Study On Insulation Influencing Factors Of Heat Distribution Pipeline

There are many heat distribution pipelines in petroleum and petrochemical industry.Insulation of heat distribution pipelines not only can improve thermal economy of heating network,reduce heat loss,save energy,but also can prolong service life of heating network,maintain good working environment.The results of insulation effect from field test show that the change of own structure such as insulation structure breakage,insulation material settlement and air gap between protection layer and insulation]ayer affect heat distribution pipelines insulation effect.The studies on them are helpful to master the status of heat distribution pipelines and have guiding significance on the design of insulation structure.Considering the limitation and applicability of analyzing the influencing factors aboved only by test data,this paper analyzed the effect of three aspects aboved by combining numerical simulation with field test.Meanwhile,this paper also studied the effect of directional emissivity on the test results of thermal infrared imager in order to ensure precision of field test and put forward the solution of this problem.This paper mainly includes the following four elements:1.In order to analyze energy saving potential and insulation influencing factors,the field test of heat distribution pipelines insulation effect was done,which was based on national standard GB/T 8174-2008?Method of mearing and evaluation thermal insulation effects for equipments and pipes?.The selection of test method and operation steps were mainly introduced.2.It analyzed the accuracy of test instruments.How it was influenced by emissivity was mainly studied,and it verified that the temperature measured by an infrared thermal imager would change as the emissivity changed.Finally the solution suggestions were given.3.The influence of insulation structure breakage,insulation material settlement and air gap between protection layer and insulation layer were studied by combining numerical simulation with field test.It concluded that the heat loss was rapid increasing when conduction is transformed into convection,and the critical thickness between them were approximately 18%,40%and 3.5%of insulation economical thickness in the air layer formed by breakage,settlement and gap at the same pipe diameter.It also verified the results of numerical simulation with field test,the relative error between numerical simulation and field test were 4.7%,5.6%and 0.94%.4.The insulation status of heat distribution pipelines were evaluated by combining the results of field test with theoretical study,considering the effect of insulation structure breakage,insulation material settlement and air gap between protection layer and insulation layer.It also gave reasonable insulation structure of heat distribution pipelines.Finally the thicknesses of insulation layer after transformation were given by optimization design for thickness.The conclusion can be used for transformation of unqualified pipeline in refining enterprise.