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# Thermal Engineering - Science topic

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I am looking for useful proposals for doctoral research in the field of internal combustion engines (thermal engineering).
Hello dear Hiba Arous,
Internal combustion engines are heat engines whose heat transfer plays a very important role in their performance and efficiency. In an internal combustion engine, the cooling system is responsible for dissipating excess engine heat. The cooling system of an internal combustion engine consists of many components, one of which is the cooling passage of the cylinder block and the cylinder head. Therefore, you can focus on the effects of the new design of the cooling inlet and outlet position on the engine body temperature distribution and pump power.
Although this is not related to my field of expertise, I recommend it based on my experience working with internal combustion engines.
Good luck!
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Please suggest any simple procedure to measure it.
Carry out the tensile test and record percentage elongation (after the yielding up to the fracture)..
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Dear Researchers :
I will appreciate if someone can give me some help with this issue
I already have my 2D-model of a Power Energy Cable in COMSOL Multiphysics.
But so far I haven't been able to model the Heat Transfer and Temperature Distribution in the Cable due to the Joule Effect.
The Cable works under a DeltaV = 25 000 kV, has a Longitude of 1 m , its dimensions are given, as well as the material properties.
But I don't know how to stablish this condition in the model under the 'Heat Transfer in Solids' physics
I also selected the 'Joule Electromagnetic Heating' effect to include into my model, but I cannot solve the Temperature correctly.
How do I have to consider this condition? What Boundary Condition (or Domain Condition) do I have to use on the model ?
Thak you for any help !
Regards ! :)
Hi,
You may get some useful information from the following paper:
Solution of a coupled inverse heat conduction–radiation problem for the study of radiation effects on the transient hot wire measurements
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It is meant especially thermodynamic and gas-dynamic state.
Thank you for participating in the discussion.
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Dear Colleagues,
I would like to invite you to submit contributions to a Special Issue of Energies on the "Experimental Evaluation of Solar Thermal Engineering”. The growth in energy consumption over the past 20 years has been significant, and demand for energy will continue to grow in the future. The global commercial low-temperature heat consumption is estimated to be more than 10 EJ per year for hot water production alone, while industrial energy consumption in industrialized countries accounts for 30% of the total required energy; in Europe, two-thirds of this energy consists of thermal energy. The only way to meet this global thermal demand without contributing to climate change implies the utilization of renewable sources, and in particular of the solar source, which is the most abundant energy resource on Earth. Advancement in solar thermal engineering is therefore paramount to improve the efficiency, reliability, and sustainability of solar collectors and all related energy systems. This Special Issue will deal with innovative experimental applications and systems belonging to the solar thermal engineering field.
Topics of interest for publication include, but are not limited to:
• Thermo-optical properties of materials and heat-transfer fluids;
• Solar collectors: flat-plate, evacuated tube, compound parabolic, linear Fresnel, parabolic trough, parabolic dish, heliostat field;
• Solar cookers;
• Solar ponds;
• Solar-thermal-based applications: water heating, space heating and cooling, industrial processes, drying, distillation, power systems;
• Thermal energy storage: solid, liquid, phase change, chemical.
Please note that a certain discount can be offered to selected contributions. Contact me if you are interested. Additional information can be found at:
Dr. Gianluca Coccia
Guest Editor
I would love it but it is very expensive for me at this time. Thanks Dear Gianluca Coccia .
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How to calculate velocity in natural convection using experimental results in the attachment?
HTF is water at 5 Celsius degrees, cooled medium is paraffin with following thermo-physical:
Data sheet for RT21 (Rubitherm, n.d.)
Melting area °C 18-23, typical 21°C
Congealing area °C 22-19, typical 22°C
Heat storage capacity kJ/kg 134
Density solid at 15°C Kg/l 0.88
Density liquid at 25°C Kg/l 0.77
Volume expansion % 14
Heat conductivity W/(m•K) 0.2
Specific heat liquid kJ/(kg•K) 2.4
Specific heat solid kJ/(kg•K) 1.8
Geometry and temperatures are presented in the attachment.
Thanks,
Ivica
Grashof’s Number.
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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.

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Dear all,
I want to find enthalpy and entropy of Libr-water solution at 25 oC  temperature and 1 bar pressure. Is there any standard formula available for calculating enthalpy and entropy of LiBr-water solution having various concentration percentage of LiBr in solution?
A very useful link to find the thermodynamic parameters ( △G°, △H° and △S° ) form experimental data.
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As insulation materials are generally used in the pre melting or much safer temperatures, I am finding difficulty in getting data such as latent heat of fusion of any insulation materials. Can anybody provide me with the latent heat data of any insulation material, glass wool or rock wool?
Measurement of thermal properties at elevated temperatures By : Robert Jansson
Organized Framework of Main Possible Applications of Sheep Wool Fibers in Building Components
By: Monica C.M. Parlato and Simona M.C. Porto
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In the first lecture of heat transfer course, generally it is told that with Thermodynamics, it is not possible to get the heat transfer rate of a process. But in steady flow energy equation (time basis) has the term dQ/dt. So can we say that telling Thermodynamics is incapable of finding heat transfer rate is wrong?
As Nazaruddin S. pointed out, when having a system in a Thermodynamic Equilibrium, you can compute the Heat Rate using the First Law: dU=dW-dQ , where dW and dW must be inexact differentials.
I think the equation you mentioned in your question is the General form for the Energy Balance of a system. This is the general equation you start with when you want to make an Energy Balance in the general scenario: (open, closed, steady-state, transient state.. ) and is it used well in Tranport Phenomena like Fluid Dynamics, Mass Transfer and Heat Transfer problems.
Actually the First Law of Thermodynamics comes from applying an Energy Balance in the differential form assuming the scenario of Thermal, Dynamical and Chemical equilibrium.
So, Yes, you can calculate the Heat Rate of the system with the First Law. But, this is just for a system in Thermal Equilibrium
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1-Looking to do a reduced scale test chamber for building thermal behavior, should the test chamber be reduced completely in size (as in all enveloped and volume reduced accordingly) or only the internal volume (keeping the envelope with the same specification (as thicknesses and U-values)
2- How to implement or simulate internal gains.
3- Any previous studies looked critically at those issues?
There are papers in this regard, but mostly to support Euler number, Reynold number, Much Number, Jensen number, Strouhal number and Cauchy number such as dimensionless numbers . The actual stratification, indoor temperature gradient, mixing of the air mass, a number of air changes and pressure variations cannot be scaled in reduced study models for thermal behavior. Addressing the Isothermal mass related absorption, heat loss to the floor and occupancy related heat generation is practically difficult.
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Many "open Air" sites appear to have suffered from Frost Creep from occupation zones that were on chalk escarpments. For MSA (cerca 50 ka) sites not subjected to glaciation, there can be vestiges of the original sites still visible on a Google Earth survey. I tested 2 such sites (France and the UK) and found lithics at these locations.
Se hay alguno interese, puedo colaborar en el pre-análisis de las imágenes. Como brasileño, hablo el portunhol pero lego en español.
Sds Cordiales
Alan Cannell
Curitiba ISIPU
Olá Santiago
Tengo algunas dificuldades de desarollar las encuestas y que vivo en el Brasil.... Pero me parece que funciona e espero que otros puedam utilizar esta metodología.
My main worry is in the location of wind farms as these are often in locations that fit the checklist or algorithm.
I hope to see profesionals developing this to the point where all wind farms carry out a quick survey to rule out any MSA sites being damaged.
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Hello
I studied the heat transfer in a semi-transparent material under fluent ansys,.
Depending on the flow time I keep the temperature in my front side, and the variation of radiant heat flux, and the beam radiation that I added as a UDF.
The problem is at the level of radiation heat flux variation that had negative value at the beginning of computation. can anyone explain to me why? and how can i solve the probleme?
Here the variation of the beam radiation (UDF) it appears as I programmed under udf, the other figure is the variation of radiation heat flux.
Because the temperatures of material used are higher than ambeient.
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Dear all,
I am trying to find cooling power to weight ratio for vapour compression and vapour absorption chiller. If you have any relevant information please share.
Cooling power is the amount of energy/sec require to derive the cooling system like vapor compression or vapor absorption and mass flow rate of refrigerant is directly proportional to the cooling capacity of system.so the cooling power and mass ratio can be calculated by using refrigeration table
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In natural gas power plant, we have cooling tower 13 cells, 2 gas turbines, and 1 steam turbine (full load). I would like to know if we start 1 gas turbine and 1 steam turbine (half load), but the cooling towers still  work by 13 cells. Will this affect to effectiveness of cooling tower? Because the effectiveness of cooling tower did not change too much during switch from full load to half load.
Yours sincerely,
The flow rate still constant
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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?
dq-dw=d(h)=d(u+pv)
Now if we neglected the heat transfer and the change in the internal energy, then
-dw=d(pv) = pdv+vdp
Since dv almost equal zero for liquid (v is almost constant for liquid), then the integration yields to:
w=v*( change in pressure)
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I am looking for literature to aid me with the explanation and discussion of experimental results (saturated pool boiling of water at atmospheric pressure on copper surfaces) where a shift of the boiling curve towards lower superheats and a decrease of CHF were recorded; this trend was noted after the first onset of CHF. I am interested in literature that deals with the change of both the boiling process and surface characteristics (wettability, topography, chemistry etc.) after the first onset of CHF. Also, any literature about the (possible) shift of the boiling curve in repeated experiments on the same surface (as a consequence of CHF onset and transition to film boiling, where possible low-temperature annealing occurs) would be most welcome. So far, a search lasting several hours yielded no results.
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Where could I find related literature regarding this? I am currently working on studies on heat pipe and I would like to conduct some experiments on wicked heat pipe as a part of my research.
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Can you please differentiate the both using some practical or numerical examples?
Dear esteemed colleagues,
Yes there is difference between assumption and approximation. Assumption value may not be true value but approximation value is within the exact value. We assume to prevail upon a problem in order to arrive at a solution. For example, we which to calculate the period of oscillation of a simple pendulum and we do not know the exact acceleration due to gravity of that location. In order to solve the existing problem we have to assume a value for the acceleration due to gravity which may not be the exact value of the acceleration of that location when experimented. Then in assuming, we use the word taking the acceleration due to gravity to be 9.8 mls2 which we know may not be 100 % correct but we have to use the value to solve the problem in order to move on. The knowledge of value to be used for assumption are some things obtained from literature (that is value of that physical quantity obtained in another location).
For approximation, value are approximated when figures of the value obtained are complex or look ambiguous.
Example let say the value obtained from the calculation of the period of oscillation of the simple pendulum is
T = 2.35485939549384938484873948734899587939494 seconds
then we may decide to approximate to 2 d.p in order for the value obtained to be more clearer. it is just that the more you approximate the figures the less accurate the value obtain is.
Best regards.
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Which method is better for spray characterization of velocity- PIV (particle image velocimetry) or shadowgraphy?
For 2D fields there is also the fundamental difference, that during PIV the particles are illuminated by a laser sheet and thus the cross correlation is calculated only from the particles in your plane of interest. Shadowgraphy however (such as Schlieren) is a line-of-sight averaged technique, where all density fluctuations in your flow are projected on an image plane. If you do your cross-correlation on these Shadowgraph images, you will take into account all movements in the other planes of view, which will falsify your results. Taking this difference into account I would definitely go for PIV.
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Dear All,
How to find mass concentration (x) of ammonia refrigerant in  ammonia/NaScn solution. I did not find any correlation between Concentration (X), Temperature (T) and Pressure (P) for ammonia/NaScn solution. Is there any correlation available of x at different temperature and pressure. Please give your valuable reply.
Dear Bhargav Pandya,
Hope my recent publisded paper is helpful to you!
Best
Comparative study on ATR-FTIR calibration models for monitoring solution concentration in cooling crystallization (pls see the homepage)
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Exergy / Available energy is being lost in several engineering processes. It is of prime interest in the field of heat transfer. Is there any numerical models (or) some minor numerical works developed based on exergy destruction?
You must take into account two thing:
1.- Exergy destruction is an internal phenomenon, refers to the exergy destroyed due to irreversibilities within a component system (like irreversibilities inside a combustion, exergy destruction during the combustion process as function of engine operating and design parameters)
2.- Exergy losse is seen as external irreversibilities (Transfer of exergy from the overall system to its surroundings. This exergy transfer is not further used in this or another system)
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Materials and Mechanical Engineers: Thermal conductivity of SiO2 nanoparticles is about 1.4 W/mK at 25C. Can you help me obtain thermal conductivity values by 60 C?
Thermal  conductivity of silica is in between 1.5-2 W/m.K. But nano particles have high specific surface area which should enhance the conductivity to a great extent. I suggest that the thermal conductivity of silica nano particles would be much higher than 1.5 W/m.K as specified.
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I am currently studying the deposition on heat exchangers due to the presence of solid ash particles and vapours in hot flue gas.
I am currently using DEFINE_DPM_BC on the surface of the cylinder (heat exchanger) to study the particle hits but I read several papers where they used DEFINE_DPM_EROSION. I tried to use it but with some problems.
If anyone is using this UDF I would like to ask some questions.
Thank you,
Chiara
DEFINE_DPM_EROSION should be OK to predict the deposition rate. You can use F_STORAGE_R(f,t,SV_DPMS_ACCRETION) to store your deposition rate. More details could be helpful for us to understand your problem.
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Can anyone recommend me publications on storing seasonal thermal energy storage using paraffin as PCM in concrete?
I want to run warm/cold water in tubes embedded in paraffin/concrete to store heat in summer and use it in winter (and vice versa).
Thanks,
Faizal
Yes, PCM can store thermal energy in itself that can be used further for various applications of cooling and heating. By storing renewable sources of energy, PCM significantly reduces dependence on non-renewable sources of energy. The energy saving attribute of PCM has attracted significant government support.
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Dear all,
Does any one know how to calculate the gas recirculation ratio in the mild/flameless combustion mode as shown in the picture?
I am simulating the reacting flow in my combustion chamber and would like to calculate its gas recirculation ratio for achieving MILD or Flameless combustion regime .
I think it can be calculated using FLUENT CFD-post, but I don't know how to put that equation in CFD-post...
Have anyone guide me for this matter?
Thank you very much for helping...
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Hi
I have a problem I need to solve. The system consists of a hot plate type heater that is either on or off. The bag of fluid lays on top of it. There is a sensor that the bag of fluid rests on and checks it temperature. There is also a sensor that checks the hot plate temperature. The bag of fluid needs to be heated to and kept at 40 C. It cannot go above 41C. Fluid may start as low as 1C with the heater element off. The rise time from start (can be any temp) to set point (40 C) can be no longer than 1/2 hr. I was researching a pid controller for the heater, but am concerned about any overshoot. Some articles I've read about the MPC (Model Predictive Controller) makes it sound like it may be better suited to this application. If someone has worked on a problem like this, I would like to hear about your experiences.
Thanks...
If you add current control, or PWM, a PID controller might be used.
If the fluid is used incrementally, a flow-through heater at the point of use may be more appropriate than heating the entire bag. A lot easer to control.
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How much is the thermal conductivity of the high temperature grease lubricants Appearance Smooth blue buttery Visual Dropping Point ºC 360
magnitude of thermal conductivity of blue grease can be tested in some way.maybe you could ask some testing agencies to test  the grease.
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Dear fellow researchers,
I am currently working on a design to heat a swimming pool indirectly- via radiant floor heating. Water at 80 deg C will be flowing into PEX pipes. The pipes are placed on the surface the pool and covered with a layer of foam and fiberglass for aesthetical purposes. What are the calculation procedures for finding the heat emitted per unit area.
Thank you.
Thank you Sir. Very helpful indeed.
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I would like to model transient thermal:
- A breakthrough part
- A convective exchange in the hole (to simulate the passage of a fluid without performing simulation Fluent)
- Regulating the heat with a power
For convection, I know how to apply a temperature and convective heat exchange coefficient. Now, I would like to apply a heating power and a convective heat exchange coefficient.
Any idea ? Turorials ?
Thanks a lot
Use this forum. Good luck.
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Do you know about the ability of Lattice-Boltzmann method to model nanofluids flow in some complex geometries?
Thanks all
Dear Timm Krüger,
Liquid impingement jets in cooling of electronic chips.
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Hi,
I wish to calculate HVAC noise, using HVAC drawings. Does anyone know how to calculate the regenrated noise from elements like dampers, bends and T junctions (and also duct reduction)?
Is there any simple formula to apply ?
I am not able to find such thing in the ASHRAE Chapt. 48 Noise and Vibration). My only chance looks like to pick the equations from CIBSE Guide B5 Appendix A2, but I do not have access to the pressure loss factor (i only know flow velocity and local pressure at sections of the HVAC system).
Sylvain,
This out of print book, by Douglas Reynolds, is the basis for some of the commercial software used do do such calculations.
Mike Schwob
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I am currently looking for literature, which offers an "easy" overview of thermal conductivity in general, measurement methods, modelling etc - all the literature  available is very specific and detailed in certain research topics...
I am more looking for general information like offered in teaching books or uni courses - which unforunately are not available online - can anyone help on this?
John H Lienhard IV and John H Lienhard V, 'A Heat Transfer Textbook', Third Edition, Phlogyston Press, Cambridge, Massachusetts
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Bulk mean temperature of the fluid is generally calculated by taking the average of inlet and exit temperatures of the fluid for constant wall temperature boundary condition.but in case of constant heat flux boundary condition; the temperature of the fluid is rapidly increasing even in the thermally fully developed region.Therefore, there is a big difference between inlet and outlet temperatures for constant heat flux boundary condition. So, how to account for the property variations with this large temperature difference??
I believe, the best way is to use the energy equation which takes in to account the property variation. Eg: del/delX of (k delT/delX) instead of k( del 2T/Delx2). Use auxiliary equations to describe the variation of viscosity and thermal conductivity with temperature. It's almost like compressible flow, except, you do not bother about density variation with pressure.
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Some countries like Malaysia faced with hot climatic conditions that might affects the gas turbine performance. Besides fogging method, does anyone know what is another alternative ways to overcome this issue?
Look at this doc it may be helpful for you topic. Good luck
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I am using off the shelf temperature sensors. I want to use the temperature value to display the corresponding color of that temperature just like a thermal camera. So far I have used Wien's Equation to determine the corresponding wavelength of the temperature. I want to find the color between 0 degree Celsius to 100 degrees Celsius. I found a paper that allows to convert wavelength to RGB value, but the values are from 410nm to 780nm which is outside my spectrum range. Can anyone help me?
So far I have used the temperature value to get the corresponding wavelength value using Wien's Equation. Now I just need a law or algorithm to convert it to an RGB value.
Note: I do not want to consider the Emissivity concept or in my case a constant Emissivity of 0.95 can be considered if necessary.
Reference:
The displays in thermal cameras use a false color concept.  They arbitrarily map a temperature to a color.  A simplified form of this is to use a gray scale mapping so that (usually) white is the hot end of the range and black is the cold end of the range.  Since the mapping is arbitrary it can also be white is cold and black is hot.  The latter is sometimes preferred for visual presentation of some scenes.
There is no RGB equals T or equals wavelength direct, physical, immutable correspondence.  If you look at the various displays used by IR cameras to present temperature maps, you will find various palettes used with names like Rainbow, Ironbow, Medical, etc.  Each maps a different portion of the detected temperature to a different color.  Some, like Ironbow, are fairly continuous and rely on the colors displayed by metal as it is heated for a guide.  However, this is only a convenience.  Others are selected to maximize the visibility of T differences or of a particular portion of the T range.
You already have temperature.  You indicate that the range is 100K.  You can decide how many colors to use for your display and arbitrarily assign them to a T range.
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I am trying to calculate the reflection coefficient between  VO2 and Vacuum For Evanescent waves in p polarization I find them greater than one,can anyone help me whether this result is reasonable or not?
No, it is more general. It is due to evanescent photons and not only to surface waves which are resonant surface modes. In principle, without surface phonon polariton or surface plasmon the reflection coefficients can be larger than one in near-field.
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I have a copper assembly made of two components and is use for heat transfer. One side or part is completely dipped  in dry ice bath. And the second components is at ambient temperature. I need the heat transfer coefficient value for both cases.
As per question, i think setup can be divided into three parts for heat transfer - one is from ambient to copper rod through convection, second is in rod through conduction and last in dry ice through conduction or convection depending upon state of dry ice. In all three section total heat will be equal. Then by equation it can be solve.
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Hello everybody,
I'm modelling the heat transfer in a combustion chamber for an engine with various temperature of the combustion chamber.
Is anyone can help me for finding data of the boiling temperature of the fuel (petrol and diesel) regarding the pressure and the temperature. (from 100 to 600 degree C).
On the internet it is possible to find the boiling point for some values, I would like to find a diagram to see the evolution of the boiling point with the pressure and the temperature.
Thanks!
Diesel fuel is a complex mixture of hydrocarbons. you should know the fuel component by using  Chromatography and then do what the previous researcher talk about.
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Dear Colleagues
I have many difficulties in finding electro-thermal parameters of styrofoam (polystyrene) and laboratory glass (polypropylene)? In literature the authors rather have not mentioned which parameters they used in numerical simulations. I am especially interested in such parameters:
Relative Permittivity
Electrical Conductivity [S/m]
MassDensity [kg/m3]
Specific Heat [J/(kg K)]
Thermal Conductivity [W/(m K)]
for frequencies in the range of 100 kHz - 1000 kHz.
Maybe do you know the publications with such parameters?
I will be grateful for your help!
Best Wishes,
Piotr
Vitalii, you help me a lot!
Best Wishes,
Piotr
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Hi all,
For natural convection inside a inclined glass tube subjected to a uniform heat flux, what would be the range of heat transfer coefficient?
Any specific range would be there? or it entirely depends on the modeling and boundary conditions of my problem, which i defined?
Dear Arun Raj,
the correlation you are looking for can be found in Bergman et al.(known also by Incropera) book of heat transfer.
kindly find attached the chapter concerning the natural convection their book.
Good luck.
Kind regards,
kifah
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I came to know about the rectifier as a high heat flux ELECTRONIC components/device, so need deep technical details, its specification, uses, dimensions & working so i study in details about the rectifier.
Thanking You.
Vitalii Pertsevyi :  thanks for literature...
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In design of super critical thermal power units no latent heat is absorbed in Boiler furnace by the circulating power cycle fluid: steam/water since it is being operated above 225 kg/sq.cm. How much it is contributing in enhancing the efficiency of the super critical units in this way?
Dear Xianglong Luo, Can you please elaborate your idea on increase of efficiency in super critical thermal power unit, in which no latent heat is absorbed by steam in steam generator. How is it working to improve efficiency other than a sub-critical unit?
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Hello every one. Good morning.
I would like to create a regression equation from the available experimental data in the following format.
U=D. A^x. B^y. C^z
But, i am getting the equations in the below format.
U = D + xA + yB + zc.
How to get the equation in “U=D.A^x.B^y.C^z” format using Minitab, Excel or any other software?
You could transform this equation by taking the logarithm of both sides of the equation to convert it to a linear equation and then perform linear regression. After that you can the anti-log.
Here is how your equation will look like after the logarithmic transformation:
Log(M) = x.log(A) + y.log(B) + z.log(C)
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I need to measure the Mean Radiant Temperature in a closed room and in an outdoor spaces. What are the sensors I need to conduct such measurements?
The easiest way would be to use a "black-globe thermometer".  Nothing fancy is required here.
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Dear Friend
I have evaluated the steady state analysis of LiBr-Water absorption refrigeration cycle. But i got confused in evaluating the transient analysis for this system. If you have any valuable suggestion than please inform me.
Dear Pandya,
I think you need to use  the TRNSYS simulation program. TRNSYS is an acronym for a ‘transient simulation program’ and is a quasi-steady simulation model. This program was developed by the University of Wisconsin by the members of the Solar Energy Laboratory (Klein et al., 1998). It is written in ANSII standard Fortran-77.
I attached a paper, in which the authors  used the TRANSYS simulation program in their analysis.
Best regards
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Specific heat capacity
You need not use domestic oven for determining heat capacity. Try to make a simple compact insulated container with a reliable temperature monitoring system as suggested  by Dr. Garry. That will solve your purpose.
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IN A WOODEN BOX, PELTIER MODULES ARE ATTACHED ON THE WALLS. I WANT TO CALCULATE COP OF THE SYSTEM, NOT THE PELTIER MODULE, HOW TO DO IT? ALSO I WANT TO ESTABLISH THE RELATION :
COP(REF) + 1 = COP(HEATPUMP)
HELP ME ASAP FOR PROJECT.
Dear Hardik,
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I am trying to construct a thermostat using Al block with peltier heating elements in conjunction with a thermostat circuit. I want to achieve a temperature accuracy of +/- 0.01 degrees centigrade. What is the best way to go about it ? Or, is there any better alternative to control the temperature of the block?
Garry,
Thanks again ! I am looking to thermostat an Al block of mass 2.5-3 kg. And the desired temperatures are RT and 303K.
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What is the advantage of horizontal receiver over vertical receiver in refrigeration system? How can we find capacity required for the same?
V1 = Vcond x 0.2 + Vevap x 0.8 + VLL
Currently I am using above formula to find capacity for the receiver.
Where VLL is liquid line volume
Pavan Damkonde, I see three thing with a Horizontal Receiver vrs Vertical Receiver:
1. the absolute Pressure will be lower on the fluid for the columns of the substance on the bottom part of the reciever one, that increase the pressure in the pipe to transport the fluid.
2. The Stress of the base where you put the Receiver is  better distribute than the vertical one.
3. The horizontal one need more space than the vertical one.
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Dear all
I want Pressure-Temperature-Concentration diagram for H2O-LiCl solution for analysis of LiCl-water absorption refrigeration system. Is there are any resources available from which i can get Pressure-Temperature-Concentration diagram for H2O-LiCl solution.Please give me information if you have any idea about it.
This is not my field but the following file may help you:
Regards
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Hello,
I have a question regarding the paper, "Microbolometer Technology Using Serial PN-Diodes" published in IEEE. The paper was presented at  the 2013 ISCDG IEEE International Semiconductor Conference in Dresden.
In the paper the authors use 4 pn diodes connected in series as a temperature sensor. This offers an advantage over a single pn diode as the voltage temperature coefficient is increased (-7mV/K for 4 diodes as opposed to -1.7mV/K for 1). In effect the sensitivity is increased by 4.
They state and indeed show graphs as evidence that the 4 diodes have to be "electrically isolated" by etching the silicon between them. However the diodes are in effect not electrically isolated as they are connected together using metal interconnects.
I contacted the authors for more details however they were unable to assist as they are bound by intellectual property agreements with collaborators.
Any ideas?
Thanks
Thanks John  - I concur with your assessment. (sorry for the late reply).
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I am trying to find the highest thermal mass of the PCM that i can use in an underfloor heating system
Dear Rami'
I suggest you to go through review papers which provide you with the state-of-the-art of this technology. Some of these articles are:
Please let me know if you have any difficulty getting these references.
Regards
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Dear all,
I am designing an underfloor heating system and I would like some clarification concerning the flow rate or velocity of water in tubes for the underfloor heating system.
Many Thanks
Dear Sitaram,
If I suppose that the heat load (Q) is known and is constant then a preliminary estimation of the water flow rate can be made by simple energy balance i.e. m_dot=Q/(cp*dT). But in actual system the flow rate may be different from the estimated value(generally higher). For that you may need to evaluate the conduction and convection resistances  of the system (if system geometry is known). For air side average Nusselt's number calculation assume flow over a flat plate (the floor). The wall resistance calculation is straight forward. Now with the estimated water flow rate calculate water side average heat transfer coefficient using any suitable model of flow inside horizontal tubes and hence find UA (floor area is known).  let Q1= UAdT
now compare Q with Q1 and iterate for Q1 with different water flow rates till you get Q=Q1. This may give you the final water flow rate required.
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Continuation from above: Hopefully it will defy the gravity and swap the evaporator and condenser sections? What will be the major factors that are going to play vital role in thermal performance?
Thanks a lot for your support and guidance
Heat pipes
Thermal performance
Thermodynamics
axially grooved heat pipe can operate 0.1 inch against gravity. the grooves have a very high permeability, allowing very long heat pipes for operation in micro-gravity, typically several meters long. One of their weaknesses is that they are suitable only for space, or for gravity aided sections of a heat pipe. The reason is that the same large pore size responsible for the high permeability results in low pumping capability.
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If we are using a very coarse value of time step, it will not recover a very good numerical solution for problem in hand. One parameter that I can think about is the heat diffusion coefficient  ''LAMBDA''. If LAMBDA is high it mean the heat will dissipate very quickly from one part to the other and we need a small value of time step to capture the result. If our selected valued of time step is very coarse it will not be able to capture the solution correctly. Also I can think off the boundary conditions that will affect the transfer of heat. Are there  other parameter need to be considered and is there any relation from which we can select the minimum value of time step for an FEM solution with specified mesh density.
I would prefer the equation based on the thermal difusibility which is conductivity/(rho x cp) since the higher this parameter the "faster" heat penetrates (or leaves) the body. Only conductivity is not enough.
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Such as L mode , H mode and ELMs.
They are the losses present in flat plate collector.  Optical loss from glazing and absorber and heat losses from all components of dryer.  The heat losses are convective and radiative losses from glass cover, side and bottom losses in the form of convection and conduction.
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Dear Ahmed,
I hope the articles to be helpful,
With best wishes.
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What thermocouple (or other sensor ) I can use for direct measurement of temeprature in gaseous hydrogen under 1000 deg C temeprature. Any type of shielding , is not possible It has to be ver very tiny wire. From what I have found thugsten/tungsten rhenium might be the only option , but I would be really happy if someone who expirienced that issue can give some advice, Thank you!
Marek,
Sure - tungsten is a finicky metal. Cycling it from ambient up to those types of temperatures leads to embrittlement. Let's see if I can find a link:
First column, last paragraph.
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please provide the above said paper article to my id
see appendix for the above article. In addtion, the other literatures may be also useful toyou.
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Much thanks.
Hello,
Please see Appendix F - 'Vacuum Arc, Spark of Discharge' Phenomena in the thesis "Coherers, a review", which can be found on my ResearchGate page.
Note, the page numbers in the Table of Contents of this Appendix are incorrect, but they will be corrected sometime this week.
Regards,
Tom Cuff
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mass flow rate of steam in condensate= 0.00127 kg/s
mass flow rate of water in condensate= 0.62263 kg/s
Pressure = 488 kPa temperature 150.88 °C
there is a nice easy tool from shipcopumps website to get the receiver minimum size
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compressor increases project cost  which effect on  cost optimization.
If your question was more specific, it would help us answer better. However, you might want to follow a discussion in stack exchange regarding building a compressor with no moving parts.
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1) The thermal energy storage dimension is cylindrical shape with diameter 30cm and height about 30cm..
2) The fins is attached to tube along in the thermal storage.
Your question is incomplete in detail.
(1) Is it latent heat storage or sensible heat storage?
(2) You state "The fins is attached to tube along in the thermal storage." It is still not clear. If it means that fins are on the side of heat storage medium, then are you talking about latent heat storage? Fins are likely to be useful only if you are using latent heat storage. Fins will not be cost effective on waterside or the sensible heat storage side
(3) Is the heat stored in the fin itself important to you?
(4) Is the water passing through tubes inside the storage cylinder of 30 cm dia? How many such tubes are you going to have? Or is it a coil? If yes, put in multiple coils and put the fins on the outside of the water carrying tubes.
Though copper is the best, aluminium is more economical. Since you are presumably talking about temperatures < 100 C, aluminium is a good choice.
IMPORTANT: Do not use stainless steel. Make sure there is NO contact resistance between fin base and the tube surface.
Better to purchase tubes with readymade extruded fins. If you are doing in-house fabrication, theoretically speaking, you can TIGweld the fins but you need a lot of fins for effective heat storage and discharge, so self-manufacture may be inadvisable..

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In any heat exchanger, for example; in a double pipe heat exchanger,how do we decide whether the hot fluid should flow through inner tube or outer tube?. Or is it completely irrelevant whether the hot fluid is flowing through the inner tube or outer tube?
The fluid flowing through the tubes will be decided  majorly on ease of operation , frictional effects and purpose whether it is  to be cooled or heated up.For example in Gas +liquid heat ex changer ( steam condenser) it is difficult to push steam through the tubes and hence liquid is made as tube side fluid.In liquid +Liquid type the one which is having low viscosity is generally be the tube fluid.And finally hot fluid is chosen as shell side fluid for effective heat transfer and of course it vary from one application to other.
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organic heat recovery fluid
Dear Anoop,
isobutane R600a? in ASHRAE handbook page 30.48
in  2009 ASHRAE Handbook—Fundamentals (SI). available in website.
bye
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I have calculated the total free convective heat loss,total forced convective heat loss and total radiative heat loss over 23m of the kiln surface. Assuming at least 50 % efficiency of the system, the equivalent fuel savings in a year were calculated and presented as follows:
Total operating hours of the kiln in a year                    7000hrs
Heat available at the burning zone                                3, 24,862.48 Kcal/hr
Total heat recovery of proposed run around system    1, 62,431.24 Kcal/hr
Calorific value of the fuel                                               55, 00 Kcal/kg
Equivalent fuel savings                                                 29.533 kgs/hr
Equivalent fuel savings per year                                   2, 06730.7 kgs/year
I want to know the mechanism to utilized the heat around kiln so that we can save energy and cost.
If you intend to use the heat lost from the kiln to ambiance you should consider that it is at a quite low temperature so that you can use it only in preheating air for the burner or in an early stage of material drying process. In both situations you should first think about the way to capture it. this implies a space separated from ambiance around the kiln and through which you can pass air. In fact you have to build up a heat exchanger with the kiln as heat source. In case that you want to go to this solution I think that a hélicoïdal air mouvement would be the best solution in order to guide the air flow around the kiln.
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I would like to know your practical experience about Open Loop GWHP (Ground Water Heat Pump) in confined aquifer. In my case I have 1 extraction well and 1 reinjection well. The problem is the rapid worsening of absorbability of reinjection well (from 15 l/sec to 3 l/sec in 12 months).
Thank you
Hi Roberto,
It sounds like you're having an injectivity problem. What are the chemical, physical conditions of your system? Poor injectivity in such wells can be caused by various precipitation/scaling reactions, for example due to mixing of different water chemistries, or a large difference between extraction and injection temperature. If you're injecting into a different aquifer than where you are extracting from this could also be a cause.
Curious to hear more about your system. Feel free to send me a message.
Best regards,
Niels
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I have found formula for forced convective heat transfer coefficient hfc=kBRen/D
in W/m2K.
where, k=thermal conductivity of air
Re=Reynolds number
D=diameter of kiln
According to some research paper B,n constants varies with ranges of Re value.I want to know the significance of B and n with Reynolds number
If You know the amount of heat carried out by the forced working fluid by measuring mass flow rate and temperature difference between inlet and exit, then you may divide this amount by the (area of contact *temperature difference of surface and average temperature of forced flow). Alternatively, you may pick up a proper empirical relation between Nusselt number  as a function of both Reynolds number and Prandtl number and calculate the convective heat transfer coefficient.
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In evaporative pad cooling principle, the air after evaporative cooling can be reduced to wet bulb temperature. However, if I add some ice or cold water in evaporative water tank. Will the air after evaporative cooling be reduced lower than the normal case (not adding ice or cold water)?
Tt is two stage cooling process if a indirect heat exchanger is added in the path of incoming surrounding air.in the indirect heat exchangers coil one has to circulate sump water from the same evaporative cooler itself.
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I'm seeking any reference to know the basic concepts How can I obtain the relation for the leakages by seals in gas leakages in crankcase in Stirling Engines?
Have you looked at the way researchers model the gas flow through a piston-ring pack?
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What are the applications convergent, divergent and convergent nozzle?
Irrespective of applications whether subsonic or supersonic flow, the throat area has to be maintained as minimum as possible to avoid  unwanted effects in the downstream flow (possible shear layer). Increasing the throat (constant) area may cause a BL to grow which can create a secondary effect.
Convergent nozzles are preferred for subsonic nozzle and a maximum Mach number at the throat can reach 1 with a nozzle pressure ratio of 1.89 (theoretically). When the pressure ratio increase greater than 1.89, there is a possibility of shock wave (loss in pressure) in the downstream of a nozzle due to uncontrolled expansion. This lose can be avoided using a careful design of C-D nozzle which can ensure a uniform supersonic flow at the divergent portion for a given pressure ratio.
From the above explanations, one can easily understand that the convergent nozzles are used for subsonic airplanes. Where ever supersonic flow is desired, a C-D nozzle is essential (supersonic wind tunnel, supersonic aircrafts & fighter planes etc).
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during hydro thermal synthesis of zeolites, varying crystallization temperature affect crystal size. how does this affect it.
Dear David,
during   your  hydrothermal synthesis, there is a point (at given pressure P and temperature T) where your solution is at equilibrium. This means that you cannot crystallize nor dissolve your zeolite.  Let' s Peq and Teq  be the equilibrium conditions.  Let's assume that the solubility C of your zeolite increases with T. This means that if you want to crystallize, you must impose a crystallization temperature Tcr < Teq.
In this case your system becomes supersaturated and the supersaturation is  S= (Ceq-Ccr) /Ceq.  Then S increases when Ccr decreases. From the rules of the crystal nucleation it follows that the number of formed crystal nuclei  increases with the supersaturation while their size decreases with S.  This is the reason why when  the crystallization temperature changes, the crystal size changes as well...
Yours sincerely
Dino
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The kinetic parameters of ignition of a solid fuel may change with various combustion gas environments. Some reported the activation energy is independent on [O2], whilst some others argued that both the activation energy Ea and the pre-exponential factor A compensatorily increase with increasing [O2]. In my opinion, both the reactants: fuel and O2 are not changed, thus Ea is supposed to be remained. As [O2] increases, the O2 molecules increase as a sequence, resulting in a higher ratio collision factor (i.e., pre-exponential factor A). Which proposal is correct in you opinion? Thanks.
For combustion of carbonaceous solid fuels and some liquid fuels in a continuous flow system, the rate equation is often written in the generic form r = A * Tb * exp(-Ea/RT) * Sm * [O2]n. When such rate equation is used, Ea and A are supposed to be insensitive to [O2] and diluent gas concentrations in the bulk gas flow. Note that the term "diluent gases" implies that these gases only have no other effects than diluting effect, which may or may not be true depending on what gases we're talking about. However, the reaction order w.r.t. [O2] is very likely to decrease with increasing [O2], i.e. it becomes less sensitive at high O2 concentrations.
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I understand the thermal stress in metals and ceramics, and I want to understand who is the thermal stress in nano composites?
thank you