LNG空温式气化器除霜判定指标及标准研究

Research on Defrosting Judgment Index and Standard of LNG Ambient Air Temperature Vaporizer

为合理确定LNG空温式气化器的切换运行周期(除霜周期),基于LNG空温式气化器的传热模型,对其除霜判定指标及标准进行研究。从管内、管壁及管外传热和霜层生长的角度,建立非结霜工况和结霜工况下的气化器传热模型。分析环境温度对气化器传热特性的影响,定义了能源需求度、结霜热量损失系数、结霜面积损失系数和霜层覆盖率等指标,建立了LNG空温式气化器切换运行的除霜判定指标体系,由能源需求度、结霜热量损失系数、结霜面积损失系数、霜层覆盖率和运行时间组成。提出气化器运行的参考工况,讨论了LNG空温式气化器的除霜判定指标的标准。结合工程实例对提出的气化器除霜判定标准进行了评价。能源需求度、结霜热量损失系数、结霜面积损失系数和霜层覆盖率在气化器除霜判定以及除霜周期的确定方面具有重要的参考意义。

In order to reasonably determine the switching operation cycle(defrosting cycle)of LNG ambient air vaporizers(AAVs),the defrosting judgment index and standard are studied based on the heat transfer model of LNG AAVs.From the perspective of heat transfer and frost layer growth in the tube,tube wall and outside,the heat transfer models of vaporizers under non frosting and frosting conditions are established.The influence of ambient temperature on heat transfer characteristics of vaporizers is analyzed.Energy demand,frosting heat loss coefficient,frosting area loss coefficient and frost coverage rate and so on are defined,and the defrosting judgment index system for switching operation of LNG AAVs is established,which is composed of energy demand,frosting heat loss coefficient,frosting area loss coefficient,frost coverage rate and operation time.The reference operating conditions of vaporizers are put forward,and the standard for defrosting judgment index of LNG AAVs is discussed.The defrosting judgment standard of vaporizers is evaluated combined with engineering example.The energy demand,frosting heat loss coefficient,frosting area loss coefficient and frost coverage rate have important reference significance in the determination of vaporizer defrosting judgment and defrosting cycle.