本文選題：噴霧　切入點：直接蒸發(fā)冷卻　出處：《重慶大學(xué)》2014年碩士論文

【摘要】：機械制冷的普遍使用導(dǎo)致空調(diào)能耗居高不下，夏季高溫天氣亦使城區(qū)熱環(huán)境逐漸惡化。推廣蒸發(fā)冷卻技術(shù)能夠一定程度上改善機械制冷耗能、影響環(huán)境的現(xiàn)狀。近年來，作為直接蒸發(fā)冷卻技術(shù)應(yīng)用的新形式，噴霧降溫日益受到重視，具有節(jié)能、高效、環(huán)保的優(yōu)點，與常規(guī)直接蒸發(fā)冷卻空調(diào)機組相比，，無需循環(huán)水、設(shè)備結(jié)構(gòu)簡化、蒸發(fā)效率高，應(yīng)用前景廣闊。本文對噴霧直接蒸發(fā)冷卻系統(tǒng)進(jìn)行了數(shù)值模擬和實驗研究，針對噴霧降溫過程中的關(guān)鍵問題，進(jìn)行了以下探索。 首先對噴霧降溫傳熱傳質(zhì)過程進(jìn)行分析，建立液滴群與空氣熱質(zhì)交換的平衡方程，以及單個液滴與空氣傳熱傳質(zhì)的數(shù)學(xué)模型。通過數(shù)學(xué)模型分析影響傳熱傳質(zhì)過程的主要因素，并建立數(shù)學(xué)模型作為數(shù)值模擬的基礎(chǔ)，通過理論對數(shù)值模擬中模型的選擇提供了指導(dǎo)。對于直接蒸發(fā)冷卻過程的計算，無論是理論分析的方法還是實驗研究的方法都有較大的限制，對于復(fù)雜的數(shù)學(xué)模型，計算流體力學(xué)（CFD）提供了一種可行的計算方法，具有成本較低且能模擬較復(fù)雜的過程等優(yōu)點。 基于計算流體力學(xué)軟件FLUENT，對空氣中噴霧蒸發(fā)過程的模型原理和方法進(jìn)行了闡述，分別從連續(xù)相和離散相理論、相間計算的耦合方式、各相重要參數(shù)設(shè)置等問題上進(jìn)行了探索，并總結(jié)出噴霧直接蒸發(fā)冷卻過程的模擬方法。合理的數(shù)學(xué)模型和數(shù)值模擬方法對實驗研究和理論分析具有指導(dǎo)作用，可以彌補實驗工作的不足。 提出了評價噴霧降溫效果的參數(shù)和方法。搭建噴霧降溫系統(tǒng)實驗平臺，對高溫環(huán)境下的噴霧降溫效果進(jìn)行了實驗測試。通過實驗結(jié)果分析了室外空氣參數(shù)和噴霧水氣比的變化對蒸發(fā)效率和飽和效率的影響，并建立了與實驗對應(yīng)的物理模型，采用離散相計算模型進(jìn)行數(shù)值模擬，得到噴霧降溫后的溫度場、濕度場，并將實驗與模擬結(jié)果進(jìn)行了比較，證明了數(shù)值模擬方法的可行性。 采用數(shù)值模擬方法，對噴霧降溫系統(tǒng)進(jìn)行了變工況模擬，以優(yōu)化的噴霧降溫系統(tǒng)。數(shù)值模擬進(jìn)行的工況有： 1)建立管道內(nèi)噴霧蒸發(fā)冷卻系統(tǒng)，研究霧滴粒徑、噴頭間距、風(fēng)速和噴霧比等參數(shù)的改變對管內(nèi)噴霧降溫蒸發(fā)效率的影響。 2)對實驗?zāi)M模型增添模擬工況，對室外參數(shù)和水氣比變化對噴霧降溫效果的影響進(jìn)行了深入分析。 3)對室外開敞空間進(jìn)行了數(shù)值模擬，主要對風(fēng)速和噴霧流量參數(shù)對固定人行高度處的噴霧降溫效果的影響進(jìn)行了分析。 對于管道內(nèi)噴霧降溫，通過數(shù)值模擬方法進(jìn)行優(yōu)化設(shè)計后，在最優(yōu)工況下蒸發(fā)效率可以接近100%，飽和效率可達(dá)到90%以上。不同于有限空間的噴霧降溫過程，室外噴霧降溫的效果與外場風(fēng)速、風(fēng)向密切相關(guān)，降溫范圍隨風(fēng)場的擴大或縮小直接導(dǎo)致降溫效果的不同。 對于管道內(nèi)噴霧降溫系統(tǒng)，數(shù)值模擬方法在研究噴霧降溫機理、設(shè)備開發(fā)和優(yōu)化方面體現(xiàn)了重要價值。對于室外開敞空間的噴霧降溫，數(shù)值模擬能夠通過模擬進(jìn)行效果預(yù)測，對指導(dǎo)噴霧降溫系統(tǒng)的布置方案具有指導(dǎo)意義。
[Abstract]:In recent years , as a new form of direct evaporative cooling technology application , spray cooling is becoming more and more important , which has the advantages of energy saving , high efficiency and environmental protection . In recent years , as a new form of direct evaporative cooling technology application , it has the advantages of energy saving , high efficiency and environmental protection , and has the advantages of energy saving , high efficiency and environmental protection .

First , the heat and mass transfer process of spray cooling is analyzed , the equilibrium equation of droplet group and air heat mass exchange is established , and the mathematical model of the heat and mass transfer of single liquid droplet and air is established . The mathematical model is used as the basis for numerical simulation , and the mathematical model is established as the basis of numerical simulation .

Based on the computational fluid mechanics software FLUENT , the model principle and method of spray evaporation in air are described , and the simulation method of direct evaporative cooling process is summarized . The mathematical model and numerical simulation method are used to guide the experimental research and theoretical analysis , which can make up for the shortage of experimental work .

The parameters and methods for evaluating the cooling effect of spray are put forward . The experimental platform of spray cooling system is set up to test the effect of spray cooling in high temperature environment . Through the experimental results , the effects of outdoor air parameters and spray water - gas ratio on evaporation efficiency and saturation efficiency are analyzed . The physical model corresponding to the experiment is established , and the temperature field and humidity field after spray cooling are obtained by using the discrete - phase calculation model , and the experiment and simulation results are compared . The feasibility of the numerical simulation method is proved .

A numerical simulation method was used to simulate the spray cooling system to optimize the spray cooling system . The numerical simulation was carried out with the following conditions :

1 ) The effect of changing parameters such as droplet size , nozzle spacing , wind speed and spray ratio on the efficiency of spray cooling and evaporation in the pipe was studied by establishing a spray evaporative cooling system in the pipeline .

2 ) The simulation working condition is added to the experimental simulation model , and the influence of outdoor parameters and water - gas ratio changes on the cooling effect of the spray is analyzed in depth .

3 ) Numerical simulation of outdoor open space is carried out , and the influence of wind speed and spray flow parameters on the spray cooling effect at fixed pedestrian height is analyzed .

For the spray cooling in the pipeline , the evaporation efficiency can be close to 100 % and the saturation efficiency can reach more than 90 % under the optimum working conditions . The effect of the outdoor spray cooling is closely related to the wind speed and the wind direction of the external field . The temperature reduction range is directly related to the expansion or contraction of the wind field , which directly leads to the difference of the cooling effect .

For the spray cooling system in the pipeline , the numerical simulation method reflects the important value in the research of the spray cooling mechanism , the equipment development and the optimization . For the spray cooling of the outdoor open space , the numerical simulation can predict the effect through simulation , which can guide the layout of the spray cooling system .

【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU831.6

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