Science topic

# Heat Transfer - Science topic

Explore the latest questions and answers in Heat Transfer, and find Heat Transfer experts.

Questions related to Heat Transfer

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

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.

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 😊

Does stirring increase heat transfer and relationship between temperature and solubility of a solid?

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.

How do greenhouse gases affect the heat flow into and out of Earth atmosphere and difference between greenhouse gases and global warming?

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.

in the model I am simulating, the mixture of ethylene glycol and water is flowing in the hollow fiber membrane (a cylindrical hollow tube made up of porous media). during the flow, the water in the mixture of ethylene glycol+ water will selectively evaporate through the porous media due to the pressure difference inside the hollow fiber membrane and outside hollow fibre membrane. Please help me to solve this. Any software can be recommended.

Let's say a heat transfer fluid in parabolic trough collector has a maximum working temperature 590 degrees celcius. How do we control it to have exactly 500 degress in the outlet of the collector?

Hello Guys

I have a problem with simulation,

my case is Helix Grove Tube to see the enhancement for heat transfer

so its multiphysics ( copper + water )

could you help me?

please see the atthecd files .

the hot fluid is flue gas at shell side, which is mixed, the cold fluid is water at finned tube side which is unmixed?

Why transfer of heat takes place faster in liquids than in solids and what is the process where heat flows in the absence of any medium?

What is the effect of uneven heat distribution and what is the mode of heat transfer in water or gases?

Many researchers correlate their experimental data in an equation by various dimensionless parameters like Weber number, Bond number, Reynolds number, and so on for the thermal and hydraulic performance of a particular working fluid of heat exchanger. For the development of correlation of boiling and condensation heat transfer in a plate heat exchanger which are the most important dimensionless numbers?

How many data points are minimally required to develop a standard correlation?

I am trying to simulate a radiator fin on STAR-CCM+. I have read that to calculate the viscous and inertial coefficients, I need the inlet velocity and outlet pressure as boundary conditions. I do not have the pressure drop as I need to get that from the simulation to obtain Forcheimer's relation. I am quite confused and any help will be appreciated

I am trying to model a battery pack of Li-ion cylindrical cells. I read somewhere that heat transfers significantly along the plane of electrodes. means in the cylindrical cell, more heat transfer will occur in the axial direction. But in the image, which is from a research paper on designing BTMS, they didn't simulate the top and bottom parts of the cell, saying that heat transfer will occur from the side of cells. Can anyone please explain what is the correct thing?

Suppose we have

**a HEN with several multi-pass heat exchangers**. However, due to some technical constraints**all these exchangers are modelled simply using single pass equations.**What will the impact if such a simplistic model is used in optimization problems, such as

**network optimization for retrofitting or cleaning scheduling?**For instance, it is clear that we may not end up with global optimal solutions but still what will the qualitative impact of such approximations?

Hello,

I would like to analyze the heat Transfer effect and flow phenomena in hot runner System of injection mold. Basically this is a dynamic thermal Analysis, where we can give nozzle Forward and backward movement, other properties and find out the thermal and flow behaviour.

Thanks.

Where can I find the physical property formulas of terminols as in the picture I shared. Therminol 66, Therminol 62, Therminol VP-3, Therminol....(for all therminol heat transfer fluids)

Even after changed to Heat Transfer Element type, above error is coming

I am working on pressurized liquid heat transfer related problems. I got correct flow regimes for heat transfer at atmospheric pressure. Now I need to pressurize the fluid more than 300Bar and analyse how the heat transfer occurs. Even though we approximate liquids to be in-compressible, beyond 300bar the volume reduces hence the change in density comes into picture. how to model this in Ansys? What should be given in density column in material properties of liquid? I tried with compressible-liquid option and I am not getting correct flow regimes. I should find how the transfer occurs at elevated pressure ranges. Need your help!!!

Thanks

I am trying to do conjugate heat transfer analysis in Abaqus by using fluid-structure co-simulation between concrete and air. In the standard model, I have defined transient heat transfer step, whereas, flow step in CFD model with temperature energy equation. Equal step time and initial increment have been set for both steps. Same meshing element for both models. The whole model is in mm-tonne-mJ unit system. But somehow, the heat is not transferring despite of more than 500 increments...

Sometimes I get a warning " The assembly is out of date and needs to be regenerated. The input file was not generated and the co-execution was not submitted".

If someone has been through the same problem, please highlight any key points I am missing or add some helpful suggestions/recommendations.

Let's we have two equal sized conductor and an insulator materials, which are perfectly joined together. We have two senerios:

1. Insulator is heated to 300 C and temperature is measured at conductor end (let's say Point A) after 180 seconds

2. Conductor is heated to 300 C and temperature is measured at insulator end (let's say Point B) after 180 seconds

Question is: Will the temperature at point A and B will be same (as total length covered is same) or there will be different temperatures at points A and B due to difference of dT in both cases?

Both the Bell and Kern methods provide correlations for predicting the heat transfer coefficient and the pressure drop in the case of the shell-and-tube heat exchanger design. Would those correlations provide a fair estimate for heat transfer coefficient and pressure drop for fluids that involve phase change? (e.g., boiler, condenser, etc.) or would it work well for single-phase cases? Some fluids might show different behavior. In this case, can we assume that these correlations as generalized correlations independent of fluids?

I am working on design of economizer for water in and out ( 90 C/170 C) temperature and 2000 kg/hr flow rate

and exhaust gas flow 12780 kg/hr and in and out temperature ( 220C/170C)

How to design economizer?

I am simulating a flow in a 3D square pipe with a uniform heat flux applying on the outer surface.

I'm trying to calculate the heat transfer enhancement.

I found difficulties finding the (h & Nu) where I'm trying to validate my experimental results

if anyone has experience in calculating Local and Average Nusselt Number and heat transfer coefficient using Fluent ANSYS or an information that can serve the purpose.

I will appreciate the Help.

How to prevent convection for top surface of cell while having only conduction with tabs ?

Can i use simply convective boundary condition with 0 heat transfer coefficient value for whole top surface ?

What is the best software to simulate heat transfer inside a receiver tube of parabolic trough solar collector?

Greetings to all.

I am trying to simulate heat transfer between 2 parallel plates.

The source plate have heat condition and I want to get temperature profile in upper plate, where heat flow through convection between the two .

Can someone assist me with some tips?

Dear all,

I am modeling PCM in heat transfer solids and fluids using COMSOL 5.6, but I am facing some problems with the solution in the initial time steps (within 20 seconds).

The domain temperature goes below the initial temperature of the domain.

I am using a time-dependent PARDISO solver and time-stepping BDF. I am attaching an image for your reference.

Your answer will be highly obliged.

Thanking you all

I am trying to develop a UELMAT for a steady heat transfer analysis. My problem is that my element doesn't work when convection interaction is applied to it. I have tried both to apply this concentrated interaction in the nodes (since superficially it does not work in user-defined elements) and trying to add the FILM subroutine inside the UELMAT subroutine. In all it returns me the nodal temperature as 0 in all the nodes.

I wanted to simulate a 4-cylinder engine transient heat transfer. Because the combustion in cylinders has delay and not at the same time, I wanted to give different times for setting heat-flux on cylinder liners.

hello,

I am trying to calculate heat flux in different depths of a thin film. I have studied some papers specially "Solution of near-field thermal radiation in one-dimensional layered media using dyadic Green's functions and the scattering matrix method". but still I am confused.I wonder if you have any suggestion. thank you,

Consider a pipe in a cylindrical coordinate. The flow is a fully developed laminar flow and the temperature field is T(x, r, θ). At a certain cross section x_0, the mean temperature is T_m and the mean velocity is u_m (To calculate T_m or u_m, integrate the temperature or velocity over the whole cross section and divide the result by the area). A conjecture is that u*partial T/partial x=u_m*dT/dx, where partial denotes the partial derivative. This seems reasonable since the heat transfer should be easier where fluid flows faster, which leads to a smaller gradient. But how can I prove it strictly?

Dear researchers, I am currently working on a project with the aim to design a small-scale pellet stove for residential heating applications. Before making a prototype, I am required to develop a mathematical model that describes heat transfer phenomena inside the pellet stove and do a simulation about it. I'm having a hard time finding a consistent mathematical model in the literature that complies with my application. Do you know any good references that did similar work with pellet stoves or any biomass boiler in general?

Thanks in advance.

I have calculated the power losses of the system and the inlet and outlet temperatures for both air and waterside. Using LMTD method, the overall heat transfer coefficient of the CHE was found.

I am unable to proceed further, mainly because I could not find any reports on the heat exchanger(it is similar to a car radiator but smaller form factor) I am working with. How do I find the heat transfer coefficient for the air and water side?

I am unsure of which relations to use from Kays and London book on Compact Heat exchangers (CHE).

Any suggestion on software/books/reports on finding the heat transfer coefficient of this type of heat exchanger would be greatly helpful.

Thanking you in advance.

Hot water enters on the shell side and cools along the tubes. Why does the heat transfer coefficient decrease along the tubes and have a lower value at the water outlet?
And why does the heat transfer coefficient decrease when the water inlet temperature decreases?

From my heat transfer analysis work i am not getting proper Nodal Temperature variation. Although, i have provided proper temperature depended material properties. Please share your valuable suggestions.

Can anyone help me to understand/provide some reference regarding how to calculate heat flow of the area from the radioactive heat production values.

Hi, I have been trying to import the thermophysical properties of CO2 (for the supercritical region) to Fluent by using UDF (only for 80 bar). End of the analysis, the result is not correct. I think Fluent is pulling a Tref value which causes my enthalpy to go negative; therefore, the energy equation does not give accurate temperature results, so the result of thermophysical properties, which are functions of temperature, are wrong. I want to be grateful if you could share your recommendations, especially on the methods of correct calculation of enthalpy. My specific heat code is as follows:

#include "udf.h"

DEFINE_SPECIFIC_HEAT(supercritical_cp, T, Tref, h, yi)

{

real cp;

if (300. >= T)

{

cp = 2.256999118844760E-02 * pow(T, 4.) - 2.606618818487370E+01 * pow(T, 3.) + 1.129129898467780E+04 * pow(T, 2.) - 2.174235523392760E+06 * T + 1.570278261279480E+08;

}

if (306. >= T > 300.)

{

cp = 1.147018354719330E+01 * pow(T, 4.) - 1.385519872072390E+04 * pow(T, 3.) + 6.276090044658930E+06 * pow(T, 2.) - 1.263530241490370E+09 * T + 9.539285116131690E+10;

}

if (307.8 >= T > 306.)

{

cp = -1.611612838918710E+04 * pow(T, 4.) + 1.978085636985280E+07 * pow(T, 3.) - 9.104578256081260E+09 * pow(T, 2.) + 1.862478067464320E+12 * T - 1.428738938943020E+14;

}

if (310. >= T > 307.8)

{

cp = -1.576135476848110E+03 * pow(T, 4.) + 1.945866130859760E+06 * pow(T, 3.) - 9.008641337104630E+08 * pow(T, 2.) + 1.853611584329810E+11 * T - 1.430227164258690E+13;

}

if (320. >= T > 310.)

{

cp = 1.770529718817220E+00 * pow(T, 4.) - 2.242833202341920E+03 * pow(T, 3.) + 1.065432793165650E+06 * pow(T, 2.) - 2.249454519629040E+08 * T + 1.781003821884030E+10;

}

if (T > 320.)

{

cp = 2.086961941877520E-03 * pow(T, 4.) - 2.851496372954040E+00 * pow(T, 3.) + 1.461548345109060E+03 * pow(T, 2.) - 3.330816449664890E+05 * T + 2.848088978782360E+07;

}

*h = cp*(T-Tref);

return cp;

}

Dear all

Recently, I read this sentence:

" Reduced heat transfer in the axial direction at the pellet ends yields higher local temperatures, resulting in a shape that resembles an hourglass."

I would like to know why does heat transfer reduce in the axial direction at the UO2 pellet ends?

Regards

are there any accurate correlations apart from Gnielinski for heat transfer? my Reynolds number under 2500

I am going to model heat transfer in volcanic geothermal areas around intrusions. Has somebody experience with TOUGH3 and HYDROTHERM? Comparing these programs what are their advantages/disadvantages?

it is said Zukauskas Correlation can validate the heat transfer simulation over cylinder without experimental data. can we believe?

How many ways to capture radiative heat transfer and convert it into electricity?

I am looking for research journals and supporting documents that explains the physical phenomenon behind Vapour-Liquid interfacial heat ( and mass transfer) and possibly a general mathematical expression to deduce the Interfacial heat transfer coefficient (IHTC).

The intend of the same is to apply in heat transfer process to enhance the accuracy of predicting boil-off in supercooled gases.

Hello,

I am trying to model a 3D heat transfer problem in COMSOL v6. The geometry is very simple and attached below. The length of model is 2m. Rectangular block is 200mm * 160mm.

The point of interest is to calculate equivalent thermal conductivity of air. Thermal conductivity of air in this region depends on all 3 types of heat transfer. Radiation is from the enclosing material (Insulation material on inner side and steel on the outer side)

Conduction and Radiation can be modelled easily. But including the convective effects is little tricky. Ideally, whole of the system should be simulated with induced velocity. But including a lot of physics is making the computation tediously long.

Does anyone how to model this case? One way is to consider analytical Nusselt number correlations. But I do not know how to couple this correlation as my model is also dependant on radiation.

Thanks in advance.

I want the procedure to simulate the entropy generation in the enclosure with the effect of natural convection and radiation heat transfer using FLUENT / ANSYS.

I try to analyze heat transfer in biological tissue at different ambient situation.

I a have three domain that I need to assign surface boundary condition on it, but unfortunately some of my surfaces are not applicable.

I use assembly form instead of union form. after that I can assign heat flux boundary condition on that surface but I miss one of my domain.

I try to use union tool from Booleans and partitions but it made 5 domains and solution not converge after using that domain.

I will be thankful if anyone can give me any advise.

Thanks in advance.

**Info**: I was using Tzero Pan and Tzero lid, and around 8 mg of (powdery) material per pan.

**Observation**: The pan comes out of the measurement showing a slightly opened lid and some material overflow.

**My question**: From the graphs, how can I determine at what temperature did this occur? In other words, can I recognise from looking at the graph only, when some material overflows my pan?

**Example**: Looking at the heat flow below: Is it correct to analyse that the pan opened at the 160°C mark, and can be shown by a sudden sharp endo-thermal event in the heat flow.

Dear all

How can be activated the angle of magnetic field (

**) in FLUENT for convection heat transfer, as shown in Figure 1? step by step please.***γ*I'm trying to perform analysis of heat transfer for a tubing system. The tube is pumping water, we can prescribe inlet temperature down to 10C, but are limited by cooling input wattage of ~150W. The tube is exposed to conduction against human skin at ~37C, as well as free convection to air at ~23C.

By approximating surface temperature values as constant along the tube one may use existing equations to solve for the mean temperature at any point. How would one approach the problem of exposure to two constant temperature surfaces? A resistance network can be developed for each of the two cases, but the local heat transfer is dependent on the mean temperature of the fluid, and the mean temperature of the fluid is dependent on the inlet temperature and integral of the heat transferred since the flow began.

Is it possible to develop an equation which can be used to express the mean temperature in the tube as a function of distance? Is this an issue which should be approached using CFD? Any guidance is welcome.

We have the Thermo Fisher SpeedVac Savant SPD1010 system in our laboratory. The manufacturer recommends the use of Cryocool as heat transfer fluid to conducts heat away from the glass condensation flask, allowing vapors to condense on

the flask walls. However, we often need to add more fluid to complete the reccomended Cryocool level inside the chamber. Nevertheless, Cryocool is too expensive for us, and I would like to know if there is any solvent or solution that we can use/prepare to replace this heat transfer fluid without damage the equipament. Ethanol may be used instead? Thank you!

I want to specify natural convection boundary condition at the top of the wall. I am trying to reproduce some results. Author didn't specify value of h (heat transfer coefficient). He gave an expression for it. You can see it in attachment. I don't know how to incorporate this equation in my boundary. I am attaching geometry and equation that I want to apply at the top wall. Can anyone please help me in it?

Dear All,

Imagine simultaneous heat and mass transfer between gas and solid (a reacting porous particle) in a control volume.

Mass transfer takes place from only solid to gas while heat transfer could be in either direction; concerning the latter, the two likely phenomena due to temperature difference between these phases are convective and radiative heat transfer.

Another phenomenon that could contribute to the differential energy balance of solids and gas in the control volume is energy transfer due to mass transfer (from solids to the surrounding gas); is this also influenced by the temperature of these two phases? ..if so, how is that? I came across the mathematical expression shown in the attachment and am clueless.

Any inputs in this regard are highly appreciated.

Regards,

Kareem