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Thermal analysis of ventilated wall cavities with spray evaporative cooling systems.

机译：使用喷雾蒸发冷却系统对通风孔腔进行热分析。

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摘要

For low-rise buildings, it is well known that envelope systems are the main contributors to heating and cooling energy consumption. Over the last decades, there have been significant research efforts to improve the performance of building envelope systems by integrating passive cooling strategies to reduce cooling loads and maintain acceptable indoor thermal comfort. The ventilated wall cavity system is one of these passive-cooling strategies that have received considerable attention recently due to the significant benefits of reducing building thermal loads. In particular, evaporative cooling inside ventilated wall cavities is an attractive passive cooling technique especially in hot and dry climates.;Very few research studies have investigated evaporative cooling using spray systems within the ventilated wall cavities. Some reported research studies have suggested that the spray droplet size has a significant impact on the evaporative cooling performance. In this dissertation, a detailed analysis of ventilated wall cavities with spray evaporative cooling systems is carried out. First, a simulation environment has been developed using numerical models of droplet evaporation and droplet dynamics for spray systems. Then, the predictions from spray and ventilated cavity models were validated against experimental measurements and CFD analyses. The validation analyses have shown good agreement for all predicted variables. Moreover, thermal comfort indicators have been modeled using energy balance methods to estimate Predicted Mean Value (PMV) for conditioned buildings and Thermal Sensation Vote (TSV) for naturally ventilated buildings. Mold growth has been accounted for in the developed simulation environment using experimental correlations that consider temperature, humidity, and time in addition to favorable and unfavorable conditions for mold growth. The mold growth model was used as an indicator of mold risk inside the ventilated wall cavity. The developed simulation environment has been used to predict the thermal performance of the ventilated wall cavity system by integrating four modules based on the developed and validated models including indoor thermal comfort, cooling energy savings, mold growth potential, and water use.;A simple ON/OFF control algorithm has been developed to control the spray system and three dampers which regulate the amount of water usage and air flow rate. Control sequences have been developed in order to minimize water consumption, prevent mold growth inside the cavity, and eventually to maintain acceptable indoor thermal comfort. Moreover, multi-objective optimization analyses have been performed using the developed simulation environment to identify an optimum control strategy and optimum droplet size depending on both indoor and outdoor conditions. Specifically, four objective functions are considered: cooling energy, indoor comfort, water use, and mold growth index. Near optimum control strategies were provided for conditioned buildings and naturally ventilated buildings. Moreover, a new concept of evaporative cooling spray system has been introduced to generate different droplet sizes according to the changes of the surrounding environment to maintain acceptable indoor thermal comfort.;A series of sensitivity analyses have been performed to evaluate the impact of various design variables on the performance of the ventilated cavity wall and on the selection of the optimum control strategy. Overall, the ventilated cavity wall system has been found to be an energy efficient passive cooling system for buildings located in hot and dry climates especially when operated by the near optimal control strategy developed in this dissertation.
机译：对于低层建筑，众所周知，围护系统是加热和冷却能耗的主要因素。在过去的几十年中，通过整合被动冷却策略来减少冷却负荷并保持可接受的室内热舒适性，人们为改善建筑围护系统的性能进行了大量的研究工作。通风的壁腔系统是这些被动冷却策略之一，由于降低建筑物热负荷的显着优势，近来受到了广泛的关注。特别是，通风壁腔内的蒸发冷却是一种有吸引力的被动冷却技术，特别是在炎热和干燥的气候中。很少有研究对使用通风壁腔内的喷雾系统的蒸发冷却进行研究。一些已报道的研究表明，雾滴的大小对蒸发冷却性能有重大影响。本文对采用喷雾蒸发冷却系统的通风腔进行了详细的分析。首先，已经使用用于喷雾系统的液滴蒸发和液滴动力学的数值模型开发了模拟环境。然后，通过实验和CFD分析验证了喷雾和通风腔模型的预测结果。验证分析表明，所有预测变量均具有良好的一致性。此外，已经使用能量平衡方法对热舒适指标进行了建模，以估计空调建筑物的预测平均值（PMV）和自然通风建筑物的热敏投票（TSV）。在发达的模拟环境中，除了考虑到有利和不利的霉菌生长条件外，还使用了考虑温度，湿度和时间的实验相关性来考虑霉菌的生长。霉菌生长模型用作通风墙腔内霉菌风险的指标。已开发的仿真环境已被用来通过基于已开发并经过验证的模型集成四个模块来预测通风壁腔系统的热性能，包括室内热舒适度，冷却节能量，霉菌生长潜力和用水量。已经开发了/ OFF控制算法来控制喷雾系统和三个调节器，以调节用水量和空气流速。已经开发出控制顺序，以最大程度地减少水的消耗，防止型腔内霉菌的生长，并最终保持可接受的室内热舒适度。此外，已经使用开发的仿真环境进行了多目标优化分析，以根据室内和室外条件确定最佳控制策略和最佳液滴尺寸。具体而言，考虑了四个目标函数：冷却能量，室内舒适度，用水量和霉菌生长指数。为空调建筑物和自然通风的建筑物提供了近乎最佳的控制策略。此外，引入了一种新的蒸发冷却喷雾系统概念，可根据周围环境的变化产生不同的液滴尺寸，以保持可接受的室内热舒适度。;已进行了一系列敏感性分析，以评估各种设计变量的影响通风腔壁的性能以及最佳控制策略的选择。总体而言，通风空腔墙系统已被发现是一种用于处于炎热和干燥气候环境中的建筑物的节能被动冷却系统，尤其是当采用本文开发的近乎最佳控制策略进行操作时。

著录项

  • 作者

    Alaidroos, Alaa Ali.;

  • 作者单位

    University of Colorado at Boulder.;

  • 授予单位 University of Colorado at Boulder.;
  • 学科 Architectural engineering.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 315 p.
  • 总页数 315
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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