Computational fluid dynamics simulation of the supercritical carbon dioxide flow in beam dyeing

Abstract

The recent development in the technologies of supercritical carbon dioxide (S-CO 2 ) has caused a remarkable change in the dyeing process in the textile industry. The conventional wet-dyeing process using water is being replaced with the dry-dyeing process using S-CO 2 . The uniform addition of coloring material is necessary for any dyeing process. In the case of the beam dyeing process, an equal distribution of the dye fluid through the porous beam has to be ensured in order to achieve an evenly distributed dyeing. The present study focuses on the fluid dynamics aspects of the S-CO 2 beam dyeing process in order to study the flow characteristics and thereby obtain performance improvement. Computational fluid dynamics analyses were carried out and the methodology is validated with experimental results from a previous study. The flow distribution of S-CO 2 through a porous beam is analyzed at different conditions, such as varying the operating pressure, mass flow rate and inlet temperature. The comparison of compressible and incompressible flow through beam dyeing is also discussed. The current study revealed that the increase in mass flow rate through the system leads to higher non-uniformity in distribution. The operating pressure and inlet temperature were found to significantly affect the flow distribution. The flow reversal condition showed a mass flow distribution opposite to that of the normal flow condition. The cyclic flow condition with periodic normal and the reversed flow condition provide better uniformity in distribution of the flow than the normal flow condition. The present results provide guidelines to improve the levelness of the dye distribution in the fabric material. Keywords supercritical carbon dioxide, beam dyeing, porous beam, level dyeing, coefficient of dischargeDyeing is the process of adding color to textile products, such as fibers, yarns and fabrics. Dyeing is an essential process in the textile industry and uniform dyeing over the material surface is one of the objectives of the dyeing process. Dyeing processes of textile materials are carried out by allowing dye fluid to flow thoroughly. During this process, dye molecules form a strong bond with the substrates. One of the widely used types of dyeing process is beam dyeing with water as the dyeing fluid. Dry-dyeing with supercritical carbon dioxide (S-CO 2 ) has more advantage than the wet-dyeing process from both economic and environmental perspectives. S-CO 2 dyeing simplifies the dyeing process compared with wet-dyeing by eliminating contaminated water discharges, reducing consumption, excluding drying, discarding chemical level agents and diminishing air emission. The development of S-CO 2 technologies has replaced the use of dyeing fluid from water to S-CO 2 .The S-CO 2 beam dyeing process is a state-of-the-art technology in the textile industry. The main components of the beam dyeing vessel are a porous beam, a dyeing vessel and associated pipe connections. Figure 1, a schematic of the sectioned view, illustrates the

Recent advances in supercritical fluid dyeing

“…23 In the above-cited context, the academic research of recent years has often been conducted in cooperation with textile companies to improve the technology of the process, aimed at increasing the production efficiency. 1,4,13,[24][25][26][27][28] However, laboratory-scale investigations 18,[29][30][31][32] or simulation studies 33 aimed at disclosing other aspects of the process mechanism have also been conducted, as well as tests with natural or new synthetic dyestuffs. [34][35][36][37] 2.1 | Recent technological advances (2014- Table 1 provides an overview of some recent laboratory to industrial-scale prototypes and innovative technological solutions for SFD of PET.…”

“…In the above‐cited context, the academic research of recent years has often been conducted in cooperation with textile companies to improve the technology of the process, aimed at increasing the production efficiency 1,4,13,24‐28 . However, laboratory‐scale investigations 18,29‐32 or simulation studies 33 aimed at disclosing other aspects of the process mechanism have also been conducted, as well as tests with natural or new synthetic dyestuffs 34‐37 …”

“…Computational fluid dynamics has recently been used to simulate the supercritical carbon dioxide flow characteristics in fabric beam dyeing in the absence of the dye 33 . Simulation results reveal that non‐uniformity of the flow (ie the velocity profile of the fluid in the axial direction) increases with the increase in the supercritical carbon dioxide mass flow rate, while higher operating pressure, lower inlet temperature and flow reversal operation are beneficial to flow distribution levelness.…”