Browsing by Author "Aly, Wael I. A."

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Computational Fluid Dynamics and Optimization of Flow and Heat Transfer in Coiled Tube-in-Tube Heat Exchangers Under Turbulent Flow Conditions
(ASME, 2014) Aly, Wael I. A.
The present computational fluid dynamics (CFD) study was performed to investigate the 3D turbulent flow and heat transfer of coiled tube-in-tube heat exchangers (CTITHEs). The realizable k-epsilon model with enhanced wall treatment was used to simulate the turbulent flow and heat transfer in the heat exchangers. Temperature dependent thermophysical properties of water were used and heat exchangers are analyzed considering conjugate heat transfer from hot fluid in the inner-coiled tube to cold fluid in the annulus region. After simulations, Taguchi method was used for finding the optimum condition for some design parameters in the range of coil diameter from 0.18 to 0.3 m, tube and annulus flow rates from 2 to 4 and 10 to 20 LPM, respectively. Results show that the Gnielinski correlation used extensively for predicting Nusselt number for turbulent flow in ducts can be used to predict Nusselt number for both inner-coiled tube and annular coiled tube using the friction factor correlation for helical tubes of Mishra and Gupta. Contribution ratio obtained by Taguchi method shows that annulus side flow rate, tube side flow rate, coil diameter, and flow configuration are the most important design parameters in coiled tube-in-tube heat exchangers, respectively.
Correlations for heat transfer coefficient and pressure drop in the annulus of concentric helical coils
(SPRINGER, 2014) Gomaa, Abdalla; Aly, Wael I. A.; Omara, M.; Abdelmagied, Mahmoud
Heat transfer and pressure drop characteristics in the annulus of concentric helical coils heat exchangers were experimentally investigated. The effects of coil curvature ratio, flow configuration, number of turns and addition of surfactant were investigated. Five test coils were designed and manufactured to study the effect of different parameters on heat transfer and pressure drop. The liquids used in the present study were water and oleyldihydroxy- etheyl-amine-oxide (ODEAO, C22H45NO3 = 371) non-ionic aqua surfactant solution flowing through the annulus side. The inner side Reynolds number range 11,000-27,000 and the annulus side range 5,000-19,000. The results showed that the annulus Nusselt number decreases as annulus curvature ratio increases and increases when number of turns decrease. Moreover, the friction factor increases with the curvature ratio and also increases as number of turns decreases. Both Nusselt number and friction factor decrease when ODEAO concentration increases.