Flow and Heat Transfer of Impinging Jet from Notched-Orifice Nozzle

Abstract

The centerline velocity of an orifice jet increases in the downstream direction from the nozzle exit and reaches a maximum of 1.2u ce (where u ce is the nozzle exit maximum velocity) at x/d o ≈ 2 (where d o is the nozzle exit diameter) due to the vena contracta effect; this may be effective for enhancing the heat transfer performance of an impinging jet. However, the sudden contraction at the nozzle exit creates a large flow resistance. In this study, we considered the use of notches to reduce the flow resistance and increase turbulence for the sake of good heat transfer performance from the vena contracta effect. Specifically, the effects of using a notched-orifice nozzle with taper angle α on heat transfer characteristics were examined experimentally. Hot-wire measurements were also conducted to demonstrate the spreading or mixing performance of the notched-orifice nozzle. The small notches reduced the nozzle resistance or operating power as well as increased the turbulence at the nozzle exit. The heat transfer characteristics of the notched orifice jets with tapering increased significantly because of the high turbulence intensity introduced by the notches.

Design and Development of Innovative Steam Injection for High-Temperature Short-Time Liquid Foods

“…Both fluids flowed through the injection plate attached to the flow channel outlet. The injection plates were designed as a multiple impingement jet with an orifice to increase the heat transfer rate [10,14]. The injection plates were changeable to allow the investigation of different numbers of nozzles, which have an inverse relationship to the jet velocity and Reynolds number.…”

“…The orifice jet can significantly enhance the local Nusselt number. For example, it increases by 17% and 33% at the stagnation point as compared to pipe and the quadrant jets, respectively [7,14].…”

Flow characteristics of sub- and supersonic jets issued from orifice and notched orifice nozzles, and application to ejector

“…To improve the entrainment characteristics, Ori-n nozzles with two types of notches [see Figs. 1(3), (4), Shakouchi, et al, 2001, 2016, Kaushik, et al, 2006 were used.…”

“…The effects of the nozzle shape (Shakouchi et al, 2016;Zaman, 1999;Chanpagne & Wygnanski, 1971;Shakouchi, 2005;Carletti et al, 1996;Behrouzi et al, 2008;Shakouchi et al, 2001) on the flow characteristics such as the decay of the jet centerline velocity, velocity distribution at the cross section and increments in the jet-width and -flow rate to the downstream are examined. An orifice nozzle with small or large notches was used in addition to circular and orifice nozzles with various contraction area ratios.…”

1002 Resonance Jet Flow From Notched Orifice Nozzle

“…Reducing the flow resistance is essential for high performance. To reduce the flow resistance and improve the heat transfer characteristics using the vena contracta effects, we proposed a notched orifice nozzle [6] . Locating notches on the circumference edge of the orifice nozzle exit successfully reduced the flow resistance and increased the turbulence intensity.…”