Impinging jet array

Figure 1.196 Schematic design of the impinging-jet array micro mixer [54] (by courtesy of IOP Publishing Ltd.).

Figure 1.197 Schematic of the flow guidance in the impinging-jet array...

Mixer type Impinging-jet array micro mixer Nozzle length 300 pm... 

N. Sullivan. Transport Issues in the Impingement of Arrays of Flame Jets on a Rotating Cylinder. PhD thesis, University of Colorado, 1999. 

Arrays with multiple oblique impinging jets are generated via 3-D channel networks which feed fluid from a reservoir via the outlet nozzles of the network into a mixing chamber (see Figures 1.196 and 1.197) [54], Perforated plates contain such arrays. 

Two arrays of oblique impinging jets in frontal collision and in offset orientation... 

The values of the ratio of the power eonsumed to the power removed obtained from the cooling module tests are substantially higher than those shown for the orifiee plates. There are several reasons for this. Because some of the jets did not impinge on the diode sinee the area eovered by the jet array was larger than that of the diode, part of the water did not remove any heat, while still being pumped. 

The downstream jets are subjected to crossflow originating from the upstream jets. Average Nusselt number correlations appropriate for use in analyzing circular jet array impingement systems in which the flow is constrained to exit in a single direction along the channel formed by the jet plate and the impingement surface, have been developed by Florschuetz et al. [92], The correlation adopted is of the form... 

L. W. Florschuetz, C. R. Truman, and D. E. Metzger, Streamwise Flow and Heat Transfer Distributions for Jet Array Impingement with Crossflow, J. Heat Transfer, 103, pp. 337-342,1981. 

Zhao, Z., Yuen, D. W., Leung, C. W., and Wong, T. T. "Thermal Performance of a Premixed Impinging Circular Flame Jet Array with Induced-Swirl." Applied Thermal Engineering 29 (2009) 159-66. 

Impinging jet dryers are employed in the case of sheet-like materials such as cardboard, folio, polymer film, paper, textile, and veneer. Hot gas impinges from an array of nozzles onto the good. This process creates high diying rates. Sometimes the good is transported on a substrate and heated from below as well. It may also be transported on air cushions. 

A micro-thermistor sensor array was used by Wu et al. [13] to characterize a microscale heat exchanger that utilized a series of impinging jets exiting from micronozzles. The temperature... 

Wang, E.N., Zhang, L., Jiang, L., Koo, J., Goodson, K.E., Keim) T.W., Maveetu, J.G., and Sanchez, E.A., Micromachined jet arrays for liquid impingement cooling of VLSI chips, in Solid-State Sensor, Actuator and Microsystems Workshop,... 

Attalla, M., Specht, E., 2009. Heat transfer characteristics from in-line arrays of free impinging jets. Heat Mass Transfer A5[S) 537-543. 

Another well-known correlation has been used to predict heat-and mass-transfer coefficients for air impinging on a surface from arrays of holes (jets). This correlation uses relevant geometric properties such as the diameter of the holes, the distance between the holes, and the distance between the holes and the sheet [Martin, Heat and Mass Transfer Between Impinging Gas Jets and Solid... 

The surface-average heat transfer coefficients are of importance, for example, when the target to be heated or cooled is being moved beneath an array of stationary jets. The speed at which the target should be moved can be evaluated with the aid of the surface-average heat transfer coefficient. The surface-average Nusselt number from the impingement line (xld = 0) to a particular streamwise (xld) location is calculated from the equation... 

The air, after impinging on a surface from two-dimensional arrays of circular jets, is constrained to exit in a single direction along the channel formed by the surface and the jet plate. 

The model is capable of accurately simulating thermal behavior of steel strip cooled by an array of impinging water jets. The findings provide useful insights to a metallurgist for assessing the mechanical and metallurgical properties of steel, which are influenced by microstruc-... 

A. M. Huber and R. Viskanta, Effect of Jet-to-Jet Spacing on Convective Heat Transfer to Confined, Impinging Arrays of Axisymmetric Air Jets, Int. J. Heat Mass Transfer, 37, pp. 2859-2869, 1994. 

N. T. Obot and T. A. Trabold, Impingement Heat Transfer Within Arrays of Circular Air Jets. Part I. Effects of Minimum, Intermediate and Complete Crossflow for Small and Large Spacings, J Heat Transfer, 107, pp. 872-879,1987. 

Kwok, L. C., Leung, C. W, and Cheung, C. S. "Heat Transfer Characteristics of an Array of Impinging Pre-Mixed Slot Flame Jets." International Journal of Heat and Mass Transfer 48 (2005) 1727-38. 

Spent flow from individual jets or clusters of jets must be exhausted properly or the performance of adjoining jets can fall even by a factor of 2. For slot jets and rows or arrays of round jets, experimental studies have measured the effect of induced cross-flow (i.e., cross-flow due to upstream rows of jets made to cross the downstream jets to exhaust), as well as imposed cross-flow (i.e., a flow parallel to the impingement surface that is not due to upstream jets). For ASN, the effect of cross-flow is severe [6]. No more than two jet rows should be allowed prior to exhaust. For staggered ARN arrangements, the cross-flow effect is less severe an exhaust port may be provided for every three to five rows. After five rows, the cross-flow effect drops the average Nu rapidly in the downstream direction [11]. 

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