Capacity of a cooling system with active chilled beams at different air flow rates

¹ Department of Civil Engineering and Architecture, Tallinn University of Technology, Tallinn, Estonia
² Department of Civil Engineering, Aalto University, Espoo, Finland
³ Department of Mechanical Engineering, Aalto University, Espoo, Finland
⁴ Halton Oy, Kausala, Finland

^* Corresponding author: jevgeni.lukastsuk@taltech.ee

Abstract

The accuracy of dimensioning heating, ventilation and air conditioning systems (HVAC) becomes very important in the designing and construction of nearly-zero energy building (NZEBs). Over-dimensioned HVAC systems on one hand are an investment issue or on cost-effectiveness of construction works for achieving the required energy efficiency demands. On the other hand, the HVAC systems’ performance might not be optimal, especially at low heating and cooling needs. For analysing and optimizing the performance of HVAC systems during such conditions and outside working hours, detailed data about the heating and cooling room units is necessary. Cooling capacity of active chilled beams under design conditions as well as at zero airflows is an input parameter in simulation tools. Real cooling capacities of active chilled beams at lower than design and at zero air flows are largely unknown, but this data is also required for thermal comfort modelling and indoor climate systems optimal sizing in buildings with active chilled beams, where the building may overheat outside the occupied hours or to optimize the schedule of ventilation systems. The aim of this study is to map the performance of active chilled beams under varying control regimes of AHU fans. The cooling capacity of active chilled beams was measured in laboratory conditions at different air flow rates including zero air flows, when air handling units (AHU) are turned off. According to measurements, the cooling capacity of active chilled beams at zero air flows reduced to ~9% of calculated capacities at design conditions. The measurement results of the current work can be used in building simulations with active chilled beam systems for indoor thermal comfort, HVAC systems optimal sizing and operations.