Thermal and hydraulic performance of the twisted tube bank as a new arrangement and its comparison with other common arrangements

Abstract

In the current numerical study, three-dimensional heat and fluid flow over various arrangements of the tube bank are simulated via realizable K-ε as the turbulence model. A new arrangement, twisted tube bank is introduced and compared with the other common arrangements, inline and staggered. Temperature-dependent properties are assumed for the working fluids. The suggested experimental equations of the previous studies are used for the model validation. The influence of the Reynolds and Prandtl numbers, dimensionless transverse and longitudinal pitches, twist angle and dimensionless shell diameter on the thermo-hydraulic performance are perused. Two equations are proposed for estimation of the Nusselt number and friction factor as functions of these variables. Results indicate that, if the Reynolds number is doubled the Nusselt number increases by 71.2% and the friction factor reduces by 27.9%. Furthermore, it was found the twisted arrangement could increase the Nusselt number by 22.8% and 7.5% compared to the inline and staggered arrangements, respectively at the optimum twist angle (which is 79°). While, the friction factor increases only by 36% and 2.47% compared to the inline and staggered arrangements, respectively.