【摘要】：電廠冷凝器作為汽輪機(jī)機(jī)組的重要輔機(jī)之一,制約著整個(gè)熱力發(fā)電廠的安全經(jīng)濟(jì)運(yùn)行。如果凝汽器的管束布置不合適就會(huì)造成其換熱效率不高,進(jìn)而影響整個(gè)機(jī)組的經(jīng)濟(jì)性能。管束排列形式的優(yōu)劣對(duì)換熱器運(yùn)行時(shí)各項(xiàng)熱力性能指標(biāo)的好壞有重要的影響。此外決定換熱器性能好壞的參數(shù)也較多,僅憑單一參數(shù)不能決定換熱器是否為最佳。因此本文提出無(wú)量綱綜合性能系數(shù)K,且用K曲線(xiàn)的斜率作為換熱器換熱性能的評(píng)價(jià)指標(biāo)。并利用該指標(biāo)對(duì)案例進(jìn)行了分析。本文應(yīng)用FLUENT軟件,模擬水蒸氣在水平管束外遇冷凝結(jié)的流動(dòng)情況。數(shù)值模型基于多相流混合物模型,模型中加入自定義函數(shù)以實(shí)現(xiàn)蒸汽向水的轉(zhuǎn)換,利用有限體積法及SIMPLE算法求解控制方程組。本文數(shù)值計(jì)算了水蒸氣在由圓管、橢圓管和滴形管三種管型所組成的換熱器里的換熱情況,得到了在不同管型、不同排列方式及不同管間距下的水蒸氣壓力場(chǎng)、速度場(chǎng)、溫度場(chǎng)和換熱器傳熱系數(shù)的變化值。結(jié)果表明,三種管型構(gòu)成的換熱器當(dāng)進(jìn)口蒸汽流速、溫度以及壓力一定的情況下,滴形管凝結(jié)換熱效果最好,橢圓管次之,圓管最差。三種管型叉排布置時(shí)換熱效果均要優(yōu)于順排布置,其中順排布置時(shí),換熱效果最差的為倒數(shù)第二排管;叉排布置時(shí),最差的為倒數(shù)第二、三排管。三種管型順排布置時(shí),水蒸氣進(jìn)出口壓力損失都隨管束橫向間距的變大而變小,隨縱向間距的變大而無(wú)太大變化;叉排布置時(shí),水蒸氣進(jìn)出口壓力損失都隨管束橫向間距的變大而變小,隨縱向間距的變大同樣變小。三種管型換熱器傳熱系數(shù),順排布置時(shí)主要取決于管束橫向間距的大小,叉排布置則主要取決于管束的縱向間距。三種管型在最優(yōu)布置情況下,水蒸氣通過(guò)橢圓管換熱器進(jìn)出口壓損是圓管的0.62~0.64倍;不考慮壓損時(shí),溫差相差不大;在相同壓損下,流速是圓管的1.5倍;傳熱系數(shù)是圓管的1.93~2.04倍。水蒸氣通過(guò)滴形管換熱器壓損是圓管的0.67~0.70倍;溫差比圓管大1.5℃;在相同壓損下,流速是圓管的1.38~1.41倍;傳熱系數(shù)是圓管的1.84~1.91倍。該研究能為冷凝換熱器管束排列優(yōu)化設(shè)計(jì)提供可靠的參考。
[Abstract]:As one of the important auxiliary units of steam turbine, condenser in power plant restricts the safe and economical operation of the whole thermal power plant. If the tube bundle arrangement of the condenser is not suitable, the heat transfer efficiency will not be high and the economic performance of the whole unit will be affected. The arrangement of tube bundles has an important influence on the performance of heat exchangers. In addition, there are many parameters that determine the performance of the heat exchanger, and it is not possible to determine whether the heat exchanger is the best by a single parameter. Therefore, the dimensionless comprehensive performance coefficient K is proposed and the slope of K curve is used as the evaluation index of heat transfer performance of heat exchanger. This index is used to analyze the case. In this paper, FLUENT software is used to simulate the flow of water vapor in cold condensation outside the horizontal tube bundle. The numerical model is based on the mixture model of multiphase flow. The self-defined function is added to the model to realize the conversion of steam to water. The finite volume method and SIMPLE algorithm are used to solve the equations of control. In this paper, the heat transfer of water vapor in the heat exchanger composed of circular tube, elliptical tube and droplet tube is numerically calculated, and the pressure field and velocity field of water vapor are obtained under different tube types, different arrangement modes and different tube spacing. The variation of temperature field and heat transfer coefficient of heat exchanger. The results show that when the inlet steam velocity, temperature and pressure are constant, the condensation heat transfer efficiency of the droplet tube is the best, the elliptical tube is the second, and the circular tube is the worst. The heat transfer effect of the three kinds of pipe-type fork row arrangement is better than that of the forward arrangement, in which the worst heat transfer effect is the reciprocal second row, and the worst is the reciprocal second and third row. The pressure loss of water vapor inlet and outlet becomes smaller with the increase of the transverse spacing of the tube bundles, and does not change with the increase of the longitudinal spacing when the three types of pipes are arranged in a row, and the pressure loss of the inlet and outlet of the water vapor decreases with the increase of the transverse spacing of the pipe bundles. The pressure loss at the inlet and outlet of water vapor decreases with the increase of the transverse spacing of the bundle and the same with the increase of the longitudinal spacing. The heat transfer coefficient of three kinds of tube heat exchangers mainly depends on the horizontal spacing of the tube bundles and the vertical spacing of the tube bundles in the arrangement of the three kinds of tube heat exchangers. Under the optimal arrangement, the pressure loss of water vapor through the inlet and outlet of elliptical tube heat exchanger is 0.64 times of that of circular tube, the temperature difference is not different when the pressure loss is not taken into account, the velocity of flow is 1.5 times that of circular tube under the same pressure loss, and the heat transfer coefficient is 1.93 ~ 2.04 times of that of circular tube. The pressure loss of water vapor through a drop tube heat exchanger is 0.67 ~ 0.70 times of that of a circular tube, the temperature difference is 1.5 鈩，

本文編號(hào)：2265504