Study On The Distribution Of Temperature Field In The Metering Device Of Heat Pipe For Nuclear Power

The purpose of this paper is to study the distribution of temperature field in the tube.By comparing the simulated cloud chart with the experimental data before and after optimization,the heater of the metering device is arranged to ensure the uniform distribution of temperature field in the metering device.The research ideas of this paper are as follows:case analysis,scheme selection,simulation,establishment of test bench,application of measurement,results analysis,optimization,establishment of new test bench,measurement and verification,extended application.In this paper,an ICEM software is used to build a model of a steel pipe with a center as a heating bar.The structured grid is obtained through o-block segmentation,and FLUENT is imported after grid encryption and independence verification.After determining that the heat transfer mode affecting the temperature field distribution is the natural convection of air caused by density difference caused by temperature,FLUENT parameters are set,especially gravity.The temperature,pressure and velocity cloud map were analyzed to determine the annular layout of the thermocouple measuring points around the pipe wall.In this paper,a measuring device is set up according to gbt10296-2008,measuring the steady heat transfer properties of the insulation layer by circular tube method.In this experiment,the steel pipe is 1000mm long,100mm in diameter,900mm in diameter and 20mm in diameter,and the two ends are indented to 50mm,which is fixed on the steel pipe shaft and placed horizontally.The data fluctuation of the last 12 sets of observation supervisor and gap separation,analyzing that:(1)maximum temperature difference of 8 measuring points in main pipeline;(2)maximum temperature difference at the gap;(3)temperature difference between the spacer and the measuring point of supervisor 1 and 8;(4)temperature difference between the highest point and the lowest point.First,test under the working condition of 100 ?,the temperature difference between the floating around 1%12 groups of data,experimental data does not change with time,in a stable state,the head piece of data is around 1%,the maximum temperature difference between seam and maximum temperature difference is around 1%,the experimental data meet the test requirements.Second,for the first time under the working condition of 400 ?,the maximum temperature difference 12 groups of data floating 3%,have apparent fall after rise first,failed to reach a steady state,come to the conclusion that the stability of the measurement before time extended from 5 hours to 7 hours.Third,the second 400 ? condition,floating maximum temperature difference 0.8%12 groups of data,do not change over time.(1)main line 8 point maximum temperature 32.9 ?,float 8.5%,less than 10%;(2)right across the seam maximum temperature 2.9 ?,0.8%floating,left every seam 2.5 ?,float 0.7%,less than 1%;(3)1 point and every seam 14 point temperature 8.2 ?,float 2.2%,8 PM and every seam 23 point temperature 13.2 ?,float 3.5%,more than 2.5%;(4)adjacent high measuring point 5 and low measuring point 4,with a height difference of 50mm.Temperature of 7.5 ?,1.8%floating.Fourth,repeat the experiment.The average temperature of each measurement point in the five experiments was taken for correlation analysis,and the maximum deviation rate of the main measurement point was 1.9%,and the maximum deviation rate of the two gap measurement points was 1.7%and 1.5%,respectively,meeting the requirement of no more than 2%in the standard gbt10296-2008.It is proved that the metering device can provide similar values under the same experimental conditions.In view of the problem of uneven distribution of temperature field and inaccuracy of measured data in the temperature cloud map under the model,the optimization is done in this paper.FLUENT was selected to adjust the model,and the order was as follows:first,the heating rod was offset by 20mm to the negative direction of the Y-axis;second,two heating rods were used to set the axial direction and axial positive and negative direction by 20mm;third,6 heating rods were uniformly distributed near the pipe wall,and the diameter of the pipe was increased to 360mm.After optimization,the temperature field in the pipe(especially near the pipe wall)is evenly distributed.According to the final optimization model,a measurement device is set up for measurement:First,the maximum temperature difference of the 12 groups was 0.3%,which did not change with time.(1)main line 8 point narrowed,maximum temperature difference is 9.2?,2.3%;(2)every joint maximum temperature difference is not big,4.0 ?,respectively,0.8%and 2.1 ?,0.5%;(3)the supervisor and narrow seam temperature difference,2 ? respectively,0.5%and 8.6 ? 2.1%;(4)in charge of high and low points,elevation difference increased,the temperature difference is still shrinking,1 ?,0.2%.Second,repeating the experiment.Correlation analysis was performed on the mean value of the experimental temperature for 5 times,and it was concluded that the maximum deviation rate of the main body was 0.2%,and the separation joints were 1.6%and 1.3%respectively,meeting the standard requirements.By comparison,it is found that the temperature field distribution is more uniform after optimization,and the data is more accurate.Through correlation analysis,the repeated experimental results after optimization are more similar,and the optimization scheme is reasonable and feasible.At the end of this paper,under the conditions of 250mm pipe diameter and 600mm pipe diameter?4 and 8 heating rods were set evenly close to the pipe wall,and the temperature field distribution was simulated by computer to verify the feasibility of using FLUENT in other pipe diameters.The results show that the simulation effect can be improved by encrypting the heating rod in the larger pipe diameter model,and the temperature field in the pipe is more uniform.