The design and testing of an axial condenser fan

Abstract

Axial or propeller fans are a subset of turbomachinery whose application is prevalent in everyday life. In the case of heating, ventilation, air conditioning, and refrigeration (HVAC&R), fans can be a large source of inefficient energy consumption due to their physical operating nature. With the global push for more efficient systems, components of HVAC&R equipment such as fans have become a focal point for researchers in academia and industry alike. Technological improvements in research equipment such as computational fluid dynamics (CFD) and additive manufacturing play a large role in achieving these improved efficiencies. The goal of this research is to improve the efficiency of an axial fan intended for cooling a micro-channel heat exchanger that is used in rooftop condenser units. A higher efficiency retrofit fan was iteratively designed using a commercial CFD software package, Star CCM+, which constitutes much of the research conducted in this project. The iterative models show that significant efficiency gains can be achieved through incremental alterations of classical fan blade geometry elements such as pitch, camber, skew, cross section loft path, chord length, thickness, etc. A physical model of the fan design thought to be the optimal choice for experimental analysis was 3D printed and tested using an AMCA Standard 210 setup. Upon analysis of the physical test results, several discrepancies between simulated and actual results were discovered, highlighting the importance of CFD model validation in the design process. Despite the efficiency gains and advancements in user-friendly packaged software, the simulation underpredicted the power demand and incorrectly depicted the fan's performance at critical operating points showing that improper usage of these experts' tools can inadvertently lead to developed solutions with significant error. While the designed fan achieves an improved peak static efficiency and volumetric flow rate of 53.9% and 4334 CFM respectively, it ultimately did not meet the operating parameters of the specific unit it was designed for and further improvements to the CFD model are needed.