Feasibility assessment of using nanofluids in shell and tube heat exchanger of gas pressure reducing stations through a new developed OpenFOAM solver

Abstract

One of the important challenges in city gate gas pressure reduction stations is the heating of the natural gas prior to pressure reduction. Regarding the low efficiency of the common water bath heaters in these stations another type of double tube-pass shell and tube heat exchanger, equipped with flower baffles, has been proposed for heating the natural gas. Additionally, Al2O3 nanofluid has been suggested to be used in the shell side as the heating medium. Investigating the incompressible three-dimensional steady-state conjugate turbulent forced convection, the heat transfer performance, and also the distribution of the nanoparticles have been studied numerically at various shell and tube sides Peclet numbers for different nanoparticle volume fractions (ϕ = 1, 2, 3 and 4%). The open-source CFD package, OpenFOAM, has been utilized for numerical simulations. A new solver and turbulence model have been developed to implement the four-equation Buongiorno’s model to investigate the nanoparticles’ distribution as well. The results indicated that increasing the shell side nanofluid Peclet number and nanoparticle volume fraction increased the heat transfer coefficient compared to pure water. Additionally, this enhancement increased as the shell side Peclet number and nanoparticle volume fraction increased and the tube side natural gas Peclet number decreased. Thus, a maximum heat transfer coefficient enhancement of 18.1% was obtained at shell side Peclet number of 180,000, tube side Peclet number of 10,000, and a 4% nanoparticle volume fraction. Additionally, the increase in the overall heat transfer coefficient compared to pure water increased as the nanoparticle volume fraction increased. Furthermore, the enhancement in natural gas mean outlet temperature in the case of adding nanoparticles in comparison with pure water was seen to be more at lower shell side Peclet numbers. Eventually, the pressure drop demonstrated an increase with the increase in shell side Peclet number and nanoparticle volume fraction. Also, the rise in the effectiveness compared to pure water enhanced with the increase in tube side Peclet number and nanoparticle volume fraction and decrease in shell side Peclet number.