INVESTIGATION OF FACTORS AFFECTING OPERATIONAL INDUCTION RATIOS AND ASSESSMENT OF THE THERMAL COMFORT OF ACTIVE CHILLED BEAMS (ACBS) IN A FIELD STUDY

Abstract

Active chilled beams (ACBs) are an energy-efficient HVAC system that provides cooling to an indoor space by circulating water through a cooling coil. The primary supply air through nozzles can induce secondary air flow through the coil for heat transfer, resulting in more efficient cooling of the space. The ratio of the induced air flow rate to the supply air flow rate is called the induction ratio (IR). IR is a critical parameter in the design and operation of ACBs, as it affects the thermal comfort and energy consumption of the building. In this study, the IR of ACBs under different operating conditions in an office building is experimentally measured. These measurements were carried out using velocity probes under different operating conditions. The measurements indicate that for a small office room, opening the door can increase the IR by up to 20%. A high IR is obtained when the office room is unoccupied. Installing chilled beams in unobstructed areas, as opposed to areas near walls or windows, is beneficial for achieving a higher IR. The results show that IR depends on the operating conditions and therefore the variation in operating conditions should be considered when adopting ACBs. In addition, previous research has found that higher air speeds can lead to lower thermal comfort, and the supply air temperature has a significant impact on perceived comfort. However, in tropical environments, people prefer higher air speeds for thermal comfort. The second objective of this experimental study is to evaluate the thermal comfort provided by ACB in a real office environment in a tropical setting. The study evaluates the thermal comfort of the occupied area when the fan speed is increased at a fixed IR and higher room temperature. The experimental results show that increasing the fan speed while maintaining the IR can accelerate the flow of induced air, providing a comfortable indoor environment at higher room temperatures (26?). The experimental data can be used to improve the design and operation of ACB, thereby making buildings more energy-efficient and comfortable.