Science topic

# Applied Thermodynamics - Science topic

Explore the latest questions and answers in Applied Thermodynamics, and find Applied Thermodynamics experts.
Questions related to Applied Thermodynamics
Question
Recently, we are trying to aluminize a high Cr superalloy at 1000C.
Because of the high Cr(15%) content and activity inside the superalloy, the Cr formed a Cr-rich layer beneath the coating, like a barrier suppressing the Nickel from diffusion outside, and seem to stop the aluminum from diffusing inside as well.
It is probably due to the low activity of Ni and Al in a Cr-rich Ni-Al-Cr system. Does anybody have any papers or an activity diagram that can solve my problem?
Any ideas are welcome.
Question
Can absorption isotherms be used for gas-liquid absorption processes?
In fact, it is actually a bit unusual that with regard to gas-liquid absorption, no names of scholars have been assigned to particular equilibrium curves and their corresponding mathematical functions, other than William Henry.
Question
Can absorption isotherms be used for gas-liquid absorption processes?
The specific surface area and pore distribution of any sample may be obtained from the measurement and analysis of the adsorption isotherm. The gases are always physically adsorbed on the solid surface at low temperatures in the atmosphere of adsorptive gases. According to the BET multilayer adsorption model, absorption isotherms be used for gas-liquid absorption processes.
Question
In theory, martensite (a titanium alloy) begins to form at temperatures ranging from 575 oC to 800 oC. This wide range of temperature reports creates ambiguity in the descriptive analysis of the related phenomena. Therefore, how do you determine martensite start alloy using experimental work (in this case with DSC analysis) and what is the theory behind these determination temperatures?
You are most welcome dear Hasfi F. Nurly . Wish you the best always
Question
Hello,
My reseacrh area is absorbtion refrigeration system with nanofluid. I know how can I calculate the performance parameters of NH3-WATER and LiBr-WATER as a base fluid. But the thing is, how can I integrate the nanoparticles to basefluid to calculate the performance parameters theoretically using Engineering Equation Solver ? I found some articles but they were useless. After adding nanoparticles to base fluid to make a nanofluid, how can I calculate entalphy, entropy, mass flow rate, COP, circulation ratio, variation of rich and poor concentrations, condenser and absorber capacity ?
Question
In the optimization of gas turbine cycle, many researchers have used isentropic efficiency of gas turbine and air compressor as decision variables. Even I did the same. But recently while submitting a paper I got one comment from the reviewer which really made me think.
The reviewer comment:
"AC and GT isentropic efficiency are used as optimization parameters. Are these easily controllable metrics? The other metrics (pressure ratio and temperatures) are but I wonder about the isentropic efficiencies."
How should I justify?
No isentropic efficiencies are not the optimization parameters; there is not much control and also not wide range of this efficiency. It depends on the design of the compressor and turbine. Rather you should treat them as external parameters and concentrate on heat exchanger efficiency (regenerator efficiency), maximum cycle temperature, two or three stage compression with intercooling, reheating point, pressure ratio, etc.
Question
I want to create a Pressure-Enthalpy graph for Methanol in ASPEN. How can I do it?
You can plot just about anything with NIST's REFPROP. Check it out... https://www.nist.gov/srd/refprop (there's free version if you can find it)
Question
I am looking for appropriate research on the process of matching the turbocharger to marine diesel engines. If you know relevant references, books and articles in this field, I will appreciate introducing them to me. Thanks.
Dear Amirreza Javaherian,
Turbochargers
Marine Engines
Question
Where can I find the publication "The theory of moving sources of heat and its application to metal treatments Trans"?
Question
Hello,
I designed a single effect absorption cooling system working with LiBr/H2O in Aspen Plus software. But the exergy flow rates don't seem right. For example, when I try to find the exergy destruction of the pump (and other components), the result is negative. What is the reason of this? My reference conditions are 25 oC and 101.325 kPa.
Hi
I think the exergy of material streams is incorrect, and Aspen does not calculate the chemical exergy.
Best wishes;
Question
This refers to the smooth, labyrinth, honeycomb and brush seals used in steam turbines. If you know some more types, information is also welcome.
i think the article attached will help you a lot to understand.
Question
Hi, I have three constructs of my target protein that I am trying to characterize based on their Thermal Stability. Interestingly, I do not see much of Tm changes except an extra transition peak between them however, I see much of deltaH variability. Does anyone has similar experience?
Although Tm is an easy, convenient index for protein stability and to compare the stability of different proteins constructs and variants, it is quite limited and focusing on Tm alone has important caveats.
It is possible to find two proteins having very similar Tm's and very different stabilization energies at 25 oC. And two proteins having different Tm's and very similar stabilization energies at 25 oC.
The characterization of structural stability, and assessing differences in structural stability, must always involve estimation of the stabilization Gibbs energy (which requires determining, at least, Tm and unfolding ΔH)
Question
Hello dear friends
Kindly I am studying cost variations versus entropy generation for a CCHP system including prime mover, absorption chiller and borehole. There are entropy generation for chiller and entropy generation number(non-dimensional form of entropy generation(EGN)) for borehole. These two criteria are positive and independent each other. Can I study cost variations (vertical axis) versus S+EGN (horizontal axis) in which "S" is chiller entropy generation? Or the S and EGN should be in a same dimension.
regards
Regards
Question
Is there a good heuristic to set the volume interval to calculate pressure along an isotherm? I mean I would like to have a plot that will cover the sub-cooled liquid- two phase region - and super-heated vapor region with good presentation rather than trying to fix the axis limit manually.
The other question is that when using cubic equations of state the pressure inside the two phase region may go below zero. Is there a way to avoid this negative pressure?
Excellent answer from Professor Dudley J Benton . I agree with him and recommend his response.
Question
Earth's atmospheric temperature is increasing faster than climate change models predict. Heat from anthropogenic friction may explain this observation. Conservation of energy dictates that energy used to propel and stop vehicles eventually becomes heat. This previously unacknowledged heat emanates in part from vehicular boundary layer aerodynamics and braking systems. The number of aircraft and ground-based vehicles in use suggests anthropogenic frictional heat may be a significant contributor to global warming. These observations support much wider use of regenerative braking systems.
Any transformation of energy on planet contributes to all
functioning mechanisms of planet.
Question
I want a cost function about thermoeconomic analysis of a pre-burner or fuel-rich combustion chamber. I would appreciate sharing it.
I agree with Ftwi Yohaness Hagos
Question
In case of electron plasma waves we consider adiabatic compression and take gamma equal to 3 [using equation (2+N)/N]. what do we mean by adiabatic compression here?I mean physical significance.
and in case of ion waves we take gamma equal to 1. here we consider isothermal phenomena.
with kind regards,
purvi
In addition to the very completed and interesting previous answer, Dr. Purvi Kikani I would like to add that in MHD the process to take small perturbations is considered isentropic flow meaning that the perturbation in pressure field, delta p = cs2 delta rho with cs the sound speed. That is an adiabatic reversible process to describe magnetoacoustic waves, in a homogenous plasma.
See, for instance, Landau and Lifshitz, electrodynamics of continuous media, 1984, pp. 235, Pergamon.
Question
I need thermophysical and electrical oil properties to investigation of DC discharge in oil.
Are multicomponent mixture models effective and precise in such calculations? If yes, what MC-modells can You suggest?
Thank you a lot in advance!
You may try several engineering models for a reasonable temperature range up to about 600 K to 700 K. Although there are no extensive data measurements for this fluid. The one-parameter friction theory model: https://doi.org/10.1016/S0378-3812(00)00474-X, combined with the Peng and Robinson EoS can give you some reasonable pvT, viscosity, and phase behavior estimations. This approach can also be extended to thermal conductivity.
But for most of the temperature range you are looking at, the octadecane will certainly be degraded. I even doubt you will have any CH4 left at all, as it starts decomposing at about 1000 K.
So, you need to first figure out what compounds you will have left.
But, at such temperatures, you are likely only to have some light gases and C. For the fluid phase, a simple model that may be useful to consider would be the one by Chung et al.:
I would start here.
Question
Basically, it's a cylindrical tube of steel with inlet temperature of milk at 4 degrees Celsius and the outlet temperature would be 72 degrees Celsius. The mass flow rate is 1 Kg/s while the length and diameter of the tube are to be chosen, and the heat energy requirement to fulfill the above conditions is to be found.
Can someone guide me how to proceed. What is the relationship to be used, which would include these parameters, length and diameter of the Tube and the uniform heat energy supplied to the tube to make the temperature reach 72 degrees at the outlet, from the 4 degrees inlet temperature?
Q=m Cp delta T
Question
there is a formula but asks for hydrogen and water content in the fuel, which is hard to find hydrogen contents in that fuel thank you.
these are my fuels 2-Butoxyethanol, Diethyl ether and Ethylene glycol
LHV = HHV - (2.766 x W) kJ/g
Question
How to write the fuel and product exergy balances in the cascade heat exchanger in the cascade refrigeration system?
The definition of fuel and product exergies depends on the chosen reference temperature. For a heat exchanger, possible formulations of fuel/product exergies are shown in the attached figure.
For more detailed information, you can have a look at the following publication:
Question
How can I calculate boiling point of LiBr-H2O according to LiBr concentration ?
Pressure-temperature-concentration can be available in Heat and mass transfer text books. Every chemical temperature and concentration is discussed.
Question
Is it possible to calculate entalphy of LiBr/H2O or another solution if we know correlation of specific heat without using any software?
If you want to solve your problem as it appears in the image, I recommend using an equation of state for the enthalpy departure.
I also recommend the following articles:
-A computationally effective formulation of the thermodynamic properties of LiBr-H2O solutions from 273 to 500 K over full composition range
- Exergy calculation of lithium bromide-water solution and its application in the exergetic evaluation of absorption refrigeration systems LiBr-H2O
-Thermodynamic Evaluation of LiCl-H2O and LiBr-H2O Absorption Refrigeration Systems Based on a Novel Model and Algorithm
-Mathematical Model of a Lithium-Bromide/Water Absorption Refrigeration System Equipped with an Adiabatic Absorber
Question
Why is the enthalpy and entropy values of aspen plus different from engineering equation solver? Are there any conversion methods?
Each software may be using a different reference state.
To check if this is the case or not you can use a simple trick.
Just try and calculate the enthalpy or entropy difference between two states from the two software, (the same two states). If everything other than the reference state is the same, this should give you the same answer.
Question
I have completed uncertainty analysis for my heat exchanger calorimetric lab.but I am not sure the calculation of enthalpy ( it is required for Q=mr*deltaH) due to ref.prop program. Normally my main equation is U=cv*dT+P*v and I have calculated  uncertainity according to temperature and pressure sensor and I admitted constant the value of specific heat and specific weight but these values have a uncertainty due to Refprop uncertanities. I am not sure whether to add this uncertainty. I would like to learn your opinions and advices.

Question
why NIST database in ASPEN PLUS have not LIBR+H2O for experimental data ?
Hello there.
There are many compounds that are not found in ASPEN databases, new ones are incorporated in each version, but many are still missing.
One option that you have is to be able to create pseudo components and add them to ASPEN.
I leave you some tutorial links.
Regards.
Question
I need the following tutorial zip files to learn the basics of the software:
• Using sliding and dynamic meshes
• Modeling solidification
• Using the Eulerian Granular Multiphase Model with heat transfer
• Postprocessing
• Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
• Simulating a Single Battery Cell Using the MSMD Battery Model
• Simulating a 1P3S Battery Pack Using the MSMD Battery Model
Youssef Hmayed Walaikum assalam warahmatullahi wabarakatuhu.
Question
I'm using OpenFOAM to run a CFD study of thermal comfort within a hall. I'm using OpenFOAM v1912 and BouyantBoussinesq(Simple&Pimple)Foam solver. eI have 6 inlets and outlets each with specific flow rates. I specified the flow rates accordingly at the inlet using flowrateinletvelocity BC and at the outlet using flowrateouletvelocity BC. Based on the height, I computed (p-rgh)/rho and fixed it at one of the outlets.
My mesh quality is good (Non-Orthogonality less than 50). The dimension of my hall is 30m *30m *4.5m. It was okay so far when I was doing the simulation for small halls, but I'm facing this problem at the moment.
This happens each time I start the simulation, at the beginning of iterations, p rgh iteration (1st step) reaches 1000 or 2000. The final residual is very high (greater than zero). After the cumulative value (continuity error) begins to rise and becomes greater than 1. The value of Pressure ranges from 1e18 to -1e18 (Two extreme values) even after after 1 or 2 time steps, then the simulation blows off.
I have tried the following options
1)potentialFoam initialization
2)Mesh quality check
3)Defining pressure at all the outlets
4)Using prefcell and prefpoint in fvsolutions to define the pressure in fvsolutions.(if I use this I get continuity error at the start of simulation)
5)Both steady state and transient analysis
6) keeping URF very low and also reltor for pressure to 0.0 in fvsolutions
7)first order and 2nd order fvschemes
7)nNonOrthogonal correction raised to 20.
8) I have turned off turbulence.
9)simplifying the geometry.
I sorted the issue.
1) Yes your correct, but in HVAC there will be exhaust fan that sucks at particular rate. So if we let the flow dynamics to determine, then there is a chance more flow goes to one outlet than other outlet which might change the streamlines. Also in conventional CFD problem, the flow develops and leaves from one outlet. But here we need specific flow rate at each outlet. Also as there is an option (boundary condition) in openfoam to define flowrateoutletvelocity.
2) Yes as you said p-rgh is computed as you said. We have to define it based on the overall height of the domain, then only hydrostatic pressure will be computed correctly. I do accept it is constant, but if we define it 'zero' then the pressure will become negative.
Question
I am trying to model a single-effect absorption refrigeration system using LiBr/H2O in Aspen Plus. Who can help me model the absorption cooling system? Please send a private message.
Sampath Suranjan Salins I am talking about aspen plus not ansys fluent.
Question
How can I define the following mixture in Aspen Plus:
"Potassium formate-Water-AL2O3"
If you know, could you please explain step by step via some screenshots from Aspen Plus ?
Is this Ansys Fluent analysis? its multiphase flow problems. U need to model the packing first the define the desiccant and material. Then apply suitable boundary conditions to solve the problem.
Question
This is a isothermal process , So I need to If the compression ratio of a reciprocal compressor is 4.5, how many compressors are
needed in series to compress air in the cavern?
Hi,
For a near Isothermal process: (PR)^n= Pexeit/Pinlet
(4.5)^n=75/1=75, n~3
Three Compressor is optimum for you.
Question
Although there are already studies in the literature but not much , the use of potassium formate/water or potassium formate+LiBr/Water are not available in the commercial sector for absorption refrigeration systems? what is the actual reason ?
Dear Cenker Aktemur I found a report on the use of potassium formate/water (see attached) in which some severe corrosion problems were observed. They are listed on p. 21 of this report:
Besides very good results in thermal aspect, Freezium and Pekasol 50 exhibits some problems in material compatibility. This could be summarized as:
- We have observed very aggressive reaction to zinc;
- Copper pipes in contact with copper were covered by blue/green (somewhere some white layers formed at the top of this coating);
- All steel surfaces where coating was damaged corroded significantly;
- Some gaskets in valves were damaged and valves leaked.
Question
Although there are already studies in the literature but not much , the use of potassium formate/water or potassium formate+LiBr/Water are not available in the commercial sector for absorption refrigeration systems? what is the actual reason ?
Dear Cenker Aktemur I'm not an expert in this field and therefore cannot provide you with a final answer. However, I found a report on the use of potassium formate/water (see attached) in which some severe corrosion problems were observed. They are listed on p. 21 of this report:
Besides very good results in thermal aspect, Freezium and Pekasol 50 exhibits some problems in material compatibility. This could be summarized as:
- We have observed very aggressive reaction to zinc;
- Copper pipes in contact with copper were covered by blue/green (somewhere some white layers formed at the top of this coating);
- All steel surfaces where coating was damaged corroded significantly;
- Some gaskets in valves were damaged and valves leaked.
Question
I am looking for a formula to calculate specific temperature drop in duct based on airflow, knowing the specific power loss, airflow, thermal properties of the duct, and air temperatures. The goal is to be able to produce the graph attached.
I can digitize the curves and obtain a formula that will accurately reproduce them if that would help. It doesn't tell why or reveal the basis but it's something, perhaps a step toward achieving the ultimate goal.
Question
Looking forward to any research work/ mathematical equations.
Exhaust gas temperature is a function of many variables.
Engines with lower BSFC values typically have lower exhaust gas temperatures because more of the fuels energy is used in the cylinder.
Another important factor is the air/fuel ratio. If excess oxygen is in the exhaust the temperature will be higher.
Camshaft timing, ignition timing, and IN/EX flow ratios during valve overlap are factors too.
I suspect trying to get an accurate exhaust gas temperature will be difficult without having a lot of specific engine parameters.
I have personally experienced exhaust gas temperature variation between cylinders on the same engine of 50C or more.
Question
How to retrieve thermodynamic description for a phase, which is not included in the mobility database in DICTRA? I need thermodynamic description for the phases including Mg2Si, alpha-AlFeSi, beta-AlFeSi, and Al18Fe2Mg7Si10.
On thermodynamic data on Mg2Si, cf.:
A. Nadiradze, I. Baratashvili, I. Pulariani, K. Ukleba, "Thermodynamic probability of realization of the process of silicon dioxide reduction by magnesium at high temperatures", Bull. Georgian National Acad. Sci., 3(2), 2009, 95-99.http://science.org.ge/old/moambe/vol3-2.html
Y. Ben-Hai, C. Dong, "Phase transition, structural and thermodynamic properties of Mg2Si polymorphs", Chin. Phys. B, 20(3) 2011, 030508 (9 pp.); DOI: 10.1088/1674-1056/20/3/030508
Question
Hello,
I am simulating gas flow from a high-pressure (700 bar) to a low-pressure container as shown in the attached figure. The red curve shows the pressure curve obtained from the testing, while the blue curve shows the pressure curve of the lo-pressure container. I tried to change parameters and simulate, but still I end up getting more or less linear pressure curve from the simulation. I am unable to understand the root cause for the deviation.
2. After 30 to 35 ms the pressure of high-pressure container has to be 300 - 400 bar from the testing. In simulation it reduces just to 630 bar which is not acceptable.
Mass Flow Rate (MFR) has to be close to 500 g/s . This value is matches with the simulation. Only pressure behaviour is not matching.
Please find attached image for the simulation and problem details.
Any lead on suggestions are highly appreciated.
Naveen
First, I think you should investigate on the Gas model.Second, what is the value of the Mach number ? Have you used a pressure or density based solver for the simulation?
Question
I am looking for paint or in an extreme case a coating material on inAtmosphere flying object to reduce the heat dissipation caused by aerodynamic heating for a relatively longer period, considering the speed range of upper hypersonic range.
Question
I need to calculate exhaust gas temperature at the engine exhaust valve outlet theoretically since I do not have teh luxury to calculate it using EGT thermocouple sensor. Any research references/equations will be helpful.
You may find the theoretical calculations for ICE in any thermodynamics textbook. However, there are several losses that need to be considered when applying theoretical thermodynamics analysis: incomplete combustion, heat transfer losses in connections, etc.
Question
I am working on calculating the exhaust temperature in the upstream and downstream section of an IC engine catalytic converter. Please share any methodology or research article to corroborate your response.
Highly grateful.
Do you mean between the exhaust valves, the exhaust manifold, and where the CC is bolted on? And between the outlet flange of the CC, the front pipe, muffler, and tailpipe? Why not just put a thermocouple on either side of the CC and measure the temperatures? I'm sure this is different for every car design and also operating conditions. The heat loss will also vary from case-to-case.
Question
How can I theoretically calculate the mass flow rate of nanofluids such as WATER+AL2O3 ?
Equation of Nanofluids
Density .........................(1)
ρ_nf = (1-φ)ρ_f + φρ_s
Heat Capacitance ..............................(1)
(ρC_p )_nf= (1-φ) (ρC_p )_f+𝛗(ρC_p )_s
Thermal Expansion Coefficient .............................(1)
β_nf = (1-φ)β_f + φβ_s
Thermal Diffusivity ..............................(1)
α_nf =Κ_nf/(ρC_p )_nf
Effective Thermal Conductivity ...............................(1)
Κ_nf/Κ_f = (Κ_s+2Κ_f-2φ(Κ_f-Κ_s))/(Κ_s+2Κ_f+2φ(Κ_f-Κ_s))
Viscosity ..................................(1)
Brinkman model
µ_nf = µ_f/〖(1-φ)〗^(2.5)
Pak and Cho correlation
µ_nf = µ_f ( 1+39.11φ+533.9φ^2 )
Reynolds number
Re= 4Ϻ/(π.D.µ)
Ϻ= (Re.π.D.µ)/4;
where,
[M= Mass flow rate]
[Re= Reynolds number]
[D= pipe diameter]
Reference
1. Combined convection flow in triangular wavy chamber filled with water–CuO nanofluid: Effect of viscosity models
Question
Dear all,
probably it is a silly question.
I need to create a solution with a fixed quantities of N, P, K starting from different sources: NH4NO3, (NH4)3PO4, KNO3.
Namely, I have to reach the concentration 4,28M for N, 0,846M for P and 1,275M for K.
I am starting my calculation, but I suppose that I need partial volume tables of this system to take account volume variation during the mixing.
Apparently it is a silly exercise but when we analyze our solution we observed strong deviation from the ideal solution.
As anyone performs this kind of solution? It is the creation of "liquid fertilizer" from solid ones. I want to generalize this calculation to different concentration to implement in a project that I follow.
You may consider to predict the solubilities for the NH4NO3, (NH4)3PO4, KNO3 salts for their joint/mixed aq. solutions, which can be predicted after those for each single salt saturated solution, which presumably, are more readily available in the literature. That may be achieved as follows:
i) Being SNH4NO3 the solubility for NH4NO3 given in terms of molarity for its single salt saturated solution, KspNH4NO3 = [NH4+]*·[NO3-]* = (SNH4NO3)2; where C*NH4NO3 = [NH4+]* = [NO3-]* = SNH4NO3. Here C stands for formality and saturation is denoted by *.
ii) Simillarly, for a (NH4)3PO4 single salt saturated solution: Ksp(NH4)3PO4 =([NH4+]*)3·[PO43-]*.
iii) While for a KNO3 single salt saturated solution: KspKNO3 = [K+]*·[NO3-]* = (SKNO3)2; where C*KNO3 = [K+]* = [NO3-]* = SKNO3.
iv) For NH4, cation hydrolysis translates as: NH4+ + 2H2O ⇌ NH4OH + H3O+. For NH4OH ⇌ NH4+ + OH-, KbNH4OH = 1.80·10-5 = [NH4+]·[OH-]/[NH4OH]. For the hydrolysis equilibrium: KhNH4+= [NH4OH]·[H3O+]/[NH4+] = Kw/KbNH4OH = 5.56·10-10 (Kw = 1.00 x 10-14); units were omitted. Ammonium balance writes: C(NH4)3PO4 = 3·{[NH4+] + [NH4OH]}.
v) For PO43-, anion hydrolysis writes: PO43- + H2O ⇌ HPO4-2 + OH-; KhPO43-= Kw/Ka3H3PO4 = 2.4·10-2, where stands for the 3rd dissociation constant of H3PO4. Phosphate balance writes: C(NH4)3PO4 = [PO43-] + [HPO4-2].
vi) Species H2PO4-, H3PO4, NH3, and HNO3, can be neglected.
vii) Unlike the solubilities for single salt solutions; KspNH4NO3, Ksp(NH4)3PO4, and KspKNO3 can be accepted to apply also to the joint salt solution. In this case, common ion effects should be accounted for.
viii) The solubility of each salt in the joint salts solution, also given in terms of molarity (here denoted by SNH4NO3, S(NH4)3PO4, and SKNO3), can be predicted considering that for saturated joint (†) salt solutions we should have:
SNH4NO3 = C*NH4NO3 = , S(NH4)3PO4 = C*(NH4)3PO4, and SKNO3 = C*KNO3.
ix) Nitrate balance for the saturated joint salts solution writes: C*NH4NO3 + C*KNO3 = [NO3-].
x) Ammonium balance for the saturated joint salts solution writes: C*NH4NO3 + C*(NH4)3PO4 = 3·{[NH4+] + [NH4OH]}.
xi) Phosphate balance for the saturated joint salts solution still writes: C*(NH4)3PO4 = [PO43-] + [HPO4-2].
xii) Each salt (interdependent) solubilies can now be predicted for their joint solution. There are two degrees of freedom that can be fixed. We can arbitrarily fix the concentration of two of the salts, below the saturation limit for each salt single solution, to then predict the solubility of the other salt in the joint solution.
Question
How can concentration in terms of rich and poor be affected by adding nanoparticles to LiBr-Water?
Dear Kenkar,
In diffusion absorption coolers regarding to the heat performance of the system, ammonia/water couple with alumina (Al2O3) particles in nano-size can be a better option. It can provide better absorption of heat from the generator and faster evaporation of the cooler from the cooling/absorption fluid. Considering the effect of fluids containing nanoparticles the connection units of the heat transfer in the system operation time of the system might be reduced due to shorter heat transfer periods.
Ashish
Question
For calculating packing area, packing height and volumetric heat transfer coefficient is necessary. In my case study, I have the information of packing height in my hand. But I am looking toward to get the specific method to calculate volumetric heat transfer coefficient or get the data of volumetric heat transfer coefficient for Natural draft cooling tower.
I have been in and out of such plants and cooling towers all over the world for the past 40 years. I have written extensively on the subject and also developed the computer program (FACTS), which is the industry standard. You can get many of the papers and the software free at my web site http://dudleybenton.altervista.org/index.html
Question
I know that-- Temperature,Pressure,Density increases. Total temp, total enthalpy remains constant. Total Pressure increases. But why it happens?
1. Why total temp remains same but static temp increases?
2. If total temp remains same, then why total Pressure get increased?
3. Static temperature increases but total temperature remains same because the kinetic energy part of total temp transform into thermal energy and due to that static temperature increases but total temp remains same. For pressure, static pressure increases but total pressure decreases. If we explain that the kinetic energy part of total pressure transform into pressure energy, so that increasing the static pressure. As we have seen in the case of temperature. Then the total pressure should remain same. Why it is decreasing?
4. I have learned that we do not apply or extract work from flow across shock wave. Then how the static pressure & temperature increases though the process is adiabatic? Shock wave is not doing any work on the flow, then why we say that across shock wave flow gets compressed?
5. As soon as the flow approaches the shock wave, what exactly happens inside the flow? Pressure gets increased or temperature gets increased first?
Sorry for this long question list in one page.
I do agree with Markus J. Kloker .
I wanted to add an explanation, but I found the answer by dear Markus J. Kloker a complete one.
Question
May I ask a question on thermodynamic? We know that U(V,T) (caloric eq. of state) and S(P,V) (thermodynamic eq of state) can both be derived from thermodynamic potentials (U F G H) and the fundamental relations. However, U(V,T) doesn't hold full thermodynamic info of the system as U(S,V) does, yet S(P,V) also holds full thermodynamic info of the system.
In which step in derivation to get U(T,V) from U(S,V) lost the thermodynamic info? (the derivation is briefly：1.  derive U=TdS+ PdV on V, 2. replace the derivative using Maxwell eq. and 3. finally substitute ideal gas eq or van der waal eq)
Why the similar derivation to get S(P,V) retain full thermodynamic info?
Even if we only have U(T,V), can't we get P using ideal gas eq, then calculate the S by designing  reversible processes from (P0,V0,T0) to (P',V',T')? If we can still get S, why U(T,V) doesn't have full thermodynamic info?
Natural variables for U: S, V, Ni (for simple systems)
Natural variables for S: U, V, Ni (for simple systems)
T is the partial derivative of U with respect to S, maintaining V and Ni constants:
T=(∂U/∂S)V,Ni
If from the fundamental relationship U=U(S,V,N) you replace S by T just by solving for S in T=T(U,S,V,Ni) and substituting in U=U(S,V,N), then, you loose information because you are replacing a variable with a derivative with respect to that variable.
This problem is worked out with the Lengendre transform. If you search on internet, you may find simple examples: how to change y=f(x) to z=g(p), where p is ∂y/∂x=2x, in the two ways, the incorrect one (calculation of p and plain substitution of p by removing x) and the correct one (calculation of p and applying the Legendre transform, z=g(p)=px-f). In fact, because you do not loose information with the Legendre transform, you may go backwards from z to y, which is not possible with the incorrect way.
Therefore, it is a mathematical "trick".
Applying the Legendre transform to U, with respect to T and S, you get a new thermodynamic potential F=U-TS, the Helmholtz energy, whose natural variables are T, V, and Ni. Beware of the minus sign applied to the Legendre transform (i.e., F is not equal to TS-U, but U-TS).
For a system at constant U, V, and Ni, any possible process will maximize S.
For a system at constant S, V, and Ni, any possible process will minimize U, but not F.
For a system at constant T, V, and Ni, any possible process will minimize F, but not U.
The Legendre transform connecting two thermodynamic potentials parallels the Laplace transform connecting the corresponding partition functions.
The Legendre transform is not only employed in Thermodynamics and Statistical Physics, but also in Classical Mechanics and other fields.
Question
The Carnot cycle is a theoretical thermodynamic cycle proposed by Nicolas Léonard Sadi Carnot in 1824 and expanded by others in the 1830s and 1840s. It can be shown that it is the most efficient cycle for converting a given amount of thermal energy into work, or conversely, creating a temperature difference (e.g. refrigeration) by doing a given amount of work.One of the great virtues of the Carnot cycle is its potential applicability to any working substance.The Carnot cycle for a photon gas provides a very useful tool to illustrate the thermodynamics laws and it is possible to use for introducing the concepts of creation and annihilation of photons in an introductory course of physics.
Interesting thread Dear Prof. Manuel Malaver de la Fuente
I taught stat physics several years & I never asked or heard students asking about this possibility. So both distributions Fermi Dirac & Bose Einstein allow to build a Carnot cycle.
I guess that for electrons it is possible since they carry heat inside a solid (electronic heat transport & electronic specific heat), for phonons is the same
(lattice heat transport & lattice thermal heat) but for photons? Interesting, I thought photons only induce radiation in the atmosphere.
Question
What is the thermal conductivity value of graphite in the xy plane? I've seen several papers with different values so is it 100s or 1000s at room T?
The thermal conductivity of graphite depends on the anisotropy of the layers but generally it varies from 25-470 W/Mk.Generally it is “GraphiteTIM(Compressible Type) with thermal conductivity : X-Y direction 390-400W/m∙K, and in Z direction (28W/m∙K).
Why this is different?
However, controlling the orientation of GFs still remains a challenge. The corresponding thermal conductivity is as high as the thermal expansion will be less.
Reason Property
Because of the weak binding and the large lattice spacing in the c-direction, the phonon spectrum of graphite is approximately two-dimensional for frequencies above f c = 4 THz. Thus one can model the a-plane thermal conductivity by a two-dimensional phonon gas. That’s why in XY plane conductivity value is high and it is anisotropic when we compare with Z plane.
Hope it is helpful for you.
Ashish
Question
what are the drawbacks of using R744 in cascade refrigeration systems compared to R41?
Dear Nicholas,
That is true., By taking care of R41 which is flammable , performance value can be increased.
Ashish
Question
Hello to all:
I'm trying to think in the following interesting problem:
I have a system which are polycrystals (grains) of Bi2Te3 (actually this compound is a quaternary alloy of Bi, Te, Se and Sb). The grains ended coated with Carbon, in the form of Graphene Nanoplatelets: a stack of several (or could be many) Graphene single Layers.
Does anyone know, have experience or have literature references about the following questions:
1. How an increment in temperature will affect the Chemical Stability of the Bi2Te3-alloy ? for two scenarios:
i. A normal day-to-day working temperature between 10 °C - 37 °C
ii. Or in the scenario reaching the 100°C
And second. The same question but for the aging of the device, rather than the stability in function of the temperature.
or for both conditions for the matter of the subject.
If someone can comment something about, I'll appreciate it !
Best Regards !
The interface between two phases is very important (regarding to Subhasis's answer)
DOI: 10.1016/j.diamond.2019.107561
Question
Dear Colleagues :
Does anyone have literature referencing the diffusion process of Carbon (I mean Carbon atoms) into Bismuth Telluride (Bi2Te3) or into some other compound alike ? E.g. PbTe, (Sb,Se)Bi2Te3, Sb2Te3, etc ... ?
I'll really appreciate if someone can help me out
Kind Regards Sirs !
Question
A mixture of gases 11% CO2 - 89 % N2 (molar) at a temperature of 300 °C and total pressure of 1400 psi. ¿CO2 and N2 at these conditions are in the gas phase or in supercritical state? I mean, ¿what is the pressure to determine the behavior of each component (CO2, N2)?
The subject of fluid behavior is broad and diverse. I cover this at some length in my book, Thermodynamic and Transport Properties of Fluids, which will be free on 3/24/2020. https://www.amazon.com/dp/B07Q5L1CHT The software is always free at http://dudleybenton.altervista.org/software/FluidProperties.zip The fact that these gases are supercritical actually makes your work in this case easier.
Question
I am working on absorption refrigeration system using LİCl-H2O. I used state points of a article. I confronted a problem using Engineering Equation Solver (EES). Error showed by EES: This equation attempts to raise a negative number to a non-integer power.How can it be fixed ?
I haven't seen the equation, but I would imagine there are many better ways of solving it than EES. Many common equations can be solved with Excel. If you can't force EES to consider only positive values, you can simply make a change of variables. For example solving for (a^2)^(b/2) is the same as a^b except that you always have a positive result.
Question
I wish to understand how to integrate Yokozeki Equation of state for solids or any cubic equation of state in order to derive the fugacity expression for a pure component or mixture.
I discuss every cubic EoS in this book, https://www.amazon.com/dp/B07Q5L1CHT, which is free on 1/8/2020, 1/16/2020, 1/24/2020, and 2/1/2020. The software (C source code) and VBA (Excel spreadsheet) for every one is free here: http://dudleybenton.altervista.org/software/FluidProperties.zip This includes fugacity, residual enthalpy, and residual entropy too. I also compare 15 of the most common EoS for several measures against real data.
Question
If I want to calculate the energy use of an AHU fan, knowing the maximum airflow, fan efficiency, and static pressure, what would be the most accurate way?
Thanks!
I fully agree with Paul, as long as actual airflow rate and the corresponding actual pressure difference are used.
Question
We all know thermal conductivity / diffusivity of solids (metals, insulators, semiconductors) is a function of temperature. However, does it depend on mechanical stress, e.g. uniaxial? Has someone ever measured this?
UPD: I have actually just seen some papers on the stress dependence of thermal conductivity in semiconductors (e.g. Ramdane, A., Salce, B., & Challis, L. J. (1983). Stress dependence of the thermal conductivity of Cr-doped GaAs. Physical Review B, 27(4), 2554.); I think it's more or less clear that stress changes the density of electrons in the conduction band and hence the effect. However, it's not clear to me whether there is any effect of stress on the thermal conductivity of metals where the electron density is much greater than for semiconductors and the Fermi surface is simply spherical. Any thoughts on this?
Thermal conductivity refers to the intrinsic ability of solids to ensure that products behave as expected when subjected to thermal stress. Thermal stress is stress created by any change in temperature to a material. ... This type of stress is highly dependent on the thermal expansion coefficient which varies from material to material. In general the larger the temperature change, the higher the level of stress that can occur.
Question
I am fabricating magnesium composite by reinforcing alumina nanoparticles. in this connection, I want to estimate the shooting temperature (temperature rise) while incorporating the ceramic particles in magnesium at molten state. I am in need of your valuable suggestions.
Thank you all for spending your valuable time.
Question
Hi all,
I am trying to use my code in EES software and link it with Matlab to do multi-objective optimization without rewriting the code again. Does anyone know any methods or approaches?
Thank you,
Thank you C K Gomathy . Still did not work with me.
Question
I have a solar field. and I have a system.
I want my system to work in a steady state condition, but the nature and the base of solar energy is intermittent.
How can I use solar energy as a non-intermittent source? What system do I need between my solar collector and my system?
For instance, consider the following example: Solar field+ORC cycle 1 kW electricity is needed in a steady state way, but solar energy is not steady-state. What system is required between the solar field and the ORC cycle?
*I know that I should use a TES, but which one is good for this purpose?
All answer above involve usage of storage unit for electrical energy, since the question intermittent, basically we want to create constant heat source. Apart from storage, one can focus discussion on efficiency of conversion. Efficiency is kept steady, might also result in constant heat source.
Now, efficiency will depends on solar cell material, which is pretty much saturated from design point of view. Next, will be to maximize the amount of incident sunlight on solar array, which will ensure output power above certain limit i.e. a limit higher than required, so that a portion of energy is stored in storage device, utilized in extreme cases.
Now, how do we maximize amount of incident light ?. Nature provides a solution in the form of sunflower. Sunflower like few other plant, has ability to respond to incident light and change it's direction of top head at different times of daylight time to receive maximum amount of solar energy for photosynthesis.
On similar line, a solar cell array can be mounted on flexible gyro and motor coupled, with combining electronics, we can create a closed loop system, which allow solar mount to rotate and decide optimum orientation for maximum sunlight incidence. gyro would be used to create 3-d map that would have a plot of orientation vs power generated. Power generated can be calculated using a load resistance similar to electrical engineering.
In this way, we can create a closed loop mechanism, targeting maximum power at certain time in daylight, resulting maximum conversion and storage and ensuring that power staying above required levels.
Question
Guys,
I've seen the Modified Arrhenius equation in several forms. For instance, three kinds are attached.
Please consider the first attachment. There is an activation energy (Er). In some cases, authors do not use this form and they use the form just like two other form (see ar-2 and ar-3). They use "thetha" or "Tar". Now, I need to calculate Er from thetha/Tar. I think I have to multiply thetha or Tar by R. Am I right? R is universal gas constant and here its unit here is J/kgmol-K. I guess it should be 8314. Am I right?
Roh,
I'm happy you find your answer. But note that everybody is free to answer as they desire. It is up to you to decide which one work for you. Their answers are also valuable but might not point out what you meant. Then simply ignore them. They may be of interest to other people who have a similar question in the future.
Good luck.
Question
Dear scholars,
I'm working on a project that uses some waste heat to provide the motive steam for multi-effect desalination with the thermal compressor.
Pressure, Temperature, and flow rate of the motive steam are known. I need to calculate the amount of salt-free water and detailed state of the effects.
I would appreciate if anyone can help me with Matlab or EES code.
Question
Let's say I have a material with a stable phase A that transitions to another stable phase B at temperature T. If the material also has a metastable phase A', I know that if I cool B fast enough I would get:
B -> A'
and if I cool very slowly I'd get
B-> A.
If I were to look at the interface between B and the new phase and somehow extract all possible information (energy/mass transfer, etc), what signal would indicate to me that I would expect A' (metastable) to form over A?
When you refer to thermal gradients you propably refer to solidification processes. For these the temperature gradients are very important as the interface velocity is usually determined crucialy by the transport of the latent heat. Here, of course, special literature exist, but beyond what is taught in general lectures I cannot help much. Your reference to "metallurgy books" seems that there you looked at the soldification sections.
If you are more interested in solid-solid transformations, usually the thermal gradient is less important, simply becausee the latent heat associated with the transformations is much lower than for solidification (the invariant parameter is actually the transformation entropy, connected with the transformation enthalpy via the equilibrium transformation temperature). In that case there is a huge amount of concepts to describe phase transformation kinetics. Porter Easterling is a good starter (having also solidification sections). Models are of course on very different levels. If you want to find much more, you may refer to Christian.
Question
I have seen phase separation as a phenomenon taking place.However I do not understand why this phenomenon occurs as a counter example to the natural laws of diffusion along the concentration gradient.During phase separation the richer side becomes richer with the atoms which it already has and becomes more and more deficient with the poorer atoms and vice-versa.Similar things will occur in the opposite case as well.Now please give me an insight to this phenomenon with close reference to factors like Chemical Potential etc.
Phase separation and Coarsening are well known natural phenomena and important in physical chemistry and metallurgy. I would suggest you to go through the theories of spinodal decomposition which is also known as uphill diffusion (that is associated with negative diffusion constant). Ostwalds ripening is yet another example. Below I refer to some of the seminal works in these topics.
1. Cahn, John W., and John E. Hilliard. "Free energy of a nonuniform system. I. Interfacial free energy." The Journal of chemical physics 28.2 (1958): 258-267.
2. Langer, James S. "Theory of spinodal decomposition in alloys." Annals of Physics 65.1 (1971): 53-86.
3. Oono, Yoshitsugu, and Sanjay Puri. "Computationally efficient modeling of ordering of quenched phases." Physical review letters 58.8 (1987): 836.
And a video lecture
Question
I am looking for binary diffusion coefficients of water vapour in air at normal pressure for various water/air temperatures. I found the following relation
Diff (T) = 22.5*10-6 (T/273.15K)1.8   [m2/s]
However, no reference is given, where it comes from. Do you have an equation or coefficients in tabular format or a reference for the formula shown above?
You are right, Mohiuddin Ahmad. But this is a problem of the Researchgate web-site. The '-' disappears and reappears depending on the format in which you view the initial question. Better this way?
Diff (T) = 22.5E-06 * (T/273.15K)^(1.8)   [m*m/s]
Question
Hi again, while working on the carbon capture methods from a renewable energy project, i realized that thermodynamics has somewhat of a huge role to play when discussing gaseous capture, what are some of the available methods such as OxyFuel where co2 and o2 can be captured however but aren't energy intensive or are very low energy requiring methods?
Hai,
Carbon dioxide capture allows separation of CO2 from gas streams, allowing it to for post-combustion CO2 capture (PCC) as it has lower regeneration energy and include post-combustion capture, pre-combustion capture, and oxygen fuel or .Several methods, if not all, have been of interest to process intensification .. This is the thinking behind the oxygen approach, where instead of air, the power plant is fed approaches in use today requireclean-up of the NOx and SO2 prior to CO2
Best Wishes..
Question
Hello all,
This is in continuation of previous question wherein I had asked about applications of near-critical fluids. Most of the applications suggested to me were pertaining to chemical extraction, drying etc.
Does any one know about applications of these fluids space technology. Are there any applications which involve movement of these fluids from sub-critical to super-critical state?
Thank You
The transcritical CO2 refrigeration/heat pump cycle is a good example of an application where the fluid is in the near-critical region.
The refrigerant gas is evaporated and then compressed from the sub-critical pressure (Pcrit = 73.9 bar ) in a compressor to the over-critical pressure.
The heat transfer process when cooling the supercritical fluid is very efficient, and is taken advantage of in CO2 hot water heat pumps.
See this papers for more information and basics on the transcritical CO2 cycle:
- "Current Status on Heat Pumps With Carbon Dioxide as Working Fluid" by P. Neksa
Question
I am looking for material which can replace aluminium in aerospace industry as i want material which will be having high melting point and must be light in weight. As i am looking at this from commercial point of view so if that material is easily available and cheap then it would be better. Especially Aluminium 7075
Question
what could be the cause of negative average/total entropy?
1，The second law of thermodynamics is incorrect. See figure below for details.
2，The system is isothermal and exchanges heat with a large heat source to keep the temperature constant. Only volume changes are discussed.
3，The problem here is that the actual system is balanced and the second law of thermodynamics judges it to be unbalanced.
Question
I have a combustion equation with C3H8 as fuel in a rich operation regime. I want to maximize H2 and CO. How can I do this 2 together? If I maximize them at the same time I get a equivalent ration of 3,33 but if I do it just for CO I get a equivalent ratio of 1,43
I am happy I could help. Best of luck for your research
Question
I got YFeO3 and Fe2O3 by heat treating mixed powder of Fe2O3 and Y2O3 at 900C in the air. It seems that the reaction YFeO3+Fe2O3=Y3FeO12 did not happen in this situation. Should I increase the temperature or reduce the O2 pressure?
Dear Yaoshu Xie:
According to Y2O3-Fe2O3 phase diagram the stable region of Y3Fe5O12 (YIG) is very narrow and to obtain pure YIG phase. So first, take a deep consideration on the stoichiometry of the mixture and to prevent the formation of YFeO3 you can add about 5 wt% excess Fe2O3(see the literature below) . The second point is about the temperature. To obtain pure YIG phase it's better to calcine the mixture at about 900-1100 C and after that, the sintering process should be done at about 1300-1400 C.
"The behavior of high frequency tunable dielectric resonator
antenna (DRA) with the addition of excess Fe2O3 in Y3Fe5O12
(YIG) formulation"
Question
Consider the most conventional 2D phase diagram where temperature is plotted along the y axis and composition of carbon along the x axis. Phases are mapped on the phase diagram if they are thermodynamically stable at some (x,y). but between 1044K(curie temperature) and 1185K  paramagnetic beta phase is more stable than ferromagnetic aplha phase.