the Joule of heat supplied can be made available for useful work with respect to our environment at T0 ... 

Later it will become clear why this observation is important and how far-reaching the implication is of making use of the distinction between both quantity and quality of the various Joules involved in a process. 

The Acheson process is the oldest and still most important graphitization process. The carbon articles are placed with their long axes perpendicular to the direction of the electrical current in the furnace bed and are surrounded with a resistive bed of granular coke in which most of the Joule heat is produced. A constant furnace resistance is essential for uniform product quality (avoidance of local temperature peaks). The way in which the furnace is loaded is therefore critical. 

So we define the quality of heat supplied at a temperature level T > T0 as the maximum fraction available for useful work. Baehr [4] has called this part of heat the exergy of heat. The remaining part is unavailable for useful work and is called anergy. It is the minimal part of the original heat that will be transferred as heat Qo"n to the environment. In Baehr s terminology, we could say that in this instance the ideal heat engine would achieve the following separation between useful and useless Joules ... 

Earlier we mentioned that the first law deals with the quantity of energy, and the second law deals with the quality of energy. Looking at the system and its environment at the same time, we see that the first law expresses that for a real process the total number of Joules involved remains unchanged. The second law expresses that their quality declines. The total amount of... 

The rad is a unit of absorbed radiation dose in terms of energy actually deposited in the tissue. The rad is defined as an absorbed dose of 0.01 joules of energy per kilogram of tissue. The rem (radiation equivalent man) is the unit of human exposure and is a dose equivalent (DE). The international or SI unit for human exposure is the sievert, which is defined as equal to 100 rem [2]. It takes into account the biological effective of different types of radiation. The biologically effective dose in rems, is the radiation dose in rads multiplied by a quality factor, which is an assessment of the effectiveness of that particular type and energy of radiation. 

A unique quality of rubber is the Gough-Joule effect. Unlike other materials, when rubber is stretched rapidly it heats up. If rubber is stretched under a load, it will retract as the temperature is raised and it is held at the other end. 

There are some simulated running effects ofliquid injection dissolution of CO2 in oil, enhanced specific volume of the C02-loaded oil, and displacing of oil by CO2. These effects elucidate diverse benefits first, the oil yield increases, and the temperatures of the drained oil and even of the deoiled press cake drop down by the Joule-Thompson effect of the rapid degassing CO2. Thus, the quality of both the... 

SUMMERFIELD, I. PUTTER, J., KAARSTAD, O. ScHWARTZKOPF, T. 1996. Quantities and quality of CO2 which may become available from fossil fuel fired plant in the European Union and Norway. In-. Holloway, S. (ed.) The Underground Disposal of Carbon Dioxide. Final report of Joule II Project Number CT92-0031. 

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