Principles of exergy analysis in HVAC and evaluation of evaporative cooling schemes
Principles of exergy analysis in HVAC and evaluation of evaporative cooling schemes
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DOI：
10.1016/s0360-1323(01)00104-4
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发表时间：
2002-11
影响因子：
7.4
通讯作者：
Cheng-qin Ren;Nianping Li;Guangfa Tang
中科院分区：
文献类型：
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作者：
Cheng-qin Ren;Nianping Li;Guangfa Tang
通过对有关文献的分析，论述了暖通空调（HVAC）中火用分析的原理。本文提出了一种新颖的适用于暖通空调应用的死区选择方法，该方法通过消除计算环境温度（T0）下水的火用的必要性，简化了火用分析。这样的选择也将使评估蒸发冷却能力的理论极限更容易。本文还提出了一种功能分类法，将暖通空调工程分解成层次结构，进行火用分析。能量流也根据其功能分类为源能量流和服务能量流，以帮助评估系统或组件的性能。当过程中含有自由能时，则定义火用效率比来评价所购可用能的有效利用。通过应用实例分析，论证了该方法的合理性.为了评估蒸发冷却，分析了湿空气的火用，并将其分解为三个部分：热、机械和化学。每一个都用一个特殊设计的图表来表示，适用于HVAC应用中的各种条件和环境状态。借助这些图分析了蒸发冷却过程。对现有的四种蒸发冷却方案的五种情况进行了适当的评价。结果表明，回热式蒸发冷却的性能最好，间接蒸发冷却的换热效果对提高回热式蒸发冷却的火用效率比具有重要意义。
Principles of exergy analysis in heating ventilating and air conditioning (HVAC) are discussed through an analytical review of some pertinent works. An unusual selection of dead-state novel to HVAC applications is suggested, which simplifies the exergy analysis by eliminating the necessity of calculating the exergy of water at ambient temperature (T0). Such a selection will also make it easier to evaluate the theoretical limit of evaporative cooling capacity. In this paper, the authors also suggest a functional classification to break down HVAC project in a hierarchy structure for exergy analysis. Energy flows are also classified according to their functions as source energy flow and service energy flow to assist the evaluation of the performance of the systems or components. If free energy is involved in the processes, then exergy efficiency ratio is defined to evaluate the effective use of the purchased available energy. The rationality is demonstrated with the analysis of application examples. For the evaluation of evaporative cooling, the exergy of moist air are analyzed and broken down into three components: thermal, mechanical and chemical. Each of them is represented with a special devised diagram applicable to various conditions and ambient states among HVAC applications. Evaporative cooling processes are analyzed with the aid of these diagrams. Five cases of four existing schemes of evaporative cooling are properly evaluated. Results show that regenerative evaporative cooling has the best performance and the effectiveness for indirect evaporative cooling heat exchange has great importance in improving the exergy efficiency ratio of regenerative scheme.