Numerical analysis of choked converging nozzle flows with surface roughness and heat flux conditions

Abstract

Choked converging nozzle flow and heat transfer characteristics are numerically investigated by means of a recent computational model that integrates the axisymmetric continuity, state, momentum and energy equations. To predict the combined effects of nozzle geometry, friction and heat transfer rates, analyses are conducted with sufficiently wide ranges of covergence half angle, surface roughness and heat flux conditions. Numerical findings show that inlet Mach and Nusselt numbers decrease up to 23.1% and 15.8% with surface heat flux and by 15.13% and 4.8% due to surface roughness. Considering each convergence half angle case individually results in a linear relation between nozzle discharge coefficients and exit Reynolds numbers with similar slopes. Heat flux implementation, by decreasing the shear stress values, lowers the risks due to wear hazards at upstream sections of flow walls; however the final 10% downstream nozzle portion is determined to be quite critical, where shear stress attains the highest magnitudes. Heat transfer rates are seen to increase in the streamwise direction up to 2.7 times; however high convergence half angles, heat flux and surface roughness conditions lower inlet Nusselt numbers by 70%, 15.8% and 4.8% respectively.

Combined Effects of Pipe Diameter, Reynolds Number and Wall Heat Flux and on Flow, Heat Transfer and Second-Law Characteristics of Laminar-Transitional Micro-Pipe Flows

“…The author employed the present computational method in his former work [22,[33][34][35] and detailed the essentials and the sub-steps of the procedure extensively. Thus, here only the fundamental issues of the methodological structure are defined.…”

“…The influences of surface roughness and surface heat flux conditions, over the meshing intervals of the flow domain, are coupled by Direct Simulation Monte Carlo (DSMC) method. The author previously applied DMSC to compressible nozzle flow problems [21,22] and to micro-pipe flow scenarios with surface roughness [33][34][35]. The concept of triple transport conservation is as well incorporated into the DSMC, which makes it possible to sensitively evaluate the balance of heat swept from the micro-pipe walls, the energy transferred in the flow direction and also to perform accurate simulation for inlet/exit pressure boundaries.…”

“…Cao et al [20] employed non-equilibrium molecular dynamics simulation to investigate the effect of the surface roughness on slip flow of gaseous argon. More comprehensive research comprised both flow and heat transfer characteristics driven by roughness, such as Wu and Cheng [6], who reported on the Nusselt number augmentations with surface roughness, Kandlikar et al [10] findings on heat transfer manipulation due to roughness, Wen et al [11] work on the effects of the imposed wall heat flux, mass flux and strip inserts on heat transfer rates in small diameter tubes, Koo and Kleinstreuer's [12] evaluations on the temperature field with viscous dissipation, a review by Obot [16] indicating the variation of laminar Nusselt numbers with the square root of the Reynolds number and finally Ozalp's [21,22] numerical compressible flow investigations for aerospace propulsion applications.…”

Feature Extraction of Oscillating Flow With Vapor Condensation of Moist Air in a Sonic Nozzle

“…The sonic nozzle is widely used to measure mass flow rate [1]- [2]. The discharge coefficient is a crucial performance parameter for ISO 9300 sonic nozzle which is affected by humidity (by Li [3], Lim [4], Chahine [5]), roughness (by Anthony [6], Alper [7], Wang [8]), geometry (by Park [9], Kim [10]) and vapor condensation (by Li [11], Ding [12]- [13]). The non-equilibrium condensation in sonic nozzle can result in the lower measurement accuracy, due to both steady and unsteady flow which is caused by the supercritical heat addition, namely thermal choking [14], depending on the inlet stagnation condition [15], especially subcooled temperature or humidity of the moist gas.…”