Experimental And Simulation Study Of Hvls Fans And Their Combined Flow Field With Evaporative Air Coolers

Ceiling fans,as a practical air circulation device,can effectively alleviate the heat sensation of personnel in the areas they cover.However,the traditional ceiling fan greatly limits its use in demanding environments due to its small coverage area and high velocity.The HVLS(high-volume low-speed)fans effectively uses the wall jet theory,which greatly improving its flow field coverage area,can provide a lower and more uniform velocity field in a larger area,improving the use of the environment in the human body’s thermal sensation.On the other hand,the evaporative air coolers use the principle of water evaporation to cool down the dry hot air from outdoors with equal enthalpy and then send it into the room.Its simple structure,low price and energy-saving and environmental protection,it is widely used in the ventilation and cooling of large spaces.However,because the air supply temperature is limited by the outdoor wet bulb temperature,it is difficult to make the indoor temperature reach the design temperature of the air conditioning environment as defined in the current design specifications,which greatly limits the environment and scope of use of evaporative air coolers products.The purpose of this study is to use the wall jet theory to analyze and study in detail the flow characteristics and flow laws of HVLS fans on the human activity area,and to conduct experimental and simulation studies on the flow field of HVLS fans in actual engineering.In order to overcome the defect that the flow field produced by evaporative air coolers has higher temperature and poorer thermal sensation of human body,the characteristics of the combined flow field of HVLS fans and evaporative air coolers will also be studied,and the temperature field and velocity field under different combined conditions will be tested on site to analyze the thermal comfort parameters.And CFD simulation program will be used to simulate and optimize the analysis of various cases and propose the best combination of HVLS fans and evaporative air coolers.Regarding the study of the flow field of a HVLS fans,the experimental part mainly tests the flow field without constraint,the flow field with wall constraint and the flow field with mutual constraint between two ceiling fans,and the computational analysis of the ceiling fan flow field is combined with numerical simulation methods.Then the ceiling fan flow field is partitioned by using the jet mechanics theory,and the flow field distribution characteristics of each region are analyzed.Taking the flow field distribution in the unconstrained case as a reference,the influence on the flow field distribution in the case with wall constraint is analyzed,as well as the flow field distribution between two ceiling fans with mutual constraint is analyzed,and the flow field distribution from the center of the ceiling fan to the wall and the flow field distribution from the center of the ceiling fan to the intersection position of the flow field between the two ceiling fans are similar in characteristics,so the intersection of the flow field between the two ceiling fans can be viewed similarly as a virtual wall.At the same time,the analysis also obtained that the flow field distribution of the ceiling fan toward the corner of the wall and the flow field distribution between the ceiling fan sloping toward the wall direction also have high similarity.Finally,in order to further study the characteristics of the flow field distribution between the ceiling fans,numerical simulation optimization calculation of the flow field distribution between two ceiling fans at different installation distances and installation heights,respectively,and analysis to arrive at the appropriate installation distance and installation height between the two ceiling fans,to provide help for the flow field optimization analysis of the combination of HVLS fans and evaporative air coolers later.Regarding the study of combined flow field of HVLS fans and evaporative air coolers,the experimental part of this paper mainly tested six different cases of combined flow field with different numbers of HVLS fans on and different exhaust air methods,and also verified the accuracy of the experimental test by numerical simulation.Then the uniformity of the velocity and temperature fields of the combination of HVLS fans and evaporative air coolers were analyzed according to the velocity and temperature inhomogeneity coefficients,and it was obtained that the number and position of HVLS fans turned on and different air exhaust methods have influence on the uniformity of the combined flow field.Finally,in order to further study the combined flow field of HVLS fans and evaporative air coolers,numerical simulations were performed to optimize the combined flow field by changing the air supply height of the evaporative air cooler and the air supply direction of the HVLS fans to obtain the appropriate air supply height of evaporative air coolers and the air supply direction of HVLS fans can improve the uniformity of the combined flow field distribution.The research done in this paper provides a new cooling strategy to the HVAC field with some reference significance.The combined flow field of HVLS fans and evaporative air coolers issued in this paper will play a positive role in the use of large space ventilation and cooling as well as improving the comfort of personnel.