Performance evaluation of an energy efficient stand fan

Topic A7: Thermal comfort PERFORMANCE EVALUATION OF AN ENERGY EFFICIENT STAND FAN Bin YANG 1,* , Stefano SCHIAVON 2 , Chandra SEKHAR 3 , Kok Wai CHEONG 3 , Kwok Wai THAM 3 , and William NAZAROFF 4 Berkeley Education Alliance for Research in Singapore, Singapore Center for the Built Environment, University of California Berkeley, CA, USA Department of Building, National University of Singapore, Singapore Department of Civil and Environmental Engineering, University of California Berkeley, CA, USA Corresponding email: hvacyangbin@hotmail.com Keywords: Cooling fan efficiency index, Thermal manikin, Equivalent temperature, Power consumption, Air movement INTRODUCTION Elevated air speed is an effective method of cooling people in moderately warm indoor environments. In cold climates, elevated air movement can cause draft, defined as unwanted local cooling. In warm climates, on the other hand, enhanced air speeds can allow thermal comfort to be achieved in occupied spaces with elevated temperatures, which can yield energy efficiency benefits (Sekhar, 1995; Olesen and Brager, 2004; Aynsley 2005). A comprehensive review about thermal comfort and air movement pointed out theoretical support for using cooling fans (de Dear et al., 2013). Schiavon and Melikov (2009) introduce the cooling fan efficiency (CFE) index, defined as the ratio between cooling effect (as measured with a thermal manikin) generated by the fan and its power consumption, to objectively compare cooling fans in their ability to energy efficiently cool people. In this paper, an energy efficient stand fan was tested because of its special design of driving motor and fan blades. The three- phase brushless direct current (DC) driving motor can easily realize 24-grade-velocities in an energy efficient way. Specially designed fan blades, based on aerodynamics theories, can reduce flow resistance effectively. The maximum design power for this fan is 18 W, which is only 1/2 or even 1/3 of the power required for a conventional alternating current fan. Because of these advantages, the fan is envisaged to behave better than conventional fans (Schiavon and Melikov, 2009). The performance of the fan was tested and evaluated by manikin-based equivalent temperature, fan power consumption and CFE index. METHODOLOGIES Experiments were conducted in a chamber (11.0 m  7.8 m  2.6 m) with accurate control of dry bulb temperature (±0.5°C) and relative humidity (RH) (±3%). During experiments, outdoor temperature fluctuated from 31°C to 32.5°C. Room temperature was controlled by a variable air volume (VAV) air conditioning system with low background air velocity. Relative humidity was not controlled but measured. Relative humidity does not affect the thermal manikin measurements described below. One workstation was located at the centre of the chamber for measurement purposes. One commercially available stand fan with 24 speeds was employed, which was driven by direct current (DC) Ⅲ energy efficient motor. The fan was positioned at one of four locations at 1 or 2 m (3 and 6 times the swept diameter) distance