Questions related to Engineering Thermodynamics
I have implemented in Matlab a code that calculates the excess Gibbs energy for a given compound in a mixture.
The goal would be to compute the binodal curve for an ATPS system, by equaling the chemical potential of each component (3 in total) in the hypothetical top and bottom phases.
I did this by using fmincon. I fixed the polymer (PEG) concentration on the top phase and then 5 equations were solved to obtain the other 5 variables:
Sum of volume fraction top phase = Sum of volume fraction bottom phase = 1
Chemical potential i top = Chemical potential i bottom
However, every time the algorithm is run, different solutions are obtained and I think it's due to the high nonlinearity of this problem. Could you provide me a better strategy to obtain the binodal curve?
I have a 750 ml reactor and working volume is 300 ml. my working temperature is 350 C. By using ideal gas law i found at the pressure to be around 2 bar. But I need final pressure build up @ 350 C to be around 25Mpa in order to keep my solvent in liquid phase. So, how should i calculate the initial head space pressure required. I'm planing to use N2 gas for pressure build up
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 ?
In what case would a reaction rate always show direct relation with activation energy or would it always be an inverse relation? Is it a indirect relation, inverse relation or both case can hold? (Please provide supporting resource, thank you).
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.
I want to have these components in a hybrid renewable energy system (energy storage (thermal energy storage or CAES), solar collector or solar PV, solar reactor, wind turbine, CCHP plant, biomass boiler, etc.) Exergy and energy analysis is going to be performed in my project, Thanks for your participation.
I am doing CFD analysis of waste heat recovery from flue gas to remove moisture content from coal particle. I think This is problem regarding Discrete Particle Method In fluent. But Hoe to add Moisture content in in coal particle which is 50% . ?
I would like to create my own TYM2 file to run TRNSYS simulation with my own meteorological data. How should I create my weather data file?
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.
For a liquid fuel, whose composition is undetermined, given its ultimate analysis as C-x%, H-y% etc., in a temperature and pressure other than the environmental pressure and temperature, How its physical exergy, particularly enthalpy and entropy can be calculated? Any documentation related to the answer would be much beneficial.
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.
I have start my study about MD simulation of Refrigerant condensation. I am studying the LAMMPS software for my MD simulation. But I am not clear that how I could write a input script in LAMMPS for a particular refrigerant for example R600a in the capillary tube system and how to create the potential file of the Refrigerant?
Heat and Mass Transfer, Engineering Thermodynamics, Automotive Engineering, Power plant Engineering
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?
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 !
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 !
Maxwell Boltzman distribution is ni/gi =e-(εi−µ)/kT. In quantum mechanical case, +/-1 is added at the end of kT. (+) sign is for Fermi-Dirac distribution and (-) is for Bose-Einstein distribution. I want to know what is the physical significance of these signs and how can we relate this to classical (Boltzman) distribution.
After some literature review and from a turbomachinery course I identified the following limiting design parameters,
- Minimum size of last row of high pressure compressor ( about 10 mm ? )
- Maximum temperature that can be tolerated by the machine's disks (about 950 K)
- Maximum temperature allowed for effective turbine blade cooling
Are there any other? Is there a maximum allowable pressure for combustion? Is there a maximum pressure that can be handled by the turbine's outer walls?
Thank you very much in advance
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)?
I hope this question seems interesting to many. I believe I'm not the only one who is confused with many aspects of the so called physical property 'Entropy'.
This time I want to speak about Thermodynamic Entropy, hopefully a few of us can get more understanding trying to think a little more deeply in questions like these.
The Thermodynamic Entropy is defined as: Delta(S) >= Delta(Q)/(T2-T1) . This property is only properly defined for (macroscopic)systems which are in Thermodynamic Equilibrium (i.e. Thermal eq. + Chemical Eq. + Mechanical Eq.).
So my question is:
In terms of numerical values of S (or perhaps better said, values of Delta(S). Since we know that only changes in Entropy can be computable, but not an absolute Entropy of a system, with the exception of one being at the Absolute Zero (0K) point of temperature):
Is easy, and straightforward to compute the changes in Entropy of, lets say; a chair, or a table, our your car, etc. since all these objects can be considered macroscopic systems which are in Thermodynamic Equilibrium. So, just use the Classical definition of Entropy (the formula above) and the Second Law of Thermodynamics, and that's it.
But, what about Macroscopic objects (or systems), which are not in Thermal Equilibrium ? Maybe, we often are tempted to think about the Entropy of these Macroscopic systems (which from a macroscopic point of view they seem to be in Thermodynamic Equilibrium, but in reality, they have still ongoing physical processes which make them not to be in complete thermal equilibrium) as the definition of the classical thermodynamic Entropy.
what I want to say is: What would be the limits of the classical Thermodynamic definition of Entropy, to be used in calculations for systems that seem to be in Thermodynamic Equilibrium but they aren't really? perhaps this question can also be extended to the so called regime of Near Equilibrium Thermodynamics.
Kind Regards all !
Can we use infrared-transmitting materials like silicon (on upward-facing hemisphere of exhaust pipes) to dissipate heat energy from exhaust gases discharged from Generators, vehicles etc, through radiation, that can then be reflected towards space (upward forcing) by using deflectors (like aluminium coated surfaces)?
I trying to learn fluent and to calculate wall heat transfer coefficient for non circular pipe flow. Pipe has constant heat flux through the wall, flow is turbulent, temperature varies a little with both r and length.
Since i never did it before in fluent, i need community to clarify my thoughts about it.
In such simple case (pipe flow) can we use built-in fluent functions to calculate heat transfer coefficient?
If we can, we interested in surface HTC, not in wall HTC, isn`t it?
If it is so we need to change reference temperature to Tbulk. We culaculate Tbulk as mass average static temperature?
Or it`s better to caculate it "by hand"? In that case how should i extract fluxes and temperatures for 3d case?
Sometimes when I run parametric table of EES (sweep a variable) I have get unstable answer at some rages.
For example for 0, 1, 2, 3 I get 10, 0.005, 9.5, 0.00000014
But when I don't use parametric table and by running them singularly in the main window of EES with F5 key, I get 10, 9.7, 9.5, 9.3 for 0, 1, 2, 3
What's the problem?
I have reduced convergence criteria but the problem is not solved...
For example, I attached a photo. Starting and ending range of the variable are the same, but the results are not. The marked result is the true result.
The conditions which I want to know are: -
3. Internal Energy of a mixture @ the time of combustion.
4. A function through which we can find different temperature and pressure conditions at which combustion would start.
How to calculate CO/(CO+CO2) from reaction rate constant in the case of Baur-Glaessner diagrams?
I have the Log K values for the reaction at the different temperatures.
In thermodynamic tables of liquids, S is usually given without mention of constant volume or constant pressure. In solids this makes sense because Cv ~ Cp, so S should be the same. In liquids, Cp > Cv especially as temperature increases, so I'd think that S would depend on constant pressure or constant volume conditions as well.
So my question is: is S the same at constant volume as it is at constant pressure?
Hello all :
I would like to start a discussion about this topic.
I have just got myself interested on the topic of thermal transistors and started to search some readings about the subject, but it has n't come clear for me yet.
Does anyone can give a rough description of the working mechanisms of a thermal transistors ?
Is there a straightforward analogy between an Electric Transistors and a Thermal one ?
Are Thermal transistors and Heat transistors the same thing ?
Are there more than one kind of thermal transistor?
How can we associate the imput DeltaT or imput Heat Flux to the response of a Thermal Transistor.
I hope someone can give base ideas upon we can build a disscution on
Regards ! :)
One principle given in Thermodynamics, Cengel is "The steady flow compression or expansion work is directly proportional to the specific volume of the fluid. Therefore, the specific volume of the working fluid should be as low as possible during a compression process and as high as possible during an expansion process."
Can anybody explain how it is been arrived?
I got to know about the below formula (applicable in some cases) from which we can get partly the answer for the question.
Work = specific volume * change in pressure
Any other conceptual explanation for the above statements known to you?
Usually mass transfer is described with the following equation: m = A*U*dc, where dc is the difference in concentration of a component between two phases, or a phase and the interface...
Fick's law of diffusion also uses the difference in concentration.
In reality, the driving force for mass transfer is the difference in chemical potential, which depends not only on the concentration but also on temperature and pressure.
Why then is the difference in concentration usually applied? In which cases can/can't it be applied?
Hi everybody. For the project that I am working on at the moment I need to have a preliminary estimation of the weight of main engine components of a gas turbine (turbine and compressor, combustion chamber and heat exchangers). I tried to look in the open literature, however not much data are available and the only relations that I have found assume a quite detailed knowledge of design parameters which I do not have at this stage. Do you know if is there any availability of relations that allow a gross estimation of weight based on main characteristics and thermodynamics model of each component?
Thank you very much.
If overall cost is minimized for a system or cycle, does it mean that exergy destruction is minimized?
Working on Zn-Al-Ni solder alloy system. What is the best possible way to determine thermodynamic stability at different composition of the solder system ?
Generally pre-heating, humidification , re-heat used in Winter A/C. Whereas cooling coils in Summer A/C i.e. a single de-humidification process
I want to know that in an exist steam power plant, what aspects (such as heat exchanging aria, level of condensate or etc) of the steam feed water heaters can improve?
The modifications can improve efficiency or decrease the flow rate of steam to the condenser.
I am working on simulating shell and tube heat exchangers using ANSYS Fluent. I have the huge number of tubes and it is not recommended to model it. Therefore, I am trying with alternative approaches like porous medium and heat exchanger models.
*In the porous medium approach, the non-equilibrium thermal model is recommended for heat exchanger type of problems.
*In heat exchanger model, dual cell method is used to simulate shell side and tube side flow and heat transfer.
I request you guys to help me in this regard.
Thanks in advance.
A simple problem confused me:
suppose a constant amount of heat Q and a solid body with heat capacity C and initial temperature T1.
I want to calculate the final temperature of the body when heat Q transferred to the body at the following conditions:
1- irreversible heat transfer
2- reversible heat transfer
3- quasi static heat transfer
I would like to calculate the boiling point for propylene carbonate:acetone and propylene carbonate:ethanol:acetone. May i know what formula can be used for the calculation? Thanks
In the RE-FUEL POWER projects, we are considering a number of conventional power cycles, such as supercritical reheated steam cycle, and advanced power cycles, such as supercritical CO2, ethane, helium or HAT cycles. Based on your experience, what other cycles can compete with these in terms of techno-economic performance?
#powercycle #thermodynamic #economic #feasibility #cleanenergy #refuelpower
I want simulate numerically heat transfer of nanofluid in a cavity with magnetic field . I need electrical conductivity of water- Al2O3 nanofluid.
I calculated Activity coefficient of components of binary solution at infinite dilution and need to have experimental data to compare my results. I would like to know references for activity coefficient of components at infinite dilutionboth.
Suppose a high temperature sphere where is located in a stationary fluid. Is it possible the fluid surrounding the sphere moves?
What is the effect of inlet Mach No. on centrifugal compressors performance? I mean for Mc<1 i.e. without shock effects. Is it better to have lesser or higher inlet Mach Number? And why?
Which theoretical and thermodynamic equation or group of expressions and equations can be used for calculation of water loss due to evaporation and wind when it is being flown over evenly using a spraying unit or nozzle system over a smooth glass surface of the Photovoltaic panel forming a thin water film layer as part of the PV cooling system built outdoors at a desert location in North Africa? Can the Penman equation be useful in this scenario for this calculation? Suggestions and sources required from you please?
I am trying to simulate a specific type of an Absorption machine under Trnsys, the machine is a Yazaki 17.6 kWcool.
My question is how can I create a parametric file of the Type 107 to meet the performance of my AB machine ?
i made Qin= m cp delta T, with delta T outlet inlet solar colletor, where the salty water is heated, and mass flowrate of the salty water. GOR is lower than 0.1.. Seems to low..
for u-bundle heat exchanger oder any other heat exchange device
How to do geothermal power plant optimization by using EES software with turbine and condenser pressure parameters
IN THE NAME OF GOD
I want to calculate the temperature after a stage of orifice plate in which we drop pressure from P1 to P2. (So temperature drops from T1 to T2.) (For example for Methane)
I studied somewhere we can consider gas flow through an orifice as an adiabatic process.
On the other hand we have PV^k=constant for reversible-adiabatic process in which k=Cp/Cv . But I think my process is not reversible.
Can we use polytropic formula for it? If it is ok, How I can find the power of V in PV^n=constant ? (n=?)
Can I calculate it by formula or find it by using gas property tables?
What's your suggestion for calculating T2 after orifice plate?
In FSAE events we need to use a restrictor of 20mm diameter in the upstream of intake manifold. it is to restrict the intake mass flow rate. my question is how it affects the engine power output? any mathematical formula is welcomed.
A Carnot engine running between two temperatures Tc and Th has the efficiency 1-Tc/Th. According to Carnot’s theorem all reversible engines running between Tc and Th would have the same efficiency. However if I calculate the efficiency for an engine with two isotherms at Tc and Th which are connected by either isobars or isochors I get an efficiency lower than that of the Carnot process unless I let the compression ratio become infinite. How do I resolve this contradiction.
This can be attained by evaporative cooling by fog or cooling wet pads.
We need to compare between added cos and the energy benefit.
In refrigerators and air conditioners to increase the refrigeration effect, the capillary tube and suction line are placed in contact with each other to make a suction line heat exchanger usually available in two configurations.
1. Latent (Capillary having a line contact with the outer diameter of the suction line)
2. Co-axial/ Concentric (Capillary inside the suction line)
I have a cylindrical combustion chamber cookstove. The feed rate of the cook stove is 1 kg/h (CV of fuel 18.5 MJ/kg). I would like to determine the temperature distribution over the inner surface of the combustion chamber analytically. How do i determine this?
For instance, 4 inline 2.0 litre engine with V6 2.0 litre engine. Do they produce same output in terms of power and torque? One engine built with 4 piston and the other with 6. Would that effect the performance? Open for discussion.
The main function of the expansion valve in a refrigeration system is to reduce the pressure of a fluid by controlling the flow rate of the fluid. When the pressure of the fluid decrease, so thus the temperature of the fluid (according to the properties of the fluid, the pressure reduces and the enthalpy might remain unchanged, the temperature will drops). So, is it correct if I say I use expansion valve to reduce the temperature of the fluid/ refrigerant.
Hi to all,
Does anybody know any reference book or articles about modeling and control of heat recovery steam generator (HRSG) and boiler ?
LiBr-H2O Solution single effect absorption chiller Refrigeration System
1) The specific exergy is the sum on the physical exergy and chemical exergy.
a- Physical exergy : (h-h0)-To(s-so)
b- Chemical exergy: Standard exergy + Dissolution Exergy
If the chemical exergy shall be evalueted, how should I calculated the activities for H2O and LiBr ?
Can anyone provide a sample calculation ?
Do EES can provide the evaluation of the chemical exergy ? What is the function that shall be used ?
One good literature source is R. L. Webb. Principles of Enhanced Heat Transfer, Taylor & Francis, 2005. If there are more good sources to recommend?
What criteria are most applicable in practice?