Learning Forum

[chrisandrelarsen2]

Hi, nIm having some difficulties with my simulations of thermal energy storage with a very viscous PCM inside it. As a result of there be practically no movement in the liquid phase I simply solve for only energy. nI have convection at one boundary wall, this to represent heatloss til ambient/room. The entire domain I have initalized at 413K, and I then simulate the heatloss for 4 hours to see what amount of heat we can expect to get out. nThe issue comes up when I compare the heat that I get out, with the heat lost within. One would expect these two to be equal, but they are not. As of now the diffrence is around 30%. nI have attempted with a finer mesh, without any improvement. And my residuals goes from 10^-5 to 10^-9, which with my understanding is good behaviour.nSo my question is, does anyone have some suggestions to how this can be fixed? nand let me know if additional information is required. nBest Regards,nChrisn

[Rob]

Convergence sounds good. Have you accounted for the heat from the phase change, and are you correctly accounting for the heat in the domain and the heat flux from the domain? n

[chrisandrelarsen2]

The heat from the phase change is accounted for. This have been specified in the create material part with a latent heat of 151600 J/kg, solidus temperature of 402K and liquidius temperature of 407K. nThe rest of the heat in the domain is sensibel and comes from a linear Cp, and ansys calculations go along with the ones i have done on paper myself. nThe heatflux from the domain seems to be working as it should from my perspective and the development here is expected, as its developement follows a simpler estimate I have done earlier in Matlab. nWhat I have done here is just to create a report file and then use the out-file in matlab to integrate the Watts over the timeperiod. n