新型露点蒸发冷却系统理论与实验研究

发布时间：2018-09-09 11:08

【摘要】：蒸发冷却技术是一种可再生和可持续发展的冷却方式,具有节能、环保、经济的突出特点。如何提高蒸发冷却系统能量利用效率、增强其显热处理能力是目前研究的主要方向。本文针对传统蒸发冷却系统存在的问题,利用露点间接蒸发冷却热力过程理想情况下趋于可逆的特性,综合考虑热力性能、体积、实用性等因素,提出了基于复合叉流露点式间接蒸发冷却器的新型露点蒸发冷却系统,并进行了理论和实验研究。主要研究内容包括:(1)建立了传统蒸发冷却系统和新型露点蒸发冷却系统的火用分析模型,计算并分析比较了典型工况下二者的能源有效利用情况,结果新型系统火用效率提高约2%、有效输出火用增加约16.9%,表明新型系统具有更高的火用效率和更大的有效火用输出能力。此外,新型系统送风的温度和含湿量明显低于传统蒸发冷却系统,从而具有更强承担热湿负荷的能力。(2)设计并建立了单级叉流露点式间接蒸发冷却器实验系统和三级新型露点蒸发冷却实验系统,根据我国不同地区空气湿球温度的变化情况,利用实验室中空气预处理装置模拟了八种典型气候条件,对系统的冷却性能进行了实验研究,分析了影响冷却性能的因素,讨论并分别给出了单级系统和三级系统在不同工况下对八种典型气候条件的适用性,同时也获得了单级系统和三级系统在八种典型气候条件下冷却性能的变化情况。(3)建立了单级叉流露点式间接蒸发冷却器及三级新型露点蒸发冷却系统的热质交换数学模型,计算并分析了通道宽度、通道长度、开孔率、换热面积比等结构参数以及空气状态参数对湿球效率、露点效率、制冷量等冷却性能的影响规律,实现了单级叉流露点式间接蒸发冷却器及三级新型露点蒸发冷却系统结构参数以及运行参数的优化匹配。在最优结构参数和运行参数条件下,两者的湿球效率分别为122%和134%。(4)评价了改进型叉流露点式间接蒸发冷却器与传统板式间接蒸发冷却器的冷却性能,分析了两种间接蒸发冷却器冷却性能的影响因素,对二者在不同环境空气状态参数下的适用性进行了综合评价。在典型工况下,两种冷却器单独使用且空气流量较小时,露点式的冷却能力较传统板式最高提升了20.1%;两种冷却器分别用于三级蒸发冷却系统第一级时,传统板式在空气流量较大时冷却能力较露点式最高提升了9.7%;分别用于三级蒸发冷却系统第二级时,露点式的冷却能力较传统板式最高提升了42.4%。此外,揭示了改进型叉流露点式间接蒸发冷却器内热质传递规律,指出了其内部热质交换的薄弱区域,并提出了进一步提高其冷却性能的新思路。
[Abstract]:Evaporative cooling technology is a kind of renewable and sustainable cooling method, which has the outstanding characteristics of energy saving, environmental protection and economy. How to improve the energy utilization efficiency of evaporative cooling system and enhance its sensible heat treatment capacity is the main research direction at present. In view of the problems existing in the traditional evaporative cooling system, the characteristics of dew-point indirect evaporative cooling process tend to be reversible under ideal conditions, and the factors such as thermodynamic performance, volume, practicability and so on are considered in this paper. A new type of dew point evaporative cooling system based on compound cross point indirect evaporative cooler is proposed and studied theoretically and experimentally. The main research contents are as follows: (1) the exergy analysis models of the traditional evaporative cooling system and the new dew point evaporative cooling system are established, and their energy efficiency under typical working conditions is calculated and compared. Results the exergy efficiency and effective output exergy of the new system were increased by about 2 and 16. 9 respectively, which indicated that the new system had higher exergy efficiency and greater effective exergy output ability. In addition, the air temperature and moisture content of the new system are significantly lower than those of the conventional evaporative cooling system. Therefore, it has stronger ability to bear heat and humidity load. (2) the experimental system of single-stage outpouring point indirect evaporative cooler and three-stage new-type dew point evaporative cooling system are designed and established. According to the change of air wet bulb temperature in different regions of China, Eight typical climatic conditions were simulated by using the air pretreatment device in the laboratory. The cooling performance of the system was studied experimentally, and the factors affecting the cooling performance were analyzed. The applicability of single-stage system and three-stage system to eight typical climatic conditions under different operating conditions are discussed and given respectively. At the same time, the change of cooling performance of single-stage system and three-stage system under eight typical climatic conditions is also obtained. (3) the mathematical model of heat and mass exchange of single-stage outpouring point indirect evaporative cooler and three-stage new-type dew point evaporative cooling system is established. The influence of structural parameters such as channel width, channel length, opening rate, heat transfer area ratio and air state parameters on cooling performance such as wet bulb efficiency, dew point efficiency and refrigerating capacity are calculated and analyzed. The optimization and matching of the structure parameters and operation parameters of the single stage outpouring point indirect evaporative cooler and the three-stage new-type dew point evaporative cooling system are realized. Under the optimal structural parameters and operating parameters, the wet bulb efficiencies are 122% and 134% respectively. (4) the cooling performance of the improved fork point indirect evaporative cooler and the traditional plate indirect evaporative cooler is evaluated. The factors influencing the cooling performance of two indirect evaporative coolers are analyzed and their applicability under different ambient air state parameters are comprehensively evaluated. Under typical conditions, the cooling capacity of dew point type is increased by 20.1when the two coolers are used separately and the air flow rate is small, and the two coolers are used in the first stage of three-stage evaporative cooling system respectively. The cooling capacity of the traditional plate type is 9.7g higher than that of the dew point type when the air flow rate is larger, and the cooling capacity of the dew-point type is 42.4% higher than that of the traditional plate type when it is used in the second stage of the three-stage evaporative cooling system respectively. In addition, the heat and mass transfer law in the improved fork discharge indirect evaporative cooler is revealed, the weak area of heat and mass exchange in the improved fork type indirect evaporative cooler is pointed out, and a new idea for further improving its cooling performance is put forward.
【学位授予单位】：西安建筑科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU831

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