| This paper is the part of the research of the sub-project of "Eleventh Five-Year" plan major projects: take full advantage of the natural ventilation of fresh air dehumidification research (2006BAJ01A02-04-04), which is supported by Ministry of Science and Technology of China. According to meteorological data in southern and indoor outdoor ventilation requirements, the need for air dehumidification was analyzed. Take Chongqing for example,in order to meet the requirements of human thermal comfort and health, designated indoor air comfort zone, took the moisture content as the parameter to judge whether the air need to be dehumidified. If the air moisture content is higher than the maximum air moisture content in the comfort zone, the air need be dehumidified, it lasts about 6 months for fresh air dehumidification throughout the year in Chongqing, so energy consumption for fresh air dehumidification accounts for a large proportion of the total energy consumption for handling the fresh air. Because energy is shortage nowadays, looking for a use of natural energy for air dehumidification is very meaningful. Therefore, this dissertation standing at the perspective of ecology and sustainable development propose a new technology for air dehumidification which uses the plant physiology, different from the dehumidification technologies which use physical and chemical changes in the past. This paper researched from the biological, physiological and ecological characteristics of moisture absorption organ of plant - the aerial roots. Firstly, analyzed the mechanism of the aerial roots for air moisture absorption, the feasibility of air dehumidification, air moisture absorption conditions and influencing factors theoretically; Secondly, tested the air dehumidification effect of aerial roots by experiment, established the aerial roots air dehumidification system and aerial roots air moisture absorption model, lay the foundation for using aerial roots for air dehumidification in future.The function of various organs of plants has the close relationship with their growing environment, structure and physiological properties and other factors. This paper firstly described several plants with aerial roots and their growth environment, the morphology and internal anatomy of aerial root, physiological functions. According to the anatomical structures and physiological function of the aerial roots obtained, the aerial root is an organ which has dual function of the moisture absorption and transpiration, but moisture absorption is main function. Similar to underground roots when absorbing the moisture from the air, the moisture goes from the air into the aerial roots. Similar to the leaves when evapotranspirating vapor, water flowes from the aerial roots into the air. The characteristics of aerial roots are the basis of studying the moisture absorption mechanism of aerial roots.By using the concept of water potential-the driving force of flow, conditions and path of water in the soil (air)- root (aerial roots)-stem-leaf-atmospheric were analyzed. According to the concept of potential difference analyzed the conditions it need to make moisture come into aerial roots from the air, proposed the air moisture absorption mechanisms of aerial roots, combined with the analysis of spatial characteristics of plant growth proposed engineering principle of air dehumidification,proved that air relative humidity must be high or air is close to saturation, young aerial roots had the function of continuous air moisture absorption. Using aerial roots for air dehumidification is feasible. Plant is an organic whole, being complementary and inseparable among the various organs. Based on the proposed aerial roots air moisture absorption mechanism and the plants hydrological cycle, the various factors which influence the aerial roots air moisture absorption was investigated, to provide theoretical support for strengthening the ability of aerial roots to absorb moisture.In this study, aerial root of Ficus microcarpa was chosen research object. According to the influence factors of aerial roots growth and air moisture absorption the experiments were designed, to test the H2O exchange characteristics between the aerial roots and air. It proved that the aerial roots of different ages had different H2O exchange characteristics, the young aerial roots transpire mainly, whilst the mature roots were with discontinuous air moisture absorption function. The analyzation of the effect of environmental factors (air environment in which the aerial roots are) on the H2O exchange capacity of aerial roots revealed that air relative humidity was the main factor affecting the transpiration of aerial roots or moisture absorption capacity. It showed that when air relative humidity was 90% or higher, young aerial roots have the effect of air moisture absorption. It indirectly proved that aerial roots required higher air relative humidity for air moisture absorption.In view of theory and experimental data obtained, it showed that when water potential of air surrounding the aerial roots was high enough, aerial roots could absorb moisture from the air. When the water potential of air was low, an air pretreatment plant was designed to create the conditions for the aerial roots. The device used the cold soil to pre-cool the air, raising air relative humidity. The air temperature at the outlet of the device is fit for the survival of aerial roots of plants, so the outlet air of the device could be dehumidified by aerial roots. The core unit is a soil - air heat exchanger, established heat and mass transfer model of soil - air heat exchanger, to analyze the air handling capacity of the equipment; at the same time, built a air pretreatment plant testing system of aerial roots, tested and verified the correctness of the model established.The experimental system aerial for aerial root moisture absorption was designed and divided into two parts: air humidifier device and the capacity of air dehumidification using aerial roots measurement devices. Air with high relative humidity produced by humidification devices would be send into the dehumidification measurement devices with whole bundle aerial roots, to test the moisture content of air absorbed by aerial roots and their change with air temperature, as well as air relative humidity throughout the day. It proved the feasibility of air dehumidification with aerial roots by experiment. The analization on the impact of handled air temperature and relative humidity on the amount of air dehumidification was conducted in this way.The air dehumidification system using aerial roots was divided into two parts: air pretreatment plant for aerial roots dehumidification and air dehumidification using aerial roots. Work principle and control strategies of the system were proposed; Mathematical model of air dehumidification using aerial roots in the part of air dehumidification device using aerial roots was established. The mathematical model was developed on the basis of the aerial roots dehumidification mechanism which referenced to root water uptake model from the soil and at the same time in consideration of the air condition (air temperature and relative humidity) influencing air moisture absorbance by aerial roots, aerial roots itself factors (the root length density) and water metabolic factors in the whole plant (transpiration). Taking the air dehumidification capacity of aerial roots measured in the experimental and the plant transpiration rate to solve the volume of air moisture absorbed by aerial roots of a plant. Therefore, the model was built on the basis of experimental results and theoretical consideration, and it was a semi-theoretical semi-empirical model. |
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