Original article Performance comparison of a structured bed reactor with and without a chimney tray on the gas-flow maldistribution: A computational fluid dynamics study Hajer Troudi 1 , Moncef Ghiss 1 , Mohamed Ellejmi 2 and Zoubeir Tourki 1 Abstract In the present paper, two configurations of structured reactors (with and without) chimney tray placed below the packed bed have been investigated to study their effect on maldistribution factor and pressure drop characteristics. A simulation result based on a three-dimensional computational fluid dynamics was involved using ANSYS Fluent. First, maldistribution factors without chimney tray were calculated and compared to the results taken from the literature. The results were found to be in good agreement with the experimental data of Yuan et al. Second, the reactor with a chimney tray was modeled in Fluent, and steady-state simulations were performed. The uniformity due to the turbulence of the fluid was carried out using different turbulence models, and the velocity profiles along the axial direction inside the reactor were obtained. As a result, the comparison shows that the presence of a chimney tray yields lower maldistribution factor enhancement by 23% compared to the conventional structured reactor under the same operating condition. The effect of the plate orientation is also determined, and it is found that the maximum pressure drop is achieved through the rows with an orientation angle of a ¼ 45  up to 2.3% higher than of a ¼ 0  and a ¼ 90  . Keywords Computational fluid dynamics, turbulence, maldistribution factor, structured bed reactors, pressure drop Date received: 28 September 2018; accepted: 2 October 2019 Introduction During the past several decades, packed bed reac- tors (PBRs) have been widely used in chemical industries and in process engineering. Recently, the PBRs with structured packings represent a promis- ing concept in the PBRs applications as compared with spherical random packings, owing to its enhanced contact area and very low pressure drop. 1,2 The PBRs consist of complex internal struc- tures including the collectors and the distributors. Recently, it has been found that the flow uniformity inside the structured beds is one of the most important parameters that can be used to evaluate performance of the reactor and identify their prob- lems related to the geometrical features and the design. 3 Nowadays, there are two kinds of methods to assess the uniformity parameter. An experimental method performed by introducing a number of sen- sors (Thermoanemometric measurements). A numer- ical method used by highlighting the velocity contour map observed in the top surface of the PBR. The uniformity has been evaluated by the maldistribution factor proven by Petrova et al. 4 Several studies have investigated the flow maldis- tribution. They have demonstrated that this phenom- enon is related to different parameters such as the complex structure of the reactor, the disorder ranging of the packings, and the position of the inlet device below the packed bed. Many inlet devices have been developed and studied within PBR to improve the gas flow uniformity. 5–7 Actually, most of these devices are focused on bending inlet shape; however, less atten- tion has been paid on the slope and straight inlet. 8 An experimental investigation on flow maldistribu- tion has been studied by several authors. Generally, Proc IMechE Part E: J Process Mechanical Engineering 0(0) 1–15 ! IMechE 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0954408919889417 journals.sagepub.com/home/pie 1 Laboratoire de Me ´canique de Sousse, E ´ cole Nationale d’Inge ´nieurs de Sousse, Universite ´ de Sousse, Sousse, Tunisie 2 Alpha Engineering International, Sousse, Tunisie Corresponding author: Hajer Troudi, Laboratoire de Me ´canique de Sousse, Ecole Nationale d’Ingenieurs de Sousse, Universite ´ de Sousse, Sousse 4000, Tunisia. Email: hajer.troudi@eniso.rnu.tn