Experimental Research And Numerical Simulation Of Thermal Management Device Of Ultra-low Temperature Cold Storage Inspection Robot

The application of ultra-low temperature cold storage is increasingly widespread,due to restrictions such as temperature,humidity,space and biological hazards,personnel cannot enter the interior of the ultra-low temperature cold storage for inspection and maintenance,so the inspection robot with a thermal imaging camera is used to inspect the interior of the cold storage.The operator can remotely control the inspection robot and obtain the real-time scene and thermal image inside the cold storage,which is convenient for the analysis of the problems in the cold storage.The inspection robot used in the ultra-low temperature cold storage of the Wuhan P4(Biosafety level 4)laboratory needs to undergo two processes: low temperature inspection process and high temperature disinfection process.Therefore,thermal management is of great significance to the inspection robot in ultra-low temperature cold storage.In this paper,a preli??ary analysis and simple selection of the various systems of the ultra-low temperature cold storage inspection robot is made,on this basis,the experimental reaearches of the servo motor under the low temperature are carried out.Through numerical simulation,the losses of servo motor are obtained by using Ansoft Maxwell,the temperature changes of the servo motor and the visual system under different working conditions and different thermal management methods by using ANSYS Fluent.The main research contents and results are as follows:1.Through the experimental research of the servo motor which use vacuum insulation Dewar under low temperature environment of-60? and-80?:The central temperature of brake and encoder surface rises first and then decreases,in which the central temperature of the encoder surface drops the fastest;under the-60? low temperature condition,the central temperature of the surface of each part of the servo motor is above0?at 159 ?? utes;under the-80? low temperature condition,only the central temperature of brake is above 0?,the central temperature of motor drops below 0? at105 ?? utes,the central temperature of encoder drops below 0? at 65 ?? utes,but the central temperature difference of each surface decreases.The servo motor is heated by an electric heating wire with a power of 10 W,after the electric heating is turned on for 30 ?? utes,the central temperature of motor and encoder surface rises from 0?to 20?,but the central tempreature of brake surface is higher.The insulation capacity of rubber-plastic insulation cotton is better than vacuum insulation Dewar,it is found by comparing the temperature curve of the surface center of each part of the servo motor under two different thermal management methods: vacuum insulation Dewar and rubber-plastic insulation cotton.But the high temperature and low temperature can cause cracking and inelastic deformation of the rubber-plastic insulation cotton.In order to ensure the reliability of the system,the thermal management method of vacuum insulation Dewar should be selected in practical applications.2.The loss of the servo motor is simulated by the finite element electromagnetic analysis software Ansoft Maxwell,and it is used as the internal heat source of the servo motor in he ANSYS Fluent finite element analysis software.The ANSYS Fluent finite element analysis software is used to simulate the temperature field changes of the servo motor and the vision system under high temperature and low temperature conditions.The accuracy of the simulation results is verified by conparing experimental results and numerical simulation results.The temperature uniformity of vacuum insulation Dewar and servo motor is poor,the servo motor and vision systems have higher temperatures under high temperature conditions and the vision system cannot run normally for a long time under low temperature conditions.3.The Numerical simulation of vacuum insulation Dewar combined with phase change material is carried out: for formic acid and fatty alcohol(n-decyl alcohol),which are close to the phase change temperature,formic acid has better thermal insulation capacity,because it has higher latent heat;the thermal insulation ability of the phase change material increases with the thickness of the phase change material.Both phase change materials with a thickness of 3mm can ensure that the central temperature of each part of the vision system is above 0? after running for 150 ?? utes under low temperature conditions;for the servo motor,2mm thick formic acid and decanol can ensure that the central temperature of the surface of each part of the servo motor is above 0? after running for 150 ? ? utes under low temperature conditions.It has good thermal insulation effect for servo motor and vision system,but it has poor thermal insulation effect for high temperature working conditions by using lower temperature phase change materials,the thermal management of the servo motor and the visual system by using two layers of phase change materials with different phase change temperatures can keep them in the normal working temperature range for a long time under high temperature and low temperature conditions.