辐射供冷末端换热与凝露机理及其与太阳能空调匹配特性研究

发布时间：2018-04-23 11:39

本文选题：辐射 + 供冷　；参考：《上海交通大学》2014年博士论文

【摘要】：环境污染和能源危机是目前人类社会面临的两大主要课题，而消耗在空调系统上的能源占社会总能耗的比重越来越大。传统空调系统多采用电压缩制冷技术，在消耗化石能源的同时，其制冷剂对环境的污染同样不可忽视，寻求一种能够利用可再生能源，且环境友好型的制冷空调系统意义重大。本研究利用太阳能驱动的溴化锂-水吸收式空调系统，以太阳能作为其主要的驱动能源制取冷量调节建筑室内热湿环境。系统运行过程中，只使用少量的电能满足循环水泵等动力部件的运行，大大节约了建筑物内空调系统的能源消耗。特别是在夏季空调季节，能够有效消弱用电高峰能耗，减小电网压力。系统使用以溴化锂-水为制冷工质对的小型吸收机制取冷量，与传统的电压缩制冷空调相比，其制冷剂的ODP和GWP均为零，既不产生温室气体，也不会破坏臭氧层。对于地球环境保护意义重大。在室内空调末端的选择上，系统采用毛细管辐射供冷板和新风机组共同承担室内的热湿负荷。辐射供冷末端能够使用太阳能空调提供的高温冷水，通过辐射的方式将冷量传递给室内环境，不但能够提高太阳能空调系统的运行效率，，还能够减小室内空气的温度不均匀度，改善室内的热舒适性。同时辐射供冷末端的蓄冷能力能够减小系统蓄热水箱的尺寸，降低太阳能空调系统的初投资。系统采用新风机组配合辐射供冷末端，利用新风机组承担室内的潜热负荷，实现室内温湿度的独立控制。新风机组采用两级冷却，第一级预冷过程引入太阳能空调制取的高温冷水，使用一台电制冷机制取的低温冷水将新风处理到送风状态点来承担室内的潜热负荷。这种设计能够尽可能多的使用太阳能空调制取的高温冷水，减少系统对电能的消耗。毛细管辐射供冷板能够改善室内热舒适性，提高太阳能空调运行效率，然而其换热能力不足及易于在表面产生结露的特点制约着其推广使用，这是本文着重解决的一个问题。本课题对使用毛细管辐射供冷末端的太阳能溴化锂-水空调系统的运行特点和制约其推广的主要因素做了深入的研究，本研究的主要内容及结论有：（1）毛细管辐射供冷末端供冷能力主要受到毛细管内冷水流速、冷水温度及室内环境温度和相对湿度影响。研究结果表明：综合循环水泵耗能、冷水进出水温差以及毛细管辐射供冷板的换热性能之间的平衡，建议此类毛细管的管内流速为0.45m/s。随着冷水供水温度的降低或者室内环境温度的升高，辐射供冷板的换热性能增强。（2）由于辐射供冷末端冷水侧和室内环境温度之间传热温差存在，当冷水供水温度低于室内环境的露点温度时，辐射供冷末端表面不会立即产生结露现象。本文使用过冷度的概念来分析辐射供冷末端结露现象。过冷度定义为室内环境露点温度和冷水进水温度的差值。过冷度在控制系统中的采用，能够在预防毛细管辐射供冷末端表面结露现象产生的同时，最大限度的降低冷水进水温度，增加单位面积辐射供冷末端的换热性能。研究表明，在26oC，60%的热湿环境中，毛细管光管、毛细管金属板以及毛细管石膏板的过冷度分别为3.2oC、5.4oC和6.5oC。（3）与全空气系统相比，辐射供冷末端与围护结构一起安装，室内辐射供冷墙面或辐射吊顶材料的蓄热特性能够维持室内供冷表面温度的稳定性。对于太阳能空调系统，其制冷能力受到太阳能辐射强度的波动性的影响，往往需要较大的蓄热水箱。在太阳能空调系统中使用辐射供冷末端能够减小系统蓄热水箱尺寸，降低系统初投资。同时能够延长系统运行时间，以本文采用的砖墙围护结构为例，使用辐射供冷墙面可以将太阳能空调系统的运行时间延长78min。（4）相比于空气末端系统，辐射供冷末端能够直接将冷量传递给室内的目标人员，冷量传输效率高，冷量利用率好。作为室内显热负荷去除装置的辐射供冷末端能够匹配较高温度的冷水，从而改善太阳能空调系统的运行效率，节约能源。本文还研究了毛细管辐射供冷末端和风机盘管两种空调末端方式对太阳能空调系统的影响。当采用辐射供冷末端时，太阳能空调系统的COP和制冷量比采用分机盘管系统分别提高了23%和29%。同时，辐射供冷末端能够提高室内环境的热舒适性，研究表明，辐射供冷末端能够保证室内热舒适度处于CLASS-A。
[Abstract]:Environmental pollution and energy crisis are two major subjects in the human society at present, and the energy consumed in the air conditioning system is becoming more and more important in the total energy consumption of the society. The traditional air conditioning system uses electric compression refrigeration technology more. While consuming fossil energy, the refrigerant can not be ignored and can not be ignored. The use of renewable energy and environment-friendly refrigeration and air conditioning system is of great significance.
In this study, the solar energy driven lithium bromide water absorption air conditioning system is used to make the solar energy as its main driving energy to adjust the heat and humidity environment in the building. In the process of the system, only a small amount of electric energy is used to meet the operation of the power components such as the circulating water pump, which greatly saves the energy consumption of the air conditioning system in the building. Especially in the summer air conditioning season, it can effectively weaken the peak energy consumption and reduce the pressure of the power grid. The system uses the lithium bromide water as the refrigerant for the small absorption mechanism. Compared with the traditional electric compression refrigeration air conditioning, the ODP and GWP of the refrigerant are zero, neither produces greenhouse gases nor destroys the ozone layer. The environmental protection of the ball is of great significance.
In the choice of the indoor air conditioning terminal, the system adopts the capillary radiation cooling plate and the new air unit to jointly undertake the heat and wet load of the indoor air. The end of the radiation supply can use the high temperature cold water provided by the solar air conditioning, and transfer the cooling amount to the indoor environment by radiation, not only to improve the efficiency of the solar air conditioning system, but also to improve the efficiency of the solar air conditioning system. It can reduce the temperature inhomogeneity of the indoor air and improve the thermal comfort of the indoor air. At the same time, the cooling ability of the end of the radiation can reduce the size of the system's storage tank and reduce the initial investment of the solar air conditioning system. The independent control of temperature and humidity. The new air unit adopts the two stage cooling, the first stage precooling process introduces the high temperature cold water from the solar air conditioning. The low temperature cold water produced by an electric refrigerator is used to treat the fresh air to the air supply point to bear the latent heat load in the room. This design can be used as much as possible to make the high temperature of the solar air conditioning. Cold water reduces the energy consumption of the system. The capillary radiation supply plate can improve the thermal comfort in the room and improve the efficiency of the solar air conditioning. However, the lack of heat transfer capacity and the characteristics that are easy to produce dew on the surface restrict its popularization. This is a problem to be solved in this paper. The operation characteristics of the terminal solar energy LiBr water air conditioning system and the main factors that restrict its popularization have been studied deeply. The main contents and conclusions of this study are as follows:
(1) the cooling capacity at the tip of the capillary tube is mainly influenced by the inner cooling water flow rate, the cold water temperature and the indoor environment temperature and relative humidity. The results show that the balance between the energy consumption of the comprehensive circulating water pump, the difference of water temperature in and out of the cold water and the heat exchange performance of the capillary radiation cooling plate is suggested, and the flow velocity in this kind of capillary is suggested. For 0.45m/s., the heat transfer performance of radiant cooling panels increases with the decrease of cold water supply temperature or the increase of indoor ambient temperature.
(2) due to the heat transfer temperature difference between the cold water side of the radiation cooling terminal and the temperature of the indoor environment, when the cold water supply temperature is lower than the dew point temperature in the indoor environment, the end surface of the radiation cooling terminal will not appear immediately. This paper uses the concept of supercooling to analyze the condensation phenomenon of the radiation cooling terminal. The difference between the point temperature and the cold water inlet temperature. The use of the supercooling in the control system can reduce the cold water inlet temperature and increase the temperature of the cold water at the end of the cold water at the same time in preventing the condensation of the end surface of the capillary radiation supply. The research shows that the capillary is in the 26oC, 60% heat and humidity environment. The supercooling degree of light tube, capillary metal plate and capillary gypsum board is 3.2oC, 5.4oC and 6.5oC. respectively.
(3) compared with the whole air system, the end of the radiation cooling supply is installed together with the enclosure structure. The heat storage property of the indoor radiation wall surface or the radiant ceiling material can maintain the stability of the cooling surface temperature in the indoor air conditioning system. In the solar air conditioning system, the use of the radiation supply terminal in the solar air conditioning system can reduce the size of the system's storage tank, reduce the initial investment of the system and extend the operating time of the system. As an example of the brick wall enclosure used in this paper, the operation time of the solar air conditioning system can be extended by 78min.
(4) compared with the air terminal system, the end of the radiation supply can directly transfer the cooling amount to the target personnel in the room. The cooling capacity is high and the cooling capacity is good. As the indoor heat load removal device, the radiation cooling terminal can match the high temperature cold water, thus improving the efficiency of the solar air conditioning system and saving energy. The effects of two air conditioning ends on the air conditioning system are also studied. When the air cooling terminal is used, the COP and the refrigerating capacity of the solar air conditioning system are increased by 23% and 29%., respectively. The end of the radiation cooling terminal can improve the thermal comfort of the indoor environment. The research shows that the radiant cooling end can ensure indoor thermal comfort at CLASS-A.

【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU831

【参考文献】