逆流式蒸发式冷凝器传热传质性能实验研究

发布时间：2018-03-19 15:07

本文选题：热工学　切入点：蒸发式冷凝器　出处：《天津商业大学》2014年硕士论文　论文类型：学位论文

【摘要】：随着冷冻冷藏业的快速发展，势必增加能源的消耗，能源日渐短缺已经成为不争的事实，近年雾霾频现也使人们面对着巨大的挑战，因此节能环保型设备的开发和应用具有重要的意义。蒸发式冷凝器是一种高效的换热设备，因其具有节能、节水、占地少等优点，，被广泛应用于制冷行业。蒸发式冷凝器传热性能的研究对提高蒸发式冷凝制冷系统具有重要的意义。蒸发式冷凝器传热过程十分复杂，需进行详细的研究。为研究蒸发式冷凝器性能，搭建蒸发式冷凝器制冷实验台。通过理论分析和实验研究相结合的方法，研究逆流式蒸发式冷凝器的传热传质性能，主要研究迎面风速和喷淋密度对传热传质的影响，并在同一实验条件下对比了顺流和逆流两种形式的蒸发式冷凝器的传热传质性能，得到如下结论： 1）风速和喷淋密度是影响蒸发式冷凝器的两大关键因素。总传热系数随着风速的增大而增大然后趋于平缓，随着喷淋密度的增大而增大。风速主要影响空气对流传热系数，喷淋密度影响水膜传热系数。 2）对于结构给定的蒸发式冷凝器单位传热面积存在最佳风量和水量。本实验台所在测试条件下，逆流式蒸发式冷凝器最佳单位传热面积风量和水量为277.4m3/(h·m2)和0.63kg/(h·m2)，对应的迎面风速和最佳喷淋密度分别为2.96m/s和0.057kg/（m·s）；顺流式蒸发式冷凝器最佳单位传热面积风量和水量为307.4m3/(h·m2)和0.75kg/(h·m2)，对应的迎面风速和最佳喷淋密度分别为3.28m/s和0.068kg/（m·s），对蒸发式冷凝器的开发和设计有一定的指导意义。 3）逆流式蒸发式冷凝器比顺流式蒸发式冷凝器具有优越的传热性能，在实验条件下，传热系数前者比后者高17.2%。逆流式蒸发式冷凝器风速不宜过高，易产生液泛现象，影响传热性能。 4）设计过程中不仅考虑蒸发式冷凝器的传热性能，而且要考虑整个系统的性能，使EER达到最佳值。逆流式蒸发式冷凝器比顺流式蒸发式冷凝器高近8.2%。 5）蒸发式冷凝器主要利用蒸发潜热吸收热量，具有很高的传热系数。对比干工况和正常工况，前者的总传热系数约为后者的1/10左右。研究结果对蒸发式冷凝器的研究和开发具有一定的指导意义，且对逆流式蒸发式冷凝器的实验研究，对以后研究蒸发式冷凝器传热传质性能，提供了可靠的参考数据。
[Abstract]:With the rapid development of frozen cold storage industry, it is bound to increase energy consumption, energy shortage has become an indisputable fact, in recent years, haze frequency also makes people face a huge challenge. Therefore, the development and application of energy-saving and environmental-friendly equipment is of great significance. Evaporative condenser is an efficient heat exchanger, which has the advantages of saving energy, saving water and occupying less land. It is widely used in refrigeration industry. The study of heat transfer performance of evaporative condenser is of great significance to improve the evaporative condenser refrigeration system. The heat transfer process of evaporative condenser is very complex and needs to be studied in detail. In order to study the performance of evaporative condenser, an experimental bench of evaporative condenser was built. The heat and mass transfer performance of countercurrent evaporative condenser was studied by combining theoretical analysis with experimental research. The effects of wind speed and spray density on heat and mass transfer are studied. The heat and mass transfer performance of the evaporative condenser is compared under the same experimental conditions, and the conclusions are as follows:. 1) Wind speed and spray density are the two key factors affecting evaporative condenser. The total heat transfer coefficient increases with the increase of wind speed and then tends to be gentle, and increases with the increase of spray density. The wind speed mainly affects the convection heat transfer coefficient of air. Spray density affects the heat transfer coefficient of water film. 2) for the unit heat transfer area of the evaporative condenser with a given structure, there exists the optimum air volume and water quantity. The best unit heat transfer area air volume and water volume of countercurrent evaporative condenser are 277.4 m3 / h 路m2) and 0.63 kg / m ~ (-1) h 路m ~ 2 路m ~ (2), corresponding to the forward wind speed and optimum spray density are 2.96 m / s and 0.057 kg / m 路s ~ (-1), respectively, and the optimum air volume and water volume per unit heat transfer area of the downstream evaporative condenser are 307.4 m ~ 3 / h 路m ~ 2 路m ~ (2). The corresponding wind speed and optimum spray density are 3.28 m / s and 0.068 kg / m 路s-1 respectively, which are of certain guiding significance to the development and design of evaporative condenser. 3) the countercurrent evaporative condenser has better heat transfer performance than the downstream evaporative condenser. Under the experimental conditions, the heat transfer coefficient of the former is 17.2% higher than that of the latter. Affect heat transfer performance. 4) not only the heat transfer performance of evaporative condenser is considered in the design process, but also the performance of the whole system should be considered to make the EER reach the optimum value. The countercurrent evaporative condenser is nearly 8.2 higher than the downstream evaporative condenser. 5) the evaporative condenser mainly absorbs heat by evaporative latent heat and has a high heat transfer coefficient, and the total heat transfer coefficient of the former is about 1/10 of that of the latter. The results are of certain significance for the research and development of evaporative condenser and provide reliable reference data for the experimental study of countercurrent evaporative condenser and for the later study of heat and mass transfer performance of evaporative condenser.
【学位授予单位】：天津商业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB657;TK124

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