Experimental study of natural convection heat transfer from a nonuniformly heated flat plate simulating PV panel

Shuang-Ying Wu,Ying-Ying Wu,Lan Xiao,Zhen Yang 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1

In view of the characteristic of Photovoltaic (PV) conversion, an experimental study has been conducted to investigate the natural convection heat transfer from a flat plate. In order to simulate the real PV cells, three electrical heating circuits were employed to achieve a linear nonuniform heat flux boundary condition. The major parameters, such as the gradient parameter of heat flux k, tilt angle θ and heat flux q w were introduced to analyze their influence on heat transfer ability. Both the local temperature distribution and the overall trend of Nusselt number have been presented. Comparing with the uniform thermal boundary condition, the results show that the local convection heat transfer coefficient is fluctuated at the positions where heat flux has changed. When gradient parameter of heat flux increases, the difference of local convection heat transfer coefficient at the top of the plate between tilt angle θ = 0° and 90° becomes smaller. Moreover, it is observed that the gradient parameter of heat flux has a promotion effect on average convection Nusselt number at larger tilt angle, but the effect becomes complex as tilt angle is smaller. Finally, a correlation combining all significant factors has been put forward to estimate the natural convection heat transfer.

Effect of thermal radiation on convection heat transfer in cooling channel of photovoltaic thermal system

Shuang-Ying Wu,Ying-Ying Wu,Lan Xiao 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.8

The effect of thermal radiation on convection heat transfer in flat-box type cooling channel of photovoltaic thermal system with tilt angleof 30 degree was studied by 3D numerical simulation under constant heat flux boundary condition. The temperature contours andvelocity fields of fluid near the outlet were obtained. The variations of wall temperature and convection Nusselt number along flow directionfor all the separate walls composing the cooling channel were compared and analyzed. The results show that due to thermal radiation,the deflection of the maximum velocity region to heated top wall, together with the asymmetry of temperature field is weakened. Fornatural convection, radiation promotes the formation of multi-vortices. For mixed convection, heat transfer on all the cooling channelwalls is enhanced under the condition of lower heat flux while heat transfer on heated top wall is deteriorated when the heat flux is relativehigh. Also, pressure re-rising is promoted by thermal radiation.

The role of outlet temperature of flue gas in organic Rankine cycle considering low temperature corrosion

Shuang-Ying Wu,Chun Li,Lan Xiao,You-Rong Li,Chao Liu 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.12

This paper gives a special focus on the role of outlet temperature of flue gas (Tgo) in organic Rankine cycle (ORC) system for low temperatureflue gas waste heat recovery. The variations of performance indicators: net work (Wnet), exergy efficiency (ηex) and levelizedenergy cost (LEC) versus Tgo are discussed. Considering the corrosion of low temperature flue gas, the necessity and reasonability oflimiting Tgo at its minimum allowed discharge temperature (355.15 K) are analyzed. Results show that there exist optimal Tgo (Tgo,opt) forWnet and LEC, while Tgo,opt for ηex does not appear under the investigated range of Tgo. Moreover, the Tgo,opt for Wnet is always lower than355.15 K, the Tgo,opt for LEC, despite being greater than the one for Wnet, is just slightly higher than 355.15 K when the inlet temperatureof flue gas varies from 408.15 K to 463.15 K. For the waste heat recovery of low temperature flue gas, it is reasonable to fix Tgo at 355.15K if Wnet or LEC is selected as primary performance indicator under the pinch point temperature difference of evaporator (ΔTe) below 20K.

Parametric study on flow and heat transfer characteristics of porous wick evaporator based on AMTEC

Shuang-Ying Wu,Bao-Xi Cao,Lan Xiao,You-Rong Li 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.3

By establishing an axial symmetric invariable temperature phase change interface model of porous wick evaporator based on alkali metal thermal-to-electric converter (AMTEC), a parametric study has been implemented to explore the impact of effective thermal conductivity model, working fluid, wick material, porosity and particle size of porous wick on the flow and heat transfer characteristics. The results indicate that the inner surface temperature profile of wick is closely dependent on effective thermal conductivity models; it is the minimum for series model while the highest for parallel model. The inner surface temperature of wick with Na-K alloy as working fluid is obviously lower than that with sodium or potassium as working fluid. The wick made of refractory ceramics makes the minimum of inner surface temperature, while the one with nickel appears the highest temperature. Increasing the porosity can reduce the pressure drop in the wick, but also increases the temperature of evaporator.

Numerical investigation on developing laminar forced convective heat transfer and entropy generation in an annular helicoidal tube

Shuang-Ying Wu,Su-Jun Chen,Lan Xiao,You-Rong Li 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.6

In this study, numerical investigations are conducted for forced convective heat transfer in an annular helicoidal tube under uniform wall temperature condition for laminar flow including developing region. The numerical computations reveal the developments and distributions of heat transfer and flow fields in the annular helicoidal tube when the outer tube wall is heated and the inner tube wall is insulated. The effects of Reynolds number, curvature ratio, and coil pitch on the circumferential average friction factor and Nusselt number at different axial locations, and the non-dimensional entropy generation number of laminar convection in an annular helicoidal tube are investigated. In addition, the differences of flow and heat transfer characteristics between the annular helicoidal tube and circular helicoidal tube are also described.

Exergo-economic analysis of finned tube for waste heat recovery including phase change heat transfer

Shuang-Ying Wu,Jing-Rui Jiu,Lan Xiao,You-Rong Li,Chao Liu,Jin-Liang Xu 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.11

In this paper, an exergo-economic criterion, i.e. the net profit per unit transferred heat load, is established from the perspective of exergy recovery to evaluate the performance of finned tube used in waste heat recovery. Also, the dimensionless exergy change number is introduced to investigate the effect of the flow (mechanical) exergy loss rate on the recovered thermal exergy. Selecting R245fa as a working fluid and exhaust flue gas as a heat source, the effects of the internal Reynolds number Rei, the external Reynolds number Reo, the unit cost of thermal exergy εq, the geometric parameter of finned tube ηoβ and the phase change temperature Tv etc. on the performance of finned tube are discussed in detail. The results show that the higher Tv and ηoβ, and lower Rei may lead to the negligible flow (mechanical) exergy loss rate. There exists an optimal value of Rei where the net profit per unit transferred heat load peaks, while the variations of Reo, εq and Tv cause monotonic change of the net profit per unit transferred heat load. The phase change temperature exerts relatively greater influence on the exergo-economic performance of finned tube in comparison with other parameters. And there exists a critical phase change temperature, where the net profit per unit transferred heat load is equal to zero.

The critical external heat source conditions for subcritical ORC system based on thermo-economics

Lan Xiao,Shuang-Ying Wu,Chun Li 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.8

Considering the thermodynamic and economic constraints simultaneously, the critical external heat source conditions available for sub-ORC systems with pure or zeotropic mixture working fluids are clarified. The critical external heat source conditions include the maximum allowed heat source temperature T gi,max , the minimum allowed heat source temperature T gi,min and the minimum allowed heat source mass flow rate m g,min . The results show that, no matter using pure working fluid or zeotropic mixture working fluid, the maximum allowed heat source temperature T gi,max increases linearly with the increasing of its critical temperature T cr . For the pure working fluid, the minimum allowed heat source temperature T gi,min is not sensitive to the variation of T cr . While, for the zeotropic mixture working fluid, the minimum allowed heat source temperature T gi,min firstly falls down, then rises up along with the increasing of T cr . An increase in mass flow rate of heat source causes enlarged range of heat source temperature available. And the minimum allowed heat source mass flow rate m g,min reduces sharply with the increase of heat source temperature.

Flow and heat transfer characteristics of alkali metal liquid in a pipe with inscribed regular polygon porous media

Lan Xiao,Hai-Yan Wu,Shuang-Ying Wu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.4

Flow and heat transfer characteristics of alkali metal liquid in a pipe with inscribed regular polygon porous media are numerically investigated under local thermodynamic equilibrium condition. The effects of filling ways including inscribed regular polygon filling way and segmented inscribed square filling way under different Darcy number (10 -6 ≤Da≤10) are analyzed. The results show that, the velocity near the wall is violently changed by inserting partially filled porous media due to the high resistance of porous media. For inscribed regular polygon filling way, the PEC value of inscribed square is the maximum, which makes it optimal for heat transfer enhancement. For segmented inscribed square filling way, the average Nusselt number increases as the filled ratio increases while decreases as the unit length increases. Owning to the dominant role of the entrance effect, the smaller the unit length is, the larger the PEC is. The PEC of 5:5 segmented filling way is found superior to other filling ways, possibly because the heat transfer enhancement and flow resistance control reach an excellent balance for that case.

Neural correlates of the popular music phenomenon: evidence from functional MRI and PET imaging

Chen, Qiaozhen,Zhang, Ying,Hou, Haifeng,Du, Fenglei,Wu, Shuang,Chen, Lin,Shen, Yehua,Chao, Fangfang,Chung, June-key,Zhang, Hong,Tian, Mei Springer-Verlag 2017 European journal of nuclear medicine and molecular Vol.44 No.6

<P>Popular music Gangnam Style can arouse pleasure experience and strong emotional response. The left putamen is positively correlated with the mood arousal level score under the Gangnam Style condition. Our results revealed characteristic patterns of brain activity associated with Gangnam Style, and may also provide more general insights into the music-induced emotional processing.</P>