An experimental study on thermal mixing in a square body inserted inclined narrow channels ☆ Yasin Varol a, ⁎, Besir Kok b , Hakan F. Oztop c , Ismail Turkbay d a Department of Automotive Engineering, Technology Faculty, Firat University, 23119 Elazig, Turkey b Technical Vocational School, Firat University, 23119 Elazig, Turkey c Department of Mechanical Engineering, Technology Faculty, Firat University, 23119 Elazig, Turkey d Department of Mechanical Education, Firat University, 23119 Elazig, Turkey abstract article info Available online 16 July 2012 Keywords: Thermal mixing Parallel jets Heat transfer An experimental study has been performed on thermal mixing phenomena in a narrow channel by twin-jets at different temperatures. Water was used as working fluid and it is supplied by hot and cold taps. The chan- nel has a circular exit hole to supply continuity of mass. An adiabatic square shaped object, which in the thickness of the channel, is inserted into the channel to control thermal mixing as a passive technique. Other parameters in experiments are ratio of flow rate of inlet fluid, inclination angle of the channel, jet di- ameter and jet velocities. Finally, a thermal mixing index was calculated from measured values of tempera- tures for different parameters. Temperature distribution is obtained for whole channel and isotherms are plotted. The obtained results indicated that higher thermal mixing efficiency is observed for ϕ =60 o and inserted body can be a control parameter for thermal mixing for the same geometrical parameters. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Mixing processes are very crucial subjects in chemistry, mechani- cal engineering and environmental science. It can be classified in two separate groups such as flow mixing and thermal mixing. In flow mixing phenomena, the same fluid/fluids are mixed using mechanical devices such as propeller or jet mixing can be used [1]. In this context, jet mixed tanks are very popular due to low energy consuming, low investment and there is no complex mechanical part they have. This idea also can be used for thermal mixing process. Humprey et al. [2] numerically studied the time-dependent mo- tion of a constant property, Newtonian fluid in a counter current shearing flow configuration. The three-dimensional flow and mixing characteristics of multiple and multi-set three dimensional confined turbulent round opposing jets in a novel in-liner mixer are examined numerically using the standard k-ε turbulence model by Wang and Mujumdar [3]. They indicated that multiple opposing jets achieve better mixing than single opposing jets in the study. Wang et al. [4] numerically studied the laminar flow in an in-line mixer based on op- posing jet impingement. They found that unequal inlet momenta of opposing jets obtained using both equal and unequal slot widths and the addition of baffles in the exit channel yield better mixing over shorter distances after impact. In their another study, they tested the effects of type of fluid as using air and water on flow and mixing effectiveness for various temperature differences between the con- fined opposing jets of different geometries. Beuf et al. [5] studied the influence of the geometry of the cell on mixing efficiency using three different geometries as circle, square and rectangle. They indi- cated that the flows in Hele–Shaw cells are generally laminar and it can be in a first approximation considered as quasi-two dimensional. They also showed that the rectangular geometry leads to a better mixing, but also that the aspect ratio of the rectangle play unexpect- edly no important role on mixing. Walker et al. [6] made both numer- ical and experimental study to carry out mixing of coolant streams of different temperature in pipe junctions. In this way thermal fatigue may prevent in the pipe wall. They presented a distribution of time averaged mixing scalar for different velocity ratios. Wang et al. [7] studied jet mixing problem inside a slot experi- mentally. They tested the jet array effect on cooling performance. They also tested effect of orientation angle and H/D ratio. It is found that the acceptable uniform flow is observed for shallow as H/D = 1. Chang et al. [8] made a numerical analyzes to investigate the thermal mixing efficiency in Y-shaped channel. They solved two dimensional incompressible, steady state equations using Lattice Boltzmann meth- od. They inserted different types of passive element to improve ther- mal mixing efficiency. It is demonstrated that the enhanced mixing efficiency is result of an increased intersection angle between the ve- locity vector and the temperature gradient within the channel. International Communications in Heat and Mass Transfer 39 (2012) 1245–1252 ☆ Communicated by W.J. Minkowycz. ⁎ Corresponding author. Tel.: +90 424 237 0000x4219; fax: +90 424 236 7064. E-mail address: ysnvarol@gmail.com (Y. Varol). 0735-1933/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.icheatmasstransfer.2012.07.004 Contents lists available at SciVerse ScienceDirect International Communications in Heat and Mass Transfer journal homepage: www.elsevier.com/locate/ichmt