基于预测-矫正技术的超临界流体强迫对流传热能力预测方法

A new prediction method for heat transfer to supercritical fluids based on predictive-corrective technique

拟临界区剧烈变物性导致超临界流体强迫对流传热特性规律复杂.已有超临界流体传热关联式的预测能力和应用范围难以同时改善.借鉴亚临界两(多)相流分流型预测传热能力的思路,本文尝试提出了基于预测-矫正技术的超临界流体传热能力预测方法.该方法的基础包括可合理表征浮升力效应和流动加速效应强度的无量纲数Bu和Ac,以及一套完善的超临界流体对流传热关联.通过超临界二氧化碳强迫对流传热实验研究,获得了传热数据库(3696组数据),建立了一套(10个)超临界二氧化碳强迫对流传热关联式,并对新建立的传热关联式和新提出的预测-矫正预测方法进行了评价.结果表明预测-矫正计算方法可大幅提高加热段壁面温度预测精度,并有效纠正单一传热关联式预测时出现的粗大偏差.

Accurate prediction of convective heat transfer coefficient for supercritical fluids is difficult, owning to the rapid variation of thermal physical properties in pseudo-critical zoon and its complexity. The accuracy and valid range of the existing convective heat transfer correlations for supercritical fluids often cannot be guaranteed at the same time. Drawing lessons from heat transfer to two or multi-phase flow, a new approach to predict the heat transfer to supercritical fluids, called predictive-corrective method, was tried to be introduced. The basis of this approach is the two dimensionless numbers, Bu and Ac, which is able to reflect the strength of buoyancy and flow acceleration effects quantitatively, and a set of validate convective heat transfer correlations for supercritical fluids. Investigation of forced convective heat transfer to carbon dioxide was conducted experimentally, as a result constructing a heat transfer databank with 3696 screened data points, developing 10 convective heat transfer correlations for supercritical carbon dioxide.The evaluation of these new correlations and the predictive-corrective method was made. Result shows that the new introduced predictive-corrective method has the capacity to improve the prediction accuracy of heat transfer to supercritical fluids, and to correct the rough deviation of wall temperature when predicting with a single heat transfer correlation.