The subjects thermo 1 and 2 of the ME curriculum only revolves around the three laws of thermodynamics. So the whole two semesters (and all the hardships involved, because the teacher wants the subject to sound so difficult :) ) focus on these three laws only. The subject introduces and establishes these laws and then discussions would flow into applications of these into our daily human lives.

What is a law and what is a theory?

A law is a fact of life that we are able to establish by observing the things that are happening around us. We cannot derive it mathematically but we can see its consistent effects. A theory however is a "truth" established by derivation whether mathematically or logically.

So what are these three laws of thermodynamics?

These are actually the physical laws as God designed our universe. We are subject to these laws as well as matter around us.

1. The first law is a concept that we have learned since elementary grades. In its simpliest form, the law could be stated as "energy is not created or destroyed but is transformed from one form or another." This does not include nuclear physics in which energy is formed by the destruction of mass.

2. The second law in its simple language would state that the universe/environment is in a constant state of decay or that the amount of chaos or disorder in the universe is constantly increasing

3. The third law would say that there is a state of zero atomic energy and that is the point where we baseline all our energy and thermal calculations.

If there are some among us who would want to know more about this subject, you may reply to this post and I will try to answer as best as I can.

:thumb: :thumb: :thumb: ... :thumb:

cool topic...

curious lng...

Regarding the 2nd law, is it safe to say that there never been an instance that this increasing decay of the universe ever reversed or stopped at any point in the past (or in the future)?

the first law seems like to have an exception (nuclear physics). should we expect then an exception on the 2nd law?

*:shrug:

*area51 :lol: :lol: :lol: .. i wanted to react pero i will let the thread owner do it....

manung migo raymie....ngayu ako isa ka slot ha... ma react lang ko before mag ubra naman....i will try to do this as briefly and as accurate as i could...

considering time...

nuclear physics mainly talks about halflife and all those stuffs which can happen in long term... while the topic thermodynamics generally talks about what could happen in an instance or in short term....WITHOUT altering the internal (atomic/nuclear structures) of an atom...

its kinda like this... thermodynamics talks about millimeters while nuclear physics talks about lightyears.... :cheers:


---> now balik na ako sa work ko.... :lol:

Actually, the first law is encompassing but I have to explain it in layman's term so the exception. The bearing is that there is now a translation from mass to energy. In the olden days, mankind was able to see physical change (water to ice or steam) involving the rearrangement of molecules. Then we were made aware of chemical changes wherein compounds are formed from elements. These reactions (like combustion or burning) results in atoms combining into different molecule "sets". Then during the course of the last 100 years, we became aware of nuclear changes wherein we are now working in the nucleus of the atom and we now have the knowledge of producing a different element from one existing element (uranium to plutonium, etc). So in summary:

1. physical change - rearrangement of molecules
2. chemical change - formation of new molecules from atoms (electron sharing)
3. nuclear change - formation of new atoms by changes in the nucleus of an existing atom

All these changes involve energy and the first law covers all of these. It is only in the last type however that energy is directly calculated from changes in nuclear mass.


Regarding the second law, only our Creator has the ability to reverse this. Actually, as a student of the Bible, I would say that this law was implemented only (I would hate to sound religious but...) after Adam sinned. That is when our world started to decay. Since then, there is no more perfection but a continuous decay pattern for both living tissue and non-living matter. While we can locally reverse the process like when we put food in the refrigerator, the overall degree of disorder continues to increase because the disorder removed from the food is passed on to the freezer and consequently to the heat radiator at the back of the fridge, plus more due to the additional energy input to make this whole process work. So, can there be an exception to this whole decay process? Nope... at least not from me! *:shrug: :D :P

Pwede mag react of course, ikaw pa. Basta for the sake of knowledge kay tutorial section man kabay.

related to themodymanics

in a class10k cleanroom, you need to have at least 60ACH for an aircon system covering the mfg floor....old iso system uses 20-40 but new iso system made it 60ach (air change per hour)

that means, you need to recirculate the volume of air 60 times in an hour.... :smoke

by computation, V of room, times 60 + leakages + room presurization + total exhaust requirement + IAQ requirement (indoor air quality).... thats a lot of air conditioning unit.... thats also the reason why cleanrooms do have a lot of air handling unit installed.... :thumb:

share ko lang:

algo used by engineers in selecting aircon unit for residential usage:

1 Ton of Refrigeration for every 10-15 square meters.. hence of you have a slightly large room, a 1.0HP aircon will do...

Since nagkadto sa aircon ang aton discussion, I have a question which I have not researched the answer pa.

Why is there a significant increase in the COP of home air-conditioning units being sold today to the older models 10 years ago. The numbers go up to 12, some brands even claiming higher numbers. So the refrigeration load is so much increased without increasing electrical horsepower requirement. In college, we were only computing around 4 to 6. Ano ang rason why we are able to get these numbers now? <_<

try ko to answer....(though my references were left at home to technically inputa data so to speak)

COP is defined as the ratio between the net useful energy ( will call NUE) to the required input power or energy (Pi).

hence COP = NUE/Pi

there are three ways to increase COP.

1. first is to increase the NUE with the same Pi
2. decrease Pi
3. simultaneously do both

for item#1
to increase NUE, means:
1. to use stronger and more effecient refrigerant at lower pressures, notice that for the last 10 years there had been a change in "trend" from R22 (Cholodoflouromethane) to R134A (tetraflouroethane) - remember PH diagram???
at a certain temp the H of r22 is 10.6BTU/lb @38psig while R134A is 12btu/lb@21.1psia... hence it was found that R134A is more likely to be more effecient than R22....

2. Change the structure of heat exchanger (material, configurations, etc)
3. other reasons

Decrease required Pi
--> these will vary from the type of compressor, bearings, lubricants, motor insulation up to paint characteristics, location of the condenser heat ex can also be considered....



will try give factual data tomorrow :thumb:

Sige abi to^. Itemize bi in the form of:

Refrigerant = XX % contribution
evaporator design improvements = YY %
condenser = ZZ %

etc, etc.

thanks. Mayo gid ni nga learning. Anyway, sa office ni misis, I decided to go with the 0.8hp lang. Based on the COP given, more than the 1.3hp na sya sang una nga mga models. It's not that cold pero enough to get the heat out.

ay grabe nga assignment.... sukton ta gid ka prof fee waheheheheehe... :smoke

Ako dapat masukot kay ako gahatag assignment mo. :)

will try my best ah..... kay daw ka detalied gid ang ginapangayu mo bi wahehehehehe :lol:

Ti diin na? :P :P :P

wala ko pa matagaan oras ang ini nga assignment kay ginauna ko ang may mga bayad.... :lol: :lol: :lol: :lol:


pero thermodynamics-related man dyapun..... indi ko diri galing pwede i post kay real life design and estimates....confidential pa... :) :naughty:

Zeroth law of thermodynamics

hehehe... nali malipatan...

"If two thermodynamic systems are in thermal equilibrium with a third, they are also in thermal equilibrium with each other."

Ang pagkanami ni sa iya nga Law ya kay nag gwa lng siya kung san-o naglapnag na ang first 3Laws.... ano pa nangin zeroth law siya hehehe..

this is a law of thermodynamics that is a generalized statement about bodies in contact at thermal equilibrium and is the basis for the concept of temperature.

:)

wala nalipatan ah.. pero damu lang ko ubra lately.... anyway, basi pwede mo mapakita nag diperensya sang operating systems sang R22 kag R134A sa isa pa package type aircon....plot mo kang sa PH diagram....

madugay dugayan ko ni antis maubra kay amu ni ang pamangkut nga ginasabat ko subong ho "How much and how long would it take to build a 5000sqm class 10k, fully facilitized, ready to take on mfg eqpts (mostly ASMs i guess hehehehehehe)..."

means i am doing the first pass design of ahu, chiller, pumps, sewage, rodi, cooling tower, filters, respective piping system, substation, ups, switchgears, panelboards, respective wiring diagrams and sizing kag damu damu damu damu pa gid... .sensya anay kay may bayad ini ya... wahehehehehe

anyone can answer the previous COP question in details will be greatly appreciated para mag move on ang thread... :thumb:

Ti, ibutang ta anay sa higad ni e. Balikan ta na lang liwat. Kadto ta sa third law.

Paano na determine ang absolute point nga zero Kelvin or -273 degrees Centigrade?

close ko AR ko pero indi detalyado sabat ko....


"some" say that they have improved the COP of window type aircon mainly by changing hte compressor from single stage to two-stage, replace materials of heat-ex (IHX, AHX) and adding electronic devices to exhanve the motor draw out current...

as to the details... ti, sad to say, daw wala gid ko oras mag research.... :(

The kelvin scale was derived directly from the Celsius scale, its unit being identical to the Celsius degree, and its scale differing by having its zero at the thermodynamic null (so-called ‘absolute zero’), evaluated as -273.15°C, hence the synonyms absolute temperature scale and (absolute) thermodynamic temperature scale for the kelvin scale. In 1954 the roles were reversed, the kelvin becoming defined as stated above, the Celsius derived from it. The new definition uses the ‘triple point of water’, which had been determined to be very close to 0.01°C and is much more precisely definable than freezing point. The triple point is specified to be 273.16 K which, with 0 K continuing to be the null point, defines the size of the unit. Zero on the Celsius scale is then defined to be 273.15 K rather than the freezing point as such. As with other measurements, marking the triple point is subject to increasing accuracy as technology progresses. Following laboratory evaluations that showed the triple point slightly discrepant from 273.16 K as then established, a minute adjustment to the size of the kelvin was agreed in 1988, to take effect in 1990. (The adjustment applied identically to the degree Celsius, and technically repositioned the Celsius scale.)


source: internet :D

But the question remains. How did we know that there is a state of absolute zero? That means, there is no negative Kelvin possible. How did we know?

hmmm... honga no?.... :panilag: :panilag: :panilag: :panilag:

absolute zero ... or 0 Kelvin.. or 0 Rankine.... is the temperature at which the particle constituents of matter have minimal motion and can be no colder.
Temperature arises from the random submicroscopic vibrations of the particle constituents of matter.

These motions comprise the kinetic energy in a substance. More specifically, the thermodynamic temperature of any bulk quantity of matter is the measure of the average kinetic energy of a certain kind of vibrational motion of its constituent particles called translational motions. Translational motions are ordinary, whole-body movements in three-dimensional space whereby particles move about and exchange energy in collisions.


Thermodynamic temperature’s null point, absolute zero, is the temperature at which the particle constituents of matter are as close as possible to complete rest; that is, they have minimal motion, retaining only quantum mechanical motion.[1] Zero kinetic energy remains in a substance at absolute zero

Yep. The third law. But how do we know that there is such a point when in fact, nobody has been able to get there (zero K)? Why do we believe that it is -273 deg C and there cannot be a -275 deg C? Back to the same question... :)

sabtun ko bwas even palagpat..... may ka chat lang ko wahehehehhe :lol:

sabtun ko na lang gani..... brain teaser ni sa akun.. i need to satisfy your needs... wahehehehehe

there can not be a temperature colder than Zero Absolute (0 Rankine / 0 Kelvin) since at that temperature, all molecules come to hault and does not move, hence no heat can me regenerated.... kenetic energy of the molecules became Zero or abslute null.... to increase or decrease the temperature, you need heat be regenerated...

but how did we know that at -273, the molecules will have no more kinetic energy? Why not at -275 or - 200?

sa mga nabasahan ko is that it was gathered through experiments for ore than a hundred years.... shall i put in here the history of absolute temperature derivation? ;) :D

huo a. good gid nga masabat ini nga pamangkot. all our energy calculations depend on this number. that's why our gas engines are only 16% efficient.

History of Thermodynamic Temperature:


1703-1703 - Guillaume Amontons (1663 – 1705) published two papers that may be used to credit him as being the first researcher to deduce the existence of a fundamental (thermodynamic) temperature scale featuring an absolute zero. His thermometers relied upon the volume / temperature relationship of gas under constant pressure and used a "J" Thermometer BUT his calculations projected that absolute zero was equivalent to −240 degrees on today’s Celsius scale—only 33.15 degrees short of the true value of −273.15 °C.

1742: Anders Celsius (1701 – 1744) created a “backwards” version of the modern Celsius temperature scale whereby zero represented the boiling point of water and 100 represented the melting point of ice. He proposed that zero on his temperature scale (water’s boiling point) would be calibrated at the mean barometric pressure at mean sea level.

1744: Carolus Linnaeus. effectively reversed [34] Celsius’s scale upon receipt of his first thermometer featuring a scale where zero represented the melting point of ice and 100 represented water’s boiling point.

1777: In his book Pyrometrie (Berlin: Haude & Spener, 1779) completed four months before his death, Johann Heinrich Lambert (1728 – 1777)—sometimes incorrectly referred to as Joseph Lambert—proposed an absolute temperature scale based on the pressure / temperature relationship of a fixed volume of gas. Lambert stated that absolute zero was the point where a simple straight-line extrapolation reached zero gas pressure and was equal to −270 °C.

1787: Notwithstanding the work of Guillaume Amontons 85 years earlier, Jacques Alexandre César Charles (1746 – 1823) is often credited with “discovering”, but not publishing, that the volume of a gas under constant pressure is proportional to its absolute temperature. The formula he created was V1/T1 = V2/T2.

1802: Joseph Louis Gay-Lussac (1778 – 1850) published work (acknowledging the unpublished lab notes of Jacques Charles fifteen years earlier) describing how the volume of gas under constant pressure changes linearly with its absolute (thermodynamic) temperature. This behavior is called Charles’s Law and is one of the gas laws. His are the first known formulas to use the number “273” for the expansion coefficient of gas relative to the melting point of ice (indicating that absolute zero was equivalent to −273 °C).

1848:William Thomson - LORD KELVIN, (1824 – 1907) also known as Lord Kelvin, wrote in his paper, On an Absolute Thermometric Scale, of the need for a scale whereby “infinite cold” (absolute zero) was the scale’s null point, and which used the degree Celsius for its unit increment. Like Gay-Lussac, Thomson calculated that absolute zero was equivalent to −273 °C on the air thermometers of the time. This absolute scale is known today as the Kelvin thermodynamic temperature scale. It’s noteworthy that Thomson’s value of “−273” was actually derived from 0.00366, which was the accepted expansion coefficient of gas per degree Celsius relative to the ice point. The inverse of −0.00366 expressed to five significant digits is −273.22 °C which is remarkably close to the true value of −273.15 °C.

1859: William John Macquorn Rankine (1820 – 1872) proposed a thermodynamic temperature scale similar to William Thomson’s but which used the degree Fahrenheit for its unit increment. This absolute scale is known today as the Rankine thermodynamic temperature scale.

1877 - 1884:Ludwig Boltzmann (1844 – 1906) made major contributions to thermodynamics through an understanding of the role that particle kinetics and black-body radiation played. His name is now attached to several of the formulas used today in thermodynamics.

Circa 1930s: Gas thermometry experiments carefully calibrated to the melting point of ice and boiling point of water showed that absolute zero was equivalent to −273.15 °C.

1948: Resolution 3 of the 9th CGPM (General Conference on Weights and Measures) fixed the triple point of water at precisely 0.01 °C. At this time, the triple point still had no formal definition for its equivalent kelvin value, which the resolution declared “will be fixed at a later date.” The implication is that if the value of absolute zero measured in the 1930s was truly −273.15 °C, then the triple point of water (0.01 °C) was equivalent to 273.16 K. Additionally, both the CIPM (Comité international des poids et mesures, also known as the International Committee for Weights and Measures) and the CGPM formally adopted the name “Celsius” for the “degree Celsius” and the “Celsius temperature scale.”

1954: Resolution 3 of the 10th CGPM gave the Kelvin scale its modern definition by choosing the triple point of water as its second defining point and assigned it a temperature of precisely 273.16 kelvin (what was actually written 273.16 “degrees Kelvin” at the time). This, in combination with Resolution 3 of the 9th CGPM, had the effect of defined absolute zero as being precisely zero kelvin and −273.15 °C.

1967/1968: Resolution 3 of the 13th CGPM renamed the unit increment of thermodynamic temperature “kelvin”, symbol K, replacing “degree absolute”, symbol °K. Further, feeling it useful to more explicitly define the magnitude of the unit increment, the 13th CGPM also decided in Resolution 4 that “The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.”

2005: The CIPM (International Committee for Weights and Measures) affirmed that for the purposes of delineating the temperature of the triple point of water, the definition of the Kelvin thermodynamic temperature scale would refer to water having an isotopic composition defined as being precisely equal to the nominal specification of Vienna Standard Mean Ocean Water.



in summary, accodring to the experiments done over centuries by scientist, triple point is at -273.13 degC.....

:thumb: :thumb: :thumb:
Very good gid ni nga researcher si toto Rostan he he he :D :D :D

:lol: :lol: :lol: :lol: ari ko sa meeting mong.... kundi maka browse ako kadali :lol:

Amo na ya! So in short and simple terms:


We were able to "extrapolate" the absolute zero by virtue of observations in pressure and temperature dynamics within a system. Knowing that pressure and volume changes with temperature, and since ratios must be established based on absolute scales, the absolute zero then came to the concept. In the equation P1/T1=P2/T2, changes in pressures associated with measured changes in temperature would easily allow us to calculate back where the absolute zero is.

yes... .sad to say.... all our present considerations were products sang series of previous extrapolations....

on the otherhand.... its good kay may room for improvement pa kita... :thumb:

Abi let us start to examine the thermodynamic feasibility sang isa naton ka gina lauman nga solution sa gas crises. Ang water powered car ni Dingle! Sin-o makasiling nga it is fundamentally impossible and vice versa?

hehehe :D :D :D

ala eh... dapat gali ya tun-an ko man ang electrolysis para maka produce ako hydrogen fuel.... indi pa ko na kabalo ya.... pang elementary lang bala... :lol: :lol: :lol:

derive ko man diri ang formula sand temperatures ah... isa man ni ka bagay nga until now indi ko kasaulo hehehehehe


let:
C = temperature in deg C
F = temperature in deg F

it was believed that the freezing point of water is
in C = 0(zero) deg C
in F = 32 degF

boiling point of water
in C = 100C
in F = 212F

by interpolation






that way indi ka na mag memorize....

:naughty: