Presents a set of data for flow and heat transfer of finned-tube bundle under the condition of high air flow velocity. Air flow and heat transfer over a 4 × 4 （ columns × rows） finned-tube heat exchanger w...Presents a set of data for flow and heat transfer of finned-tube bundle under the condition of high air flow velocity. Air flow and heat transfer over a 4 × 4 （ columns × rows） finned-tube heat exchanger with rectangular fins was investigated experimentally in a wind tunnel with constant wall temperatures condition. The air flow velocity based on the minimum flow cross-section area over flow channel ranged from 13.8 to 50. 2 m/s, the heal transfer rate ranged from 21.8 to47. 1 kW, and the air temperatures increase ranged from 10. 9 to 19. 8 ℃. The present results were compared with results calculated from correlations proposed by CSPE. For air flow velocity less than 25 m/s, these two results of heat transfer agreed well with each other, whereas for larger velocity, our test data disagreed with the CSPE correlations. For the friction factor, present data are much higher than the predicted results in the whole range. Finally, correlations for friction factors and heat transfer coefficients are DrODosed based on the experimental results.展开更多
The typical configuration adopted by air-cooled condenser(ACC) in coal-fired power generating unit is the wave finned flat tube. The development of boundary layer between wave fins along long axis of flat tube can sup...The typical configuration adopted by air-cooled condenser(ACC) in coal-fired power generating unit is the wave finned flat tube. The development of boundary layer between wave fins along long axis of flat tube can suppress the air-side heat transfer enhancement to a great extent. It has been proved that the serrated fins can enhance heat transfer obviously by breaking the development of boundary layer periodically. In the present study,the discontinuous short wave fin was introduced to the flat tube to enhance the air-side heat transfer of ACC. Two different types of arrangements,i.e. staggered and in-line for discontinuous short wave fins on the flat tube,were designed. By numerical simulation,the heat transfer and flow performances of short wave fins were studied under different arrangements(in-line,staggered) ,and the influences on heat transfer and flow characteristics of rows of short wave fin and interrupted distance between discontinuous short wave fins were revealed numerically. The results indicated that,compared with the original continuous wave fin,the discontinuous short wave fin effectively improved the air-side heat transfer of flat tube under the air flow velocities in the practical application of engineering. Moreover,the increment of pressure loss of air-side flow was restricted for the discontinuous short wave fins because of the reduction of contact areas between the air flow and fin surface.展开更多
In this paper,we present a three dimensional numerical investigation of heat transfer in a parabolic trough collector receiver with longitudinal fins using different kinds of nanofluid,with an operational temperature ...In this paper,we present a three dimensional numerical investigation of heat transfer in a parabolic trough collector receiver with longitudinal fins using different kinds of nanofluid,with an operational temperature of 573 K and nanoparticle concentration of 1% in volume.The outer surface of the absorber receives a non-uniform heat flux,which is obtained by using the Monte Carlo ray tracing technique.The numerical results are contrasted with empirical results available in the open literature.A significant improvement of heat transfer is derived when the Reynolds number varies in the range 2.57×104≤ Re≤ 2.57×105,the tube-side Nusselt number increases from 1.3 to 1.8 times,also the metallic nanoparticles improve heat transfer greatly than other nanoparticles,combining both mechanisms provides better heat transfer and higher thermo-hydraulic performance.展开更多
基金Sponsored by the National Natural Science Special Foundation of China(Grant No.50323001)Xi'an Jiaotong University Doctoral Foundation forTeacher.
文摘Presents a set of data for flow and heat transfer of finned-tube bundle under the condition of high air flow velocity. Air flow and heat transfer over a 4 × 4 （ columns × rows） finned-tube heat exchanger with rectangular fins was investigated experimentally in a wind tunnel with constant wall temperatures condition. The air flow velocity based on the minimum flow cross-section area over flow channel ranged from 13.8 to 50. 2 m/s, the heal transfer rate ranged from 21.8 to47. 1 kW, and the air temperatures increase ranged from 10. 9 to 19. 8 ℃. The present results were compared with results calculated from correlations proposed by CSPE. For air flow velocity less than 25 m/s, these two results of heat transfer agreed well with each other, whereas for larger velocity, our test data disagreed with the CSPE correlations. For the friction factor, present data are much higher than the predicted results in the whole range. Finally, correlations for friction factors and heat transfer coefficients are DrODosed based on the experimental results.
基金supported by the National Basic Research Program of China ("973" Program) (Grant No.2009CB219804)
文摘The typical configuration adopted by air-cooled condenser(ACC) in coal-fired power generating unit is the wave finned flat tube. The development of boundary layer between wave fins along long axis of flat tube can suppress the air-side heat transfer enhancement to a great extent. It has been proved that the serrated fins can enhance heat transfer obviously by breaking the development of boundary layer periodically. In the present study,the discontinuous short wave fin was introduced to the flat tube to enhance the air-side heat transfer of ACC. Two different types of arrangements,i.e. staggered and in-line for discontinuous short wave fins on the flat tube,were designed. By numerical simulation,the heat transfer and flow performances of short wave fins were studied under different arrangements(in-line,staggered) ,and the influences on heat transfer and flow characteristics of rows of short wave fin and interrupted distance between discontinuous short wave fins were revealed numerically. The results indicated that,compared with the original continuous wave fin,the discontinuous short wave fin effectively improved the air-side heat transfer of flat tube under the air flow velocities in the practical application of engineering. Moreover,the increment of pressure loss of air-side flow was restricted for the discontinuous short wave fins because of the reduction of contact areas between the air flow and fin surface.
文摘In this paper,we present a three dimensional numerical investigation of heat transfer in a parabolic trough collector receiver with longitudinal fins using different kinds of nanofluid,with an operational temperature of 573 K and nanoparticle concentration of 1% in volume.The outer surface of the absorber receives a non-uniform heat flux,which is obtained by using the Monte Carlo ray tracing technique.The numerical results are contrasted with empirical results available in the open literature.A significant improvement of heat transfer is derived when the Reynolds number varies in the range 2.57×104≤ Re≤ 2.57×105,the tube-side Nusselt number increases from 1.3 to 1.8 times,also the metallic nanoparticles improve heat transfer greatly than other nanoparticles,combining both mechanisms provides better heat transfer and higher thermo-hydraulic performance.
