Research On The Air Induction Law Of Active Chilled Beams In Isothermal Condition

The radiation air conditioning technology has been paid great attention gradually by designers and is widely used currently. Active chilled beam is a terminal product of radiation air conditioning system that was first used in Europe, in China is seldom used. So, it has great significance to guide the product design used for different climate zones and different lifestyle in China through research on the performance of active chilled beam. Induction ratio is defined as the amount of secondary air divided by the amount of primary air, which is an important index to evaluate the performance of active chilled beams. The main research topic is the influence rules of induction ratio performance of active chilled beams.The induced phenomenon of active chilled beam is generated by the nozzle jet, which belongs to confined jet. Because the development of jet flow depends on the flow boundaries, the universal calculation analysis is difficult. This subject studied on the induction ratio performance of active chilled beam by method of experiment combining with computer numerical simulation.In this paper, the design principle of active chilled beam was proposed; induction ratio range of the two-way blowing chilled beam used in experiment has been calculated through theoretical analysis. According to the experiment, the influence of primary air flow and the interior structure parameters on induction ratio were tested and analyzed. Then FLUENT software was used to simulate the air induction of active chilled beam. The variation of induction ratio affected by the nozzle diameter and distance between nozzles was analyzed.The influence rule of primary air flow affected the induction ratio is as follows: when the primary air flow is very small, the induction ratio is relatively small; when the volume of primary air increased to a certain value, the induction ratio will remain unchanged. There isn't lager difference in the induction ratio between one way blow beam and two way blow beam. As the nozzle diameter decreases, the induction ratio becomes greater. As the distance between nozzles increase, the induction ratio becomes larger. The active chilled beam operating conditions become more stable with increases of air flow and nozzle diameter. The operating conditions of one way blow beam is more stable than that of two way blow beam. The air flow and resistance of chilled beam have the relation of fluid mechanics pipeline resistance characteristics. Increasing the opening rate of active chilled beam return panel, can reduce the resistance of secondary air, and then increase the amount of induced air.Some guiding suggestions on active chilled beam design were proposed by the above analysis on the influence rule.