Entropy In The Second Law Of Thermodynamics Construction Essay

This essay will take to specify information, and research its relevancy in the context of the 2nd jurisprudence of thermodynamics, with the aim of set uping that the thought behind entropy exists within the molecular construction of a on the job fluid ; the phenomena of self-generated burning every bit good as the Carnot and Rankine rhythms will be considered to further lucubrate on the construct of information under the 2nd jurisprudence of thermodynamics ; and at the decision of this essay, a recommendation on the footing of the algebraic expression for information would be used to understand the thought behind modern research into energy direction engineering today.

Entropy and its construct under the 2nd jurisprudence of thermodynamics

We will write a custom essay sample on
Entropy In The Second Law Of Thermodynamics Construction Essay
or any similar topic only for you
Order now

The construct of Entropy can be understood by analyzing the alteration in the molecular construction of substances undergoing a thermodynamic rhythm, and besides analyzing how its molecules interact at different phases of the rhythm. Reynolds and Perkins ( 1977 ) considered information as the entire grade of disorderliness of all the single molecules of a on the job fluid ; based on this construct, when sing the single molecules of H2O being boiled at room temperature, it will be observed that its molecular construction and grade of random gesture are different at liquid and vapor province. Cengel and Boles ( 2008 ) indicates that when a fluid is in its solid stage, its molecules are non exhibiting any random gesture but are held together by a bond ; but one time there is a rise in temperature, it changes to liquid province and so vaporizes at impregnation temperature ; while its single molecules start traveling in a disorganized random gesture, clashing with each other in the procedure and bring forthing energy in the signifier of heat ; the size of heat generated correlatives with the velocity of the random gesture of its molecules ; for this ground, if the random gesture of the fluids molecules increase, more heat is generated. Entropy is the term used to show the grade of this random gesture of the molecules of the fluid undergoing a thermodynamic procedure and at the point of highest information ( vapour province ) , higher molecular pandemonium is achieved, and more heat is generated.

Simonson ( 1993 ) elaborated this fact farther, by infering that an addition in entropy occurs when a fluid mixture in an stray system alterations from a non equilibrium province to an equilibrium province. As illustrated in figure 1, if a vapor at 100oC is mixed with another vapor at 50oc in an stray system, with no heat energy loss outside the system boundary, it would blend and settle at an equilibrium temperature over clip, as both fluids internal energy and grade of molecular disorderliness redistribute itself and alterations.

Beginning: John Simonson, 1993. Foundations of Engineering pp 322

Furthermore, sing self-generated burning of fuel, the molecules of the hydro-carbon fuel generates heat one time in the burning procedure ; at this point the single molecules collide in a random, disorganised order. Once the heat has been generated and the energy within the fuel/air vapour mixture used up, it seizes to bring forth any more energy and remains in equilibrium with its environment ; hence, the internal energy within the fluid produced as heat, generated by the random hit gesture of the single molecules of the fluid, is lost to the environment and can non be recovered. On farther analysis, it will besides be observed that at liquid province, there is high possible internal energy and lower information, and while at vapour signifier higher information occurs ; moreover, the alterations in information between both provinces are greater than when in solid or pure crystalline signifier. Thus it can be inferred that the alteration in information between provinces of the working fluid in a procedure is greater than or equal to zero ; this is in conformity with the 2nd jurisprudence of thermodynamics.

Bacon ( 1972 ) supports this construct of alteration and addition in entropy utilizing the Clausius inequality theorem by bespeaking that a alteration in information occurs in an irreversible adiabatic procedure. Bacon ( 1972 ) further suggested that in the event of a reversible adiabatic procedure, no information alteration occurs and entropy peers to zero ; and since information is an look used to demo the ratio of Heat over temperature, mathematically it could be expressed as:

S=Q/T ( where ? ( Q/T ) ? 0 ? S )

Where S= Entropy, Q= heat and T= alteration in temperature [ absolute temperature in Kelvin ] .

Rogers and Mayhew ( 1992 ) analysed the construct of the 2nd jurisprudence of thermodynamics and concluded that the 2nd jurisprudence posits that heat supplied in a thermodynamic rhythm can non bring forth a 100 % tantamount work end product ; This supports the fact that energy is lost to the milieus, and since a alteration of province occurs while energy is converted in an irreversible procedure within a fluid, the information of the fluid alterations between provinces, and can non be recovered but is lost to the milieus. Reynolds and Perkins, ( 1977 ) farther supported this construct by analyzing that a procedure affecting the transportation of heat energy to the environment consequences in a net positive addition in Entropy value.

The context of information in the 2nd jurisprudence of thermodynamic can be explored farther by recognizing it as one of the belongingss used in deducing the province of a on the job fluid. Other belongingss include temperature, force per unit area, heat content and volume ; it is besides one of the belongingss used in ciphering the sum of heat energy generated in a thermodynamic rhythm stage, by mentioning to steam tabular arraies and thermic charts.

Rogers and Mayhew ( 1992 ) shows that although the, the 1st jurisprudence of thermodynamics indicates that heat is converted to work, the 2nd jurisprudence further establishes the fact that energy loss occurs while bring forthing work, and this construct can be illustrated as shown below:

Figure 1

Beginning: Rogers and Mayhew, 1992. Engineering Thermodynamicss


QH =W + Qc ^


QH: The energy Input.

Tungsten: work [ Useful energy ]

Qc: Energy lost in the signifier of heat.

From the illustration in figure 1, the look of heat loss can be derived from information ; therefore mathematically set uping a relationship between information and the 2nd jurisprudence of thermodynamics.

Mathematically ; Q = Sa?†T.

Where S= Entropy, Q= heat and a?† T= alteration in temperature [ absolute temperature in Kelvin ] .

From the expression, it is observed that the Entropy of a on the job fluid during a thermodynamic energy transition procedure, is a map of the value of heat generated in the procedure ; therefore the look ‘Entropy in thermodynamics as a map of heat generated, during an energy transition procedure ‘ is justified. Entropy is generated when a working fluid is non in thermodynamic equilibrium and at a higher temperature from its normal equilibrium temperature e.g. H2O at room temperature compared with superheated steam at 515oC, or liquid methane at -160oC compared with methane vapors at room temperature. As a effect, energy generated in the signifier of heat is lost to the environment ; Furthermore, working fluids undergo alterations in their thermodynamic equilibrium when used in energy convertors ( engines ) to change over utile energy to a signifier of work ; for case, a fuel and air mixture in the burning chamber of a 2-stroke or 4 stroke Diesel engine has a steady information value until self-generated burning occurs at higher temperature prior to the power shot ; It will besides be noticed that while the Piston is at top-dead Centre, there is a higher temperature within the cylinder compared to, when at underside dead Centre of its shot. This instability in temperatures causes the fuel/air mixture to bring forth and let go of energy in the signifier of heat, while increasing the information in the procedure and bring forthing work [ push force ] on the Piston and linking rod.

The mathematical equation derived from the 2nd jurisprudence of thermodynamic and information can besides be used in deducing the value of work and heat in thermodynamic rhythms, and this is considered as portion of design parametric quantities used in ciphering rhythm efficiency ( ?z ) or public presentation coefficients ( COP ) for steam power workss, refrigerating workss, Diesel and flicker ignition engines. Most engine public presentations and matching informations can be illustrated in any of the five thermodynamic rhythms in general usage today, and the value of information is used in bring forthing temperature -entropy ( T-S ) diagrams, which are used with steam tabular arraies and Mollier charts in analyzing energy transition efficiency against energy input and work.

The significance of information can be farther examined by analyzing the alteration in information within the context of the 2nd jurisprudence of thermodynamics utilizing the Carnot and Rankin rhythms.


The Carnot rhythm is a basic steam rhythm for conventional steam engines running on concentrated steam ; the rhythm involves bring forthing steam by heating the working fluid [ H2O ] to its impregnation temperature. The steam generated is so used to power the steam engine and thereafter is condensed, so pumped and reheated.

Figure 2

The Carnot Cycle

Beginning: hypertext transfer protocol: //chemwiki.ucdavis.edu/Wikitexts/HOPE_343/Carnot_Cycle ( accessed 24/02/2011 )

From figure 2, the information and temperature is used to bring forth a diagram exemplifying the thermodynamic procedure happening at each phase of the Carnot rhythm.

At phase 1 to 2: Heat is applied to H2O at temperature ( T H ) over a changeless force per unit area ; thereby increasing information, and bring forthing saturated steam at phase 2.

Phase 2 to 3: The concentrated steam ( working fluid ) is used to bring forth work in a simple steam engine ; it will besides be noticed that while utile energy in the signifier of work is being converted, no information alteration occurs because the procedure is adiabatic.

Phase 3 to 4: The working fluid is so condensed/ cooled in a heat money changer after all the utile energy has be converted to work in the engine ; It can besides be observed that on chilling the working fluid, the information decreases. The rhythm so starts over once more with the H2O being pumped from phase 4 to 1.

Polak ( 1983 ) indicates that the Carnot rhythm satisfies the construct of an ideal rhythm bring forthing work and bring forthing a alteration in information during isothermal enlargement of a working fluid, nevertheless Bacon ( 1972 ) shows that the rhythm is non a realistic construct for gas rhythms due to the fact that its thermic efficiency is soon unachievable. It is of import to observe that based on the 2nd jurisprudence, the information of a on the job fluid is transferred to the environment thereby registering a net addition in information to the environment, or chilling medium in the capacitor. From the illustration of the Carnot rhythm, it can be observed that a alteration in information ( a?†S ) besides registered an energy transportation ( Q ) ; in conformance with the 2nd jurisprudence, non all the energy ( q in ) supplied in the procedure was converted into utile work ; therefore a portion of the energy was lost as heat ( q out ) .

Therefore: Qin=W + Q out

And utilizing algebra ; W=Qin – Q out

Thermal efficiency coefficient ( ?z ) = work/Energy input

E = ( Q in – Q out ) / Q in

E =a?†S ( T ( 1, 2 ) -T ( 3, 4 ) /a?†s T1, 2 ( Carnot Cycle alteration in information is the same at both phases of heat transportation )

E =T ( H ) -T ( cubic decimeter ) / T ( H )

From the illustration of the Carnot rhythm, the belongings of information and temperature has been used in deducing the expression for Work done, heat energy lost and thermic energy efficiency coefficient ; the numerical value of information can be derived from mollier chart or steam tabular arraies if other belongingss of the fluid like force per unit area and heat content is known.

Figure 3: Rankine Cycle

Beginning: hypertext transfer protocol: //commons.wikimedia.org/wiki/File: Rankine_cycle_with_superheat.jpg ( accessed 25/02/2011 )

Figure 3 illustrates the Rankin Cycle, and it is the footing for demoing a more realistic thermodynamic procedure in a steam generating works. Again, the significance of information during the different phases of the rhythm is shown.

Phase 1 to 2: The H2O is pumped at 8 saloon through a series of heat money changers and so on to the boiler at about 220oC where it is heated till impregnation temperature point ; as the H2O is heated, the information bit by bit rises.

Phase 2 to 3: Part of the heat generated in the boiler furnace is transferred to the H2O in the boiler, and at saturated liquid temperature, it begins to boil, till saturated vapour temperature is achieved ; the H2O so flashes off into concentrated steam. It will besides be noticed that as the H2O is heated up, its information rises.

Stage3 to 3* : The concentrated steam is farther heated by the fumes gas from the boiler furnace in the ace warmer, thereby deriving more heat energy, ensuing in an addition in temperature, force per unit area and information. At this phase, dry superheated steam is generated at a temperature of about 515oC.

Phase 3*to 4* : The high energy steam is transferred to the steam turbine where its high force per unit area energy is converted into kinetic energy in the turbine blades, which so spins the turbine wheels ; thereby conveying torsion to the shaft and cogwheel box. As the steam passes each phase of the turbine, energy from the steam is converted into work, until all the utile energy the turbine is capable of change overing is used up.

Phase 4*to 1: The steam is condensed/cooled in a heat money changer and it changes into H2O. As the working fluid passes through this phase, fresh heat energy in the working fluid is lost at the capacitor and information is lost to the chilling medium. Again a net addition in information to the environment occurs, thereby obeying the 2nd jurisprudence of thermodynamics.

The alteration in information of a working fluid in the Diesel rhythm is similar to the description of entropy alteration during self-generated burning of fuel as explained in earlier in this study. The construct of the 2nd jurisprudence and information alteration besides occurs in spark ignition and Jet propulsion engines, illustrated in the Otto and Brayton thermodynamic rhythms severally. However, energy direction engineering over the old ages are being researched and developed in an effort to cut down, circumvent or bound net-energy losingss over a period of clip, by change overing or reassigning a per centum of the energy into another signifier of utile work ; for case the usage of fumes gas from Diesel engines for driving turbo coursers, air current engineering, fuel cell engineering, and even re-introduction of fumes gas into the burning procedure to cut down specific fuel ingestion. But since 2nd jurisprudence of thermodynamics is a cardinal jurisprudence, energy and accordingly information is lost to the environment and can non be reconverted into utile work.


Based on the analysis of information in the context of the 2nd jurisprudence of thermodynamics, it is clear to infer that information can merely be clearly defined by analyzing the molecular activities of working fluids at different phases in a thermodynamic rhythm ; entropy exists as molecular pandemonium, and the heat loss generated from its consequence is non 100 % converted to utile work, but lost to the environment. For this ground, it has besides been established that information is a map heat generated during an energy transition procedure, and it is mathematically expressed as the ratio of heat and temperature. Based on this analogy, it is recommended that information can be reduced by either cut downing the measure of heat loss, or raising the on the job temperature of the working fluid ; with this construct in head, researches are being conducted to happen advanced ways of bettering engine efficiency and cut downing the net information loss to the environment, thereby besieging the 2nd jurisprudence of thermodynamics ; nevertheless, based on the fact that the 2nd jurisprudence is a cardinal rule, it applies to all thermodynamic procedures in energy convertors bing today.


Hi there, would you like to get such a paper? How about receiving a customized one? Check it out