地鐵列車空調機組中橢圓管換熱器的應用

李 劍 蔣 奎 張子楊 張春路

(1.中車青島四方機車車輛股份有限公司,266111,青島; 2.河北軌道運輸職業技術學院，050021，石家莊；3.同濟大學機械與能源工程學院制冷與低溫工程研究所,201804,上海∥第一作者，高級工程師)

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地鐵列車空調機組中橢圓管換熱器的應用

李 劍1蔣 奎2張子楊3張春路3

(1.中車青島四方機車車輛股份有限公司,266111,青島; 2.河北軌道運輸職業技術學院，050021，石家莊；3.同濟大學機械與能源工程學院制冷與低溫工程研究所,201804,上海∥第一作者，高級工程師)

地鐵列車空調機組功耗約占列車牽引動力的40%,合理有效提高列車空調機組能效比(COP)是降低地鐵能耗的重要課題。提出了將橢圓管換熱器應用于地鐵列車空調的設想,通過建立仿真模型,對原設計采用圓管換熱器的制冷系統與采用橢圓管換熱器的制冷系統進行了對比。結果表明：將冷凝器和蒸發器都用橢圓管優化后,制冷系統COP提升了12.4%,制冷量提升了12.6%,可以選擇小號的壓縮機來進一步降低成本。此外，對φ7 mm強化管蒸發器優化的制冷系統進行了分析,結果表明，采用強化管蒸發器的制冷系統性能也有改善,略次于采用橢圓管蒸發器的制冷系統。因此，橢圓管換熱器應用于地鐵列車空調機組中,對制冷系統性能改善顯著,對降低地鐵列車能耗有重要意義。

地鐵列車; 空調機組; 橢圓管換熱器

First-author′s address CRRC Qingdao Sifang Co.,Ltd.,266111,Qingdao,China

為保證車廂適宜的溫度與濕度,地鐵列車空調機組的配備必不可少,其消耗功率約占地鐵列車牽引動力的40%。然而，地鐵列車空調機組的COP(能效比)只有2.2～2.3,遠低于同類住宅空調機組的COP[1]。在大力倡導節能減排的今天,如何通過合理有效的設計改進來優化地鐵列車空調系統至關重要。本文從換熱器層面入手,考慮將原設計的圓管換熱器替換為橢圓管換熱器。橢圓管換熱器對管外繞流而言將脫體繞流點延遲,可減小管外壓降;對管內流動而言,管道當量直徑減小,對換熱是有利的[2];同時，橢圓管管間距減小使得同樣的空間可以布置更多的換熱管。已有試驗證明,橢圓管換熱器的風側阻力、導熱系數、換熱效率等各項性能均優于圓管換熱器[3]。橢圓管應用于制冷劑-空氣換熱器,可使管外空氣側壓降減小,換熱器換熱能力加強[4-6],使蒸發溫度升高、冷凝溫度降低,可提高空調系統COP。因此，本文提出將橢圓管換熱器應用于地鐵列車空調機組中,通過在制冷空調系統通用仿真平臺GREATLAB[7]中進行系統仿真,比較原設計的圓管換熱器與橢圓管換熱器的性能參數,驗證該方案的可行性。

1 圓管換熱器系統仿真與標定

本文研究的軌道車輛空調為雙制冷劑回路,每個制冷劑回路的設計相同。單回路制冷系統流程如圖1所示。

注：數字表示建模時的部件/流路順序

蒸發器和冷凝器均為翅片管換熱器仿真模型,采用分布參數模型[8]可以更好地反應換熱器內制冷劑和空氣不均勻流動對于換熱器及系統性能的影響。該模型在求解中將翅片管換熱器模型按換熱器結構分解為以下四個層次:換熱器模型、流路模型、換熱管模型和微元模型。計算時,由微元模型開始,根據控制體內制冷劑和空氣的狀態,選取相應的換熱關聯式,自下而上完成換熱器仿真。

基于上述分布參數模型,可以快速便捷地完成實際換熱器模型的仿真。先按照實際設計完成流路連接(見圖2),再輸入換熱器結構參數及制冷劑側空氣側工況參數,就可完成換熱器模型仿真,求解制冷劑和空氣的出口狀態、壓降和換熱量。

圖2 圓管系統換熱器流路連接

壓縮機模型采用壓縮機廠商廣泛采用的AHRI 10系數模型：

式中：

y——壓縮機的冷量、能效比、功耗、質量流量等性能參數;

c1～c10——常數項；

Te——蒸發溫度；

Tc——冷凝溫度。

蒸發器、冷凝器兩側風機采用效率模型,輸入風量及功耗;膨脹閥采用控制模型,即壓縮機吸氣過熱度為定值(換熱器、壓縮機、膨脹閥等部件模型詳見文獻[8])。名義工況下機組性能仿真結果與試驗結果的對比如表1所示。

在此基礎上,根據試驗結果對仿真模型進行標定,使得在名義工況下模型主要性能參數與試驗結果一致,從而保證后續優化結果的精度。模型標定結果如表2所示。

表2 模型標定

2 橢圓管冷凝器

2.1 橢圓管冷凝器設計

原有的圓管冷凝器設計參數與橢圓管冷凝器設計參數(管的類型皆為螺旋槽強化管)分別如表 3、表 4[7]所示。由表3、表4可知,橢圓管冷凝器管間距減小,在保持冷凝器高度不變的情況下,每排管數可以增加至22；橢圓管冷凝器排間距變化較小,排數不變。對橢圓管冷凝器流路進行重新優化設計,各流路數下換熱量對比如圖3所示。可見，11流路下換熱量最大，故選取11流路連接形式。

表3 原有的圓管冷凝器設計參數

表4 橢圓管冷凝器設計參數

原設計與新設計對比如表5所示。顯然,橢圓管冷凝器換熱量有明顯提高(+53%),空氣側壓降也有下降(-24%)。可以根據風機曲線模型對冷凝器側風機的風量、功耗重新匹配(風量將會增大)。

表5 原設計和新設計的冷凝器性能參數對比

2.2 采用橢圓管冷凝器的制冷系統

將原設計中的冷凝器替換為新的橢圓管冷凝器,并匹配相應的風機,對制冷系統進行仿真。原設計與新設計性能對比如表6所示。可見,用橢圓管冷凝器代替圓管冷凝器后,制冷量幾乎不變的情況下,COP提升了6%左右。

表6 原設計和新設計的制冷系統性能比較一

3 橢圓管蒸發器

3.1 橢圓管蒸發器設計

原有的圓管蒸發器設計參數與橢圓管蒸發器設計參數分別如表7、表8所示。

表7 圓管蒸發器設計參數

由表8計算可得,在保持蒸發器高度、寬度不變的情況下,采用橢圓管蒸發器，排數可由原來的8排變為6排,每排管數由19增加至26。重新設計換熱器流路,橢圓管蒸發器各流路數的換熱量如圖4所示。可見，26流路時換熱量最大。因此，選擇26流路下的橢圓管蒸發器。

表8 橢圓管蒸發器設計參數

圖4 橢圓管蒸發器各流路數的換熱量

表9為原設計與新設計的比較。顯然,橢圓管蒸發器換熱量有明顯提高(+37%),空氣側壓降也有下降(-25%)。因此，可根據風機曲線模型對蒸發器側風機的風量、功耗重新匹配(風量將會增大)。新設計將光管改為強化管,雖然每一流路只走6根管,少于原設計的8根管,但制冷劑側壓降仍為26.6 kPa,高于原設計的12.8 kPa。由于原設計的制冷劑側壓降不大,所以制冷劑壓降升高對制冷系統的影響比較小。

3.2 采用橢圓管蒸發器的制冷系統

將原設計中的蒸發器替換為新的橢圓管蒸發器,并匹配相應的風機,對制冷系統進行仿真。原設計與新設計的制冷系統性能對比如表10所示。可見,用橢圓管蒸發器代替圓管蒸發器后,制冷系統性能改善顯著,制冷量增加了10.3%,COP提升了7.3%。

表9 原設計和新設計的蒸發器性能參數對比

表10 原設計和新設計的制冷系統性能比較二

4 壓縮機重新選型

將冷凝器和蒸發器都替換為橢圓管后，對橢圓管換熱器與原設計的圓管換熱器相比較,如表11所示。

表11 橢圓管換熱器與圓管換熱器比較

由于冷凝器和蒸發器優化后,制冷量提升了12.6%,因此可以選擇小號的壓縮機來降低成本。同時，由于壓縮機流量減少,換熱器的相對換熱面積增大,換熱溫差減小,COP可進一步提升。原設計中壓縮機型號為ZR 94 KCE-TFD,現選擇小兩號的ZR 84 KCE-TFD型壓縮機,其性能見表12。

表12 重新選型的橢圓管換熱器的壓縮機性能表

表12中,小兩號壓縮機系統COP下降是因為在軌交空調的工況下，ZR 84 KCE-TFD的效率只有ZR 94 KCE-TFD的90%。

5 φ7 mm強化管蒸發器

5.1 強化管蒸發器設計

考慮到橢圓管換熱器在生產工藝上的復雜性,本文對地鐵列車空調機組蒸發器的優化提出另一種方案：將原有的圓管蒸發器的光管替換為φ7 mm螺旋槽強化管。其具體結構參數如表13所示。

根據表13參數,在保持蒸發器尺寸不變的情況下,每排管數可以由原來的18增加至24，排間距不變,排數不變。重新設計換熱器流路,各流路數所對應的換熱量如圖5所示。由圖5可見，24流路時換熱量最大，故選擇24流路下的強化管蒸發器。

表13 φ7 m強化管蒸發器設計參數

圖5 強化管蒸發器各流路數的換熱量

將橢圓管蒸發器與φ7 mm強化管蒸發器進行比較,如表14所示。可以看出,φ7 mm強化管蒸發器換熱性能與橢圓管蒸發器換熱性能接近,但是空氣側壓降比橢圓管蒸發器大,與原設計接近,風機風量功耗與原設計保持一致。

5.2 采用強化管蒸發器的制冷系統

將原設計中的蒸發器替換為φ7 mm強化管蒸發器,對制冷系統進行仿真。兩種蒸發器優化設計方案比較如表15所示。

表14 蒸發器優化設計比較

表15 蒸發器優化的制冷系統性能比較

在制冷系統中將冷凝器替換為橢圓管冷凝器,兩種方案的性能對比如表16所示。

表16 兩種換熱器優化方案系統性能比較

由表16可知,蒸發器和冷凝器都換為橢圓管是最佳組合；采用橢圓管冷凝器與φ7 mm強化管蒸發器的制冷系統的COP提升也較為顯著；制冷量有增長,但不足以換小一號的壓縮機(若壓縮機換為小一號的ZR 90 K3E-TWD,制冷量將降為19.42 kW)。

6 結語

本文提出了將橢圓管換熱器用于地鐵列車空調的設想,通過建立仿真模型,對原設計的采用圓管換熱器的制冷系統與采用橢圓管冷凝器和橢圓管蒸發器后的制冷系統進行對比。結果表明,采用橢圓管冷凝器,COP提升了6%左右;橢圓管蒸發器代替圓管蒸發器后,制冷量增加了10.3%,COP提升了7.3%;將冷凝器和蒸發器都用橢圓管后,COP提升了12.4%,制冷量提升了12.6%,可以選擇小號的壓縮機來進一步降低成本。考慮到橢圓管換熱器在生產工藝上的復雜性,本文對φ7 mm強化管蒸發器的制冷系統也作了分析,結果表明，采用強化管蒸發器的制冷系統性能也有提高,制冷量提升4.4%,COP提升3.4%,但整體性能不如采用橢圓管蒸發器。綜合以上分析,橢圓管換熱器應用于地鐵列車空調機組中,對制冷系統性能改善顯著,對降低地鐵列車能耗有重要意義。

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(Continued from Special Commentary)

“The 13thFive-Year Plan” works out a more ambitious blueprint for China′s economic and social developments. It points to comprehensively building a moderately prosperous society, achieves the first Centenary Goal, and fully reflects the five development concepts of “innovation, harmonization, green, openness and sharing”. Its main line is the structural reform of the supply front.

In the 25 special columns of “The 13thFive-Year Plan Outline”, the five aspects of technological innovation, structure upgrading, infrastructural facilities, ecological environment and improving people′s livelihood, etc. are involved. Among them, the objective set for rail transit is that within five years, China will improve and perfect the modern integrated transportation system. The main key projects constructions in the rail transport field are described as follows. The high-speed railway mileage in service will reach 30 000 km, linking more than 80% major cities. The intercity railway networks of the urban agglomerations of Beijing-Tianjin-Hebei, the Yangtze River Delta, the Pearl River Delta, the middle reaches of the Yangtze River, the Central Plains, the Chengdu-Chongqing, and the Shandong peninsula will be basically completed. The main skeleton of intercity rail networks of other urban agglomerations will be constructed. The demonstration project of urban areas (suburbs) railways will be implemented. The rail transit networks of super cities and mega cities will be perfected and optimized. The urban rail transit networks of those cities with more than 3 million populations will be sped up to be formed. The additional urban rail transit mileage in service will reach about 3 000 km. “Four ‘Along’s (along coasts/rivers/borders/the Belt and Road) Channels”— The high-speed railways along coasts and along rivers will be basically run-through. The railways along borders, such as the railway from Hetian to Ruoqiang, the railway along the border in Northeast China and the Sichuan-Tibet railway, etc., will be constructed. Push on the constructions of cross-border passageways linking with neighboring countries around China and the passages along “The Belt and Road”. Build the logistics platform of international trains of important node cities, such as Urumqi and Lanzhou. Construct the Shenzhen-Zhongshan Channel (the dual-channel of highway and railway from Shenzhen to Zhongshan, its subject engineering′s being the dual-purpose bridge of highway and railway with more cost-effective). “The 13thFive-Year Plan Outline” also points out that in urbanization areas, intercity railways and urban areas (suburbs) railways should be greatly developed, and using existing railways to run intercity trains should be encouraged, so as to form backbone networks of multi-level rail transit and high-efficiently connect large- medium-small cities and towns. Thus, during the period of “the 13thFive-Year Plan”, the topic words of rail transport development are “perfection and optimization”.

The intercity rail transit constructions are of great significance for advancing the new type of urbanization, the industrial structure adjustment and the technology development of the railway industry itself. The development of the high-speed rail and railway freight will not only greatly promote “the Belt and Road Initiative” constructions, but also improve the capability of independent innovation of China′s railways. Perfecting and optimizing the rail transit networks of mega cities, and speeding up to make the urban rail transit of those cities with more than 3 million people form networks are vitally interrelated with building a harmonious and livable cities and improving the people′s livelihood. “The 13thFive-Year Plan Outline” has indicated the direction and the road for our rail transit field. Our mission is both glorious and arduous. Let us work together to produce a satisfactory answer to the motherland and the people.

(Translated by SUN Zheng)

Application of Oval Tube Heat Exchanger in Air-conditioning Units of Metro Vehicles

LI Jian, JIANG Kui, ZHANG Ziyang, ZHANG Chunlu

The power consumption of air-conditioning units installed in metro vehicles accounts for about 40% of the total traction power, it is important to improve effectively the COP (coefficient of performance) of AC (air-conditioning) units installed in metro vehicles. The application of an oval tube heat exchanger in the AC units of metro vehicles is proposed, and a simulation model is built to compare the system optimized by the oval tube exchanger with the original system. The results show that system COP will be increased by 12.4% and cooling capacity be increased by 12.6% if the oval tube is applied in both evaporator and condenser. Meanwhile, a smaller compressor can be chosen to further reduce the cost. If it maintains the same efficiency, the system COP will be about 2.80, promoted by 19.7%. The system optimized by enhanced heat exchanger tube (7 mm) is analyzed, thus the system COP will also be promoted only one step short of the system with oval tube. The application of oval tube heat exchanger in AC units of metro vehicles results in significant promotion of the system COP and plays a critical role in reducing energy consumption.

metro vehicle; air-conditioning system; oval tube heat exchanger

U 270.38+3

10.16037/j.1007-869x.2016.04.024

2015-11-19)