# Simulation of air condition in room

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 May 9, 2012, 14:25 Simulation of air condition in room #1 New Member   Love Join Date: May 2012 Posts: 2 Rep Power: 0 Hi, we are two students working on a project regarding thermal comfort in a classroom at our school. Since we are new at this kind of simulations we have encountered a few problems. Some background about the model: A 3D model of the classroom was created. Due to lack of virtual memory on the school's computers we could only manage to mesh the model with five persons inside. Therefore we use the back of the seats as heat sources since they have almost the same surface area as a human. Initially we set all human (or seats) to a constant temperature of 28 C assuming that the temperature of a human is relatively constant. The inlets were set as velocity inlets with mesured speeds and temperature (1 m/s, 18 C). The outlet to flow split with a ratio of 1. The surrounding walls, floor and cieling were defined as adiabatic. The window, projector and the lamps were also set to constant temperature. The physical model used was steady state gas (air) constant density coupled turbulence model; k-epsilon coupled energy The simultation converged and the result was fairly good. The only problem is that each person (seat) does not create enough heat to make the airtemperature close to the one mesured. Therefore we tried to set each constat temperature to a heatflux source instead (which was actually what we tried in the very beginning since a human doing classroom activities generate around 70 w/m2). However this simulation gives impossible big temperatures, in sizes of 500 C, no matter what we do the rest of the boundaries in terms of setting them to constant temperatures. The high temperatures are located in the cells closest to the sources and the outlet. Is there anyone who have done similar simulations and could give us hint on how to proceed from here. Should we choose another physical model? Best regards, Love (You might find my name quite funny but it's quite common in Sweden)

 May 9, 2012, 15:14 #2 Senior Member   Join Date: Oct 2009 Location: Germany Posts: 637 Rep Power: 12 You didn't take natural convection into account, didn't you? Not sure if that will solve all your issues, but I think that might have an impact on the solution. __________________ We do three types of jobs here: GOOD, FAST AND CHEAP You may choose any two!

 May 10, 2012, 13:33 #3 New Member   Love Join Date: May 2012 Posts: 2 Rep Power: 0 Hi, thank you for your quick respons. Unfortunately using the natural convection model does not change the problem with high temperatures when applying heat flux into the model. Best regards

 May 15, 2012, 01:12 #4 New Member   Join Date: Apr 2012 Posts: 20 Blog Entries: 3 Rep Power: 5 hi,check heat flux 70 w/m2 and the related heat exchange area. Confirm whether the magnitude is suitable.

 May 23, 2012, 13:40 #5 Member     Felipe Gobbi Join Date: Apr 2012 Location: Brazil Posts: 76 Rep Power: 5 I'm also new to this kind of simulation, but as we're all here to learn, I'll risk to suggest you: maybe you could set a simmetry plane on the "humans" and put as many students as you need to make it more realistic, I think this will require less computer effort. Sorry if it sounds dumb.

 May 23, 2012, 17:02 #6 Senior Member   Join Date: Oct 2009 Location: Germany Posts: 637 Rep Power: 12 A symmetry plane on the human bodies doesn't allow to take the energy put from the humans into the room into account. It is way more realistic to set the human bodies to a fixed temperature or specify the heat flux. __________________ We do three types of jobs here: GOOD, FAST AND CHEAP You may choose any two!

 Tags air condition simulation, heat flux model, ventilation

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