Thermal comfort investigation of stratified indoor environment in displacement ventilation: Climate-adaptive building with smart windows

2019 ◽  
Vol 46 ◽  
pp. 101354 ◽  
Author(s):  
Khalesi Javad ◽  
Goudarzi Navid
Keyword(s):  
Thermal Comfort ◽  
Indoor Environment ◽  
Displacement Ventilation ◽  
Smart Windows

scholarly journals Incorporating cooling and ventilation effects into a single IEQ indicator

2019 ◽  
Vol 111 ◽  
pp. 02011
Author(s):  
Matjaž Prek ◽  
Gorazd Krese ◽  
Žiga Lampret
Keyword(s):  
Thermal Comfort ◽  
Indoor Environment ◽  
Cooling System ◽  
Ventilation System ◽  
Whole Body ◽  
Indoor Environmental Quality ◽  
Displacement Ventilation ◽  
Wall Displacement ◽  
Flat Wall ◽  
Ventilation Effectiveness

The influence of dissimilar cooling and ventilation system combinations on indoor environmental quality (IEQ) has been studied. A comparison of chilled ceiling cooling in combination with displacement ventilation, cooling with fan coil unit, and cooling with flat wall displacement inlets was performed. All observed variations were evaluated based on whole-body and local thermal comfort criteria as well as with regard to ventilation effectiveness. The analysis was made based on results of numerical simulations carried out in two steps. First, DesignBuilder was applied to model the buildings’ thermal performance and to evaluate its interaction with the environment. The latter included the calculation of heat gains as well as the heat loss on the boundary surfaces of the observed air-conditioned room. In the second step, ANSYS Fluent was used to simulate the response of indoor environment by utilizing the simulation results obtained in the first step, in order to evaluate the interaction between building and human. Afterwards, the observed thermal comfort and ventilation criteria were merged into a novel indoor environment indicator, which enables to describe the indoor environment quality with a single value. Among the analysed systems, the ceiling cooling system in combination with displacement ventilation was found to be the most suitable as it offers a high level of thermal comfort with adequate ventilation efficiency. Fan coil cooling was the least favourable option in terms of thermal comfort, while flat wall displacement inlets exhibited the lowest ventilation effectiveness. The performed investigation demonstrated the necessity to assess indoor environment with regard to IEQ in addition to energy consumption.

scholarly journals Barriers on Establishing Passive Strategies in Office Spaces: A Case Study in a Historic University Building

2021 ◽  
Vol 13 (8) ◽  
pp. 4563
Author(s):  
Nuno Baía Baía Saraiva ◽  
Luisa Dias Dias Pereira ◽  
Adélio Rodrigues Gaspar ◽  
José Joaquim da Costa
Keyword(s):  
Thermal Comfort ◽  
Indoor Environment ◽  
Hvac Systems ◽  
Heritage Buildings ◽  
Full Capacity ◽  
Free Cooling ◽  
Passive Strategies ◽  
The University ◽  
Indoor Conditions

The adaptation of spaces to different usage typologies can be complex in heritage buildings. Facilities were initially planned for a specific type of use that, when changed, require additional measures to ensure a suitable indoor environment. Passive strategies—e.g., free cooling—are commonly used as an alternative without requiring equipment installation. However, its implementation often leads to unsatisfactory conditions. Therefore, it is important to clarify the main barriers to achieving thermal comfort in readapted historic buildings. The present work investigates the thermal comfort conditions reported by workers in office spaces of a historic building in the University of Coimbra. A monitoring campaign was carried out between May and September 2020 to assess indoor conditions’ quality. Due to the current pandemic of COVID-19, offices were not occupied at full capacity. A one-day evaluation of thermal comfort was made using a climate analyzer and six occupants were surveyed on 19 August 2020. The main results highlighted discomfort due to overheating of spaces. The causes were related to the combination of inadequate implementation of the free cooling actions and the building use. Furthermore, it was recommended the installation of HVAC systems in case of full capacity.

scholarly journals Thermal comfort in winter incorporating solar radiation effects at high altitudes and performance of improved passive solar design—Case of Lhasa

2020 ◽  
Author(s):  
Lingjiang Huang ◽  
Jian Kang
Keyword(s):  
Solar Radiation ◽  
Thermal Comfort ◽  
Energy Saving ◽  
Solar Irradiance ◽  
Indoor Environment ◽  
Thermal Mass ◽  
High Altitudes ◽  
Energy Saving Potential ◽  
Environment Control ◽  
Passive Solar

AbstractThe solar incidence on an indoor environment and its occupants has significant impacts on indoor thermal comfort. It can bring favorable passive solar heating and can result in undesired overheating (even in winter). This problem becomes more critical for high altitudes with high intensity of solar irradiance, while received limited attention. In this study, we explored the specific overheating and rising thermal discomfort in winter in Lhasa as a typical location of a cold climate at high altitudes. First, we evaluated the thermal comfort incorporating solar radiation effect in winter by field measurements. Subsequently, we investigated local occupant adaptive responses (considering the impact of direct solar irradiance). This was followed by a simulation study of assessment of annual based thermal comfort and the effect on energy-saving potential by current solar adjustment. Finally, we discussed winter shading design for high altitudes for both solar shading and passive solar use at high altitudes, and evaluated thermal mass shading with solar louvers in terms of indoor environment control. The results reveal that considerable indoor overheating occurs during the whole winter season instead of summer in Lhasa, with over two-thirds of daytime beyond the comfort range. Further, various adaptive behaviors are adopted by occupants in response to overheating due to the solar radiation. Moreover, it is found that the energy-saving potential might be overestimated by 1.9 times with current window to wall ratio requirements in local design standards and building codes due to the thermal adaption by drawing curtains. The developed thermal mass shading is efficient in achieving an improved indoor thermal environment by reducing overheating time to an average of 62.2% during the winter and a corresponding increase of comfort time.

Computational Modeling of Particulate Pollutant Transport in a Ventilated Room in the Presence of Two Heated Breathing and Rotating Manikins

2017 ◽  
Author(s):  
Seyed Ali Keshavarz ◽  
Mazyar Salmanzadeh ◽  
Goodarz Ahmadi
Keyword(s):  
Air Quality ◽  
Computational Modeling ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Rotational Motion ◽  
Indoor Environment ◽  
Ventilation System ◽  
Thermal Plume ◽  
Displacement Ventilation ◽  
Simulation Results

Recently, attention has been given to indoor air quality due to its serious health concerns. Clearly the dispersion of pollutant is directly affected by the airflow patterns. The airflow in indoor environment is the results of a combination of several factors. In the present study, the effects of thermal plume and respiration on the indoor air quality in a ventilated cubicle were investigated using an unsteady computational modeling approach. The person-to-person contaminant transports in a ventilated room with mixing and displacement ventilation systems were studied. The effects of rotational motion of the heated manikins were also analyzed. Simulation results showed that in the cases which rotational motion was included, the human thermal plume and associated particle transport were significantly distorted. The distortion was more noticeable for the displacement ventilation system. Also it was found that the displacement ventilation system lowered the risk of person-to-person transmission in an office space in comparison with the mixing ventilation system. On the other hand the mixing system was shown to be more effective compared to the displacement ventilation in removing the particles and pollutant that entered the room through the inlet air diffuser.

scholarly journals Indoor Thermal Comfort Analysis: A Case Study of Modern and Traditional Buildings in Hot-Arid Climatic Region of Ethiopia

Urban Science ◽  
2021 ◽  
Vol 5 (3) ◽  
pp. 53
Author(s):  
Haven Hailu ◽  
Eshetu Gelan ◽  
Yared Girma
Keyword(s):  
Thermal Comfort ◽  
Significant Role ◽  
Indoor Environment ◽  
Thermal Sensation ◽  
Climatic Region ◽  
Contributing Factors ◽  
Objective Measurements ◽  
Indoor Thermal Comfort ◽  
Adaptive Comfort

Indoor thermal comfort is an essential aspect of sustainable architecture and it is critical in maintaining a safe indoor environment. Expectations, acceptability, and preferences of traditional and modern buildings are different in terms of thermal comfort. This study, therefore, attempts to evaluate the indoor thermal comforts of modern and traditional buildings and identify the contributing factors that impede or facilitate indoor thermal comfort in Semera city, Ethiopia. This study employed subjective and objective measurements. The subjective measurement is based on the ASHRAE seven-point thermal sensation scale. An adaptive comfort model was employed according to the ASHRAE standard to evaluate indoor thermal comfort. The results revealed that with regards to thermal sensational votes between −1 and +1, 88% of the respondents are satisfied with the indoor environment in traditional houses, while in modern houses this figure is 22%. Likewise, 83% of occupants in traditional houses expressed a preference for their homes to remain the same or be only slightly cooler or warmer. Traditional houses were, on average, in compliance with the 80% acceptability band of the adaptive comfort standard. The study investigated that traditional building techniques and materials, in combination with consideration of microclimate, were found to play a significant role in regulating the indoor environment.

scholarly journals Thermal Comfort Evaluation of Rooms Installed with STPV Windows

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 808 ◽  
Author(s):  
Hao Tian ◽  
Wei Zhang ◽  
Lingzhi Xie ◽  
Zhichun Ni ◽  
Qingzhu Wei ◽  
...  
Keyword(s):  
Thermal Comfort ◽  
Indoor Environment ◽  
Thermal Sensation ◽  
Test Results ◽  
Test Unit ◽  
Maximum Difference ◽  
Test Rig ◽  
Comfort Evaluation ◽  
The Difference ◽  
Better Than

Thermal comfort is an important aspect to take into consideration for the indoor environment of a building integrated with a semi-transparent Photovoltaics (STPV) system. The thermal comfort of units with photovoltaic windows and that of conventional windows, which is an ordinary without PV, were evaluated via on-site tests and questionnaires. Using the thermal comfort investigation of the test rig, the maximum difference in air temperature was found to be around 5 °C between test unit and comparison unit. The predicted mean vote (PMV)–predicted percentage dissatisfied (PPD) value of the test unit was better than that of the comparison unit. It was observed that on sunny days, the PMV value ranged from 0.2 (nature) to 1.3 (slightly warm) in the test unit, and that of the comparison unit was 0.7 (slightly warm) to 2.0 (warm), thereby providing better thermal comfort, especially during mornings. The maximum difference in PPD values was found to reach 27% between the two units at noon. On cloudy days, the difference was negligible, and the thermal sensation between the foot and the head were almost the same. Fifty respondents were asked to complete a carefully designed questionnaire. The thermal sensation of the test unit was better than that of comparison unit, which corresponded with the test results. Thermal, lighting, acoustic, and other environment comfort scores were combined, and the acceptance of the test unit with the STPV windows was found to be 73.8%. The thermal sensation difference between men and women was around 5%. Thus, during summer, STPV windows can improve the thermal comfort and potentially reduce the air-conditioning load.

scholarly journals The Derivation of Cooling Set-Point Temperature in an HVAC System, Considering Mean Radiant Temperature

2019 ◽  
Vol 11 (19) ◽  
pp. 5417
Author(s):  
Jinmog Han ◽  
Jongkyun Bae ◽  
Jihoon Jang ◽  
Jumi Baek ◽  
Seung-Bok Leigh
Keyword(s):  
Thermal Comfort ◽  
Indoor Environment ◽  
Thermal Characteristics ◽  
Weather Conditions ◽  
System Control ◽  
Hvac System ◽  
Mean Radiant Temperature ◽  
Point Temperature ◽  
Set Point ◽  
Radiant Temperature

Heating, ventilation, and air-conditioning (HVAC) systems usually have a set-point temperature control feature that uses the indoor dry-bulb temperature to control the indoor environment. However, an incorrect set-point temperature can reduce thermal comfort and result in unnecessary energy consumption. This study focuses on a derivation method for the optimal cooling set-point temperature of an HVAC system used in office buildings, considering the thermal characteristics and daily changes in the weather conditions, to establish a comfortable indoor environment and minimize unnecessary energy consumption. The operative temperature is used in the HVAC system control, and the mean radiant temperature is predicted with 94% accuracy through a multiple regression analysis by applying the indoor thermal environment data and weather information. The regression equation was utilized to create an additional equation to calculate the optimal set-point temperature. The simulation results indicate that the HVAC system control with the new set-point temperatures calculated from the derived equation improves thermal comfort by 38.5% (26%p). This study confirmed that a cooling set-point temperature that considers both the thermal characteristics of a building and weather conditions is effective in enhancing the indoor thermal comfort during summer.

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