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Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Computational Mechanics / Jisuan Lixue Xuebao is the property of Chinese Journal of Computational Mechanics Editorial Office, Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Technetium molybdenum isotope is widely used in the field of nuclear medicine, and its demand accounts for about 80% of the world medical isotope demand. Irradiation in reactor is an important method for production of technetium molybdenum isotope, which is mainly produced and supplied by foreign reactors at present. Therefore, it is of great significance to realize independent production of technetium molybdenum isotope in China. Prior to the radiation study of technetium molybdenum target in reactor, an outside reactor heat transfer experiment should be conducted to verify the rationality of the irradiation device design and obtain its heat transfer characteristics, so as to ensure that the radiation of technetium molybdenum target in reactor will not endanger the safety of the target and reactor. At present, most of the studies on irradiation in reactors are not equipped with forced cooling conditions, and the design of radiation testing devices for natural cooling is rarely carried out. And there are few outside reactor verification experiments for irradiation devices. If necessary outside reactor heat transfer experiments can be carried out, it will provide important technical support for the safety review and subsequent design optimization of irradiation devices. The nuclear heat release generated by the target during irradiation in the reactor test needs to be dissipated by natural convection heat transfer. In order to verify the heat dissipation capacity of the target irradiation device, it is necessary to carry out the heat transfer verification test outside the reactor. In this paper, a natural cooling of technetium molybdenum target irradiation device was designed, and an outside reactor heat transfer test platform was designed to carry out an outside reactor heat transfer verification experiment. The temperature distribution of the experimental section under different heat fluxes, different simulated target diameters and different irradiation device structures was compared and analyzed. The analysis shows that the experiment covers the maximum heat flux of the actual situation inside the reactor, and there is no underheated boiling in this power range, which proves the safety of the designed irradiation device. The design of the diversion tube in the irradiation device can delay the underheated boiling point to 1.1 times of the original thermal power and improve the natural circulation capacity of the device. The increasing of ambient temperature in a certain range is conducive to the enhancement of natural convection heat transfer ability.

Lithium niobate film on insulator (LNOI) is increasingly applied in the field of key devices in the new generation of information technology. With the development of the techniques of lithium niobate single crystal thin film and photonic integrated circuits, low cost, high integration is the eternal development direction. Therefore, it is urgently needed the largescale lithium niobate crystal. In this paper, the variation of natural convection of melt in large-sized crucible as the liquid level decrease was discussed, and the growth characteristics of Z- and X-axis lithium niobate crystal were discussed. The 8-inch Zand X-axis lithium niobate crystals with the size of larger than ϕ210 mm × 50 mm were obtained. The transmission of the spectral range of 380 ~ 3 300 nm is more than 70% for 1 mm thick X-axis lithium niobate wafers. The chip moire pattern images show the presence of refractive index ripple defects in the crystal, indicating that the quality of the crystal still needs improvement. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to consider the influence of thermal radiation and winding insulation paper on the temperature field of transformer natural convection in practice, a physical calculation model of transformer hot-spot and temperature-rise including gasket, insulation paper cylinder, pressing plate, winding insulation paper and black body thermal radiation was established based on an oil immersed transformer SSZ20- 63000/ 110. The influence of thermal radiation and winding insulation paper on the temperature field of transformer natural convection was studied through a finite element method. The results show that in the case of natural convection, thermal radiation will make the winding temperature of hot-spot and temperature-rise slightly, while the winding surface insulating paper will make the winding temperature of hot-spot and temperature-rise significantly. The thermal radiation will not affect the distribution of hot-spot, while the winding insulation paper will make the distribution of hot-spot move down. Although the thermal radiation has little effect on the temperature of hot-spot of the winding, it has a greater effect when considered together with the winding insulating paper. It can be seen that the thermal radiation and winding insulation layer should not be ignored in the simulation calculation, otherwise the difference with the actual value is too large. [ABSTRACT FROM AUTHOR]

The effect of the arrangement of thermoelectric cooler （TEC） on the natural convection characteristics of air in the cooling chamber of airborne avionics is studied by experimental research and numerical simulation. The results show that when the air is cooled, its temperature decreases while its density increases, and it begins to sink at a slow speed. Its motion form gradually transitions from deformation to rotation. It is more beneficial to the development of flow field to arrange all the TECs at the top of the chamber. However, when the air sinks to the bottom of the cooling chamber, it is easy to produce oscillation solutions, fork flow and secondary flow, and the flow enters the chaotic state. Through comparative analysis of six design cases, the best arrangement of TEC in the cooling chamber of the airborne avionics with the minimum temperature inhomogeneity coefficient and the lowest average air temperature is given. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at the uncertaity of heat storage efficiency during the melting process of phase-change materials in the heat accumulator and the natural convection heat transfer process in the phase-change region, the influence of natural convection caused by gravity on the heat storage performance of the phase change heat storage was studied by numerical simulation with the tube-type solar phase change accumulator as the basic structure and the paraffin with 10% expanded graphite as the heat storage material. The results show that the natural convection caused by solid-liquid density difference has an obvious promoting effect on the phase change heat storage process. The heat storage time of the heat accumulator considering natural convection is nearly twice that of the heat accumulator without considering natural convection. The influence of natural convection on phase change materials in every region is different. In the early stage of melting of phase change materials, the melting rate above the innertube is faster due to the influence of natural convection of liquid phase. Based on the theoretical analysis and according to the characteristics of the melting rate and melting state of the heat accumulator, the melting process is segmented, which can further understand the heat storage process of the heat accumulator and provide certain theoretical guidance for optimizing the structure of the heat accumulator.

The swimming pool-type low-temperature heating reactor (SPLTHR) has low thermal parameters, large heat capacity, and high inherent safety, so it is a suitable reactor type for nuclear heating reactors. Because the SPLTHR has a long shutdown time and the temperature difference between the cold and heat sources is small, it has certain requirements on the heat transfer capability of the passive residual heat removal system (PRHRS). Basing on the characteristics of SPLTHR, a singlephase natural circulation experiment system of PRHRS of SPLTHR was designed by H2TS (hierarchical twotiered scaling) proportion analysis method, and the flow and heat transfer characteristics of the singlephase natural circulation of the PRHRS were studied experimentally. In order to get closer to the prototype system, the center height difference of the cold and heat source of the experimental system was the same as that of the prototype system, which was 9 m. The ranges of the pool water temperature, air temperature and air flow rate in the experiment were 50-90 ℃, 15-30 ℃ and 15 000-35 000 m3/h, respectively. The results show that the experimental system designed by H2TS proportion analysis method can achieve the designed heat transfer capacity when the temperature difference between the cold and heat source is 54 ℃, which means the method is suitable for the design of singlephase natural circulation system under low temperature difference. There is flow oscillation in the system startup process, and the system can be stabilized gradually with the operation. The hot and cold water in the primary loop alternately enters the heat exchanger and aircooler, causing the driving force of the system to change, which leads to fluctuations in circulation flow rate and heat transfer capacity. The change of boundary conditions mainly affects the heat transfer capacity of the system and the time to reach stability, but has little effect on the shape and number of fluctuations before the system reaches stability. For the PRHRS heat exchanger tube bundle, which is neither a constant heat flow nor a constant wall temperature boundary, it is more appropriate to use the natural convective heat transfer temperature difference as the parameter of the Grashof number. Due to the tube bundle effect, the traditional singletube natural convection heat transfer correlations have a low predictive value for the natural convection heat transfer outside the tube bundle. According to the experimental data, the correlation of natural convection heat transfer outside the tube bundle with the applicable range 351×103

Copyright of Journal of Hebei University of Science & Technology is the property of Hebei University of Science & Technology, Journal of Hebei University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Compared with traditional materials, the phase change materials based on latent heat have higher heat storage efficiency. In order to study the heat storage mechanism of phase change materials in a square cavity, the momentum satisfying the phase change was modified based on the Boussinesq hypothesis, and the fluid-solid-thermal coupling calculation model for melting heat storage of phase change materials heated from below was established. Selecting the organic phase change paraffin, the melting experiment of paraffin under bottom constant temperature was carried out to verify the correctness of the calculation model. The results show that the melting process is dominated by conduction and natural convection heat transfer. At the initial stage of melting, the melting front is basically parallel to the heating surface, and the heat transfer is mainly provided by conduction. When the liquid thickness exceeds 2mm, the natural convection heat transfer is gradually activated to accelerate the melting rate, and forms the irregular melting front. According to the characteristics of melting front and liquid flow, the whole melting process can be divided into four stages: conductive regime, stable growth regime, transition regime and turbulent regime. In addition, the natural convective heat transfer in liquid phase has a significant size effect on the improvement of melting heat storage efficiency of phase change paraffin, and intensified with the increase of cavity size. When the square cavity size is less than 2mm, the improvement efficiency of natural convection heat transfer is less than 1% and can be ignored. [ABSTRACT FROM AUTHOR]

Capillary gravity circulation cabinet is a new type of terminal equipment dominated by natural convection for cooling in summer and heating in winter. In order to study its operation characteristics, taking an office at the air conditioning end of a capillary gravity circulation cabinet in Shanghai as an example, thermocouple and data acquisition instrument were used to continuously measure the temperature and wind speed at various indoor heights for 14 days. The characteristics of indoor flow field in summer was studied, and the thermal comfort and energy saving were evaluated. The results show that: the performance of gravity circulation cabinet air conditioning is good adaptabliity with outdoor temperature changes. The wind speed at the outlet of gravity circulation cabinet is 0.41 m/s, and that at the return air outlet is 0.20 m/s, the overall wind speed of the room 0.5 m away from the cabinet is less than 0. 10 m/s. The average temperature of indoor working area is 22.5 - 25.4°C, which meets the requirements of thermal comfort, and the temperature non-uniformity coefficient is small. The temperature at the ankle is low due to the cold air inking characteristics of gravity circulation cabinet, and the temperature non-uniformity coefficient is large. The energy utilization coefficient of capillary gravity circulation cabinet air supply mode is 12.7% higher than that of side air supply mode. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Refrigeration Technology is the property of Shanghai Society of Refrigeration and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The modeling of shell-and-tube phase change heat exchanger for the direct steam generation usually does not consider the effect of the natural convection in the previous studies, which is different from the actual physical process. To overcome this issue, a numerical model considering the natural convection is established in the current work. The condensation process of saturated steam is modeled using the VOF model and Lee model, while the melting and solidification process of phase change material (PCM) is modeled using the enthalpy-porosity method. The heat transfer characteristics of shell-and-tube phase change heat exchanger for direct steam generation are studied, with and without considering the natural convection. The research indicates that the condensing amount of the steam at the outlet increases significantly after considering the natural convection. Accordingly, the mass fraction of the steam at the outlet decreases significantly, which reduces the melting time of the PCM by about 30%. Therefore, considering the natural convection effect is necessary for the numerical simulation of the shell-and-tube phase change heat exchanger for direct steam generation. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BackgroundNatural convection, heat transfer and turbulence phenomena play important roles in the gas flow and distribution in containment during a severe accident in a nuclear reactor.PurposeThis study aims to explore the gas flow and heat transfer phenomena inside the containment during the accident, and to analyze the temperature distribution under natural convection.MethodsNumerical simulation study was conducted using the computational fluid dynamics (CFD) method. Firstly, the applicability of CFD method to analyze natural convective heat transfer phenomena in a closed space was verified by using experimental data of differential thermal cavity, and then, the geometric model corresponding to the Thermal-hydraulics, Hydrogen, Aerosols and Iodine (THAI)-TH21 experimental device was established to analyze the pressure change in the containment during the experiments and the flow heat transfer characteristics in the device after reaching the steady state.ResultsThe results show that the calculation method used in this paper has good applicability for analyzing the gas flow heat transfer in the containment. The simulated quasi-static pressure is 1.61% higher than the experimental pressure, and the temperature distribution near the cold wall is in good agreement with the experimental data, and the temperature distribution error near the hot wall surface is within 2%.ConclusionsThe study contributes to the validation and development of relevant numerical methods and models, and can provide some reference for the gas flow and distribution in the containment during the reactor accident.

The study of intraocular aqueous humor (AH) flow is helpful to understand the mechanism of some eye diseases such as glaucoma. A numerical study of AH flow inside human eyes with the computational fluid dynamics (CFD) were carried out to address the following flow processes: AH secreted in the posterior chamber by the ciliary body entering the anterior chamber through the iris?lens gap of 5 µm and 30 µm respectively, and discharging through the trabecular meshwork (TM). Detailed flow fields in different eye orientations were analyzed. Results show that, in general the intraocular pressure distributions are similar in all cases; the pres? sure in the posterior chamber is around 30 Pa higher than that in the anterior chamber with the 5 µm irislens gap, and they are almost equal with the 30 µm iris?lens gap. The pressure drop in the TM is noticeable. The pressure difference between the anterior and posterior chambers drives AH from the posterior chamber to the anterior chamber, while the temperature difference between cornea and iris surfaces causes the natural convection, which is the dominant flow in the anterior chamber. The pressure difference due to natural convection is in the magnitude of millipascal, and the higher?pressure region forms where warmer AH gathers. For the vertical orientation, warmer fluid rises along the iris surface and then turns downwards as it encounters the higher resistance in the upper TM regions. The flow then descends along the corneal surface toward the lower TM. For the upward?facing position, AH entering the pupil rises along the center line of the anterior chamber, and moves down along the cornea surface leading to axisymmetric recirculation zones. For the downward?facing position, the circulation route is opposite to that of the upward?facing position. With no buoyancy, the averaged velocity will be 1 to 2 orders of magnitude smaller than that with buoyancy. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BackgroundCOMSOL is considered to be an ideal approach to study the complicated physical processes in the corium pool because of its good simulation ability in multiphysics field.PurposeThis study aims to build a computational model by COMSOL to explore the turbulent flow field and phase change in the corium pool.MethodsBased on non-isothermal flow calculation module, the non-eutectic binary mixture of 20%NaNO3-80%KNO3 used in COrium Pool Research Apparatus (COPRA) experiment was simulated by using phase-change material model. The radiation heat transfer in the closed cavity at the top of corium pool was translated into the radiation heat transfer between the upper surface and the environment available as boundary condition in COMSOL.ResultsSimulation results show that in addition to the evident natural convection main flow, a mass of vortexes are existed in the corium pool, which lead to the thermal stratification of the corium pool in steady-state. Under the influence of natural convection main flow and gravity, the crust thickness along the cooling wall surface decreases with the vessel polar angle of corium pool increases.ConclusionsThe current computational model is helpful for severe accident mitigation system design.

3 experimental devices were designed to investigate the internal heat transfer characteristics of 2,4-dinitroanisole(DNAN)-based melt-cast explosive in slow cook-off test, and tested by scaled thermal explosion experiment. The temperature curves of internal monitoring points in the explosive under a thermal stimulus with the rate of 1 K/min were obtained. It is found that the phase-transition temperature is 73 ℃, the ignition temperature is 205 ℃, and the incomplete combustion reaction occurs after ignition. The ignition location is estimated to be on the upper half of bomb body. The changing process of internal temperature of DNAN-based melt-cast explosive is described. The internal temperature field was analyzed by numerical simulation, and the whole process of phase transition was observed. The results show that the internal temperature field of explosive in solid phase is elliptical, and its internal temperature field in liquid phase is layered. A natural convection arises inside the explosive after phase transition, which is a major factor to affect the ignition location distribution of the explosive. [ABSTRACT FROM AUTHOR]

Lattice Boltzmann method is adopted to investigate the characteristics of double-diffusive natural convection around a heated cylinder in square enclosure with coupled Soret and Dufour effects. The inner heated cylinder is located at the center of the enclosure and four surrounding walls are assumed to be low temperature and concentration. With different parameters of buoyancy ratio Br (-5 ≤ Br ≤ 5), Soret number Sr (-0.4 ≤ Sr ≤ 0.4) and Dufour number Df (-0.4 ≤ Df ≤ 0.4), the double-diffusive natural convective characteristics in the enclosure are analyzed. The results show that, at the same Br, and with the simultaneously increasing Sr and Df, both the heat and mass transfer capacities are weaken. At the same Sr and Df, the heat and mass transfer capacities are first weakened and then enhanced as Br increases. The simulation study of this physical model can provide the theoretical support for the analysis of indoor fire and pollutant diffusion. [ABSTRACT FROM AUTHOR]

Based on the original horizontal external convection test system, four sets of experimental pipe sections were designed and checked, and the thermocouple compensation of free-junction in the experimental system was also modified. The experimental results show that the stability of the experimental system is improved, the fitting curve is closer to the theoretical curve than before, and the measurement results are evenly distributed. We also discussed the effect of preheating time on the experimental results. It is found that the experimental results of 7-hour preheating time are able to meet the experimental requirements. What’ s more, the longer the preheating time is, the closer the measurement results are to the theoretical value. It showTs that the maximum error is 5.2% after modification through error analysis, which indicates good performance of the modified system. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Henan University of Science & Technology, Natural Science is the property of Editorial Office of Journal of Henan University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Air convection wall, which was developed in recent years, is a new mode of Chinese solar greenhouse (CSG) wall. Two rows of vent holes, located in the upper and the lower part of the wall, make air exchange available between the environment in CSG and the hollow layer of the wall. During the daytime, the indoor temperature in CSG rises and keeps a higher level than the air temperature inside the hollow wall. The hot air enters the hollow layer through the upper vent holes and the cold air inside the wall enters the CSG through the lower vent holes with the increasing of temperature difference between inside and outside of the hollow wall. Hence, it forms a natural air convection. Then the heat can be transfered and stored into the wall from the flowing air during the daytime. Similarly, there is a different air convection with a reverse air flow at night, which transfers heat from the hollow wall into the flowing air and releases the stored heat into the CSG environment through the vent holes. So the heat storage and release properties of the wall are strengthened by the air convection between the CSG environment and the wall cavity. This study aims to investigate the characteristics of heat storage and release of the air convection hollow wall as well as its effects on the thermal environment in CSG. A comparison experiment was carried out in Tongzhou District, Beijing City. The tested CSG was seperated to control (without air convection holes) and test (with air convection holes) areas. The measurements included the temperature distribution inside the wall and its daily variation, the heat storage and release properties of the wall as well as the temperature variation during the day and night in the CSG. The environmental parameters were also investigated, like the temperature of wall and environment, and the surface heat flux of the wall. Additionally, the wind velocity and wet and dry bulb temperature of the vent holes were recorded to analyze the changes of air convection and heat exchange amount. The results showed that the temperature distribution of air convection wall was different from non-convection wall. Higher average temperature and magnified daily temperature variation inside the air convection wall indicated that the area of the wall (depth or volume) involved in heat storage and release was expanded under air convection conditions. The wind velocity showed that there was a good air convection and the speed of wind was corresponding to the temperature difference between the CSG and the hollow layer of the wall. The best convection performance appeared at noon with 0.6 m/s maximum wind velocity and 32.22 kW largest heat exchange amount. Compared with non-convection hollow wall, air convection wall increased the capacity of heat storage by 15.1% during the day and the capacity of heat release by 14.7% at night. The hollow layer of the wall contributed 1/3 of the total heat storage and release and improved the lowest temperature by 2.2 ℃ at night, so the heating performance during the night was clearly improved. Moreover, a cooling effect during the day appeared with the 6.2 ℃ maximum temperature difference at noon. In conclusion, the study shows that the new structure of air convection hollow wall enhances the heat storage and release properties of the wall effectively and improves the lowest temperature environment at night in CSG. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Using the molten salt lithium nitrate as the working fluid, the natural convection heat transfer of a horizontal circular tube under the wall is numerically simulated. The change of upper-wall on the buoyant plume generated above the heated tube, and the influence of the spacing between the tube and upper-wall (h/d) on the natural convection heat transfer characteristics around the heated tube were investigated. The results show that when h/d=1, with Ra increases, the stagnant region between the upper-wall and heat tube is gradually compressed, the rising thermal plume of heated tube shifts from the upper right and upper left to the top, the main mode of heat transfer at the top part of tube is transferred from conduction to natural convection. The natural convection heat transfer characteristics of the heated tube gradually increase and then tend to be stable with the increase of h/d, and the critical spacing is decreasing with the increase of Ra, For the natural convection of Ra≥10 000, the upper-wall has almost no effect on the heat transfer of heated tube when h/d≥3. [ABSTRACT FROM AUTHOR]

In order to study the effects of stochastic boundary conditions on natural convection heat transfer in square cavities, a Monte-Carlo stochastic finite element method was developed to solve uncertainty propagation of natural convection heat transfer under stochastic boundary condition. The input random parameters were expanded through the Karhunen-Loeve expansion and the random samples of boundary condition were generated with the Latin sampling method. The flow field and temperature field in the square cavity for different random samples of boundary condition were calculated numerically. The mathematical expectations and variances of stochastic output fields were calculated with the sampling statistical method. The stochastic finite element program with the MATLAB language was coded to solve the uncertainty propagation of natural convection heat transfer in cavity under stochastic boundary condition based on the computational framework. The effects of the correlation length and the variance of stochastic boundary condition on natural convection uncertainty were analyzed. The results show that the mean temperature field and flow field are basically the same as the deterministic temperature field and flow field, respectively. The probability distribution of the Nusselt number under stochastic boundary condition is a normal distribution. The mean Nusselt number increases with the correlation length and the variance, the variance has a greater influence on natural convection heat transfer than the correlation length. [ABSTRACT FROM AUTHOR]

The Chebyshev spectral collocation method (CSCM) was used to simulate natural convection in the square porous cavity under a local thermal equilibrium condition. Using the Chebyshev-Gauss-Lobatto collocation points， the dimensionless govering equations can be spatially discredited. The matrix diagonalization method was used to solve these discredited equations. The simulation results were in well agreement with the existing data. Meanwhile， the exact solutions were further constructed to valid the method and the CSCM effectiveness was proved. Finally， the effects of Rayleigh number on the streamlines， the isotherms and the Nusselt number were studied based on the CSCM simulations. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of Beijing Institute of Technology is the property of Beijing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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In order to obtain heat transfer law at different interface angle, numerical simulation on 6 different inclined angles coal-rock combination bodies were studied. Porous medium steady heat transfer models at different porosity and permeability were established. Considered gravity acceleration of y-axis, viscous resistance coefficient and internal resistance coefficient, used heat transfer, fluid mechanics, porous medium convective heat transfer and some related theory, Brinkman-Forchheimer's extend Darcy model was introduced and the coal-rock combination bodies model was used to control volume method. The results show that, from the temperature field, with the increase of angle, thermal conductivity of the lower part of high temperature boundary increases. The convective heat transfer in the central of the coal-rock combination bodies begin to play a major role and the thermal conductivity of upper part of low temperature boundary decreases. From the flow field, the convection effects in the central of the rock part is the weakest (φ = 0.000 1), and the convection effects near the boundary conditions is strongest (φ = 0. 001 3). The convection effects decrease with the angles increase. Flow state of interface has mutation, temperature field and streamline corresponding each other. [ABSTRACT FROM AUTHOR]

For the thermal characteristics of an array of highpower LED lamps for spotlight, the heat dissipation of critical structures was simulated by Icepak, and the flat fin heat-sink were optimized by central composite design and response surface methodology. The fin height, fin spacing and fin thickness are selected as the three response factors, and the temperature of the heat sink as the response value. By using the Design Expert 8.06 software, the data can be obtained the best combination, and finally get the polynomial quadratic equations between the three-factor and response value, also have the three-dimensional response surface diagrams of the interaction between the three-factor. The results show that the optimum condition is as follows: the fin height is 23.92 mm, the fin spacing is 5.99 mm the fin thickness is 1.03 mm, and the temperature is 45.182 2 °C. through comparison between the Icepak simulation value and the measured data obtained by central composite design, the calculation error of temperature is as low as +0.575%. This reveals the applicability of central composite design and response surface methodology to the optimization of flat fin heat-sink. [ABSTRACT FROM AUTHOR]

To better understand the heat-transfer character and flow of liquid gallium, a natural convection flow of liquid gallium was numerically simulated by using single phase method on the heat transfer of liquid gallium in a two dimensional enclosure. The effects of boundary condition and Grashof number on the flow and the convective heat transfer behavior are investigated. The numerical results which include temperature and velocity graph are compared with the experimental data and reasonable agreement is achieved. In a case that thermal conductivity takes a leading part, when Grashof number goes up, convection will gradually play a more important role. [ABSTRACT FROM AUTHOR]

The numerical study on natural convection in a horizontal hexagonal honeycomb enclosure was performed, the results of flow and heat transfer were obtained on adiabatic side wall thermal boundary condition for Rayleigh numbers in the range of 500 to 105. The finite volume method with SIMPLEC algorithm was used in the numerical calculation, and the temperature dependency of the fluid properties was considered. The numerical results show that the air in a closed cavity becomes unsteady at Ra = 1 000. The second order upwind scheme and QUICK scheme give almost the same results of flow and heat transfer in the honeycomb, while one order upwind scheme will result in some error. The numerical results also show that the Boussinesq approximation will bring large error for big wall temperature difference. [ABSTRACT FROM AUTHOR]