超临界天然气在蛇形盘管内流动与传热的数值模拟
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摘要
为了更好地研究LNG浸没燃烧式气化器管内流体的流动传热特性,建立了浸没燃烧式气化器管内高压天然气升温跨临界流动传热过程的数值模型,对其轴向与环向的流动传热特性及操作参数的影响进行相关研究,并将模拟结果与现有管内超临界流体传热的关联式进行对比。发现管内传热系数随换热管长先增大后减小,在拟临界点位置达到峰值,且弯头处出现局部传热强化;提高管内质量流量能够显著强化管内传热,但流体跨临界位置也会相对延后;提高管程入口温度和水浴温度均使流体跨临界位置提前,而较高的水浴温度会使传热系数峰值偏低;模拟结果与现有传热关联式的对比结果发现,Jackson&Hall公式更能准确预测超临界天然气在蛇形盘管内的传热特性,但不能体现弯头处的局部传热强化。研究结果为浸没燃烧式气化器的设计工作提供了依据。
In order to investigate the flow and heat transfer characteristics in submerged combustion vaporizer( SCV),a numerical model was developed to describe the trans-critical flow and heat transfer process of high-pressure natural gas( NG). The characteristics of the flow and heat transfer in the axial and circumferential direction were investigated and the effects of operating parameters were obtained. Besides,the results were compared with the heat transfer correlations that predict the heat transfer coefficient inside the tube. It can be concluded that the heat transfer coefficient value firstly increases and then decreases with the change of tube length,and the peak value appears in the vicinity of the pseudo-critical point. Furthermore,the heat transfer at elbow is improved abruptly. The heat transfer in tubes can be enhanced with the increase of mass flow,but the trans-critical process appears later correspondingly. Increasing the inlet temperature of tubes and bath temperature both can result in an earlier occurrence of trans-critical process,and a higher bath temperature can result in a lower peak value of heat transfer coefficient. By comparing with simulation results,it is indicated that Jackson& Hall equation is more accurate in predicting the heat transfer characteristics of supercritical NG in serpentine tube among the correlations. However,it loses its accuracy at elbow due to the local heat transfer enhancement. This study can provide a theoretical guidance for the design of SCV.
In order to investigate the flow and heat transfer characteristics in submerged combustion vaporizer( SCV),a numerical model was developed to describe the trans-critical flow and heat transfer process of high-pressure natural gas( NG). The characteristics of the flow and heat transfer in the axial and circumferential direction were investigated and the effects of operating parameters were obtained. Besides,the results were compared with the heat transfer correlations that predict the heat transfer coefficient inside the tube. It can be concluded that the heat transfer coefficient value firstly increases and then decreases with the change of tube length,and the peak value appears in the vicinity of the pseudo-critical point. Furthermore,the heat transfer at elbow is improved abruptly. The heat transfer in tubes can be enhanced with the increase of mass flow,but the trans-critical process appears later correspondingly. Increasing the inlet temperature of tubes and bath temperature both can result in an earlier occurrence of trans-critical process,and a higher bath temperature can result in a lower peak value of heat transfer coefficient. By comparing with simulation results,it is indicated that Jackson& Hall equation is more accurate in predicting the heat transfer characteristics of supercritical NG in serpentine tube among the correlations. However,it loses its accuracy at elbow due to the local heat transfer enhancement. This study can provide a theoretical guidance for the design of SCV.
引文
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[13]PETUKHOV B S,KRASNOSHCHEKOV E A,PROTOPOPOV V S. An investigation of heat transfer to fluids flowing in pipes under supercritical condition[J]. ASME international developments in heat transfer,1961,3:569-578.
[2]YU Shuiqing,LI Huixiong,LEI Xianliang,et al. Influence of buoyancy on heat transfer to water flowing in horizontal tubes under supercritical pressure[J]. Applied thermal engineering,2013,59(1/2):380-388.
[3]GU Hongfang,LI Hongzhi,WANG Haijun,et al. Experimental investigation on convective heat transfer from a horizontal miniature tube to methane at supercritical pressures[J]. Applied thermal engineering,2013,58(1/2):490-498.
[4]粘权鑫,郭少龙,方文振,等.液化天然气浸没燃烧式气化器数值模拟方法研究[J].西安交通大学学报,2016,50(1):67-71,114.
[5]HAN Dongyan,XU Qinqin,ZHOU Dan,et al. Design of heat transfer in submerged combustion vaporizer[J]. Journal of natural gas science and engineering,2016,31:76-85.
[6]靳书武,武锦涛,银建中.水平圆管内超临界甲烷对流换热数值模拟[J].应用科技,2015,42(5):67-71.
[7]张康,韩昌亮,任婧杰,等. SCV蛇形换热管内超临界LNG传热特性数值模拟[J].化工学报,2015,66(12):4788-4795.
[8]董文平,任婧杰,韩昌亮,等.浸没燃烧式气化器换热管内跨临界液化天然气的传热特性[J].化工进展,2017,36(12):4378-4384.
[9]陶文铨.数值传热学[M]. 2版.西安:西安交通大学出版社,2001.
[10]DITTUS F W,BOELTER L M K. Heat transfer in automobile radiators of the tubular type[J]. International communications in heat and mass transfer,1985,12(1):3-22.
[11]JACKSON J D. Consideration of the heat transfer properties of supercritical pressure water in connection with the cooling of advanced nuclear reactors[C]//Proceedings of the 13th Pacific Basin Nuclear Conference. Shenzhen,China,2002.
[12]JACKSON J D,FEWSTER J. Forced convection data for supercritical pressure fluids[M]. Manchester:Simon Engineering Laboratory,University of Manchester,1975.
[13]PETUKHOV B S,KRASNOSHCHEKOV E A,PROTOPOPOV V S. An investigation of heat transfer to fluids flowing in pipes under supercritical condition[J]. ASME international developments in heat transfer,1961,3:569-578.