湿球温度与闭式冷却塔蒸发冷却能力关系的研究

以探究环境湿球温度对闭式冷却塔蒸发冷却能力的影响为研究目的,以理论模型闭式冷却塔、实际产品闭式冷却塔以及开式冷却塔为比较对象,给出了不同闭式冷却塔塔型以及同一塔型在不同管材、管径、壁厚等设计细节时环境湿球温度与被冷却水出口温度间的对应关系,并与开式冷却塔作了比较.     

鲁奇副产蒸汽管壳型和I.C.I.四段冷激式甲醇合成塔的数学模拟和比较 Ⅰ.鲁奇副产蒸汽管壳型甲醇合成塔的数学模拟

本文建立了鲁奇副产蒸汽管壳型甲醇合成塔催化床的双速率二维模型,求得反应管内轴向及径向的浓度及温度分布的数值解。由于管间副产40kg/cm~2的蒸汽,其温度与管内催化床的温度接近,反应管内外的温度差小,反应管内径向温度差小。模拟计算结果表明,由于径向温度分布均匀,工业装置的计算可采用一维模型。     

循环冷却水系统中逆流湿式冷却塔的特性研究

以循环冷却水系统中的逆流式湿式冷却塔为研究对象,详细阐述了空气湿球温度、水流量和进塔水温对冷却塔热力学性能的影响。水温降低幅度越大,冷却塔冷却效能越好。结果表明:增加进口空气湿球温度或水与空气进料质量比,冷却塔冷却效能降低;水进口温度的变化对塔冷却效能影响较小;水与空气进料质量流量比高时,沿塔高显热交换潜力降低,质量流量比低时,沿塔高显热交换潜力增加。     

循环冷却水系统优化与冷却塔改造

针对某化工厂生产装置的东西两线循环冷却水来水水温冬季存在差异以及夏季给水水温不达标的问题,对现有循环冷却水系统水量、水温及运行情况进行分析,采取了优化水量、水温分布及对冷却塔改造等措施,平衡了给水温度差异、降低了出塔水温,满足了生产运行要求。     

氯化钠水溶液膜蒸馏过程的传质传热数值模拟

利用自制管式煤基炭膜开展膜蒸馏氯化钠溶液(模拟海水)的研究。在实验的基础上,采用计算流体力学方法进行模拟,用C语言编写UDF后代入FLUENT软件,结合实验数据计算得到相关传质过程参数。二维传质模拟结果表明,沿流体流动方向,管内浓差极化因子逐渐增大、传质系数降低;在料液入口温度为60℃、浓度10 g/L时,随着流量的增加,传质系数增大。三维传热模拟结果表明,在料液流量40 L/h、温度60℃、质量浓度20 g/L情况下,沿流动方向,膜管内压力降低,管中心速度增加,温度降低;边界层充分发展后,管内速度分布基本保持不变。     

如何选择冷却塔设计所需的气象参数

<正> 在带有冷却塔的二次循环供水系统设计中,气象参数是一个很重要的原始数据。在冷却水量不变的情况下,室外空气计算温度采用值越高,则冷却塔的尺寸越大,基建投资也随之增加;反之,如采用值过低,则在夏季冷却塔出口的实际水温将会长时间的超过设计水温,这样既不能满足正常的生产要求,又会大大降低其运行的经济性。因此如何正确的收集、统计、整理和使用气象参数则是大家所关心的问题。     

布朗工艺一段转化炉的模拟计算

在建立炉膛燃烧传热模型和管内气固相催化反应模型的基础上对布朗工艺合成氨装置一段炉辐射段进行模拟计算.炉膛燃烧传热过程采用Hottle区域法建立三维辐射换热模型,与管内的气固相催化反应动力学模型迭代求解,得出了炉膛三维温度分布以及管内温度、压力、组成随高度的分布.计算结果与实测值基本吻合.由于炉膛燃烧传热模型采用三维模型,与传统的一维和二维模型比较,计算结果更为精确.计算方法和结果对于节能降耗以及设备的改进等都有非常重要的意义.     

浅谈民用建筑循环冷却水系统的设计

在民用建筑循环冷却水系统的设计中,设计人员往往对一些细节问题关注不够,造成冷却水系统水温降不下来,系统能耗过大,控制操作不便等问题。认为采取选用集水型冷却塔或在冷却塔外部设集水池、在水泵吸水口处设储水罐、加大水泵吸水管的管径等方法,可满足冷却水泵的吸水要求。对于冷却塔的选型及设计,要考虑噪声扰民问题;对于大流量的冷却水系统,可采用横流塔;冷却塔选型时应考虑一定的余量等。冷却水系统的节能可从以下几方面考虑:冷却塔设在多层或高层建筑的屋面时,集水池不应设在底层,以避免浪费有效水压而增加循环泵的扬程;冷却水泵的扬程要根据冷却水系统的循环阻力、输水高差及自由水头确定;空调系统的冷却水泵可采用变频调速技术等。并附有典型的流程图,以供设计人员设计时参考。     

蒸发式空冷器热质传递实验及计算模拟研究

为分析空冷器传热传质性能,搭建工业用8排圆管管束中型蒸发冷却实验台对其进行实验和模拟研究。分别利用Poppe和Merkel类似假设建立控制方程对空冷器热质传递性能进行模拟。为保证模拟精度,依据实验数据拟合了蒸发空冷器传热传质经验公式。采用分段计算法在Matlab平台编写模拟计算求解程序。Poppe法和Merkel法模拟计算所得管内工质出口温度、空气出口焓值和喷淋水温与实验对比一致性较好,均可用于空冷器不同工况下换热性能预测。管束30分段已满足计算精度要求,模拟所得各参数分布可为空冷器进一步分析提供依据。相比Merkel法,Poppe法计算所得的空气出口焓值及喷淋水温误差更小,但需要更长的计算时间。     

三套管连续换热式氨合成塔催化床的二维模型

本文建立了三套管连续换热式氨合成塔催化床的二维数学模型,用逸度表示反应速率,求得了床层内轴向和径向温度及浓度分布的数值解。模拟计算结果表明,由于冷却段催化床内插冷管,冷管内与床层内的温差较大,使床层的径向存在较大的温差。采用一维模型进行计算与实际情况存在一定的偏差,这一点在反应器的设计和催化剂的还原中是不容忽视的。     

MINLP optimization of mechanical draft counter flow wet-cooling towers

In this paper, the problem of the optimal design of mechanical draft counter flow cooling towers that meets a set of specified constraints is formulated as a mixed-integer nonlinear programming (MINLP) problem. The Merkel's method is used to specify the characteristic dimensions of cooling towers, together with empirical correlations for the loss and overall mass transfer coefficients in the packing region of the tower. Water-to-air mass ratio, water mass flow rate, water inlet and outlet temperatures, operational temperature approach, type of packing, type of draft, height and area of the tower packing, total pressure drop of air flow, power consumption of the fan, and water consumption provide the set of optimization variables. The MINLP problem is formulated so as to minimize the total annual cost of the cooling tower. The performance of the proposed procedure is shown with the solution of six examples.     

白雾防止型密闭式喷淋冷却塔试验研究

为了防止冷却塔产生白雾,设计并制造了一种密闭式喷淋冷却塔。在该冷却塔中,冷却水分成两路分别在湿式换热器和干式换热器中冷却降温。湿式换热器采用铜翅片管,冷却水通过铜管向喷淋水释放热量,而喷淋水则和来流空气在翅片管表面进行传热传质。低温高湿的空气流过干式换热器后被铜铝复合翅片管内的冷却水加热,因此空气出口温度升高,使得出口空气和外部空气混合后的状态点不与饱和空气线相交,从而避免了白雾的产生。     

冷却塔配水管喷头流量的三维数值计算方法

冷却塔配水计算和优化可提高冷却塔的性能,目前通用的一维水力学方法没有考虑配水系统各部件的三维湍流影响。为准确计算冷却塔配水管喷头流量,提出了一种三维数值计算方法,该方法对配水管进行三维建模并对配水管内三维水流场进行模拟计算。采用该方法对1根典型的具有30个喷头的配水管实例进行数值模拟,计算得到喷头的流量分布合理,说明该方法是可行的,原则上该方法也可用于配水主管和竖井系统的配水计算和优化。     

鼓风式机械通风冷却塔数值模拟分析及优化

针对鼓风式机械通风冷却塔的研究比较少,现有的规范对其设计也没有明确的规定,采用CFD技术对鼓风式逆流式机械通风冷却塔群的塔排间距、出口速度、环境风及周边建筑物对湿空气回流率的影响进行了模拟计算.计算结果表明:塔排间距减小,回流率增高;冷却塔的出口流速增大塔的回流率减低;当冷却塔周围建筑较远时,冷却塔排布置宜将长轴与主导...     

空气与水逆流直接接触热质交换模型计算及与实验比较

According to general equations deducted from a model of heat and mass transfer of air and water in direct contact counter flow reported in the author‘s previous work, the outlet parameters of air and water counter flow through a paper wet pad were calculated by using the MATLAB-software. Comparing the calculation results with experiment data of prior researchers, the deviation of calculated outlet air wet bulb temperature from experimental outlet air wet bulb temperature was less than 10%, the deviation of calculated outlet water temperature from experimental outlet water temperature was less thang 9%, and the deviation of calculated outlet air dry bulb temperature from experimental outlet air dry bulb temperature was less than 10% when NTUh was more than 0. 6. The deviation of calculated outlet air dry bulb temperature from experimental outlet air dry bulb temperature was more than 10% when NTUh was less than 0. 6. The model calculations were in good agreement with experiments and the general equations could be used to design evaporation cooling equipment, such as wet pad and so on.     

复杂冷却循环水系统的建模与优化

建立了新的复杂冷却循环水系统的费用模型。利用优化软件GAMS求解了各冷却塔的最佳进出塔水温、用户进出水温、分配系数、循环水量、风量和循环水泵及风机功率等参数。通过工程实例验证了其可行性,并将其与原模型相比较。结果表明,新模型的操作费用减少了13%左右。因此,当处理复杂循环水系统时,应选取新模型。     

Analysis of fouling characteristic in enhanced tubes using multiple heat and mass transfer analogies☆

This paper provides a comprehensive analysis on cooling tower fouling data taken from seven 15.54 mm I.D. helically ribbed, copper tubes and a plain tube at Re=16000. There are two key processes during fouling formation:fouling deposition and fouling removal, which can be determined by mass transfer and fluid friction respectively. The mass transfer coefficient can be calculated through three analogies:Prandtl analogy, Von–Karman analogy, and Chilton–Colburn analogy. Based on our analyses, Von–Karman analogy is the optimized analogy, which can well predict the formation of cooling tower fouling. Series of semi-theoretical fouling correlations as a function of the product of area indexes and efficiency indexes were developed, which can be applicable to different internally ribbed geometries. The correlations can be directly used to assess the fouling potential of enhanced tubes in actual cooling tower water situations.     

A universal model to calculate cyclone pressure drop

The definition and composition of the pressure drop over a tangential inlet, reverse flow cyclone have been analyzed. It is assumed that two factors mainly contribute to the pressure drop, i.e., the local loss and the loss along the distance. The former includes the expansion loss at the cyclone inlet and the contraction loss at the entrance of the outlet tube (or vortex finder). The latter consists of the swirling loss resulting from friction at the cyclone walls and the dissipation of gas dynamic energy in the outlet tube. By use of the measured results of the flow field in cyclones, the calculation methods for each loss have been developed. And a universal model to predict the cyclone pressure drop is thus obtained simply by summing each loss. A detailed comparison between the calculated and experimental results shows that this accurate model is suitable either for pure or for dust laden gases at normal or high temperatures and can meet the requirement of most cyclone designs.     

基于最小二乘支持向量回归机的光管污垢特性预测

搭建了污垢实验系统以测得管壁温度和出、入口温度等参数,并将这些参数作为模型的输入变量,以污垢热阻值作为模型的输出变量,利用最小二乘支持向量回归机搭建了污垢预测模型,对光管的污垢特性进行了预测。一方面,通过与测量结果相比较,验证所搭建的模型是合理可行的;另一方面,通过对多次预测结果分析比较得出,该模型不但适用于流速、水浴温度、材质等参数为定值的情况,而且当这些参数发生改变时,该模型也是适用的。