Cooling Effectiveness Research Articles

The Influence of Thrust Chamber Structure Parameters on Regenerative Cooling Effect with Hydrogen Peroxide as Coolant in Liquid Rocket Engines

Liquid rocket engines with hydrogen peroxide and kerosene have the advantages of high density specific impulse, high reliability, and no ignition system. At present, the cooling problem of hydrogen peroxide engines, especially with regenerative cooling, has been little explored. In this study, a realizable k-epsilon turbulence model, discrete phase model, eddy dissipation concept model, and 10-step 10-component reaction mechanism of kerosene with oxygen are used. The increased rib height of the regenerative cooling channel causes the inner wall temperature of the engine increases, the average temperature of the coolant outlet decreases slightly, and the coolant pressure decreases. The overall wall temperature decreases as the rib width of the regenerative cooling channel increases. However, in the nozzle throat area, the wall temperature increases, the average coolant outlet temperature decreases, and the coolant pressure drop increases. A decrease in the inner wall thickness of the regenerative cooling channel results in a significant decrease in the wall temperature and a small increase in the average coolant outlet temperature. These findings contribute to the further development of the engine with hydrogen peroxide and can guide the design of its regenerative cooling process.

WAAM of Al–Cu Alloy: Effect of Cooling and Remelting on Grain Size and Mechanical Properties

WAAM of Al–Cu Alloy: Effect of Cooling and Remelting on Grain Size and Mechanical Properties

COMPUTATIONAL ANALYSIS OF A CONVERGENT-DIVERGENT VORTEX TUBE TO ENHANCE ITS COOLING EFFECT

COMPUTATIONAL ANALYSIS OF A CONVERGENT-DIVERGENT VORTEX TUBE TO ENHANCE ITS COOLING EFFECT

Urban cooling island vs urban heat island, who is the winner? Study of the green spaces effect in coolingdown of urban heat in Kapanewon Depok, Sleman, Yogyakarta, Indonesia

Urban heat zone are the major problem affecting human health through the microclimatological effect. Green Spaces are like a natural air conditioners that can cool dense urban environments from hot air. The cooling effect of urban heat from the presence of Green Space is called the Urban Cooling Effect (UCE) while the cool air produced is called Urban Cooling Island (UCI). This research aims to analyze the extent to which UCI is able to neutralize UHI by urban cooling. This study of this research was conducted in Kapanewon Depok around the North Ringroad zone. In the research, the Remote Sensing method was used utilizing Landsat-8 and processed with ArcGIS to determine the patterns and dynamics of UCI and UHI and was equipped with field data measurement and interviews data using questionnaires. The results obtained were that the coldest and largest UCI Spot was at Babarsari Camping Ground, 27,777°C in 159,218 m2, with green space types consisting of shrubs, grass, plants, mixed trees and flowing river. Questionnaire results show that the majority of residents still feel hot. It was concluded that although Green Space is useful in cooling cities, but UCI VS UHI is still dominated by UHI’s influence.

Land–Atmosphere Feedbacks Weaken the Cooling Effect of Soil Organic Matter Property toward Deep Soil on the Eastern Tibetan Plateau

Abstract Soil organic matter (SOM) is enriched on the eastern Tibetan Plateau, but its effects on the hydrothermal state of the coupled land–atmosphere system remain unclear. This study comprehensively investigates these effects during summer from multiple perspectives based on regional climate modeling, land surface modeling, and observations. Using a regional climate model, we show that accounting for SOM effects lowers cold and wet biases in simulations of this region. SOM increases 2-m air temperature, decreases 2-m specific/relative humidity, and reduces precipitation in coupled simulations. Inclusion of SOM also warms the shallow soil while cooling the deep soil, which may help to preserve frozen soil in this region. This cooling effect is captured by both observations and offline land surface simulations, but it is overestimated in the offline simulations due to no feedback from the atmosphere compared to the coupled ones. Including SOM in coupled climate models could therefore not only imrove their representations of atmospheric energy and water cycles, but also help to simulate the past, present, and future evolution of frozen soil with increased confidence and reliability. Note that these findings are from one regional climate model and do not apply to wetlands. Significance Statement The eastern Tibetan Plateau is rich in soil organic matter (SOM), which increases the amount of water the soil can hold while decreasing the rate at which heat moves through it. Although SOM is expected to preserve frozen soil by insulating it from atmospheric warming, researchers have not yet tested the effects of coupled land–atmosphere interactions on this relationship. Using a regional climate model, we show that SOM typically warms and dries the near-surface air, warms the shallow soil, and cools the deep soil by modifying both soil properties and energy exchanges at the land–atmosphere interface. The results suggest that the cooling effect of SOM on deep soil is overestimated when atmospheric feedbacks are excluded.

The Climate Adaptive Characteristics of Urban Inside/Outside Water Bodies Based on Their Cooling Effect in Poyang and Dongting Lake Regions, China

The Climate Adaptive Characteristics of Urban Inside/Outside Water Bodies Based on Their Cooling Effect in Poyang and Dongting Lake Regions, China

Effect of Abutment Cooling on Reverse Torque Values of Abutment Screws: An In Vitro Study.

Purpose: To evaluate the effect of cooling on the reverse torque values of different abutments in bone-level and tissue-level implants. The null hypothesis was that there would be no difference in reverse torque values of abutment screws when cooled and uncooled implant abutments were compared. Materials and Methods: Bone-level and tissue-level implants (Straumann, each n = 36) were placed in synthetic bone blocks and subdivided into three groups (each n = 12) based on the abutment type (titanium base, cementable abutment, abutment for screw-retained restorations). All abutment screws were tightened to 35 Ncm torque. In half of the implants, a dry ice rod was applied on the abutments close to the implant-abutment connection for 60 seconds before untightening the abutment screw. The remaining implant-abutment pairs were not cooled. The maximum reverse torque values were recorded using a digital torque meter. The tightening and untightening procedure was repeated three times for each implant including cooling for the test groups, resulting in 18 reverse torque values per group. Two-way analysis of variance (ANOVA) was used to analyze the effect of cooling and abutment type on the measurements. Post hoc t tests were used to make group comparisons (α = .05). The P values of post hoc tests were corrected for multiple testing using the Bonferroni-Holm method. Results: The null hypothesis was rejected. Cooling and abutment type significantly affected the reverse torque values in bone-level implants (P = .004) but not in tissue-level implants (P = .051). The reverse torque values of bone-level implants significantly decreased after cooling (20.31 ± 2.55 Ncm vs 17.61 ± 2.49 Ncm). Overall mean reverse torque values were significantly higher in bone-level implants compared to tissue-level implants (18.96 ± 2.84 Ncm vs 16.13 ± 3.17 Ncm; P < .001). Conclusion: Cooling of the implant abutment led to a significant decrease in reverse torque values in bone-level implants and may therefore be recommended as a pretreatment before the application of procedures to remove a stuck implant part.

Effect of Heating and Cooling of Aluminium-Based Fibre-Metal Laminates on Their Tensile Strength

The widespread use of composite materials in the construction of machines encourages to better understand their properties and the impact of various external factors on these properties. Fibre metal laminates (FMLs) consist of alternating layers of metal and a polymer matrix laminate reinforced with continuous fibres. The aim of this work was to investigate the effect of cyclical temperature changes and thermal shocks (heating the sample to a high temperature in a short time) on the strength properties of FMLs from AW-1050A aluminium sheet, glass fibre fabric and carbon fibre fabric. The research concerns the determination of how cyclical temperature changes affect the tensile strengths properties of FMLs. The results indicate a small effect of the cycles on the tensile strength of the composites. The composites with glass fibre reinforced laminate also showed high resistance to delamination, moreover, the samples did not delaminate even after they were broken. The carbon fibre reinforced laminate composites showed a tendency to delaminate after heat treatment.

Quantification and Mapping of the Cooling Effect of Urban Parks in the Temperate Monsoon Climate Zone: A Case Study of 6 Megacities in China

Quantification and Mapping of the Cooling Effect of Urban Parks in the Temperate Monsoon Climate Zone: A Case Study of 6 Megacities in China

수치해석을 통한 치과용 LCD 3D 프린터의 냉각성능 분석

In order to maintain the performance of the 3D printer, it is important to satisfy the temperature requirements of the parts inside the device. Unlike the existing FDM type, the LCD type printer has a peculiarity that radiant heat transfer must be considered, and it is difficult to measure it experimentally. In this study, the flow characteristics of the light source of the LCD printer were analyzed through numerical analysis considering radiative heat transfer. Numerical analysis was performed according to the number and location of cooling fans on the front of the product to analyze the flow characteristics of the light source and the cooling effect of parts. When two fans are installed in parallel on the front part, a 6℃ temperature reduction effect was obtained on the LCD and 1.5℃ temperature reduction effect on the LED panel was found to show the most efficient cooling effect.

구조용 목재의 축열성능 향상을 위한 상변화물질/바이오차 적용 복합 교차집성재 개발

In this study, phase change materials (PCM) was applied to the core-layer of cross-laminated timber (CLT) to improve the low thermal storage performance of CLT. To solve the phase leakage of PCM, PCM/biochar composites were prepared in a vacuum state by impregnating PCM (n-heptadecane) in biochars that were pyrolyzed at 400 and 500 °C, respectively. Gypsum boards with improved thermal storage performance was prepared by mixing 10 wt% of the prepared PCM/biochar composites, and these were applied to the core-layer of the CLT to develop a hybrid CLT. The physical and chemical properties of PCM/biochar composite were evaluated through FT-IR, SEM, TGA, and DSC analysis, and the thermal performance of P/B board and hybrid CLT was evaluated through heat transfer experiments. The surface temperature reduction and heat transfer delay effect of hybrid CLT to which biochar produced at a pyrolysis temperature of 400 °C was applied was excellent.

High Dispersed Pd, Pt Supported on La, Ce-Alumina for Excellent Low Temperature Toluene Oxidation: Effect of Calcination Temperature and Ascorbic Acid Reduction

High Dispersed Pd, Pt Supported on La, Ce-Alumina for Excellent Low Temperature Toluene Oxidation: Effect of Calcination Temperature and Ascorbic Acid Reduction

“Phase Diagram” of Surface Temperature Distribution of Sessile Droplets and the Effects of Evaporative Cooling

“Phase Diagram” of Surface Temperature Distribution of Sessile Droplets and the Effects of Evaporative Cooling

Analysis of the Cooling and Humidification Effect of Multi-Layered Vegetation Communities in Urban Parks and Its Impact

As urbanization continues to accelerate, the urban heat island effects have become one of the most important issues affecting the urban environment and people’s living experience. Numerous studies have shown that urban parks and green spaces can effectively alleviate the problem of the urban heat island effect and provide cooling and humidifying effects. Vegetation communities are a fundamental part of urban parklands, and multi-layered vegetation communities are considered to have better cooling and humidifying effects. Previous studies have focused on comparative analyses between different cover types of vegetation communities but have not explored the differences in the cooling and humidifying effects of multi-layered vegetation communities of the same cover type. Therefore, the Olympic Forest Park in Beijing was selected as the subject of this study, and multi-layered vegetation-covered (tree-shrub-grass) with different degrees of densities and uncovered squares were selected for the control and comparison. The cooling and humidifying effects of multi-layered vegetation communities with different canopy densities at different times of the day through field measurements were studied, and the influencing factors for this were analyzed. The results show that the tree cover is the core factor affecting temperature; the degree of the canopy density of multi-layered vegetation communities is significantly and positively correlated with the intensity of cooling and humidification, and the cooling and humidifying effect of multi-layered vegetation communities increases as the degree of canopy density increases. The results of this study can provide some references for the planning and design of urban parks and green spaces.

Effects of Blowing and Density Ratios on Unsteady Film Cooling Effectiveness Using Fast-Response Pressure-Sensitive Paint

Abstract The transient effect of unsteady wakes on film cooling effectiveness using a fast response pressure sensitive paint (PSP) was studied. Testing was performed in a five-passage, low-speed wind tunnel using a scaled-up high pressure, blade profile. The blowing ratios studied include 0.4, 0.8, and 1.2 with a density ratio of 1.0 and 1.5 at each blowing ratio. An upstream wake generator produced Strouhal numbers of 0.1 and 0.3 while the wind tunnel inlet mainstream Reynolds number was held at a constant value of 300,000 for every test case. The results in this paper confirm the overall time averaged reduction in film cooling effectiveness with the addition of an unsteady wake while providing more detailed information on the transient response of the film cooling effectiveness, presented in the form of film cooling effectiveness RMS values. Results show that film cooling effectiveness RMS values increase on the leading-edge region of the blade and show little change on the pressure side of the blade with an increase in the Strouhal number. On the suction side, the area-averaged effectiveness RMS values decrease for the 0.8 and 1.2 blowing ratios and remain unchanged for the 0.4 blowing ratio. A change in the density ratio of the coolant from 1.0 to 1.5 has a minimal effect on area-averaged effectiveness RMS values for all areas of the blade.

Zoning Optimization Method of a Riverfront Greenspace Service Function Oriented to the Cooling Effect: A Case Study in Shanghai

Blue-green space commonly provides multiple ecological service functions, especially thermal environment comfort for citizens. The greenspace of the riparian buffers along 22 river channels in Shanghai was selected as the study object, and remote sensing and GIS technologies were used to obtain the quantitative composition and morphological indices of riverfront greenspace and the spatial distribution data of the land surface temperature in the study area. Through BRT modelling and statistical analyses, the interactive correlations among the three aspects, namely, the spatial patterns of riverfront greenspace, their specific functional zoning, and cooling island differentiation characteristics, were explored. The results showed that different river types served for different functional zones of the city, namely, high-density built-up zoning, new urban-growth zoning in built-up areas, suburban areas, and rural areas, and had specific regular patterns of morphosis and service function of riverfront greenspace. These also led to a significant spatial differentiation pattern of cooling intensity levels, which generally appeared in the approximate circle differentiation structure of the cooling island in the city riverfront area. The study further proposed the key factors and corresponding strategies for optimizing the greenspace pattern to strengthen the cooling intensity levels of different river types. This study summarizes the landscape composition paradigm of riverfront greenspaces at the urban mesoscale and provides adaptive planning methods for better local microclimate conditions.

Quantifying the cooling effect of urban green space: A case from urban parks in a tropical mega metropolitan area (India)

• Local cooling effects of urban parks were analyzed. • Cooling effect was estimated using novel ring based method and multiple greenness and thermal parameters. • Findings revealed cooling effect is largely determined by the greenness of the parks. • Conservation and management of urban parks is essential for climate mitigation in tropical cities. Green space (GS) plays a crucial role in reducing the urban heat island (UHI) effect and helps in mitigating climate change. In Indian cities, GS are highly vulnerable due to rapid urbanization and infrastructural development. This study aims to assess the cooling effect of urban parks such as GS on the thermal environment in Kolkata Metropolitan Area (KMA), India. Five urban parks were selected from different parts of KMA for the assessment during the summer season. Three greenness indices (normalized difference vegetation index, enhanced vegetation index and soil adjusted vegetation index) and two thermal indices (land surface temperature and temperature condition index) were used to find out the cooling effect on the thermal environment. Relative land surface temperature (RLST) and vegetation cooling index (VCI) was developed for a better understanding of the relationship between greenness on the thermal environment. Correlation and regression analysis was also performed to show the relationship as well the effect of greenness parameters on thermal conditions. From the result, it was found that urban parks had a substantial impact on the cooling effect. (i) Botanical Park was the coldest park with an average LST of 33.55⁰C, followed by Nicco park (34.33⁰C), Nature park (34.48⁰C), Rabindra Sarabor (34.55⁰C), and Central Park (36.65⁰C) (ii) RLST had a negative correlation with PV (R = -0.51 for Botanical Park; R= -0.65 for Nature park; R= -0.57 for Central park) and (iii) finally, greenness had a negative impact on the thermal pattern in KMA (R = -0.16). Thus, from the results, it was documented that urban parks (as GS) had CA on the surrounding areas. Therefore, the conservation of GS is essential to achieving sustainable development goals (particularly goals- 3, 11, 13, and 15).

녹지 조성 시나리오에 따른 도시 열환경 개선 효과 분석†

To alleviate the urban heat island phenomenon, this study aims to quantitatively analyze the effects of neighborhood green spaces on the improvement of the thermal environment based on detailed scenarios of five types of green spaces, including parks, pocket parks, parking lot greening, roadside planting, and rooftop-wall greening. The ENVI-met 4.4.6v model, a microclimate simulation program, was used to analyze the effects of green spaces. As a result, it was found that the air temperature decreased as the planting density of the park increased, but the thermal comfort index PET, which is the degree of heat sensation felt by humans, was not directly proportional to temperature. The establishment of a pocket park reduced air temperature up to a radius of 56m, while the range of temperature reduction increased by about 12.5% when three additional pocket parks were established at 250m intervals. Unlike the air temperature, PET was only affected in the vicinity of the planted area, so there was no significant difference in the thermal comfort of the surrounding environment due to the construction of pocket parks. Changing the surface pavement from asphalt to lawn blocks and implementing rooftop or wall greening did not directly act as solar shading but positively affected air temperature reduction; PET showed no significant difference. Roadside planting showed a higher air temperature reduction effect as the planting interval was narrower, but PET was not directly proportional to tree density. In the case of shrub planting under trees, it did not significantly affect the air temperature reduction but positively affected the improvement of thermal comfort. This study can outline strategies for constructing neighborhood green spaces to solve the urban heat island phenomena and establish detailed strategies for efficient thermal environment improvements.

Experimental Analysis of Cooling Effects on Mechanical Properties of Steel for Reinforced Concrete After High-Temperature Exposure

This article examines the mechanical properties of hot rolled FeE500-3 steels, used for reinforced concrete, with a nominal yield strength of 500 MPa. These steels are intended for the manufacture of beams, columns, and composite slabs made of reinforced concrete. This analysis is centered on small diameter ribbed bars (6 mm, 8 mm, and 10 mm) massively used for residential construction projects. It includes tensile tests carried out on specimens cooled to ambient temperature after a heating cycle at several temperature levels from 300 °C to 900 °C. Two cooling methods are studied to assess their influence on the residual mechanical properties of the steel material (elastic strength, ultimate strength, Young's modulus, strain at yield point, strain at the ultimate point, and strain at failure). The results have showed that the reinforcements cooled by air lose approximately 30% of their resistance from 700 °C and 20% in the case of cooling by water. The type of cooling has a negligible effect on the Young module. Ductility is the most impacted mechanical property. Significant degradation of ultimate strain and strain at failure has been noted for bars heated beyond 600 °C and cooled by water. However, ductility has improved for natural air cooling. Curves and predicted equations of the main residual mechanical properties of hot-rolled FeE500-3 steel are presented in this study. They can be used to rehabilitate damaged buildings and improve their safety.

Dominance of Influencing Factors on Cooling Effect of Urban Parks in Different Climatic Regions.

The enhancement of the park cooling effect (PCE) is one method used to alleviate the urban heat island (UHI). The cooling effect is affected by park factors; however, the importance of these factors in the case of the PCE is still unclear. Optimizing or planning urban parks according to the importance of the influencing factors can effectively enhance the PCE. Herein, we selected 502 urban parks in 29 cities in China with three different climatic regions and quantified the PCE based on the park cooling intensity (PCI) and park cooling area (PCA). Subsequently, the relative importance of the influencing factors for the PCE was compared to identify the main factors. Consequently, certain park planning suggestions were proposed to enhance the cooling effect. The results show that: (1) the PCE increased in the order of arid/semi-arid, semi-humid, and humid regions. (2) The main factors of the PCI differed significantly in different climatic regions; however, the waterbody within a park significantly affected the PCI in all three climates. However, for the PCA, park patch characteristics were the dominant factor, contributing approximately 80% in the three climates regions. (3) In arid/semi-arid and semi-humid regions, the optimal area proportion of waterbody and vegetation within the park were approximately 1:2 and 1:1, respectively, and the threshold value of the park area was 16 ha. In contrast, in the humid region, the addition of a waterbody area within the park, to the best extent possible, enhanced the PCI, and the threshold value of the park area was 19 ha. The unique results of this study are expected to function as a guide to future urban park planning on a regional scale to maximize ecological benefits while mitigating the UHI.