Current Flow of Chinese Animation Movies and Development of Shanghai Art Film Production

Gong Jianying(貢建英) 한국만화애니메이션학회 2004 한국만화애니메이션학회 학술대회자료집 Vol.2004 No.11

Experimental and numerical investigation of heat transfer characteristics in a square channel with various truncated ribs

Jianying Gong,Xiong Zhang,Junxiong Zeng,Tieyu Gao,Weifeng Wu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.8

Oblique ribs are widely applied to the internal cooling of turbine blades to promote the heat transfer between blade wall and coolant. In this study, the effect of several new types of truncated ribs on the heat transfer characteristics in 45° oblique rib channels is investigated experimentally and numerically. The numerical results obtained by the SST k-ω turbulence model agree well with the experimental data for the Reynolds number ranging from 10000 to 60000. The results indicate a significant entrance effect on the heat transfer in truncated rib channels. The numerical results show that ribs continuously truncated at 3.8 mm gives the best heat transfer performance among the newly truncated ribs. Compared with the original structure, the Nusselt number and heat transfer enhancement factor of newly truncated ribs increased by 24.6 % and 17.8 %, respectively. Concurrently, the friction factor is reduced by 5.1 %.

Contrastive experimental study on heat transfer and friction characteristics in steam cooled and air cooled rectangular channels with rib turbulators

Jianying Gong,Tieyu Gao,Guojun Li 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.9

The present experiment compares the heat transfer and friction characteristics in steam cooled and air cooled rectangular channels(simulating a gas turbine blade cooling passage) with two opposite rib-roughened walls. The Reynolds number (Re) whose length scale isthe hydraulic diameter of the passage is set within the range of 10000-60000. The channel length is 1000 mm. The pitch-to-rib heightratio, the channel aspect ratio and the channel blockage ratio is 10, 0.5 and 0.047, respectively. It is found that the average Nu, the averagefriction coefficient, and the heat transfer performance of both steam and air in the ribbed channels show almost the same changetrend with the increase of Re. Under the same test conditions, the average Nu of steam is 30.2% higher than that of air, the average frictioncoefficient is 18.4% higher, and the heat transfer performances of steam on the ribbed and the smooth walls are 8.4% and 7.3%higher than those of air, respectively. In addition, semi-empirical correlations for the two test channels are developed, which can predictthe Nu under the given test condition. The correlations can be used in the design of the internal cooling passage of new generation steamcooledgas turbine blade/vane.

Heat transfer and friction characteristics in steam cooled rectangular channels with rib turbulators

Jianying Gong,Tieyu Gao,Guojun Li 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.1

We studied the heat transfer and friction characteristics in steam-cooled rectangular channels with rib turbulators on W side or H sidewalls in the Reynolds number (Re) range of 10000-80000. Each of the test channels was welded by four stainless steel plates to simulatethe actual geometry and heat transfer structure of blade/vane internal cooling passage. The length of the channel L was 1000 mm, thecross section of the channel was 40 mm × 80 mm, and the pitch-to-rib height ratio p/e was kept at 10. The channel blockage ratio (W/H)was 0.047. Results showed that the Nusselt number (Nu) distributions displayed different trends at the entrance region with the increaseof Re for the rib turbulators on the W side walls. The heat transfer performance of the rib turbulators on the H side walls was about 24-27% higher than that on the W side walls at the same pumping power. In addition, semi-empirical correlations for the two cases, rib turbulatorson W side walls and rib turbulators on H side walls, were developed based on the heat transfer results, which could be used in thedesign of the internal cooling passage of new generation steam-cooled gas turbine blade/vane.

Mesoscopic investigation of frost crystal nucleation on cold surface based on the lattice-Boltzmann method

Jianying Gong,Jianqiang Hou,Liangwei Yang,Weifeng Wu,Guojun Li,Tieyu Gao 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.4

A lattice Boltzmann method (LBM) two-dimensional (2D) mesoscopic model is presented for studying the frost crystal nucleation process involved in liquid-solid phase change on a cold surface. In order to make the simulation more realistic, the actual frost crystal nucleus deformation process is considered in this model. The simulation results agree well with our experimental results. Detailed analysis was made on the dynamic behavior of liquid-solid phase change and heat transfer happening in the frost crystal nucleation process. Results are presented for the evolution law of frost crystal nucleus deformation, dynamic solid-liquid phase change process as well as the dynamic distribution of frost nucleus interior temperature during frost crystal nucleation. In addition, the occurrence of frost crystal nucleus deformation is explained by the theory of crystal growth. Finally, where and why the initial position of frost crystal growth happens is also revealed. Furthermore, the reason why the hydrophobic surface can delay the droplet freezing and why the frost growth is faster on the hydrophobic surface after the droplet is frozen is analyzed based on this model.

Modeling the airside dynamic behavior of a heat exchanger under frosting conditions

Tieyu Gao,Jianying Gong 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.10

A general distributed model with a non-steady-state heat exchanger model coupled with a frost model was developed to study the dynamic behavior of an airside heat exchanger in an air-to-water heat pump heater/chiller unit. The effects of water vapor diffusion and uneven fin temperature distribution were considered. The model was found to agree well with reported experimental results. Compared with the routine model, the present model has higher precision of frost layer thickness especially on the fin surface. Results include the propagation of frost formation along the tube and its effect on the dynamic characteristics of refrigerant, air, and tube sides. According to the results, the temperature difference between air and tube surface temperature was proposed to be the main driving force of frosting. Tube surface temperature is the most important factor affecting frosting when there is little variation in air humidity. Frost at the fin base was found to be thicker than that at the fin tip due to the fact that the frost layer grows faster with lower tube surface temperature.

Effects of operating conditions on flow and heat transfer characteristics of mist cooling in a square ribbed channel

Tieyu Gao,Junxiong Zeng,Qingfeng Xia,Jun Li,Jianying Gong 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3

Flow and heat transfer characteristics of mist/steam cooling and mist/air cooling in a square channel with 60º rib angle are numerically investigated for a wide range of operating parameters, such as Reynolds number ranging from 10000 to 60000, reference pressure from 0.1 MPa to 0.5 MPa and inlet temperature from 120 °C to 200 °C. Also, the heat transfer characteristics of mist cooling are compared with the corresponding cases of single-phase coolant such as steam and air. The 3D steady Reynolds-averaged Navier–Stokes equations with a standard k-ω turbulent model are solved by using commercial software ANSYS CFX. The CFD model has been validated by experimental data for steam-only case with a good agreement. In addition, distribution and evolution of secondary flow in the ribbed channel are analyzed by vortex core technology and their effects on heat transfer are investigated for these four coolants. The results show that the strength of longitudinal secondary flow has a significant influence on the Nusselt number (Nu) distribution on the ribbed surface. The Nusselt number distribution is periodical in stream-wise direction for steam and air cooling, whereas Nusselt number gradually increases for mist/steam and mist/air cooling. It is found that longer travelling distance of droplets in the ribbed channel result in a higher heat transfer enhancement of mist cooling. The heat transfer characteristics of mist cooling are insensitive to pressure, but inversely correlated with coolant inlet temperature compared with steam and air cooling for the tested parameter ranges.

Effects of rib angle and rib orientation on flow and heat transfer in two-pass ribbed channels

Tieyu Gao,Junxiong Zeng,Jiangnan Zhu,Jun Li,Jianying Gong 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1

The secondary flows generated by the rib and the U-shaped bend play a vital role in heat transfer enhancement in two-pass ribbed channels. This paper focuses on the combined effects of rib orientations (N-type and P-type) and rib angles (from 30º to 75º) on flow and heat transfer in two-pass ribbed channels. The 3D steady Reynolds-averaged Navier–Stokes equations coupled with SST k-ω model are solved by using commercial software ANSYS CFX. The CFD model has been validated by experimental data with a good agreement. In addition, the comprehensive evolution of secondary flows and its effect on heat transfer are analyzed in detail by using vortex core technology. The results indicate that the key factor for local heat transfer enhancement is to transport more secondary flows into downstream passage without weakening local secondary flow and energy dissipation of upstream secondary flow. Furthermore, the rib orientation in passage 2 should consider the influence of rib angle so that the local main flow secondary flow has the same rotational direction with the most powerful upstream secondary flow to reduce the energy loss and speed up the growth of local main flow secondary flow as much as possible.