Thomson

Thank you for the reply. Sorry I didn't know that it was to be posted in another section. I will do so right now. Regarding principles of heat transfer, I am only aware of 2: Fourier's law and that of Stephan Boltzman The question is in fact last part of a series of questions. In the first few questions, we need to find the heat flux at the interior of the wall for conditions given: External temp (T) =Tint + Asinwt where Tint Internal temp = 19 degree and A(amplitude) = 10 degrees and period = 24 hours; thickness of wall = 20 cm and that of insulation = 12cm. Conductivity of wall = 2 SI and of insulation = 0.2 SI. We need to first evaluate flux density for a given period ( between 14th and 15th day, etc.). That's not so difficult as we can employ software (like COMSOL). Now the last question. It is in french so I try my best to translate: ' If we use theoretical expression, noted here T(x), of the temperature as obtained in the model of a semi infinite wall, at what position of x should we evaluate -Kdt/dx to find the value of flux density obtained in questions above ( I obtained 3,4 W/m2)

Hello everyone,I am a new user of the forum. I hope with the supportive people out there I can get help with my studies and if possible help others too. To start with I have a question related to heat transfer through a wall. The question requires us to find the position x, using the expression of temperature T(x) in a semi-infinite wall for which the value of -Kdt/dx (it's delta in the question but unable to insert a symbol I replaced with d) is equal to given values of heat flux ( for eg; 3.4 W/m2). I searched for an aid throughout but only found really complicated ones. My guess is that I need to first find an algebric expression of temperature T(x) for a semi-infinite wall and then find its derivative and then solve the equation for the flux. But I don't have 'aucune' clue for that. Any help would be highly appreciated. I need to find the solution by tomorrow