The flow maldistribution and the effect of different inlet configuration on the flow distribution in platefin heat exchangers were studied experimentally. It is found that the flow maldistribution is serious because o...The flow maldistribution and the effect of different inlet configuration on the flow distribution in platefin heat exchangers were studied experimentally. It is found that the flow maldistribution is serious because of the defects of inlet configurations, while the inlet configuration and Reynolds number are the main factors affecting the flow distribution. The improved inlet configurations, which are the header with a two-stage distributing configuration and the guide vane with a fluid complementary cavity were proposed and tested in this paper. The experimental results show that the improved inlet configurations can effectively improve the performance of flow distribution in heat exchangers.展开更多
Mathematical model of cross type multi-stream plate-fin heat exchanger is established.Meanwhile,mean square error of accumulative heat load is normalized by dimensionless,and the equations of temperature-difference un...Mathematical model of cross type multi-stream plate-fin heat exchanger is established.Meanwhile,mean square error of accumulative heat load is normalized by dimensionless,and the equations of temperature-difference uniformity factor are improved.Evaluation factors above and performance of heat exchanger are compared and analyzed by taking aircraft three-stream condenser as an example.The results demonstrate that the mean square error of accumulative heat load is common result of total heat load and excess heat load between passages.So it can be influenced by passage arrangement,flow inlet parameters as well as flow patterns.Dimensionless parameter of mean square error of accumulative heat load can reflect the influence of passage arrangement to heat exchange performance and will not change dramatically with the variation of flow inlet parameters and flow patterns.Temperature-difference uniformity factor is influenced by passage arrangement and flow patterns.It remains basically unchanged under a certain range of flow inlet parameters.展开更多
Flow characteristics in the entrance of plate-fin heat exchanger have been investigated by means of particle image velocimetry (PIV). The flow field was measured using the two-frame cross-correlation technique. Stream...Flow characteristics in the entrance of plate-fin heat exchanger have been investigated by means of particle image velocimetry (PIV). The flow field was measured using the two-frame cross-correlation technique. Streamline and velocity contour graphs at different cross-sections were obtained in the experiment. The experimental results indicate that flow maldistribution in the conventional header is very serious, while the improved header configuration with punched baffle can effectively improve the uniformity. The flow maldistribution parameter in plate-fin heat exchanger has been reduced from 1.21 to 0.21, and the ratio of the maximum velocity to the minimum is reduced from 23.2 to 1.8 by install-ing the punched baffle. The results suggest room for the optimum design of plate-fin heat exchanger.展开更多
Objective To investigate the flow distribution in plate fin heat exchangers and optimize the design of header configuration for plate fin heat exchangers. Methods A mathematical model of header was proposed. The e...Objective To investigate the flow distribution in plate fin heat exchangers and optimize the design of header configuration for plate fin heat exchangers. Methods A mathematical model of header was proposed. The effects of the header configuration on the flow distribution in plate fin heat exchangers were investigated by CFD. The second header configuration with a two stage distributing structure was brought forward to improve the performance of flow distribution. Results It is found that the flow maldistribution is very serious in the direction of header length for the conventional header used in industry. The numerical predictions indicate that the improved header configurations can effectively improve the performance of flow distribution in plate fin heat exchangers. Conclusion The numerical simulation confirms that CFD should be a suitable tool for predicting the flow distribution. The method has a wide variety of applications in the design of plate fin heat exchangers.展开更多
A two-step method for stacking arrangement of passages in multistream plate-fin heat exchanger is proposed. The first step (predict step) is to initialize the arrangement according to a local-balance principle, and th...A two-step method for stacking arrangement of passages in multistream plate-fin heat exchanger is proposed. The first step (predict step) is to initialize the arrangement according to a local-balance principle, and the second step (correct step) is to resadust the arrangement according to the results of differential computation of the temperature distribution. The computer implementation process of the local balance principle is described in detail and three examples are illustrated to show the feasibility of this principle. A subroutine program is provided to facilitate the reader to adopt this principle.展开更多
As the power density of the power transmission device increases,heat exchangers are required to dissipate more heat and provide better flow resistance in the limited space of the vehicle.In this study,the synergy mech...As the power density of the power transmission device increases,heat exchangers are required to dissipate more heat and provide better flow resistance in the limited space of the vehicle.In this study,the synergy mechanism of the temperature field,pressure field,and velocity field in the serrated fin channel of the plate-fin heat exchanger(PFHX)was thoroughly analyzed under the guidance of the three-field synergy principle.This study also quantitatively revealed the distribution of the angleθbetween the temperature gradient and velocity,and the angleαbetween the pressure gradient and velocity.For the regions in the channel whereθwas too large(i.e.,poor synergy between temperature and velocity fields)andαwas too small(i.e.,poor synergy between pressure and velocity fields),high-efficiency and low-resistance fin structures were proposed.The performance improvement of the new structures was quantified using the comprehensive heat transfer and flow resistance performance evaluation plot in the three-field synergy standard.The results indicate that the new structures improve the synergy of the three fields in the channel.When the air velocity is 15 m s^(-1),the average synergy angleθmbetween the temperature gradient and the velocity of the two structures,changing the inlet flow direction and the slotted fin,decreases from 83.4° to 80.3° and 82.8°,respectively.The outlet temperature increases by 2.3 and 1.6 K,respectively,compared to the basic structure,indicating enhanced the heat transfer of the PFHX.By changing the shape of the fin cross-section,the average synergy angleαmbetween the pressure gradient and the velocity increased from 143.6°to 150.8°,whileθmincreased by only 0.6°.The pressure loss was reduced by 15.2% compared to the basic structure,resulting in a significant decrease in pressure drop while maintaining essentially the same heat transfer performance.Meanwhile,the optimized PFHX can increase the heat transfer rate by 0.2%–8% under identical pump power.This work provides guidance on selecting high-efficiency and low-resistance vehicle-mounted PFHXs.展开更多
基金Supported by the Doctoral Foundation of Xi'an Jiaotong University (No. DFXJTU2002-12) the Foundation for Excellent Doctoral Dissertation Author by Minister of Education, China (No. 199933).
文摘The flow maldistribution and the effect of different inlet configuration on the flow distribution in platefin heat exchangers were studied experimentally. It is found that the flow maldistribution is serious because of the defects of inlet configurations, while the inlet configuration and Reynolds number are the main factors affecting the flow distribution. The improved inlet configurations, which are the header with a two-stage distributing configuration and the guide vane with a fluid complementary cavity were proposed and tested in this paper. The experimental results show that the improved inlet configurations can effectively improve the performance of flow distribution in heat exchangers.
文摘Mathematical model of cross type multi-stream plate-fin heat exchanger is established.Meanwhile,mean square error of accumulative heat load is normalized by dimensionless,and the equations of temperature-difference uniformity factor are improved.Evaluation factors above and performance of heat exchanger are compared and analyzed by taking aircraft three-stream condenser as an example.The results demonstrate that the mean square error of accumulative heat load is common result of total heat load and excess heat load between passages.So it can be influenced by passage arrangement,flow inlet parameters as well as flow patterns.Dimensionless parameter of mean square error of accumulative heat load can reflect the influence of passage arrangement to heat exchange performance and will not change dramatically with the variation of flow inlet parameters and flow patterns.Temperature-difference uniformity factor is influenced by passage arrangement and flow patterns.It remains basically unchanged under a certain range of flow inlet parameters.
基金Supported by the Foundation for Excellent Doctoral Dissertation Author by Ministry of Education of China (No.199933).
文摘Flow characteristics in the entrance of plate-fin heat exchanger have been investigated by means of particle image velocimetry (PIV). The flow field was measured using the two-frame cross-correlation technique. Streamline and velocity contour graphs at different cross-sections were obtained in the experiment. The experimental results indicate that flow maldistribution in the conventional header is very serious, while the improved header configuration with punched baffle can effectively improve the uniformity. The flow maldistribution parameter in plate-fin heat exchanger has been reduced from 1.21 to 0.21, and the ratio of the maximum velocity to the minimum is reduced from 23.2 to 1.8 by install-ing the punched baffle. The results suggest room for the optimum design of plate-fin heat exchanger.
文摘Objective To investigate the flow distribution in plate fin heat exchangers and optimize the design of header configuration for plate fin heat exchangers. Methods A mathematical model of header was proposed. The effects of the header configuration on the flow distribution in plate fin heat exchangers were investigated by CFD. The second header configuration with a two stage distributing structure was brought forward to improve the performance of flow distribution. Results It is found that the flow maldistribution is very serious in the direction of header length for the conventional header used in industry. The numerical predictions indicate that the improved header configurations can effectively improve the performance of flow distribution in plate fin heat exchangers. Conclusion The numerical simulation confirms that CFD should be a suitable tool for predicting the flow distribution. The method has a wide variety of applications in the design of plate fin heat exchangers.
文摘A two-step method for stacking arrangement of passages in multistream plate-fin heat exchanger is proposed. The first step (predict step) is to initialize the arrangement according to a local-balance principle, and the second step (correct step) is to resadust the arrangement according to the results of differential computation of the temperature distribution. The computer implementation process of the local balance principle is described in detail and three examples are illustrated to show the feasibility of this principle. A subroutine program is provided to facilitate the reader to adopt this principle.
基金supported by the National Science and Technology Major Project of China(Grant No.J2019-Ⅲ-0021-0065)the Inner Mongolia Science and Technology Major Project(Grant No.2021ZD0036)the Key R&D Special Program of Shaanxi Province(Grant No.2022GXLH-01-04)。
文摘As the power density of the power transmission device increases,heat exchangers are required to dissipate more heat and provide better flow resistance in the limited space of the vehicle.In this study,the synergy mechanism of the temperature field,pressure field,and velocity field in the serrated fin channel of the plate-fin heat exchanger(PFHX)was thoroughly analyzed under the guidance of the three-field synergy principle.This study also quantitatively revealed the distribution of the angleθbetween the temperature gradient and velocity,and the angleαbetween the pressure gradient and velocity.For the regions in the channel whereθwas too large(i.e.,poor synergy between temperature and velocity fields)andαwas too small(i.e.,poor synergy between pressure and velocity fields),high-efficiency and low-resistance fin structures were proposed.The performance improvement of the new structures was quantified using the comprehensive heat transfer and flow resistance performance evaluation plot in the three-field synergy standard.The results indicate that the new structures improve the synergy of the three fields in the channel.When the air velocity is 15 m s^(-1),the average synergy angleθmbetween the temperature gradient and the velocity of the two structures,changing the inlet flow direction and the slotted fin,decreases from 83.4° to 80.3° and 82.8°,respectively.The outlet temperature increases by 2.3 and 1.6 K,respectively,compared to the basic structure,indicating enhanced the heat transfer of the PFHX.By changing the shape of the fin cross-section,the average synergy angleαmbetween the pressure gradient and the velocity increased from 143.6°to 150.8°,whileθmincreased by only 0.6°.The pressure loss was reduced by 15.2% compared to the basic structure,resulting in a significant decrease in pressure drop while maintaining essentially the same heat transfer performance.Meanwhile,the optimized PFHX can increase the heat transfer rate by 0.2%–8% under identical pump power.This work provides guidance on selecting high-efficiency and low-resistance vehicle-mounted PFHXs.
