Hi Rémi, I do not think that there is an error. The formulation of the conductive heat transfer in Type 19 is the result of an energy balance on surface i, as follows:
Energy in: - Q_i : Conductive heat transfer - A*s : Radiation absorption on the surface (absorption of solar radiation) Energy out: - A*h_c*(T_s,i - T_z) : convective heat transfer to the zone - A*h_r_ij*(T_s,i - T_s,j) : radiation exchange between surface i and surface j, using a linearized radiation coefficient. (For simplicity, let's assume that there are only two surfaces, i and j) Energy balance yields: Q_i + A*s = A*h_c*(T_s,i - T_z) + A*h_r_ij*(T_s,i - T_s,j) You can rearrange these terms as: (Q_i/A + s)/h_c = (1 + h_r_ij/h_c )*T_s,i - h_r_ij/h_c*T_s,j - T_z This equation is written in matrix form in equations 5.7.3.19 - 5.7.3.22. I guess that the confusion is given by the second part of the paragraph, where it explains that Q_i should be evaluated using T_eq. I have to admit that I am not entire sure of this: if Q_i only has conductive heat transfer through the wall, you would only need the actual temperatures on the surfaces to calculate it. I will appreciate the comments from the experts on this list. Best regards, Diego Charron wrote: > Hello, > > I believe there is a mistake in the formulation of the conduction input wall > for Trnsys Type 19, can someone confirm? > > Equation 4.8.3.22 in the manual states that X_i=(Q_i/A_i +s_i)/hc_i for > conduction input walls and that the equivalent temperature should be used in > calculating Qi or else the effects of absorption of radiation on the inside > surface would not be correctly accounted for. > > Equivalent temperature includes effects of s_i and the longwave radiation > from other surfaces. Wouldn't including s_i in equation 4.8.3.22 be double > counting of the absorbed radiation on the surface if T_equivalent is used? > If we use zone temperature instead of equivalent temperature, the effect of > longwave radiation would not be included. > > Rémi > > _______________________________________________ > TRNSYS-users mailing list > [email protected] > https://www.cae.wisc.edu/mailman/listinfo/trnsys-users > -- Diego A. Arias TRNSYS Coordinator Solar Energy Laboratory University of Wisconsin - Madison 1500 Engineering Drive Madison, WI 53706 _______________________________________________ TRNSYS-users mailing list [email protected] https://www.cae.wisc.edu/mailman/listinfo/trnsys-users
