Optimal Minimum Airflow for Air Circulation of Single-Duct VAV Terminal Boxes

2008 ◽  
Author(s):  
Young-Hum Cho ◽  
Mingsheng Liu
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Thermal Discomfort ◽  
Variable Air Volume ◽  
Air Handling Unit ◽  
Optimal Value ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Air Circulation ◽  
The Impact

Thermal comfort in an area is directly controlled by terminal boxes in variable air volume (VAV) air-handling unit (AHU) systems. The terminal box either modulates airflow or adjusts the discharge air temperature. Reduced air circulation will cause thermal discomfort in a conditioned space if the airflow and discharge air temperature are not suitable. The objective of this study is to identify an optimal value for airflow and discharge air temperature that will maintain room thermal comfort. Optimal room airflow and discharge air temperature is analyzed, and the impact of room airflow and discharge air temperature on thermal stratification is verified through CFD (Computational Fluid Dynamics) simulations.

A comparison of the thermal comfort performances of a radiation floor cooling system when combined with a range of ventilation systems

2019 ◽  
Vol 29 (4) ◽  
pp. 527-542 ◽  
Author(s):  
Jiying Liu ◽  
Zhuangzhuang Li ◽  
Moon Keun Kim ◽  
Shengwei Zhu ◽  
Linhua Zhang ◽  
...  
Keyword(s):  
Thermal Comfort ◽  
Cooling System ◽  
Whole Body ◽  
Equivalent Temperature ◽  
Thermal Discomfort ◽  
Computational Fluid Dynamics Simulations ◽  
Radiant Floor Cooling System ◽  
Personalized Ventilation ◽  
Dynamics Simulations ◽  
Ventilation Systems

This study conducted a series of computational fluid dynamics simulations to evaluate the thermal comfort performance of a radiant floor cooling system when combined with different ventilation systems, including mixed ventilation (MV), stratum ventilation (SV), displacement ventilation (DV) and ductless personalized ventilation (DPV). A window temperature of 32°C and three different floor temperatures including 20, 22 and 24°C were set in summer. We used the vertical air temperature differences (VATD) at ankle and head level, the percentage of dissatisfied, the draught rate at the ankle level and the equivalent temperature as our main evaluation indices. Our results show that the VATD in DV system can reach up to about 5°C, compared with about 2°C in MV and SV systems. For the DPV system, there is only a marginal drop in the VATD. For the DV and DPV cases, with a rate of air changes per hour (ACH) of 2.4−1, we recorded a higher draught rate at the ankle level, ranging from 6.55% to 9.99%. The lower equivalent temperature values for the foot and calf segments occur when the floor temperature is 20°C. In all cases, the equivalent temperature values of the whole body indicate an acceptable level of thermal discomfort.

scholarly journals The impact of thermal comfort in the perceived level of service and energy costs of three Brazilian airports

2013 ◽  
Vol 7 (2) ◽  
pp. 192-206 ◽  
Author(s):  
Jacqueline Elhage Ramis ◽  
Emmanuel Antonio dos Santos
Keyword(s):  
Thermal Comfort ◽  
Air Conditioning ◽  
International Standards ◽  
Combined System ◽  
Service Levels ◽  
Transportation Demand ◽  
Temperature And Humidity ◽  
Air Conditioning Systems ◽  
Air Circulation ◽  
The Impact

To evaluate airports' current thermal comfort temperature and humidity were registered in three main Brazilian international airports, other variables were local region climate characteristics and the constructive types of passenger terminal buildings. The Brazilian air transportation demand has considerably grown over the last decade, with some airports reaching their capacity. Thermal discomfort may be a key driver of passenger perceptions of airport service levels, specially under capacity overload situations. Therefore, to achieve airport thermal comfort within this new scenario, and with the imminent and future expansions of the airport system, certainly put extra work on the existing air conditioning systems, consequently increasing energy consumption and its associated costs. Collected temperature and humidity from each study case subsided the data for the psychrometric charts. The evidences showed temperatures below the international standards requirements for thermal comfort levels. These charts also indicated that adequate building types with natural air circulation, provides the best levels of thermal comfort. Results suggest the importance of considering the implementation of a combined system using artificial and natural air conditioning in the planning of future expansions.

scholarly journals Building and Urban Cooling Performance Indexes of Wetted and Green Roofs—A Case Study under Current and Future Climates

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6192
Author(s):  
Madi Kaboré ◽  
Emmanuel Bozonnet ◽  
Patrick Salagnac
Keyword(s):  
Thermal Comfort ◽  
Emission Scenario ◽  
Green Roof ◽  
Heat Fluxes ◽  
Temperate Climate ◽  
Passive Cooling ◽  
Thermal Discomfort ◽  
Indoor Thermal Comfort ◽  
Performance Indexes ◽  
The Impact

We developed and studied key performance indexes and representations of energy simulation heat fluxes to evaluate the performance of the evaporative cooling process as a passive cooling technique for a commercial building typology. These performance indexes, related to indoor thermal comfort, energy consumption and their interactions with their surrounding environments, contribute to understanding the interactions between the urban climate and building for passive cooling integration. We compare the performance indexes for current and future climates (2080), according to the highest emission scenario A2 of the Special Report on Emission Scenario (SRES). Specific building models were adapted with both green roof and wetted roof techniques. The results show that summer thermal discomfort will increase due to climate change and could become as problematic as winter thermal discomfort in a temperate climate. Thanks to evapotranspiration phenomena, the sensible heat contribution of the building to the urban heat island (UHI) is reduced for both current and future climates with a green roof. The performance of the vegetative roof is related to the water content of the substrate. For wetted roofs, the impacts on heat transferred to the surrounding environment are higher for a Mediterranean climate (Marseille), which is warmer and drier than the Paris climate studied (current and future climates). The impact on indoor thermal comfort depends on building insulation, as demonstrated by parametric studies, with higher effects for wetted roofs.

scholarly journals User Thermal Comfort in Historic Buildings: Evaluation of the Potential of Thermal Mass, Orientation, Evaporative Cooling and Ventilation

2020 ◽  
Vol 12 (22) ◽  
pp. 9672
Author(s):  
Mamdooh Alwetaishi ◽  
Ashraf Balabel ◽  
Ahmed Abdelhafiz ◽  
Usama Issa ◽  
Ibrahim Sharaky ◽  
...  
Keyword(s):  
Thermal Comfort ◽  
High Altitude ◽  
Air Temperature ◽  
Thermal Performance ◽  
Indoor Air ◽  
Computer Modelling ◽  
Evaporative Cooling ◽  
Comfort Level ◽  
Thermal Mass ◽  
The Impact

The study investigated the level of thermal comfort in historical buildings located at a relatively high altitude in the Arabian Desert of Saudi Arabia. The study focused on the impact of the use of thermal mass and orientation on the level of thermal performance at Shubra and Boqri Palaces. Qualitative and quantitative analyses were used in this study, including a questionnaire interview with architecture experts living at the relatively high altitude of Taif city, to obtain data and information from local experts. The computer software TAS EDSL was used along with on-site equipment, such as thermal imaging cameras and data loggers, to observe the physical conditions of the building in terms of its thermal performance. The study revealed that the experts’ age and years of experience were important aspects while collecting data from them during the survey. The use of thermal mass had a slight impact on the indoor air temperature as well as the energy consumption, but it helped in providing thermal comfort. Use of ventilation can improve thermal comfort level. Evaporative cooling technique has a considerable impact on reducing indoor air temperature with 4 °C drop, improving the thermal comfort sensation level. The novelty of this work is that, it links the outcomes of qualitative results of experts with field monitoring as well as computer modelling. This can contribute as method to accurately collect data in similar case studies.

Optimal Outside Airflow Control of an Integrated Air-Handling Unit System for Large Office Buildings

2004 ◽  
Vol 126 (1) ◽  
pp. 614-619 ◽  
Author(s):  
L. Song ◽  
M. Liu
Keyword(s):  
Air Temperature ◽  
Linear Optimization ◽  
Optimization Method ◽  
Geometric Optimization ◽  
Variable Air Volume ◽  
Unit System ◽  
Analytical Functions ◽  
Air Handling Unit ◽  
Conventional Systems ◽  
Air Control

This paper presents optimal outside air control schedules for an integrated air-handling unit system for large commercial buildings (OAHU). The schedules are developed using the geometric linear optimization method and expressed as analytical functions of the outside air temperature and enthalpy, the interior zone airflow ratio, and the exterior zone supply air temperature. The optimal outside air control schedules can be applied to both constant and variable air volume systems. When the schedules are implemented, the OAHU system can significantly improve indoor air quality (IAQ) and use significantly less thermal energy than conventional systems. The geometric optimization method can also be used in other linear HVAC optimizations with non-liner constraint conditions.

Towards Pedestrian Microclimatic Comfort: A Rapid Predication Model for Street Winds and Pedestrian Thermal Sensation

Nano LIFE ◽  
2018 ◽  
Vol 08 (02) ◽  
pp. 1840006
Author(s):  
Jing Li ◽  
Mengnan Qi ◽  
Qiuhua Duan ◽  
Lei Huo ◽  
Julian Wang
Keyword(s):  
Wind Speed ◽  
Built Environment ◽  
Thermal Comfort ◽  
Air Temperature ◽  
Goodness Of Fit ◽  
Comfort Level ◽  
Outdoor Thermal Comfort ◽  
Design Parameters ◽  
Rapid Urbanization ◽  
The Impact

Significant changes in the urban built environment have occurred due to rapid urbanization and increases in the urban population. Such alterations may produce environmental health-related issues such as urban heat stress, air pollution and traffic noise. This research undertook a field study to collect data including urban design parameters, micro-environmental factors and city climatic information. This work was conducted over a two-year period on three pedestrian streets located in high-density urban areas in Beijing. These areas were selected in order to study the influences of urban street canyon texture within a particular geometric layout, wind flow corridors and variations in air temperature on pedestrian microclimatic comfort. The results will facilitate the work of urban planners by providing them with information for use in improving outdoor thermal comfort through their designs. A total of 60[Formula: see text]485 samples were organized into training, validation and test sets. We confirmed our hypothesis that internal wind speed ([Formula: see text] is attributable mainly to the urban texture coefficient ([Formula: see text], air temperature ([Formula: see text] and leading-in wind speed ([Formula: see text]. The model was tested using the test data collected onsite, which demonstrated a very accurate goodness-of-fit; the model achieved an R-squared value of 0.82, which meant that [Formula: see text] as a dependent variable was 82% correlated to the three predictors as independent variables. With this computer simulation, urban planners can now predict and visualize the impact of changes on the built environment in terms of either the direction of solar radiation received or increases in wind speed, in return for the desired thermal comfort level for residents of the neighborhood.

Impact of Optimal Discharge Air Temperature and Minimum Airflow

2009 ◽  
Author(s):  
Young-Hum Cho ◽  
Young-hoon Jung ◽  
Mingsheng Liu
Keyword(s):  
Air Temperature ◽  
Thermal Stratification ◽  
Room Temperature ◽  
Energy Savings ◽  
The Other ◽  
Waste Energy ◽  
Heating Load ◽  
Save Energy ◽  
Air Circulation ◽  
The Impact

Airflow and discharge air temperature can be varied to maintain room temperature setpoint according to heating load. Increasing discharge air temperature and the decreasing airflow can save energy, but it causes reduced air circulation as supply air temperature rises above the space temperature. On the other hand, increasing airflow can improve air circulation; however, it may waste energy. The objective of this study is to identify the correlation between the minimum airflow and discharge air temperature that will maintain room thermal comfort. Optimal room airflow and discharge air temperature were analyzed, and the impact of room airflow and discharge air temperature on thermal stratification was evaluated and potential energy savings was estimated. Its performance was conducted through field experiment.

scholarly journals Impact of the Design of Walls Made of Compressed Earth Blocks on the Thermal Comfort of Housing in Hot Climate

Buildings ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 157 ◽  
Author(s):  
Césaire Hema ◽  
Adamah Messan ◽  
Abdou Lawane ◽  
Geoffrey Van Moeseke
Keyword(s):  
Thermal Comfort ◽  
Inside Surface ◽  
Living Room ◽  
Thermal Discomfort ◽  
Hot Climate ◽  
Compressed Earth Blocks ◽  
Concrete Blocks ◽  
Earth Blocks ◽  
Annual Reduction ◽  
The Impact

This study investigated the impact of the design of wall systems, mainly made of compressed earth blocks (CEB), on the indoor thermal comfort of naturally ventilated housing in hot climates of Burkina Faso. Conventional housing was modeled and calibrated using the WUFI® Plus dynamic simulation tool based on typical field surveys and the literature. This allowed testing the ability of different wall designs to impact thermal comfort. Thermal discomfort was assessed through an adaptive approach and was based on the annual weighted exceedance hours of overheating. Six designs of walls made of CEB and other locally available materials were simulated and compared to those made of classical hollow concrete blocks. The results of the simulation reveal that the profiles of thermal discomfort vary depending on the wall designs and building spaces. Thus, the wall made, from the outside toward the inside surface, of plywood of 2 cm, an insulation layer of 5 cm and a CEB layer of 29 cm thickness is the most suitable for an annual reduction in overheating for the living room. Regarding the bedroom, the most suitable wall is made of a 14 cm CEB layer, 5 cm insulating layer and 2 cm wood layer from the outside toward the inside surface.

scholarly journals Hybrid Ventilation in an Air-Conditioned Office Building with a Multistory Atrium for Thermal Comfort: A Practical Case Study

Buildings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 625
Author(s):  
Hao-Hsiang Hsu ◽  
Wei-Hwa Chiang ◽  
Jian-Sheng Huang
Keyword(s):  
Thermal Comfort ◽  
Public Space ◽  
Office Building ◽  
Practical Case ◽  
Displacement Ventilation ◽  
Cold Air ◽  
The Public ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Stack Ventilation

This study involved a series of computational fluid dynamics simulations to evaluate the effectiveness of stack and displacement ventilation in providing better thermal comfort in an air-conditioned office building. To reduce energy consumption, the public area of the studied building is cooled by air from air-conditioned rooms with lower temperatures. The air, which is driven by buoyancy, then, flows outside through the multistory atrium. The simulation results indicated that displacement ventilation provides superior thermal comfort performance relative to stack ventilation. A design with a higher ceiling, a higher heat source and a lower inlet with cold air can substantially enhance the efficiency of displacement ventilation. Furthermore, handrails near the atrium play a crucial role because they help to retain cold air in the public space for a longer period, thereby contributing to a better predicted mean vote value.

scholarly journals AIR TEMPERATURE AND RELATIVE MOISTURE OSCILLATIONS IN RECIFE – PE

2019 ◽  
Vol 9 (1) ◽  
pp. 30
Author(s):  
Manoel Vieira De França ◽  
Romildo Morant de Holanda De Holanda ◽  
Raimundo Mainar De Medeiros
Keyword(s):  
Quality Of Life ◽  
Relative Humidity ◽  
Air Temperature ◽  
Large Scale ◽  
Statistical Parameters ◽  
Thermal Discomfort ◽  
Deviation Coefficient ◽  
Air Circulation ◽  
The City

The objective of this study was to study temperature variability and relative humidity, comparing the 1962-1990 and 1991-2016 periods with the averages of 1931-2016 and 1962-2016, respectively, with the aim of quantifying climate change and identifying the influence Of large-scale El Niño events, aiming to contribute to the managers responsible for urban planning and improving the quality of life of the inhabitants and the ecosystem. Air temperature and relative humidity data provided by the National Institute of Meteorology (INMET) were used. Basic statistical parameters were calculated as: mean, standard deviation, coefficient of variance, variations of annual anomalies in order to identify buoyancy in the data and the influence of extreme events. The city of Recife suffered from disorderly growth, with no specific patterns of planning in urbanization that caused variations in the microclimate of the urbis, causing thermal discomfort and reducing the quality of life of its inhabitants. There is intense flow of automotive vehicles and people throughout the day due to activities related to work, commerce and services, as well as the concentration of various buildings, waterproofed areas as well as buildings, making the local air circulation difficult. It is suggested an increase in green areas from the afforestation that has been shown as an alternative to improve the quality of life in urban spaces.

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