Flow structure and heat transfer analysis of the floatation nozzle with a moving wall

Purpose This study aims to investigate the effects of different surface-to-jet velocity ratios (Rsj) on the flow structure and the heat transfer of the floatation nozzle under different ratios (h/w) of the separation distance (h) to the slot width (w) and the differences of the flow structure and the heat transfer between the floatation nozzle and the slot nozzle. Design/methodology/approach The Nusselt number (Nu) and the pressure distribution of the floatation nozzle with a stationary wall are measured. Then the experimental results are used to validate the numerical model. Finally, a series of numerical simulations is carried out to achieve the purpose of this study. Findings The flow structure and heat transfer differences between the floatation nozzle and the slot nozzle are clarified. The floatation nozzle has more than 18 times the floatation ability of the unconfined slot nozzle. The Nu and pressure distributions of the floatation nozzle are experimentally measured. The effects of wall motion on the Nu and pressure distributions are identified. Originality/value The effects of the wall motion on the flow structure and the heat transfer of the floatation nozzle, and the differences between the floatation nozzle and the slot nozzle are first obtained. Therefore, it is valuable for engineers in engineering design of the floatation nozzle.

Study on Pressure Coefficient in Process of Double Slot Nozzle Jet Impingement on Sinusoidal Colliding Strip

Air cushion furnace is widely used in the heat treatment process of aluminum strip, copper strip and silicon steel, and the double slot nozzle is the core part of the air cushion furnace device. Studying the distribution characteristics of the surface pressure coefficient of the strip during the suspension process could provide important theoretical references for the high-efficiency and high-value production of the air-cushion furnace. In this paper, the distribution of pressure coefficients is studied under the conditions of Re=48 194~12 048, high H/D=1~3, spacing L/D=17.2 and sinusoidal amplitude A=0~30 mm. The results show that with the decrease of L/D, the position of the main stop point moves to the center line of the nozzle, and the value of the second stop point increases gradually, and with the increase of the sinusoidal amplitude A, the position of the main stop point moves gradually to x/D=0. The pressure coefficient Cp decreases with the increase of sinusoidal amplitude A, the pressure coefficient Cp decreases with the increase of H/D, and the difference between the pressure coefficient at the stationary point of the double-slot nozzle and the pressure coefficient at the non-stationary point increases with the increase of H/D. This study provides an important theoretical basis for the design of double slot nozzles in air cushion furnace.

HYSTERESIS OF PLANAR DOUBLE SLOT IMPINGING AIR JETS

In present study, the bistability and hysteresis of the non-isothermal flow behind two slot nozzle is numerically investigated. Theoretical review of bistability of isothermal stagnation flow is presented and both flow field patterns that exist in the region of bistability are commented on. Hysteresis is found in number of conducted simulations and effects of various parameter changes are discussed. Moreover, the mechanism of transition from one flow field pattern to another is discussed for both transition directions. In conclusion, validity of 2D simulation results against real 3D problems is of concern and general contribution of this research is discussed. Throughout this work, emphasis is on applications regarding heat transfer.