Natural convection heat transfer control between two asymmetric heated vertical plates deduced from open boundary flow

摘要

In this study, the possibility of the heat transfer control in a vertical channel is analyzed, starting from a numerical solution of the governing equations. The developing convection in connection with an upward forced flow will be characterized by the appropriate parameters. The simulation when the average Nusselt number defined at the cold wall becomes physically insignificant, is presented in detail for different aspect ratios (A=H/L=4;8;16) and Rayleigh numbers (Ra=10~5-10~7). When the incoming fluid temperature is the same as the cold plate, there exists a critical Reynolds number which gives a sharp drop of cold wall Nussel number. For large aspect ratios (A>=8) the values obtained fro this parameter are found to be independent of Ra and proportional to A~2. Analyzing the influence of the fluid temperature entering in the channel on the critical Reynolds number, we found the existence of a minimum cold wall Nusselt number. The minimum Nusselt number, which depends on the entering fluid temperature, follows a curve which eventually converges (for A>8) to the critical value considered for zero entrance temperature, say the value related to the Re_cr for heat transfer.