实验研究了Al_2O_3-水纳米流体在泡沫金属填充管内的流动和传热特性,泡沫金属孔密度(pores per 0.0254m,PPI)为20~40,孔隙率为90%,Al_2O_3-水纳米流体的质量分数为0.1%~0.5%。实验结果表明:以压降为代价的前提下,泡沫金属与纳米流体相...实验研究了Al_2O_3-水纳米流体在泡沫金属填充管内的流动和传热特性,泡沫金属孔密度(pores per 0.0254m,PPI)为20~40,孔隙率为90%,Al_2O_3-水纳米流体的质量分数为0.1%~0.5%。实验结果表明:以压降为代价的前提下,泡沫金属与纳米流体相结合的方式总是能显著强化传热。相同工况下,更大的PPI可以提高努塞尔数。去离子水工况下,40PPI泡沫金属对流换热效果最好,努塞尔数最大提高650%。泡沫金属PPI越大,压降增加越多,40 PPI泡沫金属的压降是光管的19倍。相比20 PPI泡沫金属,30 PPI的泡沫金属使努塞尔数最多提高15%,压降增加5%;40 PPI的泡沫金属可以使努塞尔数最多提高38%,压降增加38%。纳米流体的质量分数也对流动和传热有重要影响。根据实验数据开发了适用于纳米流体在泡沫金属强化管内的传热及流动的关联式。展开更多
采用水热处理对γ-Al2O3载体改性,并进行XRD、N2物理吸附-脱附、热重、NH3-TPD及H2-TPR表征。结果表明,γ-Al2O3经过"再水合-焙烧"过程,晶型变好,表面总酸量降低,Pt-Al2O3相互作用增加,提高了Pt Sn K/Al2O3催化剂的丙烷脱氢...采用水热处理对γ-Al2O3载体改性,并进行XRD、N2物理吸附-脱附、热重、NH3-TPD及H2-TPR表征。结果表明,γ-Al2O3经过"再水合-焙烧"过程,晶型变好,表面总酸量降低,Pt-Al2O3相互作用增加,提高了Pt Sn K/Al2O3催化剂的丙烷脱氢转化率、选择性及稳定性。其中,140℃处理4 h时,氧化铝负载的Pt Sn K催化剂表现出最优的丙烷脱氢性能,100 h内平均转化率为33.6%,平均选择性97.3%,失活参数为15.9%。展开更多
The initial hydration of steel slag with high Al2O3 content and its influence on the initial hydration of cement were investigated in this study.Steel slag with high Al2O3 content may contain much calcium aluminate mi...The initial hydration of steel slag with high Al2O3 content and its influence on the initial hydration of cement were investigated in this study.Steel slag with high Al2O3 content may contain much calcium aluminate mineral but very little gypsum.The steel slag hydrates much more quickly than cement in the initial hydration period,producing many flake products which have a great influence on the fluidity,initial setting time,and adsorption level of superplasticizer of paste.Replacing part of cement by steel slag with high Al2O3 content can change the hydration condition of calcium aluminate mineral of the cement by decreasing the gypsum to calcium aluminate mineral ratio,resulting in accelerating the hydration rate of calcium aluminate mineral in the initial hydration period.Paste containing steel slag with high Al2O3 content has a shorter initial setting time,higher adsorption level of superplasticizer,and greater loss in fluidity than the pure cement paste.展开更多
文摘采用水热处理对γ-Al2O3载体改性,并进行XRD、N2物理吸附-脱附、热重、NH3-TPD及H2-TPR表征。结果表明,γ-Al2O3经过"再水合-焙烧"过程,晶型变好,表面总酸量降低,Pt-Al2O3相互作用增加,提高了Pt Sn K/Al2O3催化剂的丙烷脱氢转化率、选择性及稳定性。其中,140℃处理4 h时,氧化铝负载的Pt Sn K催化剂表现出最优的丙烷脱氢性能,100 h内平均转化率为33.6%,平均选择性97.3%,失活参数为15.9%。
基金supported by the National Natural Science Foundation of China(Grant No.51108245)the State Key Laboratory of Silicate Materials for Architectures of China(Grant No.SYSJJ2012-10)
文摘The initial hydration of steel slag with high Al2O3 content and its influence on the initial hydration of cement were investigated in this study.Steel slag with high Al2O3 content may contain much calcium aluminate mineral but very little gypsum.The steel slag hydrates much more quickly than cement in the initial hydration period,producing many flake products which have a great influence on the fluidity,initial setting time,and adsorption level of superplasticizer of paste.Replacing part of cement by steel slag with high Al2O3 content can change the hydration condition of calcium aluminate mineral of the cement by decreasing the gypsum to calcium aluminate mineral ratio,resulting in accelerating the hydration rate of calcium aluminate mineral in the initial hydration period.Paste containing steel slag with high Al2O3 content has a shorter initial setting time,higher adsorption level of superplasticizer,and greater loss in fluidity than the pure cement paste.
