Orthogonal Pattern Louver Mixer for Two-Dimensional Air Mixing in HVAC Applications: Performance and Design Optimization

Abstract

This article focuses on the investigation of the mixing and hydraulic performance of an orthogonal pattern louver mixer in a square duct. The investigation includes various configurations, including the following parameters: mixer spacing and louver pattern orientation for a pair of mixers, as well as louver angle and louver array size were for both a single and a pair of mixers. Additionally, operational parameters such as mixing length, total flow rate, and flow rate ratio between cold and warm air were considered. Experimental testing was conducted to assess the performance of the orthogonal pattern louver mixer across various parameter combinations. Additionally, a numerical model was developed to enhance understanding of the mixing pattern and flow behavior. Numerical results highlighted that the two-dimensional mixing flow, characterized by multiple vortices generated through the unique louver design, significantly contributed to rapid and robust mixing, effectively reducing maldistribution within a short mixing length. The performance of the orthogonal pattern louver mixer from the experimental results was compared to other mixer types, such as orifice type mixers and ASHRAE Standard 41.2-based “cheese grater” baseline louver mixers. The orthogonal pattern louver mixer was found to be outstanding, with a maximum mixing effectiveness of 88 % for a mixing length of 2.0 Dh. Although it caused a higher static pressure drop than the baseline louver mixers, it was still acceptable for industrial use. The findings indicate that the orthogonal pattern louver mixer is a promising option due to its simple design, easy fabrication, high mixing performance with low pressure drop, and two-dimensional mixing. The orthogonal pattern louver mixer was also less sensitive to flow rate and velocity maldistribution than orifice-type mixers. This article provides useful guidelines for designing and selecting the best mixer type for HVAC applications, considering factors such as cost-effectiveness, mixing performance, pressure drop, and sensitivity to flow rate and velocity maldistribution. In addition, the article offers valuable insights into the performance characteristics of single or dual-use orthogonal pattern louver mixers, as well as the importance of carefully selecting the louver angle and array size when configuring the mixer.