and take alook at i.e. Is there an alternative way to assign a surface radiation boundary condition? In order to understand how this works, enable the Equation View, and look at the implementation of the Dirichlet condition (in this case, a prescribed temperature):. March 15, 2018. The basic heat transfer in two solids of material iron. I have tried all the possibilities but still I am not able to get the solution. www.comsol.com/community/forums/general/thread/34647/, Calculating the Heat Transfer Coefficient for Flat and Corrugated Plates, Heat source for conjugate heat transfer model, Can the convective heat transfer at the solid-liquid interface be obtained during convective heat transfer, Solving Models with Step Changes to Loads in Time. You just need to add the volumetric heat source to fluid and solid domains separately. Your internet explorer is in compatibility mode and may not be displaying the website correctly. Version 5.5 The time-dependent solver result (for your reference) is attached herewith. I should get a maximum temperature in the fluid domain not in the solid domain because of higher light absorption characteristic of fluid. I knew that in v3.5 it was physics>equation system>boundary setting. Two physics (bioheat physics and moving mesh physics) are included in model to simulate a laser ablation over a part of the bone. However, in my version, this option is not available (second photo attached). Solving Models with Step Changes to Loads in Time, Applying boundary condition on imported mesh, Modeling Laser-Material Interactions with the Beer-Lambert Law. App . Note that while COMSOL employees may participate in the discussion forum, COMSOL software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version "" COMSOL Multiphysics App . Avoid run-on sentences. rgds The COMSOL model calculated CBL height, TBL height, and MTC scales with v bulk raised to the-0.44,-0.50, and 0.38 respectively. . Be concise and articulate as much as possible. [/QUOTE] 1 Reply, Please login with a confirmed email address before reporting spam. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Your internet explorer is in compatibility mode and may not be displaying the website correctly. COMSOL provides the forum service for the benefit of our users to share content with the community. Hence, they will not be held liable. That boundary condition accounts directly for heat loss from the solid through conduction and the fluid flow that results accounts for convection. Posted May 11, 2022, 8:53 p.m. EDT 0 Replies . Note that while COMSOL employees may participate in the discussion forum, COMSOL software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team. Hi!! You acknowledge that all posts made to these forums express the views and opinions of the author and not the administrators, moderators, or webmaster (except for posts by these people). anup, [QUOTE] comsol heat transfer boundary conditions. Format your post in a legible manner. Please check to see if a topic has already been posted. The COMSOL Access administrators will reserve the right to permanently remove a user account without notice if any of the rules are not followed. COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH), Using the Inflow Boundary Condition in Nonisothermal Flow Simulations, Modeling Natural and Forced Convection in COMSOL Multiphysics, Derivative Boundary conditions for heat and mass transfer, How to Make Boundary Conditions Conditional in Your Simulation. Loud; laissez un commentaire; Boundary conditions in heat transfer. It worked well when there is only bioheat physics, but when i use . If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base. you can use infinite elements. The equation is q = h*(Ts - Tc)^(2.5) [Here q is the heat flux, h is the heat transfer coefficient, while Ts and Tc are the surface and coolant temperatures respectively]. Posted 21.12.2009, . Hence the Q variable or q0_htgh internally enters directly thermal power onto the boundary, while the "h" is proportional to the temperature difference in K of Tinf-T and T is the temperature you are solving for, so Tinf yould be your constant blood temperature, then h should be . I'm using COMSOL 5.3 to simulate laminar flow in a microchannel that has few internal closed features inside. I want the boundary to simulate the material being continuous outside of the model. Physics - Equation Systems - Boundary Settings It works well, except for the boundary conditions. -- You agree to comply with all rules applicable to each service you access through your COMSOL Access account. Hello, I am using COMSOL 5.3a and solving a 3D model using the conjugate heat transfer, laminar flow study. This periodicity can be continuous (the default) or anti-periodic and can control which of the dependent variables that the. Nonisothermal flow combines CFD and heat transfer analysis. Replying my own question in case it helps others. Hi. "The heat flux can only be use for external boundaries. It works well, except for the boundary conditions. Discussion Closed This discussion was created more than 6 months ago and has been closed. Hi all Battery Design Module Updates. Posted: 10 years ago. The goal of COMSOL Access is to provide a forum for you to communicate effectively with COMSOL as well as your colleagues within the multiphysics simulation community. Because I want to consider the heat loss, I tried adding the convective cooling. I am using comsol 5.3a version The heat source is only active initially, and I would expect the model to reach thermal equilibrium with the surroundings/boundary conditions. For example, you may have a tube in which the helium will flow through and inside that tube you will have your heated metal bar. Discussion Closed This discussion was created more than 6 months ago and has been closed. Heat Transfer Boundary Condition. The new Thermal Connection multiphysics couplings are designed to define a continuity condition between two temperature fields, computed by a domain heat transfer interface and a Heat Transfer in Shells interface, respectively. 3 Replies, Please login with a confirmed email address before reporting spam. . The max temp is obtained at the solid domain rather than fluid. listed if standards is not an option). You agree that you will not otherwise use your COMSOL Access account to violate or to assist anyone in violating any law. There is no need for a different thermal boundary condition there. Now to understand how COMSOL isusing these and how they are related (Tinf is only linked to "h") take a look at the equations: You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Posted Dec 21, 2009, 2:36 p.m. EST Please login with a confirmed email address before reporting spam . Does the nitf node of COMSOL account for this loss? There is no need for a different thermal boundary condition there. Review your post before publishing it. In my simualtion the thin film is irradiated by a laser beam, and the substrate is transparent to the wavelenght. Try to avoid using text speak, net speak, or slang. My model is similar to the tutorial here. Anyway, I'll just leave it at that for the moment. Please login with a confirmed email address before reporting spam . Dear Dr. Elabbasi, please how comsol assume, boundary at solid-solid Interface? The pipe was settled vertically . When posting, understand that you are trying to communicate with other people. Got my help from Comsol tech support. in doing so you, for the purpose of analyzing heat transfer efficiently comsol multiphysics software is one of them which has been taken as a helpful tool for making analysis on the processes of heat transfer in this thesis the author introduces comsol multiphysics software and analyzes heat transfer processes, burlington vt comsol inc 4 / 16 Send Private Message Flag post as spam. Your internet explorer is in compatibility mode and may not be displaying the website correctly. I dont think any special treatment is needed at the fluid-solid boundary. I need to impose a user defined boundary condition at the surface of the solid which is in contact with the coolant. The heat source is only active initially, and I would expect the model to reach thermal equilibrium with the surroundings/boundary conditions. Im a beginner with COMSOL and I don't understand how it calculates the normal heat flux on a boundary. Hello, I am using COMSOL 5.3a and solving a 3D model using the conjugate heat transfer, laminar flow study. For users of the Battery Design Module, COMSOL Multiphysics version 6.1 introduces a new interface for modeling multiple batteries, the ability to simulate heat transfer in battery layers, and the addition of the Parameter Estimation study step. Thanks. ,but the result show that there are no heat transfer between solid and liquid!! listed if standards is not an option). You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version rgds I want the boundary to simulate the . You represent and warrant that you are not subject to any comprehensive sanction or embargo by the U.S. or any other country, nor are you identified on any list maintained by the U.S. government that identifies persons for which the U.S. maintains restrictions. You agree that you will not use your COMSOL Access account in violation of any applicable export control laws. that once rearranged this means: The moderators of the forums will remove any generally objectionable material as quickly as possible. COMSOL hereby grants you a license to copy and/or use content from the forums solely for your own internal purposes. listed if standards is not an option). The Periodic Condition node adds a periodic boundary condition. The simulation for the heat transfer is quiet good but the not in the mass transport. Coupling Heat transfer in solids with heat transfer in a porous medium (geothermal application), Manually Setting the Scaling of Variables, Guidelines for Equation-Based Modeling in Axisymmetric Components, Enclosed Geometry Heat Transfer in Solids. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help. Send Private Message Flag post as spam. Discussion Closed This discussion was created more than 6 months ago and has been closed. Always do a quick check for spelling/grammar mistakes. Whilst the heat source is active the model heats, then it holds at the max temperature instead of dissipating the heat. 0 Replies, Please login with a confirmed email address before reporting spam, Dear all Heat Transfer & Phase Change 11 Replies, Please login with a confirmed email address before reporting spam. Enabling the Equation View.. In the Joule heating module (2 D), I want to know what are the boundary conditions required for the temperature rise in nanowire, when 1 mA current is passed through the wire having cross-sectional area150 x 150 nm^2 and 5 micron length. I am using a fixed constraint boundary condition on the surface where the part . please help in this regard. Am I doing it correctly? Try to catch typos. Your Discussion has gone 30 days without a reply. Ivar. Your Discussion has gone 30 days without a reply. When registering for COMSOL Access, you agree to provide your complete and truthful information for all fields requested on your COMSOL Access account registration page. hello. You agree that the webmaster, administrator, and moderators of the forums have the right to remove, move, or close any topic at any time as they see fit. That boundary condition accounts directly for heat loss from the solid through conduction and the fluid flow that results accounts for convection. To start a new discussion with a link back to this one, click here. Two physics (bioheat physics and moving mesh physics) are included in model to simulate a laser ablation over a part of the bone. -h_htgh*T+q0_htgh+h_htgh*Tinf_htgh The constraint is formulated as ht.T0-ht.Tvar, which . Anup, Hi Anup, If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help. Hi everyone. Hi, I am trying to model the time dependent thermal diffusion in a solid with the Heat Transer in Solids physics. . Your internet explorer is in compatibility mode and may not be displaying the website correctly. But , results shows exactly opposite. much better if you upload your file for the other members to comment and have their suggestions. What I would like to inquire right now is the problem on the heat loss due to evaporation. Thank you. We investigated the dynamics of nanofluid and heat transfer in a three-dimensional circular annular using the turbulence model and energy equations. I need an immediate help for the thread : www.comsol.com/community/forums/general/thread/34647/ Please read the discussion forum rules before posting. Learn about these updates and more below. Ishant Jain, Dear friends In cases where the temperature of the fluid at an inlet is a known quantity, a Temperature boundary condition can be used. Version 5.1 Posted Oct 2, 2012, 7:25 a.m. EDT Posted Jul 29, 2020, 12:37 a.m. GMT+2 The heat flux through internal boundaries can be automatically computed. Cheers How to set flux and temperature continuity at interface. Use the Preview button often. The purpose of language is to be understood. I think I am mis-using a boundary condition but I am not sure. A heat flux boundary condition was executed at the inner cylinder of the annular. As a user of COMSOL Access, you agree to any information you have entered into any of the forums being stored in a database. The moderators reserve the right to remove, edit, or move posts at their discretion. Neither COMSOL, the authors, nor the copyright owners of submitted materials warrant that the programs will be error-free, uninterrupted, virus-free, secure, and suitable for your needs, produce specific results, or that errors or failures will be corrected. Use correct punctuation. Furthermore, you agree not to submit any information relating to your employer through your COMSOL Access account without your employers authorization. If you are familiar with LaTeX, please use this to write mathematical equations. Although many COMSOL Access members are not fluent in English, the official language of this forum is English. All content is provided "as is" without warranty of any kind, express or implied, including without limitation, warranties of merchantability, noninfringement, design, operation, and fitness for a particular purpose, and the entire risk as to the quality and performance of the programs is with you. Do not post multiple threads on the same topic. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version I have tried the open boundary as well as symmetry conditions but in both cases there seems to be no conduction outside of the model. If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base. please help me Hi, I am trying to model the time dependent thermal diffusion in a solid with the Heat Transer in Solids physics. Jonathan Perez. How to find the boundary equation setting in the new versions 4.4 If you want to add heat flux on internal boundary you can use boundary heat source node." It worked for me. Heat Transfer & Phase Change Hi, I am trying to model the time dependent thermal diffusion in a solid with the Heat Transer in Solids physics. I managed to get results, but am not quite satisfied yet. Veryst Engineering, thanks .thanks a lot. Note that while COMSOL employees may participate in the discussion forum, COMSOL software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team. April 22nd, 2019 - Heat Transfer Module Updates For users of the Heat Transfer Module COMSOL Multiphysics version 5 3 includes new functionality to model heat and moisture transport in air a new solver for modeling heat transfer in the I am somewhere stuck up in meshing part, thus, request you to please reply. I am trying to simulate the behaviour of optics components when being cooled down from 293K to 4K.I am using Solid Mechanics and Heat Transfer to Solids, where i am applying they temperature to all boundaries. If my explanation is correct, how to resolve this issue? Is there any other way to do this so that the heat loss can be included in the analysis? In order to make this an efficient and pleasant experience for you and other members of COMSOL Access, we ask that you follow a few rules and guidelines. COMSOL imposes temperature continuity at the fluid-structure boundary in a conjugate heat transfer problem. You agree to maintain your COMSOL Access account for use solely by you, not to share your username and password with anyone else, and to take appropriate precautions to restrict access to your username and password from others. Hi Yeal You might have found out by now, I hope so, but in anycase, in the boundary condition Heat flux you have 2 variables Q and h, you might either choose one or the other, or both. Animation of the temperature distribution as the prescribed temperature spot travels along the bar. Check the application library model in Heat Tranfer Module > Tutorials Conduction > carbon_fibers_infinite_elements to learn how it works. However, I am having some problems because the boundaries of the grains are inactive (Attached picture). I am solving for transient case for total time of 300secs with time step of 0.1sec [free time step (not strict)]. Its fine that comsol itself taking care of interface boundary condition as heat loss from the solid. In the tutorial (@ 11:49) the narrator assigns a "Surface-to-Ambient Radiation" boundary condition on the outer surface of the model (screen shot attached). 0 Replies, Please login with a confirmed email address before reporting spam. Capitalize correctly. Matthew, Posted . Hence the Q variable (or q0_htgh internally) enters directly thermal power onto the boundary, while the "h" is proportional to the temperature difference (in K) of (Tinf-T) and T is the temperature you are solving for, so Tinf yould be your constant blood temperature, then h should be scaled to take into account . For example, write "COMSOL Multiphysics" and not "CMP". You also agree to maintain the accuracy of all information associated with you on your COMSOL Access account. Discussion Closed This discussion was created more than 6 months ago and has been closed. rgds Hi, can I give a absorbing boundary condition for a transient heat transfer problem. To start a new discussion with a link back to this one, click here. listed if standards is not an option). my model is solid with heat flux on the upper face and fluid moving under the lower face , I used Conjugate heat transfer Veryst Engineering Posted May 12, 2022, 2:53 a.m. GMT+2 In order to evaluate how to derive values in the Results section, I have followed the Heat sink tutorial included in COMSOL 4.2a and once I get the results of the simulation, I calculate the Surface Integration of the Total normal heat flux (nitf.ntflux) on surfaces 2, 3, 4 . Hence the Q variable (or q0_htgh internally) enters directly thermal power onto the boundary, while the "h" is proportional to the temperature difference (in K) of (Tinf-T) and T is the temperature you are solving for, so Tinf yould be your constant blood temperature, then h should be scaled to take into account the liquid solid exchange, but perhaps next step to take into account the blood flow, or total volume passing through, as the blood temperature might not manage to take/give all the heat, unaffected, if you have a sever feber, but I would propose not to use non-linear terms to start with. Nagi Elabbasi The Equation View for the Temperature node.. Thanks. Never invent acronyms and use as few acronyms as possible. In the tutorial (@ 11:49) the narrator assigns a "Surface-to-Ambient Radiation" boundary condition on the outer surface of the model (screen shot attached). If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help. Good luck My model is similar to the tutorial here. Dhiman das. However, in my version, this option is . mohamed farahat . Nagi Elabbasi Your internet explorer is in compatibility mode and may not be displaying the website correctly. Now under step size, some times it appears "out" and sometimes different values. is this right to assign heat fkux and temperature for the same surface? Eman Salman . listed if standards is not an option). That boundary condition accounts directly for heat loss from the solid through conduction and the fluid flow that results accounts for convection. Posted May 1, 2020, 6:00 a.m. EDT The condition can be set on a boundary shared by the two interfaces or on two boundaries facing each other. There is no need for a different thermal boundary condition there. Heat Transfer Boundary conditions in heat transfer. Maybe there are some issues on the type of mesh that I am using. It works well, except for the boundary conditions. If you have your metal bar in a flow of helium and want to model the removal of heat by convection then you need to make a boundary for which that helium will be flowing through. by the way you know about this book: http://www.comsol.com/academic/books/imtp/ COMSOL imposes temperature continuity at the fluid-structure boundary in a conjugate heat transfer problem. you should have a look, it's excellent for your type of activities (I just got it a week ago) absorbing boundary condition for heat transfer problem. There is no need for a different thermal boundary condition there. Is there a way to go about this? That boundary condition accounts directly for heat loss from the solid through conduction and the fluid flow that results accounts for convection. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help. The pipe contained two concentric and rotating cylinders with a constant speed in the tangential direction. Note that while COMSOL employees may participate in the discussion forum, COMSOL software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team. Jun 11, 2009 #5 mherna48 43 0 according to comsol help files: "Tinf is the external bulk temperature" and this is from the section of . I am doing a simulation on the heat ans mass transfer in some grains using both the conjugate heat transfer in solids (nitf) and transport of diluted species (chds). Modeling Natural and Forced Convection in COMSOL Multiphysics, Calculating the Heat Transfer Coefficient for Flat and Corrugated Plates, Using the Inflow Boundary Condition in Nonisothermal Flow Simulations. These rules are subject to change. Thank you very much in advance. The passing of the heat air to the surface of the solid boundary caused heat and mass transfer at the same time resulting to some degree of heat loss. You agree not to post or link to any material that is abusive, obscene, vulgar, slanderous, hateful, threatening, sexually oriented, or that infringes upon or violates any third-party rights or any other material that may violate any applicable laws. The data agrees with the Sherwood and Blasius correlations, however. Hi everybody, COMSOL imposes temperature continuity at the fluid-structure boundary in a conjugate heat transfer problem. Particular services accessible with your COMSOL Access account may be subject to additional rules. Heat Transfer & Phase Change Further, you represent and warrant that you are not subject to any restriction on the receipt of technology or products under the export control laws of the U.S. or any other country. It worked well when there is only bioheat physics, but when i use . COMSOL imposes temperature continuity at the fluid-structure boundary in a conjugate heat transfer problem. This is to avoid the heat wave reflecting at the boundary and contributing to the temperature rise. The heat source is only active initially, and I would expect the model to reach thermal equilibrium with the surroundings/boundary conditions. However, there are some important situations where this is not the case, and an Inflow boundary condition can improve the model accuracy and reduce . Edgar. Posted 18 mai 2018, 19:20 UTC+2 Heat Transfer & Phase Change 0 Replies . Once you have selected 2D "htgh" BC's "Heat transfer" and the boundary of interest go to : h_htgh* (Tinf_htgh-T) + q0_htgh. It is difficult to read posts that are written entirely in uppercase or lowercase. Nagi Elabbasi Thermal Connectors Between Shells and Domains. Ivar Kjelberg COMSOL Multiphysics(r) fan, "retired" but still part time CSEM SA (CH) Send . 4th row (for "T" as the 4th dependent variable u,v,p,T,J), you should see something like: Whether solid or fluid gets higher temperature depends also on the distance the laser travels through them as well (not just their absorption characteristics). Check the application library model in Heat Tranfer Module > Tutorials Conduction > carbon_fibers_infinite_elements to learn how it works. Boundary condition for heat transfer. Here are some important guidelines of language: By submitting content to the forums, you hereby grant COMSOL a nonexclusive, royalty-free, perpetual, worldwide, and unrestricted license to reproduce, publicly display, publicly distribute, and prepare derivative works of the content. model heat convection between the tissue and blood I want to use on interior boundaries between the blood vessel the "heat flux discontinuity" boundary condition. I noted that I should use internal boundary to define the non-slip boundary . Note that while COMSOL employees may participate in the discussion forum, COMSOL software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

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