The article presents the influence of winglet vortex generators （WVGs） placed in the core flow area on ther- mal performance enhancement of a tube heat exchanger. The experiment was carried out in a uniform wall hea...The article presents the influence of winglet vortex generators （WVGs） placed in the core flow area on ther- mal performance enhancement of a tube heat exchanger. The experiment was carried out in a uniform wall heat-fluxed tube by varying turbulent airflow for Reynolds number ranging from 5300 to 24000. In the pres- ent work, the WVGs with an attack angle of 30° were inserted into the test tube at four different winglet pitch ratios （Rp = P/D） and three winglet-width or blockage ratios （Ra = e/D）. The experimental results at various Rp and RB values were evaluated and compared with those for smooth tube and tubes with twist- ed tape or wire coil. The measurement reveals that the WVGs enhance considerably the heat transfer and friction loss above the plain tube, wire coil and twisted tape. The Nusselt number and friction factor increase with the increment Of RB and Re but with the decreasing Rp. The average Nusselt numbers for the WVGs with various Ra are in the range of 2.03-2.34 times above the plain tube. The thermal performance for the WVGs is found to be much higher than that for the wire coil and twisted tape and is in a range of 1.35-1.59. Also, a numerical investigation is conducted to study the flow structure and heat transfer enhancement mecha- nisms in the winglet-inserted tube.展开更多
In this work,an approach is proposed to acquire synonymous attribute phrases of named entities(NEs) from an online encyclopedia.Synonymous attribute phrases are the phrases that express the same attribute with differe...In this work,an approach is proposed to acquire synonymous attribute phrases of named entities(NEs) from an online encyclopedia.Synonymous attribute phrases are the phrases that express the same attribute with different surface forms for a class of NEs.Specifically,the proposed approach is composed of three stages.Firstly,the entries related to a given NE class are automatically selected from an online encyclopedia.Secondly,attribute phrases are extracted based on the statistics of phrase frequency.Thirdly,synonymous attributes are identified in a pairwise manner through a classification framework combining multiple features.The proposed approach is applied on Baidu Baike,a Chinese online encyclopedia,for four different NE classes.Experimental results show that the approach obtains an average precision of 74%and an average F-value of 65%for the four NE classes.In particular,thousands of synonymous attribute phrase pairs are acquired for each class,which demonstrates the effectiveness of the proposed approach.展开更多
基金Supported by the Thailand Research Fund(TRF)(Grant No.PhD/0143/2552)
文摘The article presents the influence of winglet vortex generators （WVGs） placed in the core flow area on ther- mal performance enhancement of a tube heat exchanger. The experiment was carried out in a uniform wall heat-fluxed tube by varying turbulent airflow for Reynolds number ranging from 5300 to 24000. In the pres- ent work, the WVGs with an attack angle of 30° were inserted into the test tube at four different winglet pitch ratios （Rp = P/D） and three winglet-width or blockage ratios （Ra = e/D）. The experimental results at various Rp and RB values were evaluated and compared with those for smooth tube and tubes with twist- ed tape or wire coil. The measurement reveals that the WVGs enhance considerably the heat transfer and friction loss above the plain tube, wire coil and twisted tape. The Nusselt number and friction factor increase with the increment Of RB and Re but with the decreasing Rp. The average Nusselt numbers for the WVGs with various Ra are in the range of 2.03-2.34 times above the plain tube. The thermal performance for the WVGs is found to be much higher than that for the wire coil and twisted tape and is in a range of 1.35-1.59. Also, a numerical investigation is conducted to study the flow structure and heat transfer enhancement mecha- nisms in the winglet-inserted tube.
基金Supported by the National High Technology Research and Development Programme of China(No.2008AA01Z144)the National NaturalScience Foundation of China(No.61073126,61073129)
文摘In this work,an approach is proposed to acquire synonymous attribute phrases of named entities(NEs) from an online encyclopedia.Synonymous attribute phrases are the phrases that express the same attribute with different surface forms for a class of NEs.Specifically,the proposed approach is composed of three stages.Firstly,the entries related to a given NE class are automatically selected from an online encyclopedia.Secondly,attribute phrases are extracted based on the statistics of phrase frequency.Thirdly,synonymous attributes are identified in a pairwise manner through a classification framework combining multiple features.The proposed approach is applied on Baidu Baike,a Chinese online encyclopedia,for four different NE classes.Experimental results show that the approach obtains an average precision of 74%and an average F-value of 65%for the four NE classes.In particular,thousands of synonymous attribute phrase pairs are acquired for each class,which demonstrates the effectiveness of the proposed approach.
