Graphite Nitridation in Lower Surface Temperature Regime

2010 ◽  
Vol 24 (1) ◽  
pp. 212-215 ◽  
Author(s):  
Toshiyuki Suzuki ◽  
Kazuhisa Fujita ◽  
Takeharu Sakai
Keyword(s):  
Surface Temperature ◽  
Temperature Regime ◽  
Lower Surface ◽  
Lower Surface Temperature

Research on Heat-Transfer Process of the Radiant Ceiling Cooling System

2012 ◽  
Vol 512-515 ◽  
pp. 2171-2174 ◽  
Author(s):  
Quan Ying Yan ◽  
Ran Huo ◽  
Li Li Jin
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Cooling System ◽  
Numerical Models ◽  
Cooling Water ◽  
Lower Surface ◽  
Cooling Capacity ◽  
Heat Transfer Process ◽  
Lower Surface Temperature ◽  
Selection Of

Physical and numerical models of the radiant ceiling cooling system were built and numerically simulated. The results showed that the lower the temperature of cooling water is, the lower surface temperature the ceiling has, and the bigger the cooling capacity is. The bigger the depth of tubes is, the higher the surface temperature and the smaller the cooling capacity. The differences are not evident. The bigger the distance of tubes is, the bigger the surface temperature is and the smaller the cooling capacity is. The diameter of tubes has a few influences on the surface temperature and the cooling capacity. Results in this paper can provide basis and guide for the design of the project, the selection of parameters and the feasibility of the system.

The effect of heating rate on the stability of stationary fluids

1967 ◽  
Vol 29 (2) ◽  
pp. 337-347 ◽  
Author(s):  
I. G. Currie
Keyword(s):  
Rayleigh Number ◽  
Surface Temperature ◽  
Fluid Layer ◽  
Critical Rayleigh Number ◽  
Lower Surface ◽  
Published Data ◽  
Heating Rates ◽  
Lower Surface Temperature ◽  
The Stability ◽  
Horizontal Fluid Layer

A horizontal fluid layer whose lower surface temperature is made to vary with time is considered. The stability analysis for this situation shows that the criterion for the onset of instability in a fluid layer which is being heated from below, depends on both the method and the rate of heating. For a fluid layer with two rigid boundaries, the minimum Rayleigh number corresponding to the onset of instability is found to be 1340. For slower heating rates the critical Rayleigh number increases to a maximum value of 1707·8, while for faster heating rates the critical Rayleigh number increases without limit.Two specific types of heating are investigated in detail, constant flux heating and linearly varying surface temperature. These cases correspond closely to situations for which published data exist. The results are in good qualitative agreement.

Lower surface temperature at Bright Ephemeral Feature site on Titan’s north pole

2021 ◽  
Author(s):  
Rajani D. Dhingra ◽  
Donald E. Jennings ◽  
Jason W. Barnes ◽  
Valeria Cottini
Keyword(s):  
Surface Temperature ◽  
Lower Surface ◽  
North Pole ◽  
Lower Surface Temperature

Plasma-assisted ammonia synthesis in a packed-bed dielectric barrier discharge reactor: roles of dielectric constant and thermal conductivity of packing materials

2021 ◽  
Author(s):  
Jin Liu ◽  
Xinbo Zhu ◽  
Xueli Hu ◽  
Xin Tu
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Constant ◽  
Surface Temperature ◽  
Packed Bed ◽  
Lower Surface ◽  
Active Species ◽  
Dielectric Constants ◽  
Packing Materials ◽  
Specific Input Energy ◽  
Lower Surface Temperature

Abstract In this article, plasma-assisted NH3 syntheses directly from N2 and H2 over packing materials with different dielectric constants (BaTiO3, TiO2 and SiO2) and thermal conductivities (BeO, AlN and Al2O3) at room temperature and atmospheric pressure are reported. The higher dielectric constant and thermal conductivity of packing material are found to be the key parameters in enhancing the NH3 synthesis performance. The NH3 concentration of 1344 ppm is achieved in the presence of BaTiO3, which is 106% higher than that of SiO2, at the specific input energy (SIE) of 5.4 kJ·l−1. The presence of materials with higher dielectric constant, i.e. BaTiO3 and TiO2 in this work, would contribute to the increase of electron energy and energy injected to plasma, which is conductive to the generation of chemically active species by electron-impact reactions. Therefore, the employment of packing materials with higher dielectric constant has proved to be beneficial for NH3 synthesis. Compared to that of Al2O3, the presence of BeO and AlN yields the 31.0% and 16.9% improvement in NH3 concentration, respectively, at the SIE of 5.4 kJ·l−1. The results of IR imaging show the addition of BeO decreases the surface temperature of the packed region by 20.5% to 70.3°C and results in an extension of entropy increment compared to that of Al2O3, at the SIE of 5.4 kJ·l−1. The results indicate that the presence of materials with higher thermal conductivity is beneficial for NH3 synthesis, which has been confirmed by the lower surface temperature and higher entropy increment of the packed region. In addition, when the SIE is higher than the optimal value, further increasing SIE would lead to the decrease of energy efficiency, which would be related to the exacerbation in reverse reaction of NH3 formation reactions.

scholarly journals Effect of moisture buffering on surface temperature variation: study of different indoor cladding materials

2020 ◽  
Vol 172 ◽  
pp. 06002
Author(s):  
Clémence Legros ◽  
Amandine Piot ◽  
Monika Woloszyn ◽  
Mickael Pailha
Keyword(s):  
Surface Temperature ◽  
Building Materials ◽  
Well Being ◽  
Lower Surface ◽  
Comfort Perception ◽  
Lower Surface Temperature ◽  
The Difference ◽  
Materials Used ◽  
Surface Temperature Variation ◽  
Moisture Buffering

The building materials used indoors constantly interact with the environment in which the occupants live. Recent studies have shown that natural materials, such as wood, can improve human well-being. In addition, the building materials facing the indoor air are able to adsorb and desorb water vapour from their surface and exchange it with the surrounding air. This mass exchange comes along with heat exchange, modifying their surface temperature, and thus the indoor environment. Therefore, in this article, we are investigating whether moisture buffering has an impact on comfort. For this purpose, room-scale numerical simulations have been carried out with WUFI Plus, comparing two types of interior cladding materials: painted plasterboards and a raw spruce panelling. The results show a slightly lower surface temperature and air temperature during the summer period when using spruce. A higher hygroscopicity of the spruce than the gypsum can explain this difference in behaviour between the two studied materials. Thus, spruce exchanges more latent heat with the surrounding air. However, only this thermal difference cannot explain the difference in comfort perception between the gypsum and the wood.

scholarly journals ROOFTOP GARDENING A SOURCE OF ENVIRONMENT CONSERVATION AND CROP PRODUCTION WITH CHANGING CLIMATE FOR DHAKA CITY

2020 ◽  
Vol 4 (1) ◽  
pp. 01-04
Author(s):  
Mohammad Mahbub Islam ◽  
Shahidul Islam ◽  
Suraya Parvin ◽  
Tahmina Akter Rimi ◽  
Ziasmin . ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Crop Production ◽  
Electricity Consumption ◽  
Pilot Project ◽  
Lower Surface ◽  
Dhaka City ◽  
Changing Climate ◽  
Lower Surface Temperature ◽  
Increasing Temperature ◽  
Roof Garden

The cities of the world are facing serious problems due to environmental hazards. The Department of Agricultural Extension has been implementing a pilot project on expansion of roof gardening in the Dhaka city since 2018 to reduce the increasing temperature, air pollution and for food production. However, no study has been conducted to find out the suitable technologies for producing fresh, safe and nutritious foods in the roof garden and to investigate the role of this roof garden on environment conservation for the Dhaka city dwellers with changing climate. Therefore, a research based roof garden model was developed at Sher-e-Bangla Agricultural University with the financial help of NATP-2 project. The experimental results showed that roof garden reduced upper surface temperature of roof more than 9°C and lower surface temperature of roof by 1.74°C and believe to reduce the electricity consumption for cooling the room of the top floor of the building during summer season. The oxygen and carbon dioxide percent were higher and lower, respectively in the garden than the bare roof. Therefore, the results suggest that urban crop production and environmental balance can be achieved to a certain extent by increasing the intensity of roof gardening in the Dhaka city

Incorporating Phase Change Materials to Mitigate Extreme Temperatures in Asphalt Concrete Pavements

2016 ◽  
Author(s):  
Bhagya Athukorallage ◽  
Darryl James
Keyword(s):  
Thermal Conductivity ◽  
Surface Temperature ◽  
Asphalt Concrete ◽  
Phase Change Materials ◽  
Volume Fraction ◽  
Lower Surface ◽  
Extreme Temperatures ◽  
Thermally Induced ◽  
Lower Surface Temperature ◽  
Maximum Surface Temperature

The use of Phase Change Materials (PCMs) in asphalt pavement mixtures potentially offers a solution for regulating extreme temperatures that can cause thermally-induced rutting in pavement systems. The primary objective of this study is to fundamentally understand the effect on the heat transfer and maximum surface temperature in flexible pavement systems that includes PCMs. In particular, we consider a pavement structure in which PCM is embedded in the asphalt-concrete layer with varying volume fractions. Our simulation results show that the pavement system embedded with PCMs yield lower surface temperature values than systems without PCM (maximum temperature decrease is 1.5°C for the distributed PCM with a volume fraction of 30%). Further, we observe a higher temperature drop through the PCM-embedded asphalt layer compared to a pavement without PCM, and regions possessing temperature values less than 45°C that may help to reduce the thermally induced rutting problems. The simulation yields another interesting result: increasing PCM volume fraction beyond 60% results in higher surface temperature values. This increase in the maximum surface temperature may be explained by the fact that the PCM used in the simulation has a lower thermal conductivity than that of the asphalt-concrete that ultimately results in a lower effective thermal conductivity value for the system. Finally, we observe that an increase in the effective thermal conductivity yields lower surface temperature for the PCM embedded pavement system.

A Numerical Study of the Development of Convective Motion in a Bottom Heated Square Enclosure Containing Ice and Water

1999 ◽  
Author(s):  
P. H. Oosthuizen
Keyword(s):  
Wall Temperature ◽  
Freezing Point ◽  
Numerical Study ◽  
Convective Motion ◽  
Lower Surface ◽  
Uniform Temperature ◽  
Density Maximum ◽  
Square Enclosure ◽  
Finite Element Procedure ◽  
Lower Surface Temperature

Abstract A numerical study of the steady state flow in a square enclosure with two vertical walls which are adiabatic and with two horizontal isothermal walls has been undertaken. The enclosure contains water and the upper wall is maintained at a uniform temperature that is below the freezing point of water while the lower wall is maintained at a uniform temperature that is above the freezing point of water. The upper portion of the enclosure is thus filled with ice and the lower portion is filled with water. The conditions considered in the present study are such there can be significant natural convection in the water and the effect of the density maximum that exists in the water at approximately 4°C can have a significant effect on this flow. The main aim of the study was to determine how far above 4°C the hot wall temperature can be before significant convective motion develops in the water. The governing equations have been expressed in dimensionless form and solved using a finite element procedure. The effect of the various governing parameters on the mean Nusselt number has mainly been considered and the effect of the lower surface temperature has, in particular, been studied. The results obtained, which indicate that convective motion does not occur until the lower hot wall temperature is well above the maximum density temperature, can be used to determine the actual hot wall temperature at which significant convective motion develops.

The Influence of Micro Scale Ratchet Depth on the Motion of Leidenfrost Drop

2015 ◽  
Author(s):  
Jeong Tae Ok ◽  
Sunggook Park
Keyword(s):  
Surface Temperature ◽  
Water Drop ◽  
Lower Surface ◽  
Driving Mechanism ◽  
Entire Surface ◽  
Depth Effect ◽  
Micro Scale ◽  
Temperature Range ◽  
Aspect Ratios ◽  
Surface Temperatures

The influence of ratchet depth on the motion of Leidenfrost water drop was investigated as a continuous effort to reveal the driving mechanism. Continuous directional rebounding behavior of the drop was observed only at below 200°C on both micro ratchets with two different depth-to-period aspect ratios (1:5 and 1:10) and sharp ridges. Overall, the shallow ratchets generated more efficient drop mobility in the entire surface temperature range of 193–299°C due to the increased area between the bottom of the drop and the ratchet surface, caused by the geometrical benefit. However, the depth effect was only critical at relatively lower surface temperatures.

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