Numerical Study on Coupled Operation of Stratified Air Distribution System and Natural Ventilation under Multi-Variable Factors in Large Space Buildings

Stratified air distribution systems are commonly used in large space buildings. The research on the airflow organization of stratified air conditioners is deficient in terms of the analysis of multivariable factors. Moreover, studies on the coupled operation of stratified air conditioners and natural ventilation are few. In this paper, taking a Shanghai Airport Terminal departure hall for the study, air distribution and thermal comfort of the cross-section at a height of 1.6 m are simulated and compared under different working conditions, and the effect of natural ventilation coupling operation is studied. The results show that the air distribution is the most uniform and the thermal comfort is the best (predicted mean vote is 0.428, predicted percentage of dissatisfaction is 15.2%) when the working conditions are 5.9% air supply speed, 11 °C cooling temperature difference and 0° air supply angle. With the coupled operation of natural ventilation, the thermal comfort can be improved from Grade II to Grade I.

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Numerical study of different ceiling-mounted air distribution systems for a virtual classroom environment

Indoor and Built Environment ◽

10.1177/1420326x16659325 ◽

2016 ◽

Vol 26 (10) ◽

pp. 1382-1396 ◽

Cited By ~ 2

Author(s):

Eusébio Z. E. Conceição ◽

Cristina I. M. Santiago ◽

Hazim B. Awbi

Keyword(s):

Air Quality ◽

Thermal Comfort ◽

Air Temperature ◽

Distribution Systems ◽

Numerical Study ◽

Virtual Classroom ◽

Comfort Level ◽

Air Distribution ◽

Air Supply ◽

Distribution Index

This paper presents a comparative numerical study of different ceiling-mounted-localized air distribution systems placed above students in a virtual classroom in summer conditions. The influence of four different ceiling-mounted-localized air distribution systems, using vertical descendent jets, on the thermal comfort, local thermal discomfort, and air quality levels was numerically evaluated. The air distribution index, developed previously, was used for non-uniform environment. This index considers the thermal comfort level, air quality level, effectiveness for heat removal, and effectiveness for contaminant removal. Numerical simulations were conducted for a virtual classroom equipped with one of four different ceiling-mounted-localized air distribution systems and with 6 desks, 6 or 12 students, and 2 upper airflow outlets. Inlet air supply temperature of 20 and 24℃ and an outdoor air temperature of 28℃ were used. The simulation results show that the air supply system having a vertical air jet placed at 1.8 m above the floor level (Case III), and with an inlet area of 0.01 m2 and a supply air velocity of 3 m/s would represent the best option in comparison with other air supply methods. In general, the air distribution index value decreases with an increase in inlet air temperature and the number of occupants. The air distribution index values are highest for Case III representing a classroom with 6 or 12 occupants with an inlet air temperature of 20 or 24℃.

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A Study on Evaluation of ADPI and Ventilation Performance of a Small Auditorium with Unevenly Arranged Return Diffusers

International Journal of Air-Conditioning and Refrigeration ◽

10.1142/s2010132517500298 ◽

2017 ◽

Vol 25 (04) ◽

pp. 1750029

Author(s):

Yong-il Kwon

Keyword(s):

Distribution System ◽

Distribution Systems ◽

Numerical Study ◽

Side Wall ◽

Air Distribution ◽

Rear Wall ◽

System Parameters ◽

Ventilation Efficiency ◽

Ventilation Performance ◽

Air Diffusion

The ventilation performance and thermal comfort characteristics on placing the supply or return diffusers for the air distribution systems applied to an auditorium with high ceiling heights must be inherently considered. A numerical study has been conducted to simulate the airflow and ventilation characteristics in a small auditorium with the uniformly installed supply diffusers on the ceiling surface, and with the unevenly installed return diffusers on the side wall of the stage, the left and rear wall. It is the objective of the present study to investigate the effects of various air distribution system parameters on air diffusion performance index (ADPI), air change efficiency and scale of ventilation efficiency NO.4 (SVE4) of return diffusers in the auditorium with the movable audience seat on the flat floor. This paper focuses mainly on the effect of the unevenly installed return diffusers on the low part of the side wall of the auditorium with the movable audience seat.

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CFD-Based Parametric Analysis on the Performance of Personalized Partition Air Distribution Systems

Solar Energy ◽

10.1115/isec2006-99001 ◽

2006 ◽

Author(s):

Kybum Jeong ◽

Moncef Krarti ◽

Zhiqiang Zhai

Keyword(s):

Thermal Comfort ◽

Air Temperature ◽

Distribution System ◽

Distribution Systems ◽

Comfort Level ◽

Cfd Modeling ◽

Air Distribution ◽

Air Velocity ◽

Comfort Index ◽

System Mode

The partition air distribution systems evaluated in this study allow occupants to control the system mode (on/off) and the supply air velocity and direction with similar flexibility as occupants in automobiles. To find optimal specifications for the partition air distribution systems that are able to achieve comfortable micro-environment, a CFD modeling tool was used to simulate the airflow and thermal performance of the partition air distribution systems in a typical office space. By analyzing the distribution characteristics of indoor air temperature, air velocity and thermal comfort index, the study assessed the performance of the partition air distribution systems with different operating parameters. The simulation results were analyzed and evaluated to assess both occupant’s thermal comfort and system energy consumption. The study shows that space cooling energy can be reduced while maintaining acceptable indoor thermal comfort level using a partition air distribution system with a higher supply air temperature.

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Thermal Comfort Evaluation of a Mixed-mode Ventilated Office Building with Advanced Natural Ventilation and Underfloor air Distribution Systems

Energy Procedia ◽

10.1016/j.egypro.2017.03.214 ◽

2017 ◽

Vol 111 ◽

pp. 520-529 ◽

Cited By ~ 8

Author(s):

Xiang Deng ◽

Georgios Kokogiannakis ◽

Zhenjun Ma ◽

Paul Cooper

Keyword(s):

Thermal Comfort ◽

Mixed Mode ◽

Distribution Systems ◽

Natural Ventilation ◽

Office Building ◽

Air Distribution ◽

Comfort Evaluation ◽

Underfloor Air Distribution

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Indoor Environment Numerical Simulation of All Cold Air Distribution System With Stratified Air Conditioning

ASME 2008 2nd International Conference on Energy Sustainability, Volume 1 ◽

10.1115/es2008-54112 ◽

2008 ◽

Author(s):

Wei Bing ◽

Li Li ◽

Jiang Lu ◽

Zhang Wei

Keyword(s):

Numerical Simulation ◽

Distribution System ◽

Air Conditioning ◽

Distribution Systems ◽

Dew Point ◽

Air Distribution ◽

Large Space ◽

Cold Air ◽

Point Temperature ◽

Dew Point Temperature

At present all cold air distribution systems are being used widely due to their advantages of smaller ductwork, shorter floor-to-floor height and less energy consumption etc. They are mostly used in VAV (Variable Air Volume) systems or with the radiant panel systems in the office and residential buildings at the supply air dew point temperature of 6∼10°C, rarely used in large space buildings. The technology of stratified air conditioning is one of the energy saving technologies to large space buildings, which has been popularly used in the conventional air supply systems with the supply air dew point temperature of 11∼16°C. In this paper, the cold air distribution system and the stratified air conditioning technology in a large space building are combined to study. With the method of CFD, the indoor thermal environment of a large space workshop is simulated. The velocity and the temperature as well as the relative humidity fields under different air flow modes are presented, analyzed and compared. With the help of numerical simulation results, the optimal airflow mode is proposed, which show that the all cold air distribution with the stratified air conditioning is a good option for large space buildings. All these above will be good references to the application of cold air distribution system and the selection of the airflow mode in large space buildings.

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Numerical Study on Effects of Air Return Height on Performance of an Underfloor Air Distribution System for Heating and Cooling

Energies ◽

10.3390/en13051070 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1070

Author(s):

Yaming Fan ◽

Xiangdong Li ◽

Minfeng Zheng ◽

Rengui Weng ◽

Jiyuan Tu

Keyword(s):

Energy Consumption ◽

Air Quality ◽

Thermal Comfort ◽

Distribution System ◽

Numerical Study ◽

Air Distribution ◽

Cooling Mode ◽

Design And Optimization ◽

Heating And Cooling ◽

Heating Mode

The exhaust/return-split configuration is regarded as an important upgrade of traditional under-floor-air-distribution (UFAD) systems due to its higher energy efficiency. Moreover, existing studies are mostly focused on the effect of the return vent height on the performance of an UFAD system under cooling conditions. Knowledge of the performance under heating conditions is sorely lacking. This paper presents a numerical evaluation of the performance characteristics of an UFAD system with six different heights of the return vents in heating operation by comprehensively considering thermal comfort, air quality, and energy consumption. The results show that, in the heating mode, the general thermal comfort (predicted mean vote-predicted percentage dissatisfied (PMV-PPD) values) and indoor air quality indices (mean age of air and volatile organic compounds (VOCs) concentration) were greatly improved and energy consumption was slightly reduced with a lower return vent height. Although these were opposite to the findings of our previous study regarding the performance in cooling mode, an optimal return vent height in terms of the comprehensive all-year performance can be recommended. This method provides insight into the design and optimization of the return vent height of UFAD for space heating and cooling.

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Influence of air distribution in modern large university lecture hall on thermal comfort

International Review of Applied Sciences and Engineering ◽

10.1556/1848.2019.0010 ◽

2019 ◽

Vol 10 (1) ◽

pp. 63-69

Author(s):

Mária Budiaková

Keyword(s):

Thermal Comfort ◽

Distribution System ◽

Air Conditioning ◽

Distribution Systems ◽

Winter Season ◽

Point Of View ◽

Air Distribution ◽

Lecture Hall ◽

Globe Temperature ◽

Air Conditioning Systems

The paper is focused on the influence of air distribution in modern large university lecture hall on the thermal comfort. Providing the optimal parameters of the thermal comfort in the interiors of a university is immensely important for the students. Meeting these parameters is inevitable not only from physiological point of view but also to achieve the desirable students' performance. Parameters of the thermal comfort are also influenced by air distribution system in large university lecture hall. Correct position of supply air and extract air is very important. Experimental measurements of thermal comfort were carried out in the winter season in the large lecture hall of Vienna University of Economics and Business. The device Testo 480 was used for the measurements. Obtained values of air temperature, air relative humidity, air velocity, globe temperature, indexes PMV and PPD are presented in the charts. Modern air distribution system and air conditioning system of the large university lecture hall were evaluated on the basis of thermal comfort parameters. Conclusion of this paper states the principles of how to design modern air distribution systems and air conditioning systems in the new large university lecture halls.

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Thermal Comfort and Energy Analysis of a Hybrid Cooling System by Coupling Natural Ventilation with Radiant and Indirect Evaporative Cooling

Energies ◽

10.3390/en14227825 ◽

2021 ◽

Vol 14 (22) ◽

pp. 7825

Author(s):

Pradeep Shakya ◽

Gimson Ng ◽

Xiaoli Zhou ◽

Yew Wah Wong ◽

Swapnil Dubey ◽

...

Keyword(s):

Thermal Comfort ◽

Hybrid System ◽

Natural Ventilation ◽

Cooling System ◽

Evaporative Cooling ◽

Supply System ◽

Hybrid Cooling ◽

Air Supply ◽

Radiant Cooling ◽

Indirect Evaporative Cooling

A hybrid cooling system which combines natural ventilation with a radiant cooling system for a hot and humid climate was studied. Indirect evaporative cooling was used to produce chilled water at temperatures slightly higher than the dew point. With this hybrid system, the condensation issue on the panel surface of a chilled ceiling was overcome. A computational fluid dynamics (CFD) model was employed to determine the cooling load and the parameters required for thermal comfort analysis for this hybrid system in an office-sized, well-insulated test room. Upon closer investigation, it was found that the thermal comfort by the hybrid system was acceptable only in limited outdoor conditions. Therefore, the hybrid system with a secondary fresh air supply system was suggested. Furthermore, the energy consumptions of conventional all-air, radiant cooling, and hybrid systems including the secondary air supply system were compared under similar thermal comfort conditions. The predicted results indicated that the hybrid system saves up to 77% and 61% of primary energy when compared with all-air and radiant cooling systems, respectively, while maintaining similar thermal comfort.

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