Experimental Evaluation of Indoor Air Distribution in High-Performance Residential Buildings: Part I. General Descriptions and Qualification Tests

This paper demonstrates the potential impact of indoor air distribution on the energy consumption of central HVAC systems with cognizance of human thermal comfort. The study focuses on a hypothetical high-performance house incorporating a split heat pump system. The air distribution of this building incorporates high sidewall supply-air registers and near-floor, wall-mounted return-air grilles. Heating-mode stratification resulting from this prevalent configuration is a prime example of situations in which challenges regarding energy efficiency, comfort, and ventilation effectiveness emerge. These challenges underline the importance of adopting a comprehensive design strategy for high-performance buildings. Two indoor air distribution scenarios were analyzed: (1) theoretically well mixed and (2) poorly mixed, representing a realistic case. The former scenario was evaluated using an analytical approach, whereas the latter was investigated through computational fluid dynamics (CFD) simulations. For heating mode, the results indicated the presence of a pronounced thermal stratification resulting from poor air mixing. At 50% of the design heating load, for the well-mixed case, the HVAC system energy consumption was significantly higher. Considerably better air distribution performance was observed with cooling mode, in which the relative energy penalty for the well-mixed scenario was noticeably less. In real-world applications where measures must be taken to achieve near perfectly mixed indoor conditions for better comfort, the energy use is expected to be even higher. However, in the absence of such measures, the thermostat setpoint is likely to be readjusted, leading to a higher energy use without necessarily improving the overall comfort level, as demonstrated in this paper. The limitation of increasing the supply-air flow rate to enhance air mixing and diffusion is also discussed in terms of the system moisture removal capability.

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Indoor air distribution in a room with underfloor air distribution and chilled ceiling: Effect of ceiling surface temperature and supply air velocity

Indoor and Built Environment ◽

10.1177/1420326x19853605 ◽

2019 ◽

Vol 29 (2) ◽

pp. 151-162 ◽

Cited By ~ 2

Author(s):

Jie Gao ◽

Haichao Wang ◽

Xiaozhou Wu ◽

Fenghao Wang ◽

Zhen Tian

Keyword(s):

Surface Temperature ◽

Air Temperature ◽

Indoor Air ◽

Residential Buildings ◽

Air Distribution ◽

Cooling Load ◽

Air Velocity ◽

Underfloor Air Distribution ◽

Chilled Ceiling ◽

Cooling Loads

An underfloor air distribution (UFAD) system integrated with a chilled ceiling (CC) cooling system may be a potential advanced heating, ventilation and air conditioning system in modern non-residential buildings with high sensible cooling loads. This article presents an experimental study concerning the effect of ceiling surface temperature and supply air velocity on the indoor air distribution in a room with UFAD as the internal and external sensible cooling loads change. The vertical distributions of indoor air temperature, air velocity and contaminant (CO2) concentration were evaluated by vertical air temperature difference (VATD), turbulence intensity (TI) and contaminant removal effectiveness (CRE), respectively. The results showed that the average VATD, TI and CRE levels were 0.5°C–1.0°C, 31%–41% and 0.85–1.06 when both internal and external sensible cooling loads were 41.5 W/m2. These evaluation indices varied clearly when the external sensible cooling load increased from 41.5 W/m2 to 69.5 W/m2, whereas they remained almost the same when the internal sensible cooling load increased from 41.5 W/m2 to 69.5 W/m2. The maximum TI coincided with the minimum CRE under the condition of a constant sensible cooling load. Moreover, an air diffusion performance index clearly reduced with an increase in the heat removal effectiveness. It is recommended that it is important to balance the indoor air quality and energy consumption in a room with UFAD + CC.

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Impact of different mechanical ventilation strategies for night purging on indoor air quality in public buildings

E3S Web of Conferences ◽

10.1051/e3sconf/202124611003 ◽

2021 ◽

Vol 246 ◽

pp. 11003

Author(s):

Sami Lestinen ◽

Simo Kilpeläinen ◽

Risto Kosonen ◽

Juha Jokisalo

Keyword(s):

Air Quality ◽

Indoor Air Quality ◽

Indoor Air ◽

Residential Buildings ◽

Thermal Conditions ◽

Building Envelope ◽

Air Distribution ◽

Test Case ◽

Night Time ◽

Ventilation Strategies

Night-time ventilation has been used in non-residential buildings to enhance indoor air quality before occupied periods. However, many hypotheses exist on how this ventilation should be used. A typical choice has been to shut down the ventilation after occupancy and restart the ventilation again 2 hours before occupancy. Another option has been to ventilate the buildings continuously. In this study, the shut-down, continuous, and intermittent ventilation strategies were compared by evaluating indoor air quality. The daily occupied-hour ventilation was kept as usual. Each test case lasted for 2 weeks. Indoor air quality was assessed by measuring TVOC concentrations. Also, the thermal conditions, carbon dioxide, and pressure differences over the building envelope and over the air distribution devices were measured. The results show that the averaged TVOC concentrations were at the same level in the mornings with all those ventilation strategies. The evening concentrations reached a minimum level after a 2-hour purging period. TVOC concentrations were higher during the day than at night. This reveals that space usage had the largest effect on TVOC concentrations. The results indicate that a 2-hour purging is enough to cleanse indoor air before occupancy, and therefore the continuous night-time ventilation is not necessary.

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Enhancing Formaldehyde Selectivity of SnO2 Gas Sensors with the ZSM-5 Modified Layers

Sensors ◽

10.3390/s21123947 ◽

2021 ◽

Vol 21 (12) ◽

pp. 3947

Author(s):

Wei Wang ◽

Qinyi Zhang ◽

Ruonan Lv ◽

Dong Wu ◽

Shunping Zhang

Keyword(s):

Gas Sensors ◽

Indoor Air ◽

High Performance ◽

Screen Printing ◽

Gas Sensing ◽

Oxide Semiconductors ◽

Screen Printing Method ◽

Gas Sensing Properties ◽

Zeolite Films ◽

Insufficient Knowledge

High performance formaldehyde gas sensors are widely needed for indoor air quality monitoring. A modified layer of zeolite on the surface of metal oxide semiconductors results in selectivity improvement to formaldehyde as gas sensors. However, there is insufficient knowledge on how the thickness of the zeolite layer affects the gas sensing properties. In this paper, ZSM-5 zeolite films were coated on the surface of the SnO2 gas sensors by the screen printing method. The thickness of ZSM-5 zeolite films was controlled by adjusting the numbers of screen printing layers. The influence of ZSM-5 film thickness on the performance of ZSM-5/SnO2 gas sensors was studied. The results showed that the ZSM-5/SnO2 gas sensors with a thickness of 19.5 μm greatly improved the selectivity to formaldehyde, and reduced the response to ethanol, acetone and benzene at 350 °C. The mechanism of the selectivity improvement to formaldehyde of the sensors was discussed.

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The Improvement of Indoor Air Quality in Residential Buildings in Dubai, UAE

Buildings ◽

10.3390/buildings11060250 ◽

2021 ◽

Vol 11 (6) ◽

pp. 250

Author(s):

Chuloh Jung ◽

Jihad Awad

Keyword(s):

Computer Simulation ◽

Air Quality ◽

Indoor Air Quality ◽

Indoor Air ◽

Building Materials ◽

Field Survey ◽

Residential Buildings ◽

Radon Gas ◽

Volatile Organic ◽

Residential Projects

Due to unprecedented urbanization, UAE had built many new residential projects with poor choices of material and ventilation. This social phenomenon is leading UAE to Sick Building Syndrome (SBS) faster than any other countries. The Dubai Municipality regulates the indoor air quality with strict stipulation, but the detailed regulations are still insufficient. The objective of this paper is to measure the indoor air quality of new residential projects in Dubai to suggest the improvement of the regulations for indoor air quality. As a methodology, a field survey was conducted to investigate the status of indoor air pollution in residential buildings. Based on the field survey data, lab experiments for building materials were conducted and a computer simulation on radon gas was conducted. The result had shown that radon gas was mainly detected in new townhouses and labor camp houses, and its concentration was found to exceed the standard. Volatile organic solvents (VOCs) and formaldehyde (CH2O) were mainly detected in showhouses and new townhouses, and the concentration distribution was about 10 times higher than that of outdoors. It was proven that emission concentration of radon gas from various building materials were detected, and the order was red clay, gypsum board, and concrete. Volatile organic solvents (VOCs) are mainly detected in oil paints and PVC floor and the radiation amount of all pollutants increased with temperature increase. In computer simulation, it was found that a new townhouse needs a grace period from 20 days to 6 months to lower the radon gas concentration by 2 pCi/L. This study will serve as a basic data to establish more detailed regulation for the building materials and improve the IAQ standards in Dubai.

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The impact of mechanical ventilation operation strategies on indoor CO2 concentration and air exchange rates in residential buildings

Indoor and Built Environment ◽

10.1177/1420326x20960767 ◽

2020 ◽

pp. 1420326X2096076

Author(s):

Pedro F. Pereira ◽

Nuno M. M. Ramos

Keyword(s):

Mechanical Ventilation ◽

Air Quality ◽

Exchange Rates ◽

Indoor Air Quality ◽

Indoor Air ◽

Residential Buildings ◽

Ventilation Strategy ◽

The Impact ◽

Mechanical Extraction ◽

Air Exchange

In Portugal, residential buildings commonly have their ventilation strategy changed after commissioning. This occurs due to the building managers' willingness to reduce shared costs with the electricity needed for fan operation. However, this option is not technically supported, and the effects of such a strategy on indoor air quality-related to human pollutants are yet to be quantified. CO2 was monitored in 15 bedrooms and air exchange rates were calculated for each room. The air exchange rate values ranged from 0.18 to 0.53 h−1 when mechanical extraction ventilation was off, and from 0.45 to 0.90 h−1 when mechanical extraction ventilation was on, which represents an average increase of 119%. With the current intermittent ventilation strategy, all rooms remain above 1500 ppm for a given percentage of time, and 12 rooms presenting CO2 concentrations above 2000 ppm. Simulations of theoretical CO2 concentrations, for a non-interrupted mechanical ventilation strategy show that no rooms would accumulate CO2 concentrations above 2000 ppm, and only 25% would present CO2 concentrations above 1500 ppm. Pearson correlations between the monitored CO2 and human and spatial factors identified two relevant parameters. Those parameters correspond to ratios between CO2 generation and floor area ([Formula: see text]), and airflow with CO2 generation ([Formula: see text]). The proposed ratios could be used as ways to optimise ventilation costs and indoor air quality.

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Impact of façade design on indoor air temperatures and cooling loads in residential buildings in the tropical climate

Energy and Buildings ◽

10.1016/j.enbuild.2021.110972 ◽

2021 ◽

Vol 243 ◽

pp. 110972

Author(s):

Shanshan Tong ◽

Jianxiu Wen ◽

Nyuk Hien Wong ◽

Erna Tan

Keyword(s):

Indoor Air ◽

Residential Buildings ◽

Tropical Climate ◽

Air Temperatures ◽

Cooling Loads

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Kitchen and Toilet of the Residence Exhaust Flow Field Analysis

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.354-355.726 ◽

2011 ◽

Vol 354-355 ◽

pp. 726-731

Author(s):

Yue Ren Wang ◽

Cong Xue ◽

Jing Zhang

Keyword(s):

Indoor Air ◽

Cfd Simulation ◽

Simulation Software ◽

Field Analysis ◽

Air Distribution ◽

Volume Changes ◽

Air Volume ◽

Secondary Pollution ◽

Comparison Results ◽

Flow Field Analysis

Adopting the k-ε standard model, the CFD simulation software to simulate the indoor kitchen and toilet different row of indoor air volume air distribution in natural ventilated circumstance, by comparison results show that different row of indoor air volume changes in the rate of secondary pollution rate, and then to provide the change rule of indoor air quality protection reference basis.

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DESIGNING A SMALL CLIMATE CHAMBER TO CHARACTERIZE PEOPLE AS A SOURCE OF DETERIORATION OF INDOOR AIR QUALITY BY RESPIRATION

CBU International Conference Proceedings ◽

10.12955/cbup.v7.1484 ◽

2019 ◽

Vol 7 ◽

pp. 954-959 ◽

Cited By ~ 1

Author(s):

Detelin Ganchev Markov ◽

Sergey Mijorski ◽

Peter Stankov ◽

Iskra Simova ◽

Radositna A. Angelova ◽

...

Keyword(s):

Carbon Dioxide ◽

Water Vapor ◽

Air Quality ◽

Indoor Air Quality ◽

Indoor Air ◽

Carbon Dioxide Concentration ◽

Air Distribution ◽

Vapor Concentration ◽

Cfd Simulations ◽

Climate Chamber

: People are one of the sources for deterioration of the indoor air quality. They worsen indoor air quality by their presence (respiration, bio-effluents), activities and habits. Through respiration, people decrease the oxygen concentration in the air of the occupied space and increase carbon dioxide and water vapor concentration in the indoor air as well as its temperature. The goal of the AIRMEN project is to find out if the rate of consumption of oxygen and emission of carbon dioxide (and water vapor) by people depends on the indoor air temperature as well as carbon dioxide concentration in the inhaled air. In order to achieve this goal a small climate chamber must be designed and constructed which allows for controlling and measuring both inflow and exposure parameters as well as for measuring outflow parameters. The principal goal of this paper is to present some important details, obtained by CFD simulations, from the design process of the climate chamber which precondition the air distribution in the chamber and hence the exposure parameters.

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