scholarly journals Theoretical analysis of the lifetime of sessile evaporating droplet with surface cooling effect

2020 ◽  
Author(s):  
Yang Shen ◽  
Yongpan Cheng ◽  
Jinliang Xu ◽  
Kai Zhang
Keyword(s):  
Theoretical Analysis ◽  
Cooling Effect ◽  
Surface Cooling

scholarly journals Cooling of a Processor With the Use of a Heat Pump

2018 ◽  
Vol 28 (1) ◽  
pp. 16-25
Author(s):  
Zygmunt Lipnicki ◽  
Hanna Lechów ◽  
Katarzyna Pantoł
Keyword(s):  
Theoretical Analysis ◽  
Heat Pump ◽  
External Surface ◽  
Cooling System ◽  
Heat Distribution ◽  
Surface Cooling ◽  
Cooling Systems ◽  
Model Calculations ◽  
Systems Model ◽  
Liquid Evaporation

Abstract In this paper the problem of cooling a component, in the interior of which heat is generated due to its work, was solved analytically. the problem of cooling of a processor with the use of a heat pump was solved based on a earlier theoretical analysis of authors of external surface cooling of the cooled component by using the phenomenon of liquid evaporation. Cases of stationary and non-stationary cooling were solved as well. The authors of the work created a simplified non-stationary analytical model describing the phenomenon, thanks to which heat distribution within the component, contact temperature between the component and liquid layer, and the evaporating substance layer thickness in relation to time, were determined. Numerical calculations were performed and appropriate charts were drawn. The resulting earlier analytical solutions allowed conclusions to be drawn, which might be of help to electronics engineers when designing similar cooling systems. Model calculations for a cooling system using a compressor heat pump as an effective method of cooling were performed.

Satellite-based investigation on the surface cooling effects of urban parks and their range – a case study for North Rhine-Westphalia, Germany

Erdkunde ◽  
2021 ◽  
Vol 75 (3) ◽  
pp. 209-223
Author(s):  
Leonie Krelaus ◽  
Joy Apfel ◽  
Andreas Rienow
Keyword(s):  
Green Infrastructure ◽  
Land Surface ◽  
Methodological Approach ◽  
Urban Parks ◽  
Cooling Effect ◽  
Landsat 8 ◽  
Surface Cooling ◽  
Mixed Pixels ◽  
Cooling Effects ◽  
The Impact

Green infrastructure (GI) has a cooling effect owing to shading and evapotranspiration and therefore has a climate regulating function within metropolitan areas. Urban parks are a type of GI that act as park cool islands (PCIs) and play a major role in mitigating the surface urban heat island. This study aims to (1) investigate the status quo of the surface cooling effect intensity of selected urban parks in North Rhine-Westphalia (NRW), including their cooling range, and to (2) propose a methodological approach for investigating the PCI intensity using remote sensing data considering the occurrence of mixed pixels. To achieve these tasks, land surface temperature values based on Landsat 8 images from three different days in 2018 and 2019 were observed. In addition, a method for the reduction of mixed pixels was developed. The results confirm a surface cooling effect of 1–5 K and thus the existence of a PCI. The impact of the surface cooling effect was found within a minimum range of 150 m. However, the process of identifying the cooling area was complicated by the high proportion of GI in cities in NRW, compared to other study areas. Further research on the influencing parameters of the surface cooling effect is needed.

scholarly journals Seasonal Local Temperature Responses to Paddy Field Expansion from Rain-Fed Farmland in the Cold and Humid Sanjiang Plain of China

2018 ◽  
Vol 10 (12) ◽  
pp. 2009 ◽  
Author(s):  
Tingxiang Liu ◽  
Lingxue Yu ◽  
Kun Bu ◽  
Fengqin Yan ◽  
Shuwen Zhang
Keyword(s):  
Paddy Field ◽  
Sanjiang Plain ◽  
Paddy Fields ◽  
Cooling Effect ◽  
Local Temperature ◽  
Surface Cooling ◽  
Humid Climate ◽  
The Sanjiang Plain ◽  
Near Surface ◽  
Temperature Responses

Numerous studies have documented the effects of irrigation on local, regional, and global climate. However, most studies focused on the cooling effect of irrigated dryland in semiarid or arid regions. In our study, we focused on irrigated paddy fields in humid regions at mid to high latitudes and estimated the effects of paddy field expansion from rain-fed farmland on local temperatures based on remote sensing and observational data. Our results revealed much significant near-surface cooling in spring (May and June) rather than summer (July and August) and autumn (September), which was −2.03 K to 0.73 K and −1.08 K respectively. Non-radiative mechanisms dominated the local temperature response to paddy field expansion from rain-fed farmland in the Sanjiang Plain. The contributions from the changes to the combined effects of the non-radiative process were 123.6%, 95.5%, and 66.9% for spring (May and June), summer (July and August), and autumn (September), respectively. Due to the seasonal changes of the biogeophysical properties for rain-fed farmland and paddy fields during the growing season, the local surface temperature responses, as well as their contributions, showed great seasonal variability. Our results showed that the cooling effect was particularly obvious during the dry spring instead of the warm, wet summer, and indicated that more attention should be paid to the seasonal differences of these effects, especially in a region with a relatively humid climate and distinct seasonal variations.

scholarly journals Theoretical Analysis of a Sessile Evaporating Droplet on a Curved Substrate with an Interfacial Cooling Effect

Langmuir ◽  
2020 ◽  
Vol 36 (20) ◽  
pp. 5618-5625 ◽  
Author(s):  
Yang Shen ◽  
Yongpan Cheng ◽  
Jinliang Xu ◽  
Kai Zhang ◽  
Yi Sui
Keyword(s):  
Theoretical Analysis ◽  
Cooling Effect ◽  
Curved Substrate

Dynamic Behavior of Cryogen Spray Cooling: Effect of Spray Distance

2003 ◽  
Author(s):  
G.-X. Wang ◽  
G. Aguilar ◽  
J. S. Nelson
Keyword(s):  
Heat Transfer ◽  
Skin Surface ◽  
Spray Cooling ◽  
Heat Fluxes ◽  
Cooling Effect ◽  
Dermatologic Surgery ◽  
Measured Temperature ◽  
Surface Cooling ◽  
Spray Distance ◽  
Cryogen Spray Cooling

Cryogen spray cooling (CSC) is used to minimize the risk of epidermal damage during laser dermatologic surgery. During CSC, skin surface is cooled by a short spurt of refrigerant R134a with boiling point of −26.2°C. Since R134a is volatile in open atmospheric conditions, the atomized liquid droplets undergo continuous evaporation as they fly in air, leading to a lost momentum and mass. Therefore, the cooling effect of CSC depends strongly on the spray distance between the nozzle and the skin surface (L). The objective of this study was, therefore, to investigate the effect of L on the dynamic heat transfer of CSC. A skin model system made of poly methyl-methacrylate resin (Plexiglass®) is used to simulate CSC during laser dermatologic surgery. A fast-response temperature measurement sensor is built using thin (20 μm) aluminum foil and placed on top of the plexiglass with a 50 μm bead diameter thermocouple positioned in between. Variation of the surface temperature is then measured under various spray distances. The surface heat flux (q) as well as the heat transfer coefficient (h) between the surface and the cryogen is estimated by solving an inverse heat conduction problem with the measured temperature data as input. The effect of L on surface cooling in CSC is then investigated systematically. Both the estimated q and h show strong dynamic characteristics and are strong functions of the L. Two distinct spray-surface interaction mechanisms are identified within the spray distances studied. For short L (< 30 mm), the spurt droplets impinge on the substrate violently, resulting in a fairly thin cryogen film deposited on the surface. Strong dynamics and high q result in this case, corresponding to a high h as well. Interestingly, h becomes strongly fluctuating and even larger after spurt termination for these cases. For long L (> 30 mm), q is lower and it steadily decreases after spurt termination. The dynamic variation of h in this case is similar to that of q. These results should help in the selection of optimal CSC parameters, which are needed to produce high heat fluxes at the skin surface and thus obtain maximal epidermal protection during various dermatologic laser therapies.

scholarly journals Assessing the Effects of Photovoltaic Powerplants on Surface Temperature Using Remote Sensing Techniques

2020 ◽  
Vol 12 (11) ◽  
pp. 1825
Author(s):  
Xunhe Zhang ◽  
Ming Xu
Keyword(s):  
Remote Sensing ◽  
Surface Temperature ◽  
Surface Albedo ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Rapid Development ◽  
Cooling Effect ◽  
Surface Cooling ◽  
Thermal Infrared Remote Sensing ◽  
The World

The rapid development of photovoltaic (PV) powerplants in the world has drawn attention on their climate and environmental impacts. In this study, we assessed the effects of PV powerplants on surface temperature using 23 largest PV powerplants in the world with thermal infrared remote sensing technique. Our result showed that the installation of the PV powerplants had significantly reduced the daily mean surface temperature by 0.53 °C in the PV powerplant areas. The cooling effect with the installation of the PV powerplants was much stronger during the daytime than the nighttime with the surface temperature dropped by 0.81 °C and 0.24 °C respectively. This cooling effect was also depended on the capacity of the powerplants with a cooling rate of −0.32, −0.48, and −0.14 °C/TWh, respectively, for daily mean, daytime, and nighttime temperature. We also found that the construction of the powerplants significantly decreased the surface albedo from 0.22 to 0.184, but significantly increased the effective albedo (surface albedo plus electricity conversion) from 0.22 to 0.244, suggesting conversion of solar energy to electrical energy is a major contributor to the observed surface cooling. Our further analyses showed that the nighttime cooling in the powerplants was significantly correlated with the latitude and elevation of the powerplants as well as the annual mean temperature, precipitation, solar radiation, and normalized difference vegetation index (NDVI). This means the temperature effect of the PV powerplants depended on regional geography, climate and vegetation conditions. This finding can be used to guide the selection of the sites of PV powerplants in the future.

Microdiffraction Patterns of Small Metallic Particles II; Theoretical Analysis

1982 ◽  
Vol 40 ◽  
pp. 668-669
Author(s):  
A. Gómez ◽  
P. Schabes-Retchkiman ◽  
M. José-Yacamán ◽  
T. Ocaña
Keyword(s):  
Experimental Data ◽  
Electron Diffraction ◽  
Theoretical Analysis ◽  
Size Range ◽  
Dynamical Theory ◽  
Metallic Particles ◽  
Splitting Effect

The splitting effect that is observed in microdiffraction pat-terns of small metallic particles in the size range 50-500 Å can be understood using the dynamical theory of electron diffraction for the case of a crystal containing a finite wedge. For the experimental data we refer to part I of this work in these proceedings.

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