【摘要】：超臨界水在鍋爐或反應(yīng)堆等大型換熱設(shè)備中的應(yīng)用能夠大幅提高其出口工質(zhì)熱力參數(shù),從而提高發(fā)電設(shè)備的整體經(jīng)濟(jì)性。然而超臨界水在大比熱區(qū)的特殊熱物理性質(zhì)及其在高焓值區(qū)較低的吸熱能力使得其高溫條件下的應(yīng)用受到了一定的限制,因此對(duì)超臨界水在大型換熱器中,尤其是高溫條件下的傳熱強(qiáng)化的研究十分重要。本文以超臨界鍋爐水冷壁及反應(yīng)堆堆芯為對(duì)象,利用商業(yè)CFD軟件對(duì)超臨界水在內(nèi)螺紋和定位格架等擾流部件影響下的流動(dòng)和傳熱強(qiáng)化特性進(jìn)行了數(shù)值研究,重點(diǎn)分析了受熱面內(nèi)冷通道中工質(zhì)流動(dòng)及傳熱在徑向及周向分布特性,并揭示了其相關(guān)機(jī)理。針對(duì)內(nèi)螺紋管的數(shù)值研究表明,內(nèi)螺紋的導(dǎo)流作用在垂直于主流的方向造成了較強(qiáng)的二次流場(chǎng),而主流焓值的變化對(duì)二次流場(chǎng)的基本結(jié)構(gòu)幾乎沒(méi)有什么影響。局部傳熱在內(nèi)螺紋管周向和徑向分布不均,超臨界水在螺紋頂部區(qū)域的換熱效果遠(yuǎn)好于螺紋底部。在螺紋頂部表面形成的單個(gè)旋渦產(chǎn)生一個(gè)壓力相對(duì)較低的區(qū)域,使得這個(gè)該區(qū)域傳熱得到強(qiáng)化。在大比熱區(qū),由于流體熱物性急劇變化,換熱的不均性更加顯著。螺紋底部是換熱的薄弱點(diǎn),內(nèi)螺紋管結(jié)構(gòu)優(yōu)化的重點(diǎn)應(yīng)集中在該區(qū)域。針對(duì)裝配有定位格架的反應(yīng)堆堆芯的數(shù)值結(jié)果表明,由于流動(dòng)阻塞效應(yīng)的影響,高溫條件下燃料棒包殼表面溫度周向分布不均,中心區(qū)最低而窄縫區(qū)最高。在標(biāo)準(zhǔn)型定位格架的下游,嚴(yán)重的抑流作用使得窄縫區(qū)的周向溫差增加,傳熱效果減弱；帶有交錯(cuò)葉片的定位格架的下游,包殼周向流動(dòng)與傳熱特性差異很大,在下游小部分區(qū)域傳熱性能有所增強(qiáng),但是由于旋流作用的影響,周向大部分區(qū)域的傳熱減弱,因此旋流不利于超臨界水在高焓值區(qū)的傳熱,定位格架下游的換熱弱化現(xiàn)象或許是超臨界反應(yīng)堆緊湊型堆芯的特有現(xiàn)象,須在堆芯設(shè)計(jì)中加以重視。
[Abstract]:The application of supercritical water in large-scale heat exchange equipment such as a boiler or a reactor can greatly improve the heat parameters of the working medium of the outlet, so as to improve the overall economy of the power generation equipment. However, the special thermal physical properties of the supercritical water in the large specific heat area and the lower heat absorption capacity in the high specific heat area are limited, so the research on the heat transfer enhancement of the supercritical water in the large-scale heat exchanger, in particular at high temperature, is very important. In this paper, the flow and heat transfer enhancement characteristics of the supercritical water under the influence of the internal thread and the positioning grid are numerically studied by using the commercial CFD software as the object of the water-cooled wall and the reactor core of the supercritical boiler. In this paper, the characteristics of the flow and heat transfer of the working medium in the cold channel in the heated in-plane are analyzed, and the related mechanism is also revealed. The numerical study on the internal thread tube shows that the flow-guiding effect of the internal thread causes a stronger secondary flow field in the direction perpendicular to the main flow, and the change of the main flow value has little influence on the basic structure of the secondary flow field. And the heat exchange effect of the supercritical water on the top area of the thread is far better than the bottom of the thread. A single vortex formed on the top surface of the thread creates a relatively low pressure zone such that the heat transfer in this region is enhanced. In the large specific heat area, the non-uniformity of heat exchange is more significant due to the rapid change of the thermal physical properties of the fluid. The bottom of the thread is the weak point of heat exchange, and the optimization of the internal thread pipe structure should be focused on the area. The numerical results of the reactor core with the positioning grid show that the surface temperature of the fuel rod can be distributed unevenly in the condition of high temperature due to the influence of the flow blocking effect, and the central area is the lowest and the narrow slit area is the highest. in the downstream of the standard type positioning grid, the severe flow-inhibiting effect is such that the circumferential temperature difference of the narrow-seam zone is increased, the heat transfer effect is weakened, the downstream of the positioning grid with the staggered blades, the difference between the circumferential flow of the cladding and the heat-transfer characteristic is large, and the heat transfer performance of the downstream small-part region is enhanced, However, due to the influence of the swirl effect, the heat transfer in most regions of the circumferential direction is weakened, so that the swirling flow is not favorable for the heat transfer of the supercritical water in the high-flow-value region, and the heat exchange weakening phenomenon downstream of the positioning grid may be a unique phenomenon of the compact core of the supercritical reactor, and it is necessary to attach importance to the core design.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TK172

【共引文獻(xiàn)】

相關(guān)期刊論文 前1條

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相關(guān)博士學(xué)位論文 前3條

1 阮波;超臨界壓力下正癸烷裂解吸熱和對(duì)流傳熱現(xiàn)象的數(shù)值模擬研究[D];浙江大學(xué);2013年

2 劉波;超臨界壓力流體在圓管內(nèi)對(duì)流換熱及熱裂解研究[D];清華大學(xué);2013年

3 羅峰;增強(qiáng)型地?zé)嵯到y(tǒng)和二氧化碳利用中的流動(dòng)與換熱問(wèn)題研究[D];清華大學(xué);2014年

相關(guān)碩士學(xué)位論文 前8條

1 李軍;超臨界壓力下垂直管內(nèi)水的對(duì)流換熱數(shù)值模擬方法分析[D];哈爾濱工業(yè)大學(xué);2013年

2 王雷雷;碳?xì)淙剂铣R界壓力流/固/熱耦合數(shù)值模擬研究[D];浙江大學(xué);2013年

3 劉小龍;超臨界W型火焰鍋爐水冷壁的熱應(yīng)力分析[D];華中科技大學(xué);2013年

4 鄧彥翔;超臨界直流鍋爐水冷壁流動(dòng)阻力研究[D];華中科技大學(xué);2012年

5 唐麗君;超臨界壓力下低溫甲烷在肋片冷卻圓管中的強(qiáng)化傳熱的數(shù)值模擬研究[D];浙江大學(xué);2014年

6 周昭勇;超臨界甲烷/氫混合工質(zhì)冷卻換熱特性研究[D];上海交通大學(xué);2014年

7 張婧雍;基于CFD的超臨界水棒束內(nèi)流動(dòng)傳熱研究[D];上海交通大學(xué);2014年

8 魏婷;超臨界水冷固態(tài)增殖包層熱工設(shè)計(jì)準(zhǔn)則的初步研究[D];上海交通大學(xué);2014年

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本文編號(hào)：2508287