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Show The first configuration is shown in Fig. 2(a) where combustion heated air and a cooler air shroud are injected through 2-D slots into a quiescent medium. This is a basic element of many important industrial applications. For example: 1. Glass fiber production where both temperature and fluid mechanic shear forces are important design parameters; 2. Heat transfer by direct jet impingement where the specification of jet penetration depth, momentum flux, and temperature distribution is required; and 3. High-intensity andlor high-luminosity combustion where secondary dilution air is used to moderate pollutant formation, and where the trajectory and temperature of particles (soot or fuel droplets) strongly influences the radiative heat transfer. The second flow configuration is shown in Fig. 2(b). Combustion heated air and a cooler air shroud enter a closed chamber through 2-D slots, suddenly expand to the full chamber width, and exit through a sharp contraction. This flow geometry is also common to industrial combustion processes. Such processes inc 1 ude, but are not 1 imi ted to the following: 1. Mixing and dilution of primary combustion products wi th secondary air to reduce pollutant emissions (NOx and CO); 2. High-volume drying applications where large flow rates of warm air are required; and Pig . 28 - Two-d i me nsioDa l f l ow geome tr y fo r coaxi al fr ee jets . P i g . 2 b - Two -d i me nsional flow g e o metr y f or c o ax i a l j e ts expanding into a ca vit y. 112 3. High-intensi ty "can" or "dump" combustors where the assumption of rapid chemical rates are appropriate. CO-FLOWING JETS - Many practical combustion systems utilize a complex arrangement of turbulent jets. One major example is the production of glass wool, where the length and diameter of the glass fiber are strongly dependent on the local heat transfer rates and fluid mechanic shear forces. Using this numerical model, variations of the inlet stream velocities (including direction), temperatures, and compositions can be economically evaluated. Heat transfer from hot jets to plane walls and porous media (tube bundles or porous plates) is also an important feature in gas-fired applications. In these processes, flow simulations can be used to predict jet penetration depth and available heat flux. Moreover, since obstructions in the flow alter the mass and energy transport, the numerical simulations provide adequate engineering estimates of the effect of the heat exchanger surfaces on the overall system heat transfer rates. Figure 3 illustrates the velocity field for the co-flowing jets expanding into quiescent air at 300 K. The central jet has a velocity of 80 mlsec and a temperature of 1700 K, while the peripheral jet has a veloci ty of 50 ml sec and a temperature of 500 K. The entrainment of surrounding air is initially governed by the velocity and momentum of the secondary stream. In its turn, this stream mixes with the hot core flow. The profiles in Fig. 4 provide estimates of the primary jet growth with and without the peripheral flow by examining the velocity and temperature profi les at 4.75 and 20.5 primary jet heights downstream. As can be seen, the secondary stream moderates the penetration depth and lateral spread of the central stream. The combined jets decrease in both temperature and velocity as the fluid moves into the cavity. The centerline velocity decays from a maximum (Uo) at the nozzle exit to approximately 0.33 Uo at X/H = 40. As indicated by the temperature profiles and corresponding isotherms of Fig. 5, the surrounding medium is efficiently entrained with the jet fluid. The centerline fluid temperature thus follows the velocity profile, decreasing from TITO = 1.0 to TITO = 0.37 at X/H = 40. At this point, significant amounts of ambient air have reached the center of the primary jet. It is also evident from the profiles in Fig. 5 that th e lateral diffusion of energy is noticeably less than that of momentum. Fig. 6 illustrates the predicted turbulent heat flux by showing the appropriate contours and surfaces. As may be anticipated, significant heat flux occurs at the interface between primary and secondary streams and between the secondary stream and the ambient cavity air. The highest turbulent heat |