本文選題：冷卻塔填料 + 數(shù)值模擬�。� 參考：《山東大學(xué)》2017年碩士論文

【摘要】：在電廠中,冷卻塔的作用就是冷卻溫度較高的冷卻水,通過塔內(nèi)冷卻水與空氣的熱量交換將熱量擴(kuò)散到空氣中。在冷卻塔內(nèi)部,其冷卻性能主要受填料的熱力性能、運(yùn)行的外界溫度、給水量、外界風(fēng)速、除水器等的影響。填料是冷卻塔內(nèi)非常重要的換熱元件,分析其內(nèi)部的氣液換熱性能對(duì)分析冷卻塔的性能有重要意義。液膜的流動(dòng)形態(tài)受到很多因素的影響,包括液體性質(zhì)、壁面材質(zhì)、壁面結(jié)構(gòu)、風(fēng)速、水速等,而液膜的形態(tài)是影響換熱效果的重要因素,因此,本文從液膜形態(tài)的角度分析填料通道內(nèi)氣液兩相流的流動(dòng)與換熱。本文首先通過壁面等效法建立了填料內(nèi)氣液兩相逆向流動(dòng)換熱的數(shù)值計(jì)算模型,并通過對(duì)比與其他學(xué)者的計(jì)算結(jié)果驗(yàn)證了模型的準(zhǔn)確性。通過此模型計(jì)算了彎曲的填料通道內(nèi)的氣液兩相逆流換熱的情況,分析了液相的流動(dòng)狀態(tài)隨時(shí)間的變化。給出了填料通道內(nèi)的溫度場(chǎng)、壓力場(chǎng)、液膜形態(tài)等參數(shù)隨風(fēng)速、水速、通道傾斜角度變化的規(guī)律。通過對(duì)模擬計(jì)算結(jié)果分析可知,在電廠的工況范圍內(nèi)提高風(fēng)速能夠有效的提高填料通道內(nèi)的持液量,冷卻效率,降低阻力系數(shù)。在電廠工況范圍內(nèi)提高進(jìn)水速度使得填料通道內(nèi)的液膜流動(dòng)狀態(tài)變差,冷卻效率下降且阻力系數(shù)增加。文中分析了兩種傾斜角的填料通道內(nèi)液膜流動(dòng)形態(tài)的差異,熱力特性的差異,由結(jié)果表明,30°傾斜角的模型在冷卻效果方面比45°和60°傾斜角的模型差,但在阻力方面比45°與60°傾斜角模型好,因此填料的傾斜角度的設(shè)置與實(shí)際工程的需求是相關(guān)的。通過計(jì)算三維通道內(nèi)氣液兩相逆流過程的流動(dòng)狀態(tài)與換熱,分析了三維通道內(nèi)氣液流動(dòng)過程與氣水比的關(guān)系,給出了流態(tài)、冷卻效率、阻力系數(shù)隨氣水比變化的關(guān)系。通過分析計(jì)算結(jié)果可知,隨著氣水比的增加,填料通道內(nèi)的冷卻效率明顯提高,且阻力系數(shù)有小幅度的減小。本文對(duì)不同的填料結(jié)構(gòu)進(jìn)行研究,分析了填料通道結(jié)構(gòu)與熱力特性的關(guān)系。給出了三種孔徑的填料模型在液膜流動(dòng)狀態(tài),持液量,溫度場(chǎng)、冷卻效率,阻力系數(shù)等參數(shù)的不同,并對(duì)影響差異的因素進(jìn)行深入分析。通過對(duì)比結(jié)果發(fā)現(xiàn),由于比表面積的差別,隨著填料孔徑的減小冷卻效率有明顯的提高。縮小后的阻力系數(shù)比改進(jìn)前的結(jié)構(gòu)有明顯的減小。給出了三種波形的填料模型在冷卻效率和阻力系數(shù),并對(duì)影響因素進(jìn)行了分析。由于S波通道其結(jié)構(gòu)最復(fù)雜、持液量最大、比表面積最大,所以冷卻效率最高,而斜波的比表面積最小其冷卻效率最低。斜折波由于其結(jié)構(gòu)上的優(yōu)勢(shì)而阻力系數(shù)最小,S波由于其彎曲通道的復(fù)雜性,其阻力系數(shù)最大。
[Abstract]:In the power plant, the cooling tower is used to cool the cooling water with higher temperature, which diffuses the heat into the air through the heat exchange between the cooling water and the air in the tower. In the cooling tower, the cooling performance is mainly affected by the thermal performance of the filler, the external temperature of the operation, the water supply, the external wind speed, the water remover and so on. Packing is a very important heat transfer element in cooling tower. It is very important to analyze the gas-liquid heat transfer performance of cooling tower. The flow pattern of liquid film is affected by many factors, including liquid property, wall material, wall structure, wind speed, water velocity and so on. In this paper, the flow and heat transfer of gas-liquid two-phase flow in packing channel are analyzed from the point of view of liquid film morphology. In this paper, the numerical model of heat transfer of gas-liquid two-phase reverse flow in packing is established by wall equivalent method, and the accuracy of the model is verified by comparing the results with those of other scholars. Through this model, the heat transfer of gas-liquid two-phase countercurrent in the curved packing channel is calculated, and the change of liquid phase flow state with time is analyzed. The variation of temperature field, pressure field and liquid film shape with wind speed, water velocity and channel inclination angle are given. Through the analysis of the simulation results, it can be seen that increasing the wind speed in the power plant can effectively increase the liquid holdup, cooling efficiency, and reduce the resistance coefficient in the packing channel. Increasing the influent speed in the power plant makes the liquid film flow in the packing channel worse, the cooling efficiency decreases and the resistance coefficient increases. In this paper, the differences of liquid film flow patterns and thermodynamic characteristics in two kinds of tilted packing channels are analyzed. The results show that the model of 30 擄tilting angle is worse in cooling effect than that of 45 擄and 60 擄tilting angles. But the resistance is better than that of 45 擄and 60 擄angle model, so the setting of the tilting angle of packing is related to the requirement of practical engineering. By calculating the flow state and heat transfer of gas-liquid two-phase countercurrent in three-dimensional channel, the relationship between gas-liquid flow process and gas-water ratio in three-dimensional channel is analyzed, and the relationship among flow state, cooling efficiency and resistance coefficient with gas-water ratio is given. The results show that with the increase of air-water ratio, the cooling efficiency in the packing channel is obviously increased, and the resistance coefficient is reduced to a small extent. In this paper, different packing structures are studied, and the relationship between packing channel structure and thermal characteristics is analyzed. In this paper, three kinds of packing models with pore diameter are given, and the factors influencing the difference are analyzed, such as the flow state of liquid film, liquid holdup, temperature field, cooling efficiency, resistance coefficient and so on. The results show that the cooling efficiency increases with the decrease of packing aperture due to the difference of specific surface area. The reduced resistance coefficient is obviously smaller than that of the improved structure. The cooling efficiency and drag coefficient of the packing models with three waveforms are given, and the influencing factors are analyzed. Due to the most complex structure, the largest liquid holdup and the largest specific surface area of the S-wave channel, the cooling efficiency is the highest, while the minimum specific surface area of the oblique wave is the lowest. The resistance coefficient of oblique fold wave is the smallest because of its advantage in structure. Because of the complexity of the curved channel, the resistance coefficient is the largest.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM62

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