Experimental evaluation of energy efficiency and velocity fields on a low-pressure axial flow fan (desktop type)

Energy efficiency labeling programs are worldwide applied to provide energy savings (electrical, mechanical, thermal, etc.) in machines and equipment for residential and industrial use, and also a potential reduction in greenhouse gas emissions. Actual research and development indicate that low-pressure axial flow fans represent a significant amount of energy consumption (electricity) especially in developing countries with warm climates, as in Brazil. In this work, bench tests were performed at university facilities, taking into account Brazilian standards for energy efficiency (Brazilian Labeling Program) for residential fans. Equipment under test is a free blow fan (desktop type, residential use), three-bladed with 500 mm diameter and angular speed ranging from ~ 500 up to 1500 s⁻¹. Experimental analysis and measurement employed hot-wire anemometry, tachometer, wattmeter, chronometer, and data acquisition system. The results are for performance evaluation of turbomachinery characteristic curves. It includes airflow (m³ s⁻¹), angular speed (s⁻¹), the power supplied/received (W), efficacy η_ENCE,n [(m³ s⁻¹ W) m], and non-dimensional parameters: efficiency η (%) and design flow rate, as well as velocity field, among others. Main contributions indicate that (a) velocity and airflow in turbulent and fully developed conditions are consistent with energy efficiency and efficacy literature comparison, (b) power received by the fluid flow increases ten times more than supplied electrical energy (17/1.8), in the test range, (c) maximum energy conversion efficiency is η_máx ~ 33% at ~ 1300 RPM and nominal flow rate φ ~ 0.165, (d) efficacy is lower than 0.0030 {[(m³ s⁻¹) W)] m}, classified in "D" level, and (e) expected energy savings ~ 30% by reaching "A" efficacy levels.