蓄热式波纹板孔隙率影响(火用)损特性的研究

Porosity Effects on the Exergy Loss of Regenerative Corrugated Plates

本文采用瞬态实验法对8种不同孔隙率的波纹板蓄热元件的传热和阻力性能进行了研究(500<Re<11 000)。试验得到8种孔隙率的波纹板组件对应火用损和火用损系数随雷诺数Re变化的曲线。通过计算和比较不同孔隙率的试验元件在2 000<Re<9 000范围内的平均火用损EL,avg和平均火用损系数Ravg,得出孔隙率对试验元件火用损特性的影响规律,结果显示孔隙率P为6.8%和11.8%时平均火用损均较小为33.0 k J左右,孔隙率P=4.6%平均火用损最大达到41.5 k J。平均火用损系数随孔隙率的变化趋势与平均火用损类似,在52.4%~85.8%之间浮动。不同孔隙率试验元件对应的火用损和火用损系数随雷诺数变化曲线都呈先升高后降低的趋势,峰值点也即转捩点出现在2 000<Re<4 500之间,此时流动处于过渡态,热能的品位恶化最严重。实验结果表明:孔隙率6.8%的波纹板具有较好的经济性和传热性能。考虑到不同孔隙率波纹板火用损失转捩点的差异,应尽量避免使工况处在Re<2 000或Re>6 000的范围以保证蓄热波纹板的火用损和火用损系数处于较低的水平。

To study the effect of porosity on the characteristics of heat transfer and flow resistance of the regenerative corrugated plates,8 different porosities were investigated under multiple working conditions( with Re varying from 2 000 to 11 000) by using transient test method. The results were analyzed from the viewpoint of exergy to assess the thermodynamic perfection. 8 pairs ofexergy loss and exergy loss coefficient curves corresponding to each test element were obtained with increasing Re.With Re in the range of 2 000 to 9 000,calculation and comparison of the average exergy loss,EL,avg,and exergy loss coefficient,Ravg,were done to manifest the effects of various porosity values on the overall performance of the heat transfer elements. Results showed that EL,avgreaches a minimum of 33. 0 k J when porosity equals 6. 8% or11. 8% and has the maximum value of 41. 5k J with porosity of 4. 6%. Ravgcurves have the similar trend as EL,avg,varying from 52. 4% to 85. 8%. Both exergy loss ELand exergy loss coefficient R increase first,and then decrease with Re number. The peak / critical points appear when Re is in the range of 2 000 ~ 4 500 where the air flow is transitional and heat grade worsens rapidly. Results showed that plates of 6. 8% porosity have great economical efficiency and heat transfer performance. In consideration of the variations in the critical points for plates with differentporosities,it is recommended to operate with Re < 2000 or Re > 6000 to retain ELand R in low levels.