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

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.

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Thermal Environment Analysis and Improvement on Isolated Cold Aisle Data Centers

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4045746 ◽

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.

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Study on the Thermal Environment Inside a Fully-Enclosed Subway Noise Barrier

E3S Web of Conferences ◽

10.1051/e3sconf/202014301044 ◽

2020 ◽

Vol 143 ◽

pp. 01044

Author(s):

Lei Liu ◽

Lianghan Zhang ◽

Zhongxu Kang ◽

Kun Yao

Keyword(s):

Numerical Simulation ◽

Comparative Analysis ◽

Air Temperature ◽

Thermal Environment ◽

Simulation Method ◽

Internal Environment ◽

Numerical Simulation Method ◽

Calculation Results ◽

Noise Barrier ◽

Air Vent

The thermal environment inside a fully-enclosed subway noise barrier shall be designed according to underground section tunnel standards. This article constructs a model using practical examples, simulates calculations on fully-enclosed noise barrier installations both with and without air vents via a threedimensional numerical simulation method, and then conducts a comparative analysis of the effects noise barrier lengths and air vent widths have on an internal thermal environment. The calculation results show that when the length of the fully-enclosed noise barrier without air vents was 100m, the internal thermal environment exceeded the limit; as the width of the air vents increased, the temperature in the internal environment gradually decreased, but the reduction was less once the air vent width exceeded 2 m; When the top air vent width was 2 m, and the noise barrier length was 100m, the thermal environment was found to meet requirements. As the noise barrier length increased, the internal air temperature exceeded the standards by varying degrees.

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Airflow pattern and performance of wall confluent jets ventilation for heating in a typical office space

Indoor and Built Environment ◽

10.1177/1420326x19842632 ◽

2019 ◽

Vol 29 (1) ◽

pp. 67-83

Author(s):

Diyi Tan ◽

Baizhan Li ◽

Yong Cheng ◽

Hong Liu ◽

Jinhua Chen

Keyword(s):

Air Temperature ◽

Temperature Difference ◽

Thermal Environment ◽

Ambient Air ◽

Air Velocity ◽

Text Model ◽

Jet Velocity ◽

Ventilation Performance ◽

Heating Mode ◽

Occupied Zone

To investigate an air distribution system with the potential to provide a comfortable thermal environment and efficient ventilation performance in heating mode, this study compared the numerical results of the RNG k-[Formula: see text] model, realizable k-[Formula: see text] model and SST k-ω model with experimental data obtained from a typical office with wall confluent jets ventilation (WCJV) for heating. The SST k-ω model was chosen for numerical study of WCJV. The findings showed that the WCJV performed better than mixing ventilation (MV) in the heating mode because WCJV could entrain less ambient air and maintain the jets’ momentum and energy to reach the occupied zone. The effects of supply air temperature difference (in the range of 2.00°C to 7.79°C) and supply air velocity (in the range of 2.20 m/s to 8.50 m/s) on the jet velocity profiles and ventilation performance of WCJV were also quantified. The results showed that the jet velocity profile was more sensitive to the supply air velocity than to the supply air temperature difference. Accordingly, reducing the supply air velocity might result in poorer thermal environment and air quality in the occupied zone because the warm air jets cannot spread out over the floor area. The results can be helpful in understanding WCJV used for ventilation under heating mode.

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Some Effects on the Temperature of the Mine Air at the Heading Face

Inżynieria Mineralna ◽

10.29227/im-2021-02-39 ◽

2021 ◽

Vol 1 (2) ◽

Author(s):

Van Quang NGUYEN ◽

Van Thinh NGUYEN ◽

Cao Khai NGUYEN ◽

Van Chung PHAM

Keyword(s):

Numerical Simulation ◽

High Temperature ◽

Temperature Distribution ◽

Air Temperature ◽

Significant Influence ◽

Thermal Environment ◽

Simulation Method ◽

Forced Ventilation ◽

Ansys Cfx ◽

Ventilation Method

Currently, with the increase in mining output leading to deeper mining levels, the volume ofheading face serving production has also increased. The thermal environment tends to worsen whendigging deep due to the geothermal's effect, which increases the air temperature at the heading face.According to QCVN01/2011-BCT, the temperature at the heading face is not allowed to exceed 300C. Toensure this, in Vietnam today, mainly forced ventilation method uses local fans to provide a clean amountof air to ensure a favorable environment for workers. With the forced ventilation method, the duct positionis usually arranged on the side, and the distance from the duct mouth to the heading face is determined toensure that l < 6√s. In this study, a numerical simulation method by Ansys CFX software is applied tostudy the influence of several factors such as duct position, air temperature of duct, and roughnesscharacteristics of roadway on the temperature of the mine air at the heading face. The models are set upwith six duct positions and four air temperature of duct parameters. Model 1 (y =1.1 m) is better thanmodels 2 to 6 in terms of temperature distribution and the lowest temperature values. Four models havedifferent wind temperatures, and we can see the significant influence of the inlet air temperature of theduct on the thermal environment of the heading face. The results show that with the model T = 297.15K,the temperature value on the roadway length is guaranteed as specified < 303K. The result is a referencefor determining the duct position and cool for the high-temperature heading face.

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Impact of Land Cover Composition and Structure on Air Temperature Based on the Local Climate Zone Scheme in Hangzhou, China

Atmosphere ◽

10.3390/atmos12080936 ◽

2021 ◽

Vol 12 (8) ◽

pp. 936

Author(s):

Hai Yan ◽

Shimin Yang ◽

Xiaohui Guo ◽

Fan Wu ◽

Renwu Wu ◽

...

Keyword(s):

Land Cover ◽

Air Temperature ◽

Temperature Difference ◽

Thermal Environment ◽

Urban Climate ◽

Rapid Urbanization ◽

Climate Zones ◽

Local Climate ◽

Composition And Structure ◽

Local Climate Zones

At present, conflicts between urban development and the climate environment are becoming increasingly apparent under rapid urbanization in China. Revealing the dynamic mechanism and controlling factors of the urban outdoor thermal environment is the necessary theoretical preparation for regulating and improving the urban climate environment. Taking Hangzhou as an example and based on the local climate zones classification system, we investigated the effects of land cover composition and structure on temperature variability at the local scale. The measurement campaign was conducted within four local climate zones (LCZ 2, 4, 5, and LCZ 9) during 7 days in the summer of 2018. The results showed that the temperature difference within the respective LCZ was always below 1.1 °C and the mean temperature difference between LCZs caused by different surface physical properties was as high as 1.6 °C at night. Among four LCZs, LCZ 2 was always the hottest, and LCZ 9 was the coolest at night. In particular, the percentage of pervious surface was the most important land cover feature in explaining the air temperature difference. For both daytime and nighttime, increasing the percentage of pervious surface as well as decreasing the percentage of impervious surface and the percentage of building surface could lower the local temperature, with the strongest influence radius range from 120 m to 150 m. Besides, the temperature increased with the SVF increased at day and opposite at night.

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A Study of Developing a Prediction Equation of Electricity Energy Output via Photovoltaic Modules

Energies ◽

10.3390/en14051503 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1503

Author(s):

Minsu Kim ◽

Hongmyeong Kim ◽

Jae Hak Jung

Keyword(s):

Experimental Data ◽

Real Time ◽

Air Temperature ◽

Temperature Difference ◽

Prediction Accuracy ◽

Prediction Equation ◽

Energy Output ◽

Photovoltaic Modules ◽

Mean Error ◽

Pv Module

Various equations are being developed and applied to predict photovoltaic (PV) module generation. Currently, quite diverse methods for predicting module generation are available, with most equations showing accuracy with ≤5% error. However, the accuracy can be determined only when the module temperature and the value of irradiation that reaches the module surface are precisely known. The prediction accuracy of outdoor generation is actually extremely low, as the method for predicting outdoor module temperature has extremely low accuracy. The change in module temperature cannot be predicted accurately because of the real-time change of irradiation and air temperature outdoors. Calculations using conventional equations from other studies show a mean error of temperature difference of 4.23 °C. In this study, an equation was developed and verified that can predict the precise module temperature up to 1.64 °C, based on the experimental data obtained after installing an actual outdoor module.

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Research on CFD Simulation of the Cement Slurry Mixer

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.621.196 ◽

2012 ◽

Vol 621 ◽

pp. 196-199

Author(s):

Shui Ping LI ◽

Ya Li Yuan ◽

Lu Gang Shi

Keyword(s):

Flow Field ◽

High Performance ◽

Cfd Simulation ◽

Structural Parameters ◽

Internal Flow ◽

Simulation Method ◽

Cement Slurry ◽

Fluid Machinery ◽

Computational Fluid Dynamics Cfd ◽

Machinery Design

Numerical simulation method of the internal flow field of fluid machinery has become an important technology in the study of fluid machinery design. In order to obtain a high-performance cement slurry mixer, computational fluid dynamics (CFD) techniques are used to simulate the flow field in the mixer, and the simulation results are studied. According to the analysis results, the structural parameters of the mixer are modified. The results show the mixer under the revised parameters meet the design requirements well. So CFD analysis method can shorten design period and provide valuable theoretical guidance for the design of fluid machinery.

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Temperature uniformity in the CERN CLOUD chamber

Atmospheric Measurement Techniques ◽

10.5194/amt-10-5075-2017 ◽

2017 ◽

Vol 10 (12) ◽

pp. 5075-5088 ◽

Cited By ~ 5

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.

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

Atmosphere ◽

10.3390/atmos9100402 ◽

2018 ◽

Vol 9 (10) ◽

pp. 402 ◽

Cited By ~ 4

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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