Effect of superficial gas velocity

On the top of the horizontal tube = 49.2 mm, 0 = 0°) the heat transfer coefficient in two-phase flow is less than that for single-phase water flow. 

Ghajar et al. (2004) studied heat transfer of two-phase flow in a horizontal tube of d = 25.4 mm and reported that the effect of superficial gas velocity on heat transfer depended on flow pattern and showed its own distinguished trend (Fig. 5.44). 

On the other hand Bao et al. (2000) reported that the measured heat transfer coefficients for the air-water system are always higher than would be expected for the corresponding single-phase liquid flow, so that the addition of air can be considered to have an enhancing effect. This paper reports an experimental study of non-boiling air-water flows in a narrow horizontal tube (diameter 1.95 mm). Results are presented for pressure drop characteristics and for local heat transfer coefficients over a wide range of gas superficial velocity (0.1-50m/s), liquid superficial velocity (0.08-0.5 m/s) and wall heat flux (3-58 kW/m ). 

From the results discussed above one may conclude that due to the complex nature of two-phase gas-liquid flow there is a large variation in experimental results and heat transfer correlations presented by different investigators. For channels of 

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Fig. 5.48 Effect of superficial gas velocity on heat transfer in parallel triangular micro-channels of <4 = 130 pm (a) Rols = 4, (b) Rets = 8, (c) Rols = 15, (d) Rols = 28, (e) ReLs = 56...

Effect of superficial gas velocity on growth of the green microalga Haematococcus pluvialis in airlift photobioreactor... 

The aims of the present work were to culture H. pluvialis in the airlift bioreactor in order to examine the effect of superficial gas velocities on growth of H. pluvialis. 

The effect of superficial gas velocity on gas-liquid interfacial areas for different operating pressures is shown in Fig. 1. For very low liquid or gas flow rates, a is almost independent of a change in pressure. However, for higher liquid flow rates, an increase in pressure induces a significant increase in a for gas superficial velocities above a critical gas velocity uGc = 2 to 3 cm/s. Gas and liquid superficial velocities over which pressure effects are no longer negligible are coincident with the ones for which gas hold-up becomes pressure-sensitive [6], Thus a relation between the change in interfacial areas and hold-ups due to pressure is expected. 

Fig. 29. Effect of superficial gas velocity on radial local particle velocity (after Yang et ai, 1991).

Study the effect of superficial gas velocity on dense bed density in the second stage FFB where uf is high. 

Fig. 20. Effect of superficial gas velocity on Ail and in 22.5-cm model bubble-cap plate column (S23).

Veera, U.P., Kataria, K.L., and Joshi, J.B. (2004), Effect of superficial gas velocity on gas hold-up profiles in foaming liquids in bubble column reactors, Chemical Engineering Journal, 99(1) 53-58. 

The effect of superficial gas velocity (SGV) on the performance at an inlet SO2 concentrations of 0.3 is shown in Figure 3 using AC as the flushing solvent. The average superficial liquid velocity (SLV) was 0.953 mm/s and the experiments were performed at a bed temperature of 18°C. Oxygen concentration was 5 vol% and water was 2.9 vol%. As expected from contact-time considerations, recovery of SO2 from the gas and its conversion to acid decreases with increasing SGV. The removal curve extrapolates smoothly to approximately 100% as the gas velocity goes to zero. Since conversion is measured on the... 

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