Heat Transfer - Science topic

Exploring methods like nanoparticle selection, flow optimization, and advanced modeling to improve thermal performance in nanofluid systems under turbulence.

During winter, we face significant challenges such as cold walls and condensation, even with 10 cm insulation. To address these issues, what simulation techniques can be employed to optimize heat transfer in building systems? Additionally, I’d like to perform calculations using specialized software—what tools would you recommend for this purpose?

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I want to do ED coating on , one of my aluminium part does it affect heat transfer from part.

How we can understand that flow regime in Buoyancy-driven flow is turbulent?

I use the Rayleigh number to identify this issue and consider a Rayleigh number higher than 10^9 to be turbulent flow.

Is this also true for liquid PCMs?

If you have a reliable source on this subject, I would appreciate to introduce it.

Hi i hope everyone reading this comment is doing great.

i have a question that couldn't find the answer to wherever i searched,

my question is when calculating the overall heat transfer coefficient kern's limitation for difference percentage is 30%.

if anyone know why 30 and not anyother number please share the info with me.

what did he do to set that specific number.

thank you in advance.

Hello,

We are using TA Instrument SDT Q600 tool. During clicking "Accept Results" which is the last step of heat flow calibration, we are receiving an error called "SDTX: Unspecified Error". The picture is attached.

Have you ever encountered this situation before?

We tried a few things (changing limits or final temperature, etc) to solve the problem but I was not successful.

Regards.

An amount of chicken in the form of a rectangular block, 25 mm thick is roasted in a microwave heating system. The centre temperature of the chicken block is 100°C, when surrounding temperature is 30°C. The heat transfer coefficient between the chicken block and air is 15 W/m2K. The thermal conductivity of the chicken can be taken as 1 W/m.K. Calculate microwave heating capacity during steady state operation?

Propulsion, Jet Engines, Thermal Efficiency

experimentally it is noticed that the rate of heat flow does not change in both cases of flow through thin or thick insulator. i urgently need scientific explanation

In general, the speed at which vibration travels through a medium is the speed of sound. If the essence of heat transfer is the transfer of molecular kinetic energy or momentum,then the speed of heat conduction should be comparable to the speed of sound. However, in general, the speed of heat conduction is incomparable to the speed of sound. Why is that? (⊙_⊙)?

It may seem absurd, but based on the above description, is it possible that the essence of heat transfer is not the transfer of kinetic energy or momentum of molecules, but the release of photons with different numbers through the transition of the energy level of the electron cloud, and these photons transfer energy to nearby molecules with lower temperatures, and so on. If so, the heat transfer process is not simply understood as the transfer of molecular kinetic energy or momentum, but as a complex electronic transition process. When thermal equilibrium is finally reached, the electron cloud within the molecule converges to a certain energy level with probability (similar to the Maxwell-Boltzmann distribution ?). The temperature of an object can not be said to reflect the average kinetic energy of molecules, but the average energy level of electrons ?

The above statement is the author's speculation, which may be flawed. It invites experts and scholars to provide criticism and corrections. Thank you very much for your valuable assistance.

Thanks♪(･ω･)ﾉ

I need to a "UDF" for calculating the heat transfer coefficient

where use in local thermal non eqilibrume "LTNE" method

for simulating heat transfet in porous media by Fluent!!!

I want to use local thermal non eqilibrume (LTNE) method for simulating the heat transfer in metal foam (sic).

in thise method heat transfer coefficient must be enter to calculation process with "UDF" .

i want to this "UDF". can you help me???

Hello.

I need to evaluate the nusselt number for Nu=4.36 for constant heat flux case.

My hand calculations give the Nu number at the exit gives Nu=4.36 but I'd like to evaluate properties like, the local Nu number or the local heat transfer coefficient etc..

Can anyone briefly guide me how to do it in COMSOL?

I know there are a lot of people struggle to find it but there is no brief answer for that.

Thanks

I am working on a project to recover waste heat for industrial processes and use it to heat up sand to 250 degrees Celsius. I am an electrical engineering student with not much knowledge about heat transfer and heat exchangers, but I am learning very fast about them. If there's anyone working in the thermal energy space and with heat exchangers knowledge, please assist me.

How to make buildings resistant to earthquakes?

Now in Iran, according to my suggestion, Unilit roof is used in the roofs of residential and office buildings, which is very light. I took this suggestion in an article for the seismological organization in Tehran and gave 14 suggestions to prevent the Tehran earthquake, including 2 They implemented it. One of them removed the bricks from the roof of residential and office buildings and put unilite and poured concrete on top of it, which is very resistant because there is a round rod inside the bits and it was mixed with concrete, and I also said that in metal buildings from 7 or 8 should be used next to the walls because it makes the Masguni houses stronger and also 2 parking spaces should be used under the buildings, like palm trees or dates, which have deep roots and will not fall during an earthquake. Buildings must have deep roots and also in the science of retrofitting structures, divergence is used, that is, natural or artificial rubber is used under the pillars of the houses, and steel springs are used in the middle, so that during an earthquake, the building, like a car or A car that has a spring and the springs play, the building goes up and down but does not fall, and this is a building engineering science that makes buildings resistant to earthquakes and natural disasters. And secondly, through the injection of water and salt solution, the energy of the faults can be removed. Because it comes from the earth's core, which has 6000 degrees Celsius of heat. At any moment, this heat transfers to the surface of the earth. Therefore, the energy inside the earth must be removed, and by transferring the water and salt solution that all the oil extraction companies have, which is known as the injection of water and salt solution, like a tiny needle that is inserted into a balloon so that the balloon does not burst, we humans can create an artificial earthquake. Let's prevent the earthquake explosion and create an artificial earthquake ourselves and release the pressure inside the earth. And 3, we should not build residential or office buildings where there is a fault line, because the buildings are heavy and the taller and bigger they are, the more pressure is placed on the faults. So either we have to build a single floor or not at all to prevent an earthquake from happening.

Wisam Fawzi added an answer

I saw that this technique is used in most Iranian structures and my personal opinion is a successful technique.

László Attila Horváth added a reply

Did you used technics of Ioannis Lymperis ?

László Attila Horváth added a reply

Did you used technics of Ioannis Lymperis ?

Ioannis Lymperis added a reply

The Ultimate Anti-Seismic Design Method

The design mechanisms and methods of the invention are intended to minimize problems related to the safety of structures in the event of natural phenomena such as earthquakes, tornadoes, and strong winds. It is achieved by controlling the deformations of the structure. Damage and deformation are closely related concepts since the control of deformations also controls the damage. The design method of applying artificial compression to the ends of all longitudinal reinforced concrete walls and, at the same time, connecting the ends of the walls to the ground using ground anchors placed at the depths of the boreholes, transfers the inertial stresses of the structure in the ground, which reacts as an external force in the structure’s response to seismic displacements. The wall with the artificial compression acquires dynamic, larger active cross-section and high axial and torsional stiffness, preventing all failures caused by inelastic deformation. By connecting the ends of all walls to the ground, we control the eigenfrequency of the structure and the ground during each seismic loading cycle, preventing inelastic displacements. At the same time, we ensure the strong bearing capacity of the foundation soil and the structure. By designing the walls correctly and placing them in proper locations, we prevent the torsional flexural buckling that occurs in asymmetrical floor plans, and metal and tall structures. Compression of the wall sections at the ends and their anchoring to the ground mitigates the transfer of deformations to the connection nodes, strengthens the wall section in terms of base shear force and shear stress of the sections, and increases the strength of the cross-sections to the tensile at the ends of the walls by introducing counteractive forces. The use of tendons within the ducts prevents longitudinal shear in the overlay concrete, while anchoring the walls to the foundation not only dissipates inertial forces to the ground but also prevents rotation of the walls, thus maintaining the structural integrity of the beams. The prestressing at the bilateral ends of the walls restores the structure to its original position even inelastic displacements by closing the opening of the developing cracks.

Article The Ultimate Anti-Seismic Design Method

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Miguel Angel Morales added a reply

July 9

There are two ways to achieve it. To start, we can make buildings more ductile, that is, they can withstand stronger deformations without failing; On the other hand, we can design more rigid structures, which implies that the buildings resist greater accelerations.

These systems consist of elements for energy dissipation or assimilation. The first type of system seeks to increase the capacity to "lose" energy, such as the "Saint Andrew's Cross" trusses, and others work as seismic dampers or isolators.

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Khawaja Muhammad Iftikhar added a reply

July 25

Abbas Kashani

Miguel Angel Morales

To make buildings resistant to earthquakes, it is essential to incorporate various engineering principles and design practices. Here are the key steps and considerations in detail:

By integrating these principles and practices, engineers can significantly enhance the earthquake resistance of buildings, thereby reducing the risk of damage and loss of life during seismic events.

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Sebastian Schmitt added a reply

20 minutes ago

Khawaja Muhammad Iftikhar, do you really think that a random, AI-generated answer is helpful for Abbas?

… 

I want to fix it to run APEA, the problem is when I run the APEA in the heater give me a error, but the temperatura difference is about 160 F.

Someone can help me?

The simulation is in Hysys

Excuse me about my English language skills

I am an undergraduate mechanical engineering student seeking suggestions on topics related to either thermodynamics, fluid mechanics, heat transfer or renewable energy for my final year project. The topics I have found require a higher level of education. I am trying to bring it down to an undergraduate level, however I am hoping that new suggestions might shed more light or spark a new interest.

Thank you in advance.

Heat transfer

Recently I was reproducing the Eulerian two-fluid fluidized bed with buried tubes, the purpose of which is to measure the convective heat transfer coefficient around the buried tubes, but after trying several papers I found that all of them have a layer of gas at the bottom of the buried tubes, while the bottom of my buried tubes are full of solids. Does anyone know why this is?

In Abaqus heat transfer analysis, when assigning furnace temperature to a column (H-Section), how we identify exposed and unexposed surfaces? As in a furnace, all surfaces are exposed. On which surfaces should radiation and convection interactions be assigned? As, for beams, typically, the top surface of the flange is considered unexposed while the remaining surfaces are considered exposed. What should be the approach for columns?

I am trying to design a heat removal system for a specific application. As the heat flux is very high, the only way to reduce the temperature is by increasing fluid(water) velocity. I am worried about the erosion of the channels. The material is copper and SS304. The fluid is DM water. Is there a model or empirical relation by which I can predict the erosion of the channels over time? Is there any hard limit for water velocity in cooling channels?

Can you help me find modern research to improve heat transfer by introducing obstacles (disturbances) such as rings or other things inside heat exchanger tubes?

In the field of heat transfer

I found this article: that claims circular profiles are better for heat transfer than streamlined profiles as they induce more turbulences. Is this the case with other shapes as well? what is the best profile?

I am doing the thermal analysis of FSW welding. The heat transfer coefficient is applied on the surface, but our SPH part is meshed, how can I apply this coefficient?

After finishing the analysis and drawing the temperature diagram of the particle, it can be seen that the temperature of the particle is fixed at the same maximum temperature and does not cool down because it does not know how to apply the coefficient of heat transfer to the environment.

Could anyone explain *how to* or give an example of receiving heat flow (watt) for the FE element?

I understand that *GET command is useful like

*GET, PAR, ELEM,NO_ELEM,...,SMICS

but can't get the result.

For example, I used PLANE77 or SOLID90 types of FE.

How to solve this problem when Aspen economic evaluation was performed? It said "Temperature difference is insufficient to perform the heat transfer."

Hello researchers

I'm working on a simulation in ansys fluent which is about the melting of a PCM in a vertical triplex tube.

As you see in the below pictures i did a structured mesh and then the results was good in the beginnig but after a while it's not.

I spent a lot of time in this but nothing to say.

I though maybe there's a problem in the thermophysical properties of the PCM and i did some changes like input as polynomial for some thermophysical properties but nothing it goes worst.

Heat transfer (gas radiation) does not support the second law of thermodynamics.

Please refer to the following text and pictures for details

Gas radiation and absorption occur throughout space, and gases at different locations absorb energy differently from remote radiation. The different amount of radiation absorbed by gases at different positions can lead to temperature differences. The second law of thermodynamics is invalid.

Do scientists have to wait until nuclear war breaks out to believe in the existence of perpetual motion machines?

Hi every one

I have a model in Abaqus standard with Heat transfer. When I restart this model , Abaqus exit with this error:

"Unable to open the file <rank=0,arg_name=E:\ABQ

Model>Job-2.mdl"

How I can fix this error?

Thanks

hello Everyone,

if I want to study, coal combustion in different atmospheres for example in O2/N2 and O2/CO2. I obtain the kinetics of both atmospheres using Hetrogenous models. ( Shrinking core model ) and Random pore model.

I was wondering if it’s possible in CFD to study particle profile. Does the heat transfer affect in CFD will calculated based on the Gas composition input or I should add something in UDF file.

FYI, the reaction models are based on conversion so I am not really sure how CFD will identify the differences in Atmospheres.

further, I wish If I found a sample UDF file that been used for Hetrogensous models.

Ahmad

I am simulating a transient conjugate heat tranfer for a furnace, that has three domians, two fluids and one solid. The solid domain is in between the two fluid domains. There are heating rods in both fluid domains. These heating rods are heated at given heating rates, in my case at 10 kelvin per minute upto 1080 kelvin. This gradual increase is given to the rods via profiles in boundary conditions. The fluid domains are heating up correctly, but the temperature for solid domain is increasing much slower as compared to fluid domains.

After 1700s flow time, the average temperature in fluid domain goes upto 510K but for solid it increases to just 365K. I think its because of the fact that the convective heat transfer rate is faster than conductive heat transfer rate. But does this correspond to the reality or not? I have added a temperature profile at a plane.

Further, the solid is 22mm thick and the temperature does not change along the thickness as well (the whole solid is at same temperature), although there are 4 heating rods in the lower fluid domain and 14 heating rods in the upper fluid domain. I have attcahed the geometry for clarification.

The interface between solid and fluid is coupled by wall and shadow wall. I have used share topology for interfaces as well. Right now, i have not included any velocity, all the walls except the interface walls are at zero heat flux. I am using SIMPLE solution method and an automatic solid time step calculation method for calculating solid time step. Is there any way to solve this issue?

Regards

R. M. Ziaur

contact: ziaur.math.buet@gmail.com

Hello,

I have recently switched from doing ligand into protein for ITC because my ligand is in DMSO and has low solubility at 10% DMSO; therefore, now I am doing protein into ligand -- the heat transfers are much better and seem to correlate to the protein concentration loaded in the syringe which is good to see.

However, at the end of my titration regardless of the concentration of ligand or protein added there is an increase in heat transfers. I am also seeing this in my protein injections into buffer alone.

Any thoughts on why this might be happening?

For my multiphase 2-D simulation, I am trying to add an expression HTC = q/Twall-Tsat, but it's not working any ideas on how to add this expression and then make a contour from it?

I am currently working on pin fin in microchannel. I want to calculate heat transfer and thermal boundary layer of that pin fin at different Reynolds number. Can anyone tell me how to find it in ANSYS Fluent Software?

Hi,

DFT is widely used to predict Material Properties, I wonder to what extend is it relevant in the study of solar cell, namely the phonon and heat transfer.

Thank you

Hello,

I am trying to simulate two phase flow (laminar and phase field module of comsol) inside a pipe with the heat transfer from the pipe wall. when I run the model without heat transfer module, I got the convergence but as soon as I add heat transfer module my model is not converging. The issue I am facing in coupling the two phase flow and heat transfer module.

Please suggest me if some body know how to address this issue. All type of suggestions are most welcomed.

Thanks.

-Akshay

Suppose, we need to solve 1D heat conduction equation numerically to simulate the heat transfer for a steel rod where convection occurs at its surface. Now, how to solve the 1D heat conduction equation considering the convection scenario also as boundary conditions? any suggestion or resources?

Suppose we have a 1-2 pass heat exchanger. It's U =500 W/m2K.

Now, lets say, we want to approximate it with 1-1 pass heat exchanger. Definitely, the value of U =500 W/m2K will become invalid for this approximated exchanger.

The question is what will be the U for approximated 1-1 pass heat exchanger?

Does an increment in the width of the magnet and electrode in the Riga plate affect the fluid flow behaviour in skin friction and heat transfer rate?

I want to determine the specific heat capacity of my composite samples(CF/PEEK), however I get different Cp if I use the heat flow data on heating or cooling. I thought the Cp should be the same when heating up or cooling down the material. I checked the baseline corrected heat flow data of the samples on heating and cooling and they differ the same way as their resultant Cps. Has anyone also come across this problem or knows what could cause it?

آHello all dear

What reference should I use to calculate the heat transfer coefficients of plate exchangers that has step-by-step solutions?

It's a tube & shell exchanger

Hello, the Research community,

I'm currently working on a project involving heat transfer between a solid domain and a liquid domain using Ansys Fluent, and I'm facing some challenges. Here's a brief overview of my setup:

I aim to simulate and analyze the heat transfer process between the solid domain walls and the flowing liquid. I'm seeking guidance on the further steps to solve this problem effectively. Specifically, I'm looking for advice on:

I would greatly appreciate any insights, tips, or step-by-step guidance from those with experience in conducting heat transfer simulations in Ansys Fluent. Your assistance will be invaluable in helping me advance my project.

In addition, kindly guide me through the necessary steps to create an effective heat transfer interface between the solid and liquid domains in Ansys Fluent. Any insights, tips, or tutorials to help me set up this heat transfer simulation would be greatly appreciated.

Thank you in advance for your assistance.

Thank you in advance for your support.

Best regards,

Sudeep N S

I just need the Hc

I'am trying to do a Heat transfer simulation in abaqus.

I have sucessfully passed the verification check and the link between fortran compiler and abaqus is established, and further verified as the UMAT subroutine is working.

Has anyone experinces that only the DFLUX is causing compilation errors?

Dear Genius Researchers,

I would like your guidance if anyone can help me in model (Numerically) pool boiling heat transfer phenomena. I am working on Mathematical modeling of "Quenching process", and stuck in lot of theories, still unable to find way to model the "convective heat transfer coefficient" during pool boiling in quenching a steel specimen.To make it simple can we use one dimensional FE method in doing so...? Please share your expert opinion and guidance.

Thanks

Attention to COMSOL users! I'm excited to collaborate with those who have experience in the AC/DC and Heat transfer modules. If you have an active license for V6.0 or V6.1, feel free to send me a DM. Let's work together!

Hello

According to the studies I had about the heat transfer coefficient (U-Value) of greenhouse glass, according to the standard, this value should be equal to 1.13 Btu/h.ft^2.F for single-paned glass, but this value is lower for construction glass. Does anyone have information and experience in this matter to know what kind of glass is this standard for greenhouse glass?

Thank you in advance for your time.

I'm using Fluent and NIST Real Gas Model for supercritical fluid heat transfer but am getting following error . REFPROP_error (203) from function: tprho (density) [TPRHO error 203] vapour iteration has not converged

I am attempting to create a model of speed core walls (concrete-filled panels) subjected to fire loads in abaqus, using two analyses. The first analysis involves heat transfer to obtain temperatures at the nodes, while the second analysis is a general static analysis where I apply an axial load and then incorporate the temperature. The issue I'm facing is non-convergence due to plate buckling and excessive deformations, especially at the beginning of the process. Any ideas on what I might be doing wrong? I've attached the input file for reference.

I am trying to model heat transfer as result of a fire in a reinforced concrete wall in 2D.

I get the following error when combing a 2D homogeneous part (concrete) with a 2D wire (rebar): STRESS-DISPLACEMENT ELEMENTS OR OTHER ELEMENTS WITHOUT TEMPERATURE DEGREE OF FREEDOM ARE NOT ALLOWED IN A HEAT TRANSFER ANALYSIS

have simulated a hydraulic jump. There is a difference in water and ambient(air)temperature and as such there is heat transfer across the water-air interface. I have used VOF model and Standard K-epsilon model for the simulation. Energy Model is activated. Radiation is not considered.

Is there any way to determine the total heat transfer rate across the water-air interface bounded between the two sections(vertical lines) as shown in figure below? Also, is there a way to determine heat flux across the same interface or average equivalent thermal conductivity or average heat transfer co-efficient at the interface.?

Also I tried to determine heat flux across a point at the interface in CFD post. But it was shown as "Undefined". While the heat flux at any point at solid boundary could be easily determined. Why?

Hello Everyone, I used a simple 2-D UMAT for a Coupled Heat Transfer and Displacement Problem and Generated the Stiffness Matrix through the Input file. I can see few negative nodal id, can anyone suggest what this means?

I am confused. I got the data of sample mass, time, sample temperature, heat flow, heating rate, baseline temperature.

Dear amazing members,

I have a doubt.

If I have three adjacent planes with different boundary conditions, in a 3D domain, Dirichlet (fixed temperature) on one plane, Neumann fixed flux on another plane and Neumann heat conduction on another, then what should I do?

Should I consider all the conditions on the common node? I read somewhere that if Temperature and heat flux is specified on a node then only specified temperature should be considered, but I don't know if I should ignore convective heat transfer when temperature is specified.

And in 2D case, when only temperature is specified on one edge, and convective heat transfer on adjacent edge? Then should I consider the heat convection at the common node these two edges?

Thank you 😊

How can I find value of convective heat transfer coefficient (h) of free air at -20 degree Celsius? Is there any h vs T graph? Or data table?

Description: The air is under natural free convection and the pressure is 1 bar to 0.1 bar.

I want to calculate Rayleigh number and Nusselt number of a PCM-heatsink to analyze the intensity of the natural convection of PCM. There are some fins inside my heatsink to enhance the heat transfer. Now I am having trouble calculating the characteristic length to use in Rayleigh and Nusselt dimensionless numbers.

I would be grateful if you could help me.

My model for Fluent includes solid and fluid (Fig1)

I have finished simulating flow and heat transfer in Fluent (Fig2).

I want to simulate thermal stress, so I copy the model from Fig1 to Fig3, which includes only the solid domain, and transfer the model to the Steady-State Thermal (Fig4)

However, I can't generate the mesh, and it shows that the input is wrong (Fig5)

I am trying to change the facet into solid and transfer, but not achieve it.

I am working on modeling and optimization of evaporator and condenser, both are plate type heat exchanger. The primary fluid is refrigerant mixture (zeotropic) and secondary fluid is hot water. For water, the open literature has numerous heat transfer correlations but for refrigerant mixtures I could not find any flow boiling or condensation correlation in heat exchangers. Although there are few studies that provide flow boiling or condensation correlation of zeotropic fluids in tube. But since the flow pattern is different in tube and plate heat exchanger (vortex or swirl flow), is it reasonable to use flow boiling or condensation correlation of zeotropic fluids in tube instead for flow in plate heat exchanger as well? 

The flow boiling and condensation heat transfer correlation for refrigerant mixtures in tube wi

I want to delete elements exceeding melting temp during thermal analysis.

It's transient condition, heating and cooling.

Domain is 2D.

Element used is Heat transfer.

Material is Al.

Defined temp dependent properties density, young's mod, poisons ratio, plasticity, conductivity, specific heat, latent temp, solidus temp, liquidus temp.

I am learning subroutines but please suggest simple way.

Thanks in advance.

I need to fit a multivariable non-linear correlation for a heat transfer problem. Could anyone suggest any tools or software for that?

Hi !

This seems like a not so complex problem to solve although I am not able to set up my ansys workbench, steady state thermal model correctly. Lets say we have a cylinder of length L with sides A and B. If my Ta = 500 deg C and Tb = 10 deg C, I am trying to find the time it takes for them to equilibrium around the length L. This also means that I want to see how the heat transfer looks like. I gave the upper and lower boundary temperature, although I am not sure how to setup for what I want.

The heat transfer behaviour of hydrophobic surfaces presents a fascinating and intricate phenomenon, particularly concerning the early formation of bubbles well before reaching the critical temperature. Unlike conventional surfaces, hydrophobic surfaces possess unique properties that repel water and promote the formation of a stable air layer when exposed to a liquid medium. This air layer acts as a thermal insulator, significantly reducing the direct contact between the liquid and the surface, thus impeding heat transfer.