-再沸器介绍.pdf

再沸器再沸器是蒸馏塔底或侧线的热交换器，用来汽化一部分液相产物返回塔内作气相回流，使塔内汽液两相间的接触传质得以进行，同时提供蒸馏过程所需的热量，又称重沸器。设计再沸器时，必须同蒸馏塔的操作特点和结构联系起来。工业中应用的再沸器多为管壳式换热器，主要有釜式、虹吸式立式和卧式、强制循环式和内置式等型式，见图 1。1.各种型式再沸器介绍1.1.釜式再沸器由一个扩大部分的壳体和一个可抽出的管束组成，管束末端有溢流堰以保证管束能有效的浸没在沸腾液体中，故循环在管束与其周围液体之间进行，溢流堰外侧空间作为出料液体的缓冲区，壳侧扩大部分空间作为汽液别离空间。釜式 再 沸 器 的 气 化 率 可 到 达80以上，相当于一块理论塔板的作用。其优点是维修和清洗方便，传热面积大，气化率高，操作弹性大，可在真空下操作。但其传热系数小，壳体容积大，物料停留时间长易结垢，占地面积大，金属耗量大，投资较高。1.2.热虹吸式再沸器热虹吸式再沸器为有组织的自然循环式，精馏塔底的液体进入再沸器被加热而部分汽化，形成的汽液混合物密度显著减小，并一起进入精馏塔内，在塔内进行汽液别离，利用两侧的密度差使塔底液体不断被虹吸入再沸器。虹吸式再沸器分为两类：立式和卧式，通常管内蒸发采用立式，且为单管程；壳程蒸发采用卧式，可以为多管程。炼油工业约 95使用卧式热虹吸，而化工行业约 95使用立式热虹吸，石油化工行业介于期间，其原因与装置规模及介质的结垢性有关，也与使用习惯有关。1.2.1.卧式虹吸再沸器图 1 再沸器型式壳体可采用 J、H、X 型结构。按照工艺过程卧式虹吸再沸器又可分为一次通过式和循环式，一次通过式是指塔底出产品，进再沸器的物料由最下一层塔板抽出其组成与塔底产品不同；循环式是指塔底产品和再沸器进料同时抽出其组成相同。一次通过式和循环式也可由泵强制输送。流程见图 2。卧 式 虹 吸 式再沸器的气化率不应过大，对于烃类设计的气化率一般小于 30，对于水溶 液一 般不 超过20，气化量较大时 需采 用循 环式 个 人 见 过 的ABB公司用于丙烯塔底的卧式虹吸再沸器，循环式流程，壳程采用 X 结构 4 进 4 出，气化率可到达 50，且实际运行过程没有问题。卧式虹吸再沸器的分馏效果小于一块理论塔板，且由于出口管线较长阻力降较大，不适用于低压和真空操作工况。1.2.2.立式虹吸再沸器立式虹吸再沸器一般采用固定管板、单管程、管内汽化，出口管与塔体连接，减小了阻力，适用于低压和真空操作。其分馏效果低于一块理论塔板，气化率一般按 1015考虑。按工艺过程可分为一次通过式和循环式，为了使操作稳定常在塔底部加一块隔板，流程图见图 3。图 2 卧式热虹吸再沸器流程图 3 立式热虹吸再沸器流程文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W91.3.强制循环式再沸器强制循环式再沸器依靠泵的外加机械能维持强制循环，因而循环速度便于控制和调节，物料停留时间短，适用于粘稠物料、有少量固体的悬浮液和热敏性物料，也分为立式和卧式两种，其传热和压降均可按强制对流进行。1.4.内置式再沸器将管束直接置于塔内，不需要壳体和工艺配管，结构简单，投资小，易清洗，但塔内容积有限，传热面积小，液体循环差，不适于粘稠液体，设计计算原则与釜式再沸器相同。1.5.选择再沸器应考虑的因素选择蒸馏塔再沸器时，在满足工艺要求的前提下优先选用立式热虹吸再沸器，因为它具有一系列突出的优点和良好性能，但下面情况不能选用立式虹吸再沸器。1.5.1.再沸器中静压波动较大的场合当蒸馏塔在较低液位排除塔釜液、间歇排除塔釜业、对塔釜液面不作严格控制时会产生压力波动，应采用釜式再沸器。1.5.2.高真空操作或结垢严重时1.5.3.气化率低于 5不会产生热虹吸，气化率大于40时应采用釜式1.5.4.塔的安装高度受限或没有足够空间安装立式虹吸再沸器2.再沸器设计考虑的因素2.1.结垢因素一般根据工程经验选择污垢热阻值，由于沸腾传热系数一般较高，所以指定的污垢热阻通常在总传热系数中占相当大的比例，应通过设备形式的选择和操作条件的调整，做到尽可能降低污垢热阻的影响。2.1.1.影响污垢生成的因素污垢的生成与流体流动速度、温度、汽化热有关，或三者兼而有之。含沉淀物或重残渣等介质，污垢的生成与速度关系密切，因此提高流速来减少结垢是首要问题。这种工况下应首选立式虹吸式再沸器，也可选择卧式强制循环再沸器，不能使用釜式再沸器。与流体温度有关的结垢一般是通过某种化学反应形成的，当管子温度超过反应温度时结垢速度会迅速增加。由于釜式重沸器可以在较低的有效温差下操作，是比较合适的选择。汽化敏感的结垢常发生在重组分随汽化的发生从液体中析出的时候，在釜式或液体循环速率较低的卧式虹吸再沸器中易发生，此时选立式虹吸再沸器合适。2.1.2.气化率对结垢的影响在较低的气化率下各种结垢都有减小的倾向，对容易结垢的介质其气化率以不超过20为宜。2.1.3.流动分布的影响壳程不良的流动分布将导致结垢的加快，例如管心距太小、旁路面积较大、折流板切文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9口太大或切口方位错误等都可能造成不良的流动分布。任何引起局部高气化率、高壁温或低流速的壳程几何形状都将引起严重的结垢。管子壁温高也会促进另一侧介质结垢加快。2.1.4.尽量采用符合实际的污垢系数不推荐为了保险而采用过高的污垢系数，过大的污垢系数将使换热面积过大造成浪费，并使得新设备开车时所需的T 比正常操作要小很多，再沸器操作性能变差。假设污垢热阻选择过大，会使实际运行条件和设计条件相差悬殊，开工时假设根据设计条件去分析实际运行情况就没有意义了。2.2.有效温差T再沸器设计时都要考虑一定的污垢热阻，新设备开工时需要将T、介质的膜传热系数降低到设计水平以下来补偿暂时不存在的污垢热阻。2.2.1.开工时对操作的考虑再沸器开工时需要的T远远低于到达规定的污垢热阻时的T，假设开工时对新设备提供满足设计的T就可能使再沸器处于膜状沸腾，所以开工时要使T尽可能小，然后逐渐增加T 到达设计能力，防止不必要的模式沸腾。对再沸器热源的控制是降低开工时T的有效方法。假设采用蒸汽加热，可在蒸汽进口管线上设置阀门进行节流，通过降低蒸汽的压力和饱和温度来降低T，但设备有很大潜力时，可以使用冷凝液淹没法。对于用无相变流体加热的情况可以设置旁路，开工时用旁路减小热流体流量从而降低热流出口温度，用此方法来调节T。2.2.2.在很低的T下操作由于工艺的限制，再沸器有时需要在很低的T小于 4下操作，此时泡核沸腾传热系数受外表粗糙度的影响很大，变得很不稳定。此工况下，为增强泡核沸腾效果，对于不易结垢的流体可使用多孔外表管或T 型管改变外表，使操作变得稳定。2.2.3.在较高的T下操作再沸器在较高的T下操作会产生三种不同的极限状态，即膜状沸腾、雾状流和不稳定沸腾，超过临界最大热通量会发生上述三种状态之一。有些工况需要使用高温加热介质，此时的T比泡核沸腾所需要的T要高出很多，这种情况下可以将再沸器设计成处于膜状沸腾状态，但由于操作难以控制所以除非必要一般不推荐。总之，再沸器的设计要尽量处于完全泡核沸腾状态或处于完全膜状沸腾状态，由于泡核沸腾传热系数高得多且壁温较低，总是优先考虑泡核沸腾状态。2.3.操作压力的考虑2.3.1.接近临界压力的操作接近临界压力时蒸汽密度接近液体密度，降低了循环的推动力，此时汽液别离能力较差，会使泡核沸腾的最大热通量降低。这种工况下釜式再沸器有较好的操作性能，内置式的再沸器效果会更好，假设采用立式热虹吸再沸器需要采用大直径和较短的管子、文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W92.3.2.高真空下操作由于真空条件下易产生较大的过冷区，会使沸腾传热效率下降。采用立式虹吸再沸器时过冷区长度小于等于管子长度的1/4 为宜，另外真空下泡核沸腾需要更大的空穴，最好采用多孔外表管或 T 型管来提高传热效率。大部分真空操作带来的问题属于流体动力学的问题，选择对流体动力学最不敏感的釜式再沸器是最适宜的，其次为立式虹吸再沸器但需要保证足够的循环推动力。3.釜式再沸器釜式再沸器的管束沉浸于封头液体中，液体在管束间受热沸腾，汽液化合物向上运动，而液体则自管束两边底部进入，形成空间上不均匀的循环运动，每根管的热流密度和给热系数也是不均匀的，见图 4。上部管排的传热面积会被下部管排产生的蒸汽覆盖，特别是在管间距较小时，导致给热系数减小；实际上液体的循环流动与上升气泡引起的扰动又可以促进传热，对于这两种矛盾因素的影响还没有一致的结论。3.1.沸腾传热简介按沸腾液体所处空间与流动条件的不同沸腾分为池内沸腾和流动沸腾。池内沸腾：亦称大容积沸腾，加热面沉浸于液体中，生成的气泡脱离加热面后自由浮生，液体的运动是由气泡扰动和自然对流引起的，不存在液体的平均宏观流动。流动沸腾：液体以一定的宏观流速受迫掠过加热壁面的沸腾。立式虹吸再沸器属于流动沸腾过程，釜式、内置式、卧式虹吸再沸器属于池内沸腾过程，卧式虹吸再沸器的壳程侧有一定的宏观流速，它的沸腾过程二者都有，目前设计时还是多按照池式沸腾处理。3.2.池内沸腾机理及沸腾曲线池内沸腾过程中，传热强度随着传热温差T变化，以沸腾传热强度q 作为传热温差T的函数，将沸腾过程热强度的变化汇成曲线，见图 5。自然对流区：在 AB 区，管子外表处的液体没有过热到足以产生泡核，因此没有气泡产生，此时热量靠自然对流传递。初始沸腾区：在 BC 区，随着传热温差T的升高开始有气泡产生，脱离外表后在液体中自由浮生。在 C 点附近气泡在上升的过程中逐渐消失，此时的热量传递是自然对流和泡核沸腾的结合。图 4 釜式再沸器断面文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9泡核沸腾区：在 CD 区，随着传热温差T的继续升高，近壁面的液体到达过热并开始汽化，在壁面的凹坑或划痕处形成气泡，气泡带走了相变时的汽化潜热，同时扰动了受热面附近的液体，因而也增加了对流传热。在这个区域内，气泡连续不断的在加热外表产生，设计蒸发器时要求置于泡核沸腾区内操作。D 点是产生泡核沸腾的最大热通量点，从受热面上逸出的气泡数目太多可能阻碍液体的补充，这样蒸汽在受热面上形成亦称隔绝层，使受热面温度升高产生烧毁现象亦称沸腾危机。通常把此点的温差称为临界温差，热通量称为临界最大热通量。过渡沸腾区：在 DE 区，随着传热温差T的增大，汽层和液层交替覆盖受热面，致使外表温度波动，传热效率下降，操作变得不稳定，开始向膜状沸腾过渡。膜状沸腾区：在 EF 区，管壁受热面不再存在液体，管子被一层稳定的蒸汽膜包围，随着传热温差T的进一步升高，热通量也会继续提高，这是有辐射传热造成的，温度过高会使壁面损害，没有特殊要求一般不将蒸发器设计在膜状沸腾状态。3.3.临界最大热通量maxq及其影响因素3.3.1.临界最大热通量maxq设计釜式再沸器时其热通量的上限值不应超过maxq，而下限值不应低于初期沸腾区域。临界最大热通量maxq的计算方法很多，可以采用图表法、单管修正系数法、经验关联式法等，下面介绍一下单管修正系数法，HTRI 软件中采用此方法。pRqq式 1 式中Rq 为单管的最大热通量，计算方法如下：0.280.730.7 6641RCCCPPqPPP式 2 P 为操作压力2lbin绝压CP为临界压力2lbin绝压为管束校正系数，其取值很复杂，在此不多说了图 5 池内沸腾曲线文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W9文档编码:CB5F10G7H3R3 HV4I6B1S5V6 ZE3C10W9A7W93.3.2.maxq的影响因素影响maxq的因素有流体性质、压力和设备几何形状等，介绍一下主要影响因素：3.3.2.1.压力影响根据实验数据，当比照压力操作压力比临界压力等于0.3 左右时，最大热通量通过一个峰值，比照压力大于0.3 后热通量随比照压力的增加而下降，只有当比照压力小于0.3时，最大热通量随临界温差的增加而增加。压力越大，临界温差越小到达临界热通量越快。3.3.2.2.管束几何形状的影响管束的几何尺寸中对maxq影响主要的是管子数和管间距，maxq与管间距成正比、与管子数的平方根成反比。当确定了换热管直径和管间距后，增加管子数即加大直径会使临界热通量和临界温差降低。3.3.2.3.外表粗糙度的影响外表状