科创中国

Vapor flow effect on falling film evaporation of refrigerant R134a outside horizontal tube bundle is investigated experimentally. The test space is a cube with a rectangular cross section of 0.575m (length) × 38.8mm (width). The tested tube is designed for enhancing pool boiling, which has an external fin density of 45fpi (fins per inch), and an outside diameter of 19.05mm. The transverse narrowest bundle clearance is 3.25mm where the vapor velocity can be adjusted in the range of 0 to 3.1m/s. R134a vapor is distributed uniformly from the bottom of tube array to the test section. The liquid falling film flow rate ranges from 0.07 to 0.2kg/m·s. Experiment is firstly conducted at saturation temperature of 6°C without the effect of the additional vapor flow at the heat flux of 20, 60, 100 and 180kW/m² (for the first tube row). Vapor effect experiment was carried out at three heat fluxes 20, 40 and 60kW/m². For the falling film flow rate of 0.07 kg/m·s and heat flux of 40kW/m², it is found that at the vapor velocity less than 0.5 m/s, vapor velocity has no significant effect on the falling film evaporation heat transfer. In addition, it is found that the vapor velocity effect is also dependent on the falling film flow rate: within the variation range of vapor velocity tested the variation patterns of the eight tubes are different at different flow rate.

Wen Tao Ji;Chuang Yao Zhao;雅玲 何;Guan Nan Xi;文铨 陶

2014

Heat pipe radiator was experimental and numerical studied to solve the cooling problem of high power LEDs for street lamp. Firstly, the surface temperature of the lamp housing was measured by IR sensor then surface temperature of the heat pipe radiator was also measured. Experimental results show that the average temperature of the heat pipe radiator is about 38°C and the distribution is even. So heat pipe radiator is applicable for high power LED street lamp and is one of the methods for solving the heat dissipating problem. Secondly, a mathematical model was built to simulate the distribution characteristics of the flow and temperature fields. Simulation results agree well with the experimental results and therefore the model is proved to be reliable. The results also suggest that there are several disadvantages of the heat dissipation fins. Optimizing designs and methods are discussed and put forward finally.

Rongji Xu;雅玲 何;Fuqing Cui;Yu Wang;Xun Xu

Bandaoti Guangdian/Semiconductor Optoelectronics

2010-6

Numerical simulations were carried out to study the impacts of various baffle inclination angles on fluid flow and heat transfer of heat exchangers with helical baffles. The simulations were conducted for one period of seven baffle inclination angles by using periodic boundaries. Predicted flow patterns from simulation results indicate that continual helical baffles can reduce or even eliminate dead regions in the shell side of shell-and-tube heat exchangers. The average Nusselt number increases with the increase of the baffle inclination angle α when α < 30°. Whereas, the average Nusselt number decreases with the increase of the baffle inclination angle when α > 30°. The pressure drop varies drastically with baffle inclination angle and shell-side Reynolds number. The variation of the pressure drop is relatively large for small inclination angle. However, for α > 40°, the effect of α on pressure drop is very small. Compared to the segmental heat exchangers, the heat exchangers with continual helical baffles have higher heat transfer coefficients to the same pressure drop. Within the Reynolds number studied for the shell side, the optimal baffle inclination angle is about 45°, with which the integrated heat transfer and pressure drop performance is the best. The detailed knowledge on the heat transfer and flow distribution in this investigation provides the basis for further optimization of shell-and-tube heat exchangers.

Yong Gang Lei;雅玲 何;Rui Li;Ya Fu Gao

Chemical Engineering and Processing: Process Intensification

2008-11

Surface active agent (SAA) was used to improve nanomaterial dispersion during preparation process of carbonate salt/nanomaterial composite phase change material (CPCM) by solution evaporation method. In order to investigate the effects of SAA on CPCM thermal performance, three kinds of PCM samples were prepared and their thermal performances were characterized. The results show that nanomaterial dispersion greatly affects CPCM thermal performance. For CPCM without SAA, its thermal performance is weakened instead of enhanced due to nanomaterial aggregation and the weakening phenomenon is more obvious when nanomaterial has larger specific surface area. SAA decomposes during high temperature CPCM working process. And the effect of SAA on CPCM thermal performance has duality: on the positive side, SAA can improve nanomaterial dispersion and enhance CPCM thermal performance; on the negative side, SAA decomposition products may weaken CPCM thermal performance. So, SAA and its mass fraction should be carefully selected. Sodium dodecyl sulfate (SDS) is a better SAA for high temperature nano-CPCM and a high mass ratio of SDS to nanomaterial is recommended. With mass ratio of SAA to nanomaterial 10:1, PCM thermal conductivity can be enhanced up to 58.75% by adding 1. wt.% multi-walled carbon nanotubes.

于兵 陶;C. H. Lin;雅玲 何

Applied Energy

2015-10-5

In this paper, the experimental study on wall temperature distribution of a Stirling type pulse tube refrigerator has been carried out. The influences of structural and working parameters on performance of SPTR have been studied, especially on wall temperature distributions of pulse tube and regenerator. Through a number of experiments, the rule of wall temperature distributions and the relationship of it's dependence on structural parameters and working parameters has been found, giving some hints to further improve the performance of a given SPTR, and DC flow has also been validated from temperature distribution curve.

Y. W. Liu;雅玲 何;J. Huang;X. Z. Li;C. Z. Chen

2005

The dust particles contained in the industrial flue gas are discharged from many industrial factories, which have seriously polluted the air and endangered the health of not only human beings but also the animals living on the earth, so they are gaining much attention all over the world. In order to provide possible solutions to the above problems, many filtration technologies have been proposed and developed. As a promising filtration method, the granular bed filter (GBF) based filtration technology has been widely used in the filtration of high temperature flue gas with complex components in recent years owing to its advantages of high efficiency, low cost, simplicity, and resistance to high temperature and high pressure. Inspired by the development of numerical simulation method and experimental technology, the performance of GBF has been optimized and improved, much deeper insight of the formation and growth of dust particles has been obtained. This review focus on the basic principle of the GBF and its performance investigated by numerical and experimental methods. The reviews and outlooks of investigations on the influence factors of GBF filtration performance and the development of performance optimization method of the GBF were also presented. In addition, the microscale mechanism of the agglomeration and growth of dust particles contained in the industrial flue gas during the filtration in the GBF by means of molecular dynamics simulation were introduced, the numerical and experimental method of dust particles filtration in GBF were also discussed. Finally, available recommendations for future research of GBF are proposed, which is expected to be helpful for actual industrial engineering applications.

Yinsheng Yu;于兵 陶;Fei Long Wang;Xi Chen;雅玲 何

Separation and Purification Technology

2020-11-15

In present paper, a novel airfoil printed circuit heat exchanger (PCHE) with dimples was proposed as heat exchanger for supercritical carbon dioxide (S-CO₂) Brayton cycles in the concentrated solar power plant. Firstly, a three-dimensional flow and heat transfer numerical model was developed and validated. Then, the number and arrangement of dimples were optimized, and an optimized airfoil PCHE with dimples was obtained and compared with airfoil PCHE without dimples. The results indicated that airfoil PCHE with dimples achieved the best comprehensive performance when a unit volume had two dimples which were in staggered arrangement with airfoil fins. In the range of Reynolds number studied, the comprehensive performance can be improved by 3.58.7% after replacing the original PCHE by the novel. The above results indicate that the proposed PCHE can achieve good performance in the heat transfer of S-CO₂, and can be used in solar power plant.

Hong Yuan Shi;Hua Liu;Jian Guo Xiong;Yu Qiu;雅玲 何

Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics

2019-4-1

In the paper, coupling calculation of conduction, convection and surface radiation in hollow brick walls can be effectively deal with by original computation code. The equivalent thermal conductivity of hollow brick walls have been predicted numerically under exterior insulation condition. The change of equivalent thermal conductivity of hollow brick of different hole number and arrangement under exterior insulation has been observed to emphasis the influence. The simulation results provide valuable data for the hollow brick design under exterior insulation.

Jing Ma;Lin Ping Li;文铨 陶;雅玲 何

Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics

2012-11

With the rapid increase of heat dissipation level in modern electronic equipments, the thermal management of electronic equipments becomes increasingly important. The remote radio unit (RRU) has been widely used in the third-generation mobile communication technology, and the cooling design is important to maintain the reliability and functionality of an RRU. The heat transfer and flow characteristics of an RRU are experimentally and numerically investigated under a natural convection condition. The experimental results are in good agreement with numerical results. The effects of fin density, vapor chamber, pin-fin heat sink, and surface emissivity on the heat transfer performance of the RRU are numerically investigated. The results indicate that the optimal fin number for the RRU with the given dimensions is around 25. The vapor chamber alleviates the heat spot problem on the heat sink base and improves the average heat transfer coefficient by 16.6%. The pin-fin heat sink increases the average heat transfer coefficient by 11.2%, while it decreases the heat transfer surface area by 38.6%. The augmentation of surface emissivity slightly improves the heat transfer performance of the RRU.

P. Chu;雅玲 何;R. J. Xu;H. Han

Journal of Enhanced Heat Transfer

2011

The lattice Boltzmann method (LBM), a mesoscopic method between the molecular dynamics method and the conventional numerical methods, has been developed into a very efficient numerical alternative in the past two decades. Unlike conventional numerical methods, the kinetic theory based LBM simulates fluid flows by tracking the evolution of the particle distribution function, and then accumulates the distribution to obtain macroscopic averaged properties. In this article we review some work on LBM applications in engineering thermophysics: (1) brief introduction to the development of the LBM; (2) fundamental theory of LBM including the Boltzmann equation, Maxwell distribution function, Boltzmann-BGK equation, and the lattice Boltzmann-BGK equation; (3) lattice Boltzmann models for compressible flows and non-equilibrium gas flows, bounce back-specular-reflection boundary scheme for microscale gaseous flows, the mass modified outlet boundary scheme for fully developed flows, and an implicit-explicit finite-difference-based LBM; and (4) applications of the LBM to oscillating flow, compressible flow, porous media flow, non-equilibrium flow, and gas resonant oscillating flow.

雅玲 何;Qing Li;Yong Wang;Gui Hua Tang

Chinese Science Bulletin

2009-12