Optimum orifice design of cooling fan system in outdoor unit of air-conditioner

Demand for air conditioners is steadily increasing due to rapid climate change and improved living standards. The noise as well as the energy consuming rate of air conditioners are recognized as one of the important factors that determine the air conditioners' values. The performance and noise of the air conditioner are mostly determined by those of its outdoor unit, which in turn depends on performances of cooling fan unit. Therefore, a cooling fan unit of high performance and low noise is essential for a high-performance and low noise air conditioner. In this paper, the flow performance and flow noise source of entire outdoor unit with an axial cooling fan in a split-type air-conditioner were investigated. First, a virtual fan tester constructed by using about 18 million grids are developed for the high resolved flow simulation. The unsteady RANS equations are numerically solved by using finite-volume CFD techniques of VLES. In order to verify the validity of the numerical analysis, the predicted P-Q curves of the cooling fan in full outdoor unit is compared with the measure one. There is excellent agreement between two curves. Further detailed analysis on the flow field driven by the cooling fan through the entire outdoor unit is carried out. The coherent vortex structures that adversely affects the flow performance and causes flow noise are identified. Based on the identified flow structure, the optimum orifice designs are proposed to improve the flow and noise performances and its effects are numerically and experimentally verified.