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# Thermal Engineering - Science topic

Explore the latest questions and answers in Thermal Engineering, and find Thermal Engineering experts.

Questions related to Thermal Engineering

I am looking for useful proposals for doctoral research in the field of internal combustion engines (thermal engineering).

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 ! :)

It is meant especially thermodynamic and gas-dynamic state.

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:

- Measurement of solar radiation;
- 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*

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

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.

Dear all,

I want to find enthalpy and entropy of Libr-water solution at 25

^{o}C 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?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?

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?

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?

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

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 t**he 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.**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.

Thank you for your support.

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,

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?

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.

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.

Can you please differentiate the both using some practical or numerical examples?

Which method is better for spray characterization of velocity- PIV (particle image velocimetry) or shadowgraphy?

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.

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?

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?

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

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

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...

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...

How much is the thermal conductivity of the high temperature grease lubricants Appearance Smooth blue buttery Visual Dropping Point ºC 360

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.

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

Do you know about the ability of Lattice-Boltzmann method to model nanofluids flow in some complex geometries?

Thanks all

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).

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?

thanks in advance

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??

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?

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:

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?

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.

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!

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

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?

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.

If any one can provide me literature about this or any suggestion please help.

Thanking You.

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?

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?

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?

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.

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.

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?

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

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.

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

I am trying to find the highest thermal mass of the PCM that i can use in an underfloor heating system

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

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

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.

Such as L mode , H mode and ELMs.

I'm trying to acquire as much as possible information about underfloor heating by PCM, but I haven't found much papers about this topic exactly please I appreciate any help by a link. Thanks in advance

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!

please provide the above said paper article to my id

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

Thank you in advance

compressor increases project cost which effect on cost optimization.

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.

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?

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.

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

I have found formula for forced convective heat transfer coefficient h

_{fc=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}

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)?

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?

What are the applications convergent, divergent and convergent nozzle?

during hydro thermal synthesis of zeolites, varying crystallization temperature affect crystal size. how does this affect it.

The kinetic parameters of ignition of a solid fuel may change with various combustion gas environments. Some reported the activation energy is independent on [O

_{2}], whilst some others argued that both the activation energy Ea and the pre-exponential factor A compensatorily increase with increasing [O_{2}]. In my opinion, both the reactants: fuel and O_{2}are not changed, thus Ea is supposed to be remained. As [O_{2}] increases, the O_{2}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.I understand the thermal stress in metals and ceramics, and I want to understand who is the thermal stress in nano composites?

thank you

I have found CCT of my samples using formulae. But how to plot isotemperature lines with equal Δuv lines on Chromaticity diagram using origin software to mark that point.