Application of solar radiation to the ventilation of an experimental chamber through a set of dual skin facades

2020 ◽  
pp. 25-35
Author(s):  
Eusébio Conceição ◽  
João Gomes ◽  
Mª Manuela Lúcio ◽  
Mª Inês Conceição ◽  
Hazim Awbi
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Integral Equations ◽  
Indoor Air ◽  
Carbon Dioxide Concentration ◽  
Integral Model ◽  
Experimental Chamber ◽  
Airflow Rate ◽  
Numerical Work

The aim of this numerical work is to evaluate the influence of a set of three Dual Skin Façades (DSF) on the thermal comfort and air quality inside a virtual occupied experimental chamber under various airflow rates. Each DSF is constituted by two transparent glasses and an adjustable venetian blind located in the air channel existing between the two surfaces. A system of energy balance integral equations is used to estimate the air temperature inside the virtual chamber and DSF and the temperature in the different elements of the virtual chamber and a system of mass balance integral equations is used to estimate the contaminants inside the virtual chamber and the DSF. The uncomfortable hours integral model is used to evaluate the total number of uncomfortable hours due to warm and cold indoor conditions and also due to indoor air quality conditions. The acceptable levels of indoor thermal comfort, evaluated by the Predicted Mean Vote index, must be within category C of ISO 7730 standard. The acceptable levels of indoor air quality, evaluated by the carbon dioxide concentration, must be below the limit of 1800 mg/m3 proposed by the ASHRAE 62.1 standard. Three airflow rates were chosen: 0.0389 m3/s, 0.0778 m3/s and 0.1167 m3/s. The airflow that guarantees, at the same time, the best indoor air quality and thermal comfort levels is obtained through the minimization of the total number of uncomfortable hours. As best option, it was obtained the airflow rate of 0.1167 m3/s.

scholarly journals Application of Horizontal Confluents Jets in a School Virtual Chamber

2021 ◽  
Vol 246 ◽  
pp. 02005
Author(s):  
Eusébio Conceição ◽  
Mª Inês Conceição ◽  
João Gomes ◽  
Mª Manuela Lúcio ◽  
Hazim Awbi
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Exhaust System ◽  
Comfort Level ◽  
Experimental Chamber ◽  
Airflow Rate ◽  
Inlet System ◽  
Head Level

The study presented in this work is performed in a virtual chamber, similar to an existing experimental chamber, with dimensions of 4.50×2.55×2.50 m3. The chamber, occupied with twelve virtual manikins, is equipped with six tables, twelve chairs, one exhaust system and one inlet system, based in confluents jets system. In the exhaust system are considered six air ducts, located above the head level, connected to the ceiling area. The inlet system, based in four vertical ducts, with 0.15 m diameter, located on the corners of the chamber, are equipped with consecutive holes, that promotes horizontal jets near the wall. The results demonstrate that when the airflow rate increases the air quality number increases, the thermal comfort number decreases and the ADI increases slightly. The predicted percentage of dissatisfied index values show that the thermal comfort level is acceptable, the dioxide carbon concentration values show that the indoor air quality is near the acceptable value and the Draught Risk is acceptable.

scholarly journals Comparative Study of a Clean Technology Based on DSF Use in Occupied Buildings for Improving Comfort in Winter

2021 ◽  
Vol 3 (2) ◽  
pp. 311-334
Author(s):  
Eusébio Conceição ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Maria Inês Conceição ◽  
Hazim Awbi
Keyword(s):  
Air Quality ◽  
Comparative Study ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Thermal Response ◽  
Clean Technology ◽  
Comfort Level ◽  
Airflow Rate ◽  
Winter Conditions

This paper presents a comparative study of a clean technology based on a DSF (double skin facade) used in winter conditions in the occupied buildings comfort improvement, namely the thermal comfort and air quality. The performance of a solar DSF system, the building’s thermal response, the internal thermal comfort and the internal air quality are evaluated. In this study, a DSF system, an air transport system and a HVAC (heating, ventilating and air conditioning) system based on mixing ventilation are used. The study considers a virtual chamber occupied by eight persons and equipped, in the outside environment, by three DSFs. A new horary pre-programming control methodology is developed and applied when the airflow rate is constant and the number of DSFs to operate is variable, when the airflow rate is variable and the number of DSFs to operate is constant and when the airflow rate is variable and the number of DSFs to operate is variable. This work uses a numerical model that simulates the integral building thermal behavior and an integral human thermal response. The internal air, provided by a mixing ventilating system, is warmed using the DSF system. The air temperature inside the DSF system and the virtual chamber, the thermal comfort level using the PMV index, the internal air quality using the carbon dioxide concentration and the uncomfortable hours are calculated for winter conditions. The results obtained show that the energy produced in the DSF, using solar radiation, guarantees acceptable thermal comfort conditions in the morning and in the afternoon. The indoor air quality obtained at the breathing level is acceptable. It is found that the airflow rate to be used is more decisive than the DSF operating methodology. However, when a solution is chosen that combines a ventilation rate with the number of DSF to operate, both variables throughout the day can obtain simultaneously better results for indoor air quality and thermal comfort according to the standards.

scholarly journals Thermal comfort analysis in office buildings with different air-conditioning systems

2018 ◽  
Vol 9 (1) ◽  
pp. 59-63 ◽  
Author(s):  
J. Szabo ◽  
L. Kajtar
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Air Conditioning ◽  
Carbon Dioxide Concentration ◽  
Comfort Level ◽  
Office Buildings ◽  
Ducted Fan ◽  
Air Conditioning Systems

It is a prime aim to ensure a suitable comfort level in case of office buildings. The productivity of office employees is directly influenced by the comfort. Thermal discomfort and poor indoor air quality deteriorate the intensity and quality of human work. We investigated the comfort in office buildings with on-site measurements during the summer season. The office buildings were operating with different HVAC (Heating, Ventilating and Air-Conditioning) systems: ducted fan-coil with suspended ceiling, installation, non-ducted fan-coil with floor-mounted installation, active chilled beam with fresh air supply. We evaluated the thermal comfort under PMV (Predicted Mean Vote), PPD (Predicted Percentage of Dissatisfied), the local discomfort based on DR (Draught Rate) and the IAQ (Indoor Air Quality) based on carbon dioxide concentration. The comfort measurements were evaluated. The measurements were evaluated with scientific research methods, comfort categories based on the requirements of CR 1752. The results of this comparison were presented in this article.

Evaluation of comfort levels in office space equipped with HVAC system based in personalized ventilation system using energy produced in DSF systems

2020 ◽  
pp. 65-74
Author(s):  
Eusébio Conceição ◽  
Mª Inês Conceição ◽  
Mª Manuela Lúcio ◽  
João Gomes ◽  
Hazim Awbi
Keyword(s):  
Air Quality ◽  
Numerical Model ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Numerical Study ◽  
Ventilation System ◽  
Airflow Rate ◽  
Hvac System ◽  
Personalized Ventilation

In this study the numerical simulation of a Heating, Ventilating and Air Conditioning (HVAC) system, based in a personalized ventilation system, installed in an occupied office desk is made. The energy is produced in a Dual Skin Facades (DSF) system installed in the outdoor environment. The personalized ventilation system, placed above and below the writing area, installed in the desk central area. The office desk is occupied by eight virtual manikins. The numerical simulation is made in a winter typical day. This numerical study considers a coupling of a differential numerical model and an integral numerical model. The differential numerical model simulates the Computational Fluids Dynamics (CFD), evaluates the air velocity, air temperature, turbulence intensity and carbon dioxide concentration and calculates the indoor air quality. The integral numerical model simulates the Multi-Node Human Thermo-physiology Model, evaluates the tissue, blood and clothing temperatures distribution and calculates the thermal comfort level. The HVAC system, based on a DSF system, is built using three DSF unities, is equipped with internal venetian blinds. Each one, installed in a virtual chamber, is turned to south. The personalized ventilation system, made with eight upper and eight lower air terminal devices, is installed in the desk central area. On each table top two upper and two lower air terminal devices are considered in the left and right manikin area, while on each side of the table two upper and two lower air terminal devices are placed between the manikins. The office desk is occupied by eight virtual manikins, one sitting on each table top and three sitting on each side of the meeting table. In this numerical study, carried out in winter conditions, the occupants’ clothing level is 1 clo. In these situations a typical activity level of 1.2 met is considered. The evolution of indoor environmental conditions, in the DSF and in the office room, are calculated during a full winter typical day. The thermal comfort, the indoor air quality, the effectiveness for heat removal, the effectiveness for contaminant removal and the Air Distribution Index (ADI), are evaluated. In accordance with the obtained results the thermal comfort levels increase when the air renovation rate increases and the indoor air quality level increases when the air renovation rate increases. However, the ADI is quite constant when the inlet airflow rate increases, because the thermal comfort number decreases when the inlet airflow rate increases and the air quality number increases when the inlet airflow rate increases.

scholarly journals Practical Impact of the COVID-19 Pandemic on Indoor Air Quality and Thermal Comfort in Kindergartens. A Case Study of Slovenia

2021 ◽  
Vol 18 (18) ◽  
pp. 9712
Author(s):  
Vesna Lovec ◽  
Miroslav Premrov ◽  
Vesna Žegarac Leskovar
Keyword(s):  
Carbon Dioxide ◽  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Air Temperature ◽  
Indoor Air ◽  
Carbon Dioxide Concentration ◽  
Building Stock ◽  
Practical Impact

The experimental monitoring of carbon dioxide concentration was carried out in kindergartens in Slovenia, together with indoor air temperature and relative humidity, before and during the COVID-19 pandemic. The aim of the research was to estimate the practical impact of the pandemic on indoor air quality and thermal comfort. The case study sample included buildings with different architectural typology, which are predominantly present in the building stock of Slovenia. The monitoring process lasted for 125 days before and during the COVID-19 pandemic. The results have shown a better indoor air quality in kindergartens during the pandemic, mostly due to ventilation protocols and almost imperceptibly changed indoor air temperature. The COVID-19 pandemic affected air quality in kindergarten classrooms in Slovenia by reducing the average carbon dioxide concentration when children were present in classrooms by 30%.

Numerical simulation of the influence of external urban environmental conditions in the building windows performance

2020 ◽  
pp. 112-123
Author(s):  
Eusébio Conceiçã ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Maria Inês Conceição ◽  
Hazim Awbi
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Environmental Conditions ◽  
Numerical Study ◽  
Carbon Dioxide Concentration ◽  
System Control ◽  
Hvac System ◽  
Indoor Thermal Comfort

This paper presents a numerical study of the influence of external urban environmental conditions, namely, the solar radiation, in the building windows performance. A software that simulates the building thermal behaviour with complex topology, in transient conditions, is developed and used in the study of indoor air quality and indoor thermal comfort of the occupants of a building, under typical summer conditions. As management strategy was implemented a control system to the Heating, Ventilation and Air Conditioning (HVAC) using the PMV (Predicted Mean Vote) index as controllable variable. The studied university building is located in a Mediterranean-type climate in the south of Portugal. The indoor thermal comfort, evaluated by the PMV index, and the indoor air quality, evaluated by the carbon dioxide concentration, were obtained for all occupied spaces. In order to evaluate the implemented control strategy a set of results was obtained for the situations with and without HVAC system control. To exemplify the results obtained, two large compartments were chosen, one with windows facing South and the other without windows. As main conclusion, it can be stated that the use of the HVAC system controllable by the PMV index allows acceptable levels of thermal comfort within the category C of the ISO 7730 standard, and acceptable levels of indoor air quality within the limit proposed by the ASHRAE 62.1 standard.

scholarly journals Assessing the Energy, Indoor Air Quality, and Moisture Performance for a Three-Story Building Using an Integrated Model, Part Two: Integrating the Indoor Air Quality, Moisture, and Thermal Comfort

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4915
Author(s):  
Seyedmohammadreza Heibati ◽  
Wahid Maref ◽  
Hamed H. Saber
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Integrated Model ◽  
Airflow Rate ◽  
Climate Conditions ◽  
Flow Balance ◽  
Moisture Performance ◽  
Heat And Moisture

In this paper, an integrated model that coupled CONTAM and WUFI was developed to assess the indoor air quality (IAQ), moisture, and thermal comfort performance. The coupling method of CONTAM and WUFI is described based on the exchange of airflow rate control variables as infiltration, natural and mechanical ventilation parameters between heat and moisture flow balance equations in WUFI and contaminant flow balances equations in CONTAM. To evaluate the predictions of the integrated model compared to single models of CONTAM and WUFI, four scenarios were used. These scenarios are airtight-fan off, airtight-fan on, leaky-fan off, and leaky-fan on, and were defined for a three-story house subjected to three different climate conditions of Montreal, Vancouver, and Miami. The measures of the simulated indoor CO2, PM2.5, and VOCs obtained by CONTAM; the simulated indoor relative humidity (RH), predicted percentage of dissatisfied (PPD), and predicted mean vote (PMV) obtained by WUFI; and those obtained by the integrated model are compared separately for all scenarios in Montreal, Vancouver, and Miami. Finally, the optimal scenarios are selected. The simulated results of the optimal scenarios with the integrated model method (−28.88% to 46.39%) are different from those obtained with the single models. This is due to the inability of the single models to correct the airflow variables.

CFD Analysis on Thermal Comfort and Indoor Air Quality Affected by Partitions in Air-Conditioned Building

2016 ◽  
Vol 836 ◽  
pp. 121-126
Author(s):  
Pradip Aryal ◽  
Thananchai Leephakpreeda
Keyword(s):  
Carbon Dioxide ◽  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Carbon Dioxide Concentration ◽  
Average Concentration ◽  
Cfd Analysis ◽  
Carbon Dioxide Concentrations

This paper presents a CFD analysis on thermal comfort and indoor air quality affected by partitions in an air-conditioned building. CFD experiments are carried out to simulate variables of indoor air before/after installation or removal of partitions. Accordingly, the Predicted Mean Vote (PMV) is determined as an indicator of thermal comfort while the carbon dioxide concentration within an air-conditioned space is used for the assessment of indoor air quality. Some simulated results are validated by measurements with good agreement where a case study is conducted in an air-conditioned space of a library. With the proposed methodology, it can be recommended in a case study that the significant effects of partition on thermal comfort are observed where the area with neutral sensation and slightly-cool sensation reduces significantly. The occupants feel uncomfortably cold after installing partition. The carbon dioxide concentrations slightly increase in some areas but the average concentration remains acceptable according to ASHRAE standard. Without the reinforcement of the air-conditioning units, the installation of partition at the desired location is not encouraged regarding to occupant’s thermal comfort and indoor air quality.

Effects of Partition on Thermal Comfort, Indoor Air Quality, Energy Consumption, and Perception in Air-Conditioned Buildings

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Pradip Aryal ◽  
Thananchai Leephakpreeda
Keyword(s):  
Carbon Dioxide ◽  
Energy Consumption ◽  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Energy Savings ◽  
Carbon Dioxide Concentration ◽  
Peak Time ◽  
Cfd Analysis

This research is to assess effects of a partition on thermal comfort, indoor air quality (IAQ), energy consumption, and perception in an air-conditioned space via computational fluid dynamics (CFD) analysis. The variables of indoor air are numerically determined before/after installation/removal of a partition. Accordingly, predicted mean vote (PMV) of thermal comfort, carbon dioxide concentration, rate of energy consumption in making up air, and an overall perception index are proposed to quantify effects in a partitioned space. For a case study, a partition is used to tightly separate a study area from a rest area in a library during peak time. The CFD analysis is performed so that the mean differences between the measured and simulated variables at 14 locations are less than 5%. After partitioning in the CFD analysis, it is found that the average PMV value decreases to −1.4 in the rest area, and it remains at −0.7 in the study area where occupants perceive a slightly cool sensation. In the study area, the carbon dioxide concentration increases to 450–500 ppm, while the rate of energy consumption increases by 8.3%. From the overall perception index of 0.9, the occupants feel spacious in the partitioned areas. Therefore, installing the partition is encouraged with the recommendation that cooling supply can be reduced for energy savings. It is apparent that the proposed methodology yields quantitative indicators for decision making of installation/removal of partitions. The interior investigation of partitions in buildings can be performed before making real physical changes.

Numerical and Experimental Modeling of Indoor Air Quality Inside a Conditioned Space with Mechanical Ventilation and DX-Air Conditioner

2020 ◽  
Vol 38 (9A) ◽  
pp. 1257-1275
Author(s):  
Wisam M. Mareed ◽  
Hasanen M. Hussen
Keyword(s):  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Ventilation System ◽  
Thermal Conditions ◽  
Airflow Rate ◽  
Air Conditioner ◽  
Breathing Zone ◽  
Lecture Room ◽  
Ventilation Performance

 Elevated CO2 rates in a building affect the health of the occupant. This paper deals with an experimental and numerical analysis conducted in a full-scale test room located in the Department of Mechanical Engineering at the University of Technology. The experiments and CFD were conducted for analyzing ventilation performance. It is a study on the effect of the discharge airflow rate of the ceiling type air-conditioner on ventilation performance in the lecture room with the mixing ventilation. Most obtained findings show that database and questionnaires analyzed prefer heights between 0.2 m to 1.2 m in the middle of an occupied zone and breathing zone height of between 0.75 m to 1.8 given in the literature surveyed. It is noticed the mismatch of internal conditions with thermal comfort, and indoor air quality recommended by [ASHRAE Standard 62, ANSI / ASHRAE Standard 55-2010]. CFD simulations have been carried to provide insights on the indoor air quality and comfort conditions throughout the classroom. Particle concentrations, thermal conditions, and modified ventilation system solutions are reported.

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