The Development Of Testing System On The Plate Fine Heat Exchanger Air Resistance Characteristics

The plate fin heat exchanger(PFHE)is one of the core equipment of the thermal system,having the characteristics of compact structure,good heat transfer effect,light weight.Compared with the traditional heat exchanger,the PFHE improves the heat transfer efficiency of 20%~30%,while the cost is reduced by 50%,having been widely used in air separation,petrochemical,refrigeration,automotive liquefied aviation,atomic energy and machinery etc..It is important to improve the heat transfer efficiency and energy efficiency of the heat exchanger by studying the flow characteristics of the PFHE.In order to measure the flow characteristics of the PFHEs accurately,we have designed a set of air resistance test system with advantages of high accuracy,wide range of measurement,good stability and high degree of automation.With the help of digital display and automatic data acquisition technology,the accuracy and stability of the system has been improved greatly,and the method of air resistance measurement has been reformed.Firstly,this paper summarizes the development status and the trend of the PFHEs and test and measurement system at home and abroad.Meanwhile,this paper introduces the overall design of the PFHE air resistance characteristics of the test system,the system is divided into three layers,the central control layer,data acquisition layer and infrastructure layer.The three layers also is divided into two parts,hardware and software.The hardware system includes the air flow control system and the data acquisition system.The software based on.NET platform,the main modules include:real-time data acquisition module,air volume control module,historical data query module,the sensor calibration module and so on.The software realizes the functions of initial information input,control volume,real-time data acquisition,fault alarm,data analysis and other functions,but also has a stable and friendly interface,expandability etc.In order to verify the rationality of the designed air volume measurement box and the accuracy of the measurement,the CFD analysis was carried out.In this paper,the gas flow model of the air volume measurement box is built by the momentum model,continuity equation,epsilon equation and k-? equation.The airway is divided into four parts: the straight section,the ascending segment,the flat segment and the descending segment.The grid segmentation is performed by using different meshing algorithms.Under the condition of setting a variety of inlet flow,the simulation is carried out to measure the pressure difference between the front and rear nozzles and verify the accuracy of air flow calculation and the rationality of the air volume measurement box.At the same time,the error analysis of the test system is carried out.The results show that the components have littleinfluence on the test results,the temperature and humidity have great influence,and the relevant amendments are given.Aiming at the problem of high complexity of air flow control model in this system,volume changes,laboratory experimental conditions,the system adopts fuzzy-PID control method.It realizes the function of controlling the system's air fast,accurately and efficiently.The simulation results show that,compared with the traditional PID control,fuzzy-PID has the advantages of quickly respond,highly stability and strongly adaptability,especially on the high order,large lag and variable air volume system.The hardware and software debugging and air volume accuracy verification are carried out for the air resistance characteristic test system of the PFHE.The results show that the system has high stability,high accuracy and good repeatability.