Thermal performance evaluation of hybrid heat source radiant system using a concentrate tube heat exchanger

This study developed a new radiant system concept having a concentric tube heat exchanger embedded in a radiant panel and evaluated the system characteristics. The concentric tube heat exchanger allows two fluids, air and water, to flow in the same direction. The outdoor air for the space ventilation requirement passes through an inner tube. The primary heat transfer medium, water, flows through the outer tube exchanging heat with both radiant panel and air tube. Two fluids would have an identical temperature condition by the characteristics of the heat exchanger. The system configuration enables simultaneous satisfaction of the space sensible loads and ventilation requirement. It has also flexibility to use outdoor air directly at night to reduce any heat built up during the day in the thermal mass. A numerical analysis model based on computational fluid dynamics (CFD) has evaluated this conceptual system. Comparing this new system with the performance of a typical system incorporated with a dedicated outdoor air system (DOAS), the proposed system is shown to provide a more closed the room set temperature condition and a better local thermal environment. In addition, the developed system can improve the performance of the night ventilation operation using nocturnal outdoor air.