Theoretical Study Of Heat Transfer And Structural Optimization Of Industrial Grade Core-hole Polymer Melt Cooler

Core-hole polymer melt cooler is a new type of high-efficiency,compact heat exchanger developed for the characteristics of polymer melt.Its structure is simple,and the main heat exchange parts are core-hole parts.Compared with conventional heat exchangers such as:shell and tube heat exchangers,plate heat exchangers,etc.,its main advantages are:large heat exchange area,good sealing performance,high working pressure,high heat transfer efficiency,melt pressure loss small,good uniformity of export materials.The main component of the hole core piece is the biggest feature of the hole core polymer melt cooler.The flow paths of the hot and cold fluids in the hole core piece are arranged in a staggered cross in the cylindrical hole core piece,so that the cooling can be completely completed The separation of oil and polymer melts greatly improves the sealing performance.In addition,the hole core piece is the whole part of the whole heat exchanger,which is matched with bolts and sealing rings,which is easy to disassemble and facilitate subsequent maintenance and repair.The convective heat transfer coefficient of the melt is obtained by the characteristic number,then the metal thermal resistance is obtained by analogy,and finally the total heat transfer coefficient equation of the core polymer melt cooler is obtained.In addition,using the pressure gradient method to calculate the pressure drop of a single melt hole and the simulation of the pressure drop error is small.The melt cores of the polymer in the hole core and the flow path of the cooling oil have no direct connection except for the restrictions on the spatial structure,and belong to two independent systems.In order to increase the convective heat transfer coefficient of the cooling oil,three parameters affecting the convective heat transfer of the cooling oil are analyzed:the number of cooling oil flow channel layers,the number of cooling oil flow channel folds and the cooling oil flow rate by designing the DOE test,the effects of these three factors on the cooling oil side on the performance of the heat exchanger are explored.Experimental results show that increasing the cooling oil flow rate can increase its convective heat transfer coefficient,but compared with the number of cooling oil flow channels and the number of folds,the cooling oil flow rate has the smallest effect on the heat transfer performance.Finally,it is concluded that in order to increase the convective heat transfer coefficient on the cooling oil side,the number of layers and the number of folds of the cooling oil flow channel should be increased first,and then the cooling oil flow rate should be increased.Finally,the VB6.0 software is used to design the small program of the oil temperature controler used for cooling oil,which provides guidance for the selection of the oil temperature controler.The main factors affecting the convective heat transfer coefficient on the melt side are the melt hole diameter,melt hole length and polymer output.The essence of these parameters is the influence of the thickness of the thermal boundary layer and the length of the entrance section of the thermal boundary layer on the convective heat transfer coefficient of the melt.Through the DOE experiment,it is known that the increase in the diameter and length of the melt hole will decrease the total heat transfer coefficient of the hole-core polymer melt cooler and affect the heat exchange effect.Then through comprehensive analysis of heat exchange area,pressure drop,temperature uniformity of the exit melt and melt exit temperature,When PP materials are used,the optimal diameter of the melt core is 7 mm,and when PS materials are used,the optimal diameter of the melt core is 5 mm.