Thermal Environment Analysis and Improvement on Isolated Cold Aisle Data Centers

2020 ◽  
Vol 12 (4) ◽  
Author(s):  
Lin Su ◽  
Zhilin Huang ◽  
Kaijun Dong
Keyword(s):  
Air Temperature ◽  
Data Centers ◽  
Thermal Environment ◽  
High Porosity ◽  
Temperature Uniformity ◽  
Transitional Form ◽  
Environment Analysis ◽  
Cooling Performance ◽  
Adequate Ventilation ◽  
Airflow Distribution

Abstract Isolated cold aisle airflow distribution is a transitional form from non-isolated airflow distribution to closed cold aisle airflow distribution. With the increase of the power of racks, cooling failure may happen in the layout of the isolated cold aisle. This paper presents the study on cooling performance of the racks which are improved through bottom ventilating reform and adjustment. Inlet/outlet air temperature and mass flow rate of the racks are investigated in detail under conditions of various bottom ventilated areas and various porosities of the raised floor. The characteristics of airflow distribution are contrastively analyzed through calculating indexes of the thermal environment of data centers. Results show that adequate ventilation through the bottom of the racks is good for improvement of the state of airflow distribution. There is an optimization range (0.1–0.3 m and 0.05–0.15 m, respectively) of the ventilated area at the bottom of the racks. And high porosity (above 50%) of the ventilated area can reduce the inlet and outlet temperatures of the racks and the racks in different positions have a better temperature uniformity. In conclusion, bottom ventilation of racks is a feasible plan to improve airflow distribution, and schemes of ventilated area and porosity of corresponding raised floor should be designed respectively under consideration of the layout of racks and AC.

scholarly journals Prediction and Evaluation of Dynamic Variations of the Thermal Environment in an Air-Conditioned Room Using Collaborative Simulation Method

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5378
Author(s):  
Lin He ◽  
Shunan Zhao ◽  
Guowen Xu ◽  
Xin Wu ◽  
Junlong Xie ◽  
...  
Keyword(s):  
Air Temperature ◽  
Temperature Difference ◽  
Thermal Environment ◽  
Structural Parameters ◽  
Simulation Method ◽  
Outer Diameter ◽  
Control Parameters ◽  
Temperature Uniformity ◽  
Collaborative Simulation ◽  
Dynamic Variations

In this study, a collaborative simulation method is proposed to predict dynamic variations of the thermal environment in an air-conditioned room. The room thermal environment was predicted and analyzed by varying the structural and control parameters of the air conditioner considering the dynamic coupling effect. Connections and regularities were established between the applicable parameters and evaluation indices of the thermal environment. The simulation results demonstrated the interactions among the system structural parameters, control parameters, and the thermal environment. Within a certain parameter range, the evaporator structure exhibited a significant effect on temperature uniformity and vertical air temperature difference, followed by predicted mean vote (PMV) and draught rate (DR). The associated evaluation indices were sensitive to fin spacing, tube spacing, and tube outer diameter, in the same order, which were structural parameters of the evaporator. The effect of the air supply angle on the vertical air temperature difference was evident; however, its influence on the PMV, DR, and temperature uniformity did not indicate consistent variations.

Analyzing the Cooling Efficiency of the Thermal Environment in Data Centers

2014 ◽  
Vol 6 (4) ◽  
pp. 15-27
Author(s):  
Yongmei Xu ◽  
Jingru Zhang ◽  
Yuhui Deng ◽  
Lan Du ◽  
Rong Jiao
Keyword(s):  
Energy Efficiency ◽  
Air Temperature ◽  
Thermal Load ◽  
Air Conditioning ◽  
High Speed ◽  
Data Centers ◽  
Thermal Environment ◽  
External Environment ◽  
Cooling Systems ◽  
Standard Data

Given the explosive growth of data, scalability and fault tolerance have become a fundamental challenge for data center network structures. Temperature in data centers significantly affects the failure ratio of high-speed network devices. Various types of air distribution schemes influence the temperature of network equipment differently, and the cooling cost in data centers dominates the overall energy cost. On the basis of the energy efficiency of cooling systems, this study analyzes and compares the thermal load distribution in the enclosure of standard and non-standard data centers by considering the effects of the external environment. Analysis results demonstrate that the external environment significantly affects the thermal load of non-standard data centers. By leveraging on the air temperature outside data centers and on the inlet/outlet of IT equipment, the air temperature and return air temperature of air conditioning are calculated when performing hot and cold aisle containment. The calculations indicate that sealing an appropriate aisle (hot or cold aisle) can significantly reduce the energy consumption of cooling systems in terms of the external air temperature outside data centers. Furthermore, if the air temperature outside data centers is higher than the temperature at the inlet of IT equipment, sealing the cold aisle outperforms sealing the hot aisle. By contrast, the aisle to be sealed depends on the energy efficiency ratio of the air conditioning.

scholarly journals Thermal Environment Analysis of a Scientific Laboratory using Computational Fluid Dynamics

2019 ◽  
Vol 266 ◽  
pp. 02004
Author(s):  
Qi Jie Kwong ◽  
Jim Yexin Yang ◽  
Oliver Hoon Leh Ling ◽  
Jamalunlaili Abdullah
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Air Temperature ◽  
Thermal Environment ◽  
Educational Institution ◽  
Computational Technique ◽  
Facilities Management ◽  
Indoor Environments ◽  
Environment Analysis ◽  
Scientific Laboratory

University staff and students typically spend most of their time indoors. This paper evaluates the thermal environment of an air-conditioned scientific laboratory in a tertiary educational institution in Malaysia using Computational Fluid Dynamics (CFD). This computational technique has been used in analysing the indoor environments and has been found to be useful in aiding facilities management. A pilot survey was conducted to collect the required information such as indoor parameters and boundary conditions for the setting up of a CFD model of the laboratory. The model was then simulated based on the data obtained from field observations. Results indicate that the laboratory users sitting at different rows and work desks would experience different thermal sensations. The mean air temperature was below the recommended comfort zone specified in the local energy standard, but the air velocities were generally within the acceptable range. Based on the calculated predicted mean vote (PMV) and predicted percentage dissatisfied (PPD) indices, most of the users would be thermally uncomfortable, and a warmer environment was preferred. Recommendations were made to regulate the inlet air temperature of the laboratory to improve thermal comfort of laboratory users and for energy saving purposes.

Comparison of corrosion resistance properties of Ni-P and Ni-W-P coatings obtained by electroless deposition

2020 ◽  
Vol 25 (2) ◽  
pp. 66-71
Author(s):  
A.B. Drovosekov
Keyword(s):  
Corrosion Resistance ◽  
Sulfuric Acid ◽  
Electroless Deposition ◽  
Corrosion Damage ◽  
Electrochemical Activity ◽  
High Porosity ◽  
Environment Analysis ◽  
Damage Degree ◽  
Lower Porosity ◽  
Electroless Coatings

Corrosion resistance properties, such as porosity, stability in the atmosphere of NaCl mist, and anodic electrochemical activity in a sulfuric acid solution are studied and compared for Ni-W-P and Ni-P coatings obtained by electroless deposition. The studied coatings were obtained from solutions with glycine as the main ligand and contained 10.2 to 15.6 at.% of phosphorus and up to 3.3 at.% of tungsten. It is shown that Ni-W-P coatings with a tungsten content of 2.3 to 3.3 at.% and a thickness of 15 μm have a significantly lower porosity as compared with nickel-phosphorus coatings of the same thickness. Also, significantly better stability of Ni-W-P coatings in a NaCl mist atmosphere was observed, their corrosion damage degree is less than that of Ni-P coatings, and relatively little depends on the duration of exposure in a corrosive environment. Analysis of anodic polarization curves showed an almost similar electrochemical activity upon dissolution of Ni-P and Ni-W-P coatings in sulfuric acid. Both these types of electroless coatings showed a markedly better tendency to anodic dissolution than pure nickel. Taking into account the obtained experimental data, a conclusion is made as to the better protective characteristics of Ni-W-P coatings in comparison with nickel-phosphorus coatings. The main reason of the inferior protective properties of Ni-P coatings is their relatively high porosity.

scholarly journals Optimal Air Conditioner Placement Using a Simple Thermal Environment Analysis Method for Continuous Large Spaces with Predominant Advection

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4663
Author(s):  
Tatsuhiro Yamamoto ◽  
Akihito Ozaki ◽  
Myonghyang Lee
Keyword(s):  
Air Conditioning ◽  
Thermal Environment ◽  
Fluid Dynamic ◽  
Optimal Placement ◽  
Air Conditioner ◽  
Analysis Method ◽  
Computational Fluid Dynamic Analysis ◽  
Environment Analysis ◽  
Air Conditioners ◽  
Energy Simulations

The number of houses with large, continuous spaces has increased recently. With improvements in insulation performance, it has become possible to efficiently air condition such spaces using a single air conditioner. However, the air conditioning efficiency depends on the placement of the air conditioner. The only way to determine the optimal placement of such air conditioners is to conduct an experiment or use computational fluid dynamic analysis. However, because the analysis is performed over a limited period, it is difficult to consider non-stationarity effects without using an energy simulation. Therefore, in this study, energy simulations and computational fluid dynamics analyses were coupled to develop a thermal environment analysis method that considers non-stationarity effects, and various air conditioner arrangements were investigated to demonstrate the applicability of the proposed method. The accuracy verification results generally followed the experimental results. A case study was conducted using the calculated boundary conditions, and the results showed that the placement of two air conditioners in the target experimental house could provide sufficient air conditioning during both winter and summer. Our results suggest that this method can be used to conduct preliminary studies if the necessary data are available during design or if an experimental house is used.

scholarly journals Temperature uniformity in the CERN CLOUD chamber

2017 ◽  
Vol 10 (12) ◽  
pp. 5075-5088 ◽  
Author(s):  
António Dias ◽  
Sebastian Ehrhart ◽  
Alexander Vogel ◽  
Christina Williamson ◽  
João Almeida ◽  
...  
Keyword(s):  
Steady State ◽  
Air Temperature ◽  
Elevated Temperatures ◽  
Trace Gases ◽  
Vertical Direction ◽  
Cloud Chamber ◽  
Temperature Uniformity ◽  
Atmospheric Conditions ◽  
Cloud Droplets ◽  
Experimental Conditions

Abstract. The CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN (European Council for Nuclear Research) investigates the nucleation and growth of aerosol particles under atmospheric conditions and their activation into cloud droplets. A key feature of the CLOUD experiment is precise control of the experimental parameters. Temperature uniformity and stability in the chamber are important since many of the processes under study are sensitive to temperature and also to contaminants that can be released from the stainless steel walls by upward temperature fluctuations. The air enclosed within the 26 m3 CLOUD chamber is equipped with several arrays (strings) of high precision, fast-response thermometers to measure its temperature. Here we present a study of the air temperature uniformity inside the CLOUD chamber under various experimental conditions. Measurements were performed under calibration conditions and run conditions, which are distinguished by the flow rate of fresh air and trace gases entering the chamber at 20 and up to 210 L min−1, respectively. During steady-state calibration runs between −70 and +20 °C, the air temperature uniformity is better than ±0.06 °C in the radial direction and ±0.1 °C in the vertical direction. Larger non-uniformities are present during experimental runs, depending on the temperature control of the make-up air and trace gases (since some trace gases require elevated temperatures until injection into the chamber). The temperature stability is ±0.04 °C over periods of several hours during either calibration or steady-state run conditions. During rapid adiabatic expansions to activate cloud droplets and ice particles, the chamber walls are up to 10 °C warmer than the enclosed air. This results in temperature differences of ±1.5 °C in the vertical direction and ±1 °C in the horizontal direction, while the air returns to its equilibrium temperature with a time constant of about 200 s.

scholarly journals The Street Air Warming Phenomenon in a High-Rise Compact City

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 402 ◽  
Author(s):  
Xiaoxue Wang ◽  
Yuguo Li ◽  
Xinyan Yang ◽  
Pak Chan ◽  
Janet Nichol ◽  
...  
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Thermal Environment ◽  
Urban Climate ◽  
Pollutant Dispersion ◽  
Urban Morphology ◽  
Air Temperatures ◽  
Significant Difference ◽  
Sensitivity Studies ◽  
Weather Stations

The street thermal environment is important for thermal comfort, urban climate and pollutant dispersion. A 24-h vehicle traverse study was conducted over the Kowloon Peninsula of Hong Kong in summer, with each measurement period consisting of 2–3 full days. The data covered a total of 158 loops in 198 h along the route on sunny days. The measured data were averaged by three methods (direct average, FFT filter and interpolated by the piecewise cubic Hermite interpolation). The average street air temperatures were found to be 1–3 °C higher than those recorded at nearby fixed weather stations. The street warming phenomenon observed in the study has substantial implications as usually urban heat island (UHI) intensity is estimated from measurement at fixed weather stations, and therefore the UHI intensity in the built areas of the city may have been underestimated. This significant difference is of interest for studies on outdoor air temperature, thermal comfort, urban environment and pollutant dispersion. The differences were simulated by an improved one-dimensional temperature model (ZERO-CAT) using different urban morphology parameters. The model can correct the underestimation of street air temperature. Further sensitivity studies show that the building arrangement in the daytime and nighttime plays different roles for air temperature in the street. City designers can choose different parameters based on their purpose.

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