机械专业外文翻译

机械专业外文翻译 Increase heat transfer efficiency Heat exchanger is asked wall heat transfer fluid through heat exchanger, heat and cold, heat exchanger, fluid of plates with plate for direct contact heat transfer heat transfer and convection heat transfer. Improve the heat transfer efficiency of plate heat exchanger is to improve the heat transfer coefficient and key logarithmic mean temperature difference. Improve the heat transfer coefficient of only hot and cold plates on both sides and increase the surface heat transfer coefficient, reducing the fouling layer thermal resistance, high thermal conductivity selected the slab, reducing the thickness of plate in order to effectively improve the heat transfer The heat transfer coefficient. Article link: China Chemical Network A Improve the slab surface heat transfer coefficient As the corrugated plate heat exchanger to make a smaller flow rate of fluid produced in the turbulent (Reynolds number for a 150 pm), so they can obtain a higher surface heat transfer coefficient, surface heat transfer coefficient and the geometric structure of corrugated plate, and The flow state of the media. The wave plate, including herringbone, straight, ball and so on. After years of research and experiments showed that the shape of corrugated triangular cross section (the largest sinusoidal surface heat transfer coefficient, pressure drop less uniform stress distribution during compression, but processing difficulties?) in chevron plate surface with a high pass Heat transfer coefficient, the greater the angle, and ripple, the medium flow between the plates the higher the velocity, surface heat transfer coefficient B Reduce the thermal resistance of fouling layer Reduce heat exchanger fouling layer thermal resistance, the key is to prevent the plate scale. Plate thickness of 1 mm scale, the heat transfer coefficient is reduced by about 10%. Therefore, we must pay attention to monitoring the water quality on both sides of hot and cold heat exchanger to prevent fouling plates, and to prevent debris in the water on the plate attached. Some heating units to prevent theft of water and steel corrosion in the heating medium, add the drug, attention must be given drugs to cause water quality and debris contamination stick * heat exchanger plate. Sticky debris if the water should be processed using special filters. Pharmaceutical use, the agent should choose non-sticky. C High thermal conductivity selected slab Optional stainless steel plate material, titanium, copper alloy. Good thermal conductivity of stainless steel, thermal conductivity of about 14. 4 W / (m ? K), high strength, punching performance, less susceptible to oxidation, the price is lower than the titanium and copper alloys, the most used heating project, but its corrosion resistance to chloride ion poor D Reduce the plate thickness Thickness of plate design has nothing to do with its corrosion resistance, and heat exchanger pressure capacity. Thick plate, the pressure can increase the heat capacity. Using chevron plate combination, adjacent to each other upside down plate, corrugated contact with each other, forming a dense and uniform distribution of the pivot plate angle larvae L and edge seal structure has been gradually improved, so has a good heat exchanger Bearing capacity. Domestic removable plate heat exchanger has reached a maximum pressure 2.5 MPa. Plate thickness a great impact on the heat transfer coefficient, reducing the thickness of 0.1mm, symmetrical plate heat exchanger total heat transfer coefficient increase of about 600W / (m ? K), non-symmetric increase of approximately 500 W / (m ? K ) ?. Ability to meet the pressure in the heat exchanger under the premise should try to use a smaller plate thickness. ? improve logarithmic mean temperature difference Flow plate heat exchanger with counter-current flow downstream and mixed type (both upstream there are downstream). Under the same conditions, when the logarithmic mean temperature difference between upstream maximum downstream, the smallest of the mixed flow pattern between the two asked. Improve the heat exchanger method of logarithmic mean temperature difference as far as possible upstream or close to the mixed flow countercurrent to maximize the hot side fluid temperature, reduce the temperature of the cold side of the fluid. ? to determine the location of the import and export control Process layout for a single plate heat exchanger for easy maintenance, import and export control of fluid in the heat exchanger should be arranged as a fixed end plate side. The greater the temperature difference between the medium, the stronger natural convection of fluids, stay with the impact of the formation of the more obvious, so the import and export position of the media should be motivated under the hot fluid out into the cold fluid out under the arrangement to reduce the impact of retention with To improve heat transfer efficiency. 提高传热效率 板式换热器是问壁传热式换热器，冷热流体通过换热器板片传热，流体与板片直接接触，传热方式为热传导和对流传热。提高板式换热器传热效率的关键是提高传热系数和对数平均温差。 提高换热器传热系数只有同时提高板片冷热两侧的表面传热系数，减小污垢层热阻，选用热导率高的板片，减小板片的厚度，才能有效提高换热器的传热系数。 a(提高板片的表面传热系数 由于板式换热器的波纹能使流体在较小的流速下产生湍流 (雷诺数一 150时 )，因此能获得较高的表面传热系数，表面传热系数与板片波纹的几何结构以及介质的流动状态有关。板片的波形包括人字形、平直形、球形等。经过多年的研究和实验发现，波纹断面形状为三角形 (正弦形表面传热系数最大，压力降较小，受压时应力分布均匀，但加工困难, )的人字形板片具有较高的表面传热系数，且波纹的夹角越大，板间流道内介质流速越高，表面传热系数越大。 b(减小污垢层热阻 减小换热器的污垢层热阻的关键是防止板片结垢。板片结垢厚度为 1 mm时，传热系数降低约 10%。因此，必须注意监测换热器冷热两侧的水质，防止板片结垢，并防止水中杂物附着在板片上。有些供热单位为防止盗水及钢件腐蚀，在供热介质中添加药剂，因此必须注意水质和黏 *剂引起杂物沾污换热器板片。如果水中有黏性杂物，应采用专用过滤器进行处理。选用药剂时，宜选择无黏性的药剂。 c(选用热导率高的板片 板片材质可选择奥氏体不锈钢、钛合金、铜合金等。不锈钢的导热性能好，热导率约 14( 4 W/(m?K) ，强度高，冲压性能好，不易被氧化，价格比钛合金和铜合金低，供热 工程 路基工程安全技术交底工程项目施工成本控制工程量增项单年度零星工程技术标正投影法基本原理 中使用最多，但其耐氯离子腐蚀的能力差。 d(减小板片厚度 板片的设计厚度与其耐腐蚀性能无关，与换热器的承压能力有关。板片加厚，能提高换热器的承压能力。采用人字形板片组合时，相邻板片互相倒置，波纹相互接触，形成了密度大、分布均匀的支点，板片角 孑 L及边缘密封结构已逐步完善，使换热器具有很好的承压能力。国产可拆式板式换热器最大承压能力已达到了 2.5 MPa。板片厚度对传热系数影响很大，厚度减小 0.1mm，对称型板式换热器的总传热系数约增加 600W/(m ?K)，非对称型约增加 500 W/(m ?K)? 。在满足换热器承压能力的前提下，应尽量选用较小的板片厚度。 ? 提高对数平均温差 板式换热器流型有逆流、顺流和混合流型 (既有逆流又有顺流 )。在相同工况下，逆流时对数平均温差最大，顺流时最小，混合流型介于二者之问。提高换热器对数平均温差的 方法 快递客服问题件处理详细方法山木方法pdf计算方法pdf华与华方法下载八字理论方法下载 为尽可能采用逆流或接近逆流的混合流型，尽可能提高热侧流体的温度，降低冷侧流体的温度。 ? 进出口管位置的确定 对于单流程布置的板式换热器，为检修方便，流体进出口管应尽可能布置在换热器固定端板一侧。介质的温差越大，流体的自然对流越强，形成的滞留带的影响越明显，因此介质进出口位置应按热流体上进下出，冷流体下进上出布置，以减小滞留带的影响，提高传热效率。