ANSYS CFD Tutorials | Nusselt Number Calculation in ANSYS Fluent | Convection Heat Transfer
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- Опубликовано: 11 сен 2024
- From this tutorial, you would be able to know about how to set up an axisymmetric problem. How to find out Nusselt no. by using the expression input method. Please comment if have any doubt in any stage. Subscribe to our channel and hit the bell icon. Like us on Facebook.
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hello sir i have this problem but i use Fluent 6.3 and i dont know how can i calculation Nusselt number
so i ask if you have any idea about it please
Sorry, have no experience of older versions.
whilde defining expresion for Nusselts No (@ 24:10 mins), what is the significance of 0.02 [W/m/K], where did it come from?
Thankyou and awaiting your reply.
its thermal conductivity , Nu=hL/k= q(2R)/k(Tw-Tm)
sorry the "k" is missing in the nusselt no expression.
Is it thermal conductivity of fluid or solid??
@@shuvekshasapkota5574 You are carrying a CFD simulation right!!
p.s. Solids dont flow.
1) Could you type here the bracket part of LengthInt(..?...) of Tm equation, it's all blur
2) The formula you used for Nusselt no , you missed "k" in the equation you're showing on screen but you used it while putting the equation in the software.
Thankyou
Also if you can tell how to contour plot nusselts number on absorbing surf.
Hello, Sir, thank you. The video is useful
I want to ask you about the reference values, What temperature should I choose to but it in the reference box? Is it always inlet temperature or another temperature for Nu
Keep the default reference values, it don't affect the solution.
This is so useful .
Which Ansys properties should be choosen for simulation of heat trasnfer characteristics in circular microchannel? Please reply
You need to enable the energy equation in the model. Then in the fluent solver, you need to add some additional data file questions as shown in the tutorial.
You calculated Nusselt Number for 5 points. How to plot Nusselt number for large number of points, say 500?
We have many tutorials on this.
ruclips.net/video/hO_Du_qZcqo/видео.html
ruclips.net/video/pav5rnq2jhk/видео.html
Thanks for replying
In this tutorial, the heat flux at the "heated wall" has been specified, it's easy to apply the formulas to obtain the Nusselt No at these locations. What should we do if the points were set at the the "isothermal wall" ?
You can create a polyline and plot all the Nu value on that.
ruclips.net/video/5JoL_Qbxxq0/видео.html here is a tutorial video for your reference.
my sincere regards sir
I want to know this equal if its correct or nooooo??????
the nusselt number in your video that's not the same as your expression
your written was as
(q *2*R)/ 0.02[W/K/M] (tw-tm) >>>>>??????????????????? WHAT THE VALUE 0.02 MEAN??????
Thermal conductivity
Really excellent.can you please tell me how can i design porous fin in ansys
Hello sir, I couldn’t understand the last part of your tutorial..How did you calculate average nusselt number?
Please explain it
It was really helpful as far as my project is concerned. Please try to help me with few questions: 1. How did you select the Point 1 and Point 2 in Details of "Radial" line under Geometry tab? 2. You tried to create the Table of all the points and Nusselt No. at those point, so is there any method to create that table for all possible values of R. Your reply will be very valuable. Thanks
you can select any point on the heated wall. for Re vs Nu graph you need to collect all these nu values and then plot in ms excel or origin.
Thanks for the knowledgable video sharing . could you please tell me from where did you get the symbol for "dr" which you have written after velocity u* @20:58 mins.Hope you will respond. Thank you
That is Y.
Is the nusselt number obtained from input expression method in post-cfd differs from the nusselt number obtained from facet average surface integral values in fluent itself?
Yes. Both have different methodology to calculate. For more details regarding this refer to the ANSYS fluent theory guide.
@@AnsysTutor thank you for the information
I am also trying to get values of wall temperature and static temperature from facet average in fluent and from Ensight (SpaMean->wall temperature-> then selecting the interface surface of solid-fluid), the results differ by few amounts. Also Cfd-post is freezing in my computer whenever I try to load the data (Ansys version 2022 R1 Teaching).
Hi thank you for your video. I have one issue however, I don't have access to "data file quantities", is there a way to get ? It shows up in the file tab but I can't select it.
First you need to do initialization, after that only you would be able to see the option.
Hello there..I have to simulate a flow in rectangular duct. But I don't have heat flux..all I have is temperature of heater to be 50°C which is connected at the bottom of duct. How to find nusselt no. In this case?? I was able to make a plot of surface heat transfer coefficient and surface nusselt no but I need one value to calculate total heat transfer. What should be done?
can we also calculate nusselt number using averge heat transfer coeffiecient value calculated previously
Yes.
How can i calculate average nusselt number along the whole pipe?
Thank you for the tutorial. It's quite informative. Can you please guide how to obtain the Nusselt number in case of a channel flow (plane Poiseuille flow). I am trying to validate my model with the fully developed Nu (8.235, constant heat flux) but unable to get it in this way.
same problm, are you doing of turbulent?
@@shuvekshasapkota5574 No, I am asking about laminar case.
@@somenathgorai3316 okay, then did you figure out the solution?
@somenath Gorai you need to add the surface nusselt number from the data file quantities, by doing so you can obtain the Nusselt number as the output in any outlet boundary.
@@AnsysTutor Yes I am doing so. Should I choose an axisymmetric domain in case of a 2d channel flow also as you did it for a pipe?
@16:02 nusselt number
@@rahulr3017 njan maranu poi problem...samayam kittumbo nokkam😅
Thank for your contribution. I have a question. I am simulation the same case, but in "solutions", when I do click in "run calculation", my results curves are differents, compare with your simulation. Why? decrease until 450 iteration and then increase until 800 iteration, but then decrease.....etc. Please, help me. Thank again.
check the mesh and boundary conditions.
Can I use the same method for a pipe? if yes, should be any changing in the general setting in the fluent and the boundary condition?
No need to change anything.
@@AnsysTutor sorry I mean for 3D pipes and if the flow is turbulent is there any changing in the boundary condition ?
Nusselt Number Calculation starts at 16:00.
Yes.
awesome..can u plz tell me how to design and calculate all parameters in case of hydrocyclone. plzz
i have one question as i am doing 2d simulation of flow in circular pipe i need to find Nu along the X and i have to validate that for constant wall temperature for fully developed flow Nu = 3.66 . for this i have to create multiple lines manually ( need 1000 lines). so how can i get Nu along x ?. Thanks in advance
We have some tutorials regarding this please follow these videos. ruclips.net/video/hO_Du_qZcqo/видео.html
ruclips.net/video/pav5rnq2jhk/видео.html
Why did you select periodic instead centreline in contour (@ 11:26) ?
Periodic is the surface while centerline is just a line ,we cant get the contour properly on a line thatswhy the surface is selected.
@@AnsysTutor Thanks.
@26:57 mins what you have written after velocity u* ?? . could you tell me sir
I have a question since we have exact heat flux to be q=40 W/m^2, We could calculate the average outlet temperature through using the formula that Q=q*A=mdot*cp*(Tin-Tout) where the A is the area of q=40 applied to and Tin and Tout is the temperatures of flowing air respectively at the inlet and outlet. We could go to the Nusselt number using these equations: Q=h*A*(Tsurface-To) and Nu=hD/k where Tsurface is the mean temperature at the surface which heat transfers from and To is the mean flow temperature of air, what is the point here to use Ansys, can you please describe this because I have a similar problem in my paper. Thanks.
using this formula you can get only the average nusselt no. For local nusselt no you have to follow this approach. As it is difficult to find the local convective heat transfer coefficient .
@@AnsysTutor what about if i plot graph of nusselt no wrt length and get the points and their nusselt value on surface of given length. Will it be same local nusselt no.
Dear Murat,
In a pipe flow for heat transfer there is an energy balance between the change of internal energy of the fluid and convective heat transfer. This energy balance can be written as Qdot=mdot cp Dt=h A DTln. In this relation DTln is the Logarithmic Mean Temperature Difference. You can not write this convective term directly as Qdot=h A DT. Since you don't know the outlet temperature of the fluid, first you have to find the Nusselt number and then with Nu=UDh/k you can calculate the heat transfer coefficient.
The other way is to make an experiment and measure the flow rate, inlet, outlet temperatures and then get the htc.
Hope it's clear.
Ozgun Korukcu Ph.D.
@@mehmetozgunkorukcu3711 hello im using ansys used the same method for square cavity but my average nussult no is not coming the same compared to a published paper result also coming less than 1 for rayleigh number 10^3 .plz help me
@@ninetynine5293 Hi there, are you solving the problem for forced convection or free convection? You wrote Rayleigh number? or is it Reynolds number???
So the inlet temperature is 300k? and outlet is 300k too (pressure outlet), if there are problem described?
can we set the outlet as outflow??
the working fluid is air which receives heat from the adjacent wall, the outlet tempr 300K does not mean the tempr of air will be that much at outlet, you can check after solution also, there would be rise in tempr due to heat gain from the walls.
the tempr at the pressure outlet bc denotes what are the tempr outside of this domain means the ambient condition in this case.
you can take outflow bc also.
@@AnsysTutor tks, sir. one more question about average nusselt number.
For my understanding, we can use Fluent Reports (report- area weighted value- wall flux- surface nusselt number) to find average nusselt number, just need specify the reference value on Fluent ( the length, for example, the diameter of a tube)?
correct me, if i am wrong.
👍
Thank you.
Sir please explain what you write inside the lengthint()... it's not clear
Its the integral along the length.
Excellent
Thank you:)
How to take graph between Reynolds number and Nusselt number
Hello, iss there any way to calculate average nusselt number or average heat transfer coefficient from this way?
yes ,you need to select "additional quantities" in data file quantities, you can get this option , in run calculation page, after selecting the nusselt no , initialize and solve, after calculation complete, go to reports -> surface integral ->field variables =Wall fluxes, surface nusselt no.
@@AnsysTutor thanks for the reply
Most welcome 🙂🙂🙂 Please subscribe 🙏
what about determining Nusselt in a U-shape pipe? is there a way to draw a curved line on the bend and do the rest of the work?
you can give the coordinates of the point in the curved region to get the results.
hey. Just passing by your playlist sir. I'm interested in knowing would you be teaching aerofoil and aerodynamics training?
we don't provide any training. We only help the researchers and students by tutorial videos on this youtube channel.
@@AnsysTutor so can i be getting an help aerodynamic of cars?
what if the boundary is isothermal wall
how can i calculate Nu
You can find it similarly.
@@AnsysTutor i guess i can use wall heat flux to represent q .Is that the same,right?
plaese sir how can i add a fonction of profile velovity model turbulence in the inlet
You need to write an UDF for that and then you can put that at the inlet boundary conditions. Check the ANSYS fluent UDF manual for more details regarding how to write a UDF and interprete it to the solver.
how to calculate local Nu and local h if non uniform flux is applied circumferentially (3D problem in Ansys).
You can use the probe point to find the local Nu.
Very nice sir , can u do that by CFX pls thank u
Thank you:), will try if possible.
@@AnsysTutor thank u so much appreciat that
My nusselt number value is coming in negative, what can be done to correct it?
It is not incorrect to get a negative Nusselt's number.
@@ankitsharma-lo7wt how can I solve it??
I need to get 4.37
And it is coming _0.57
@@ankitsharma-lo7wt my problem statement is of roughness modelling in the inner surface of pipe, with that roughness, nusselt number should increase right?
@@shuvekshasapkota5574 Can you enlighten me on how you know for sure that the value should be 4.37?
@@ankitsharma-lo7wt following the research paper
16:04
It is free or forced convection
Its forced convection , as there is a flow from inlet with certain velocity , if there would be no flow into the fluid domain , then we can say it as free or natural convection. We have some tutorial on natural convection you can watch them to observe the difference.
Here is the link :
ruclips.net/video/XBwDa2YsIeY/видео.html
@@AnsysTutor --- Thank you sir
How to create animation in CFD, I tried to create animation but the animation was not clear.
You should use cfd post processing for animation, you can change the video quality over there.
Hİ Sir pls can you share with me the formula of Tm and nusselt no expession ı tried to write the expression many times but all the time giving an error
we have shown the formula used in this video itself.
@@AnsysTutor yes i know and i sorted my problem out finally i wanna ask you sth why did you put 0.02 W/m/K for Nusselt formula there is nothing correspondend to this value on formula
thermal conductivity of air
how can i get friction factor with the same method plzzz
You need to select that in the data file quantities in fluent before you start the calculation process.
how to calculate the nusselt number with 3D!
similar procedure ,only you need to specify a proble point.
Can I communication with you pleas ?
Mail me on ansystutor7@gmail.com or on facebook page all the links given in the about tab of youtube channel page
Excellent
Thank you:)
How do we choose type of mesh?
You can insert the method in that you can select the mesh type.