Study On Wall Attached Multi-directional Jet Model And Its Airflow Organization Characteristics

Building good indoor air quality and reducing energy consumption has always been a key issue in HVAC.Compared with the mixing ventilation which is widely used in buildings,traditional displacement ventilation is generally regarded as an efficient and energy-saving ventilation method.However,from the author’s research,the following three shortcomings of traditional displacement ventilation have restricted the use of traditional displacement ventilation in actual projects,namely:(1)traditional replacement ventilation is likely to cause relatively large adjacent zone;(2)due to the low speed and the small temperature difference of the supply air,its cooling capacity is limited;(3)the traditional displacement ventilation diffuser is located in the lower part of the room,making the air supply flow easily blocked by obstacles,which may result in poor heat removal effect in some locations.In order to overcome the above shortcomings,our research group has proposed a new type ventilation method-multi-directional jet.Firstly,this paper derives a mathematical model applicable to the multi-directional jet to describe the development of the jet trajectory,the condition of the air flow leaving the attached wall,and the temperature change of the air flow.The numerical calculation method is used to solve the mathematical model to obtain the line graph of the model.After comparison with the experimental results,the model has high accuracy and can guide the calculation of jet parameters during actual design.Secondly,the CFD method is used many times in this paper.How to use CFD tools to accurately simulate the indoor environment is the key of this article.The turbulence model,vent model and the air density model are compared to evaluate the accuracy and economics,so as to fully prepared for simulation of the indoor environment.Thirdly,through the numerical simulation method,the flow state and airflow characteristics of the multi-directional jet are studied.Conducting a comparative study,the results show that when the two ventilation methods reach the same temperature,the multi-directional jet causes less draft in the room,and it is mainly distributed in the non-working area near the wall,which is smaller than the traditional replacement ventilation.The draft area of traditional displacement ventilation is very different in the work area.In terms of bearing the cooling load,since the multi-directional jet allows greater air speed and higher temperature difference,the maximum load capacity can up to 140W/m~2~160W/m~2.Finally,a typical office layout is used as an example to describe the"surrounding flow"characteristics of the multi-directional jet.It was found that the multi-directional jet has certain advantages over traditional displacement ventilation in overcoming the occlusion of office equipment or furniture in the work area.At the same time,this paper summarizes the types of obstacles that may be encountered when indoor airflow flows,and then proposes the basic form of a specific mathematical model of the flow around different obstacles.