Ceiling-Mounted Fresh Air Personalized Ventilator System for Occupant-Controlled Microenvironment

2012 ◽  
Author(s):  
Alain Makhoul ◽  
Kamel Ghali ◽  
Nesreen Ghaddar
Keyword(s):  
Air Quality ◽  
Flow Rate ◽  
Air Conditioning ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Air Entrainment ◽  
Breathing Zone ◽  
Cfd Model ◽  
Air Stream ◽  
Ashrae Standards

The aim of this work is to develop an effective coaxial personalized ventilator nozzle as add-on to ceiling diffuser to localize the air conditioning and fresh air needs of occupants in a space. The ceiling diffusers supply the space with circulated conditioned return air while the personalized coaxial ventilators supply fresh air directly to the breathing zone of occupants. The coaxial nozzle minimizes air entrainment between the fresh air stream and the space contaminated air and allows the effective delivery of fresh air from a substantial distance with lower amounts than what is required by ASHRAE standards. A detailed 3D CFD model was developed and used to optimize the nozzles dimensions and outlet flow characteristics. The CFD model numerical findings were then validated against experimental data where flow field measurements involving the flow rate and air quality were taken. The proposed air delivery system (coaxial personalized ventilator and angled ceiling diffuser) has substantially reduced air conditioning system energy consumption (up to 28%) when it was compared with conventional overhead mixing systems. Meanwhile, it permitted to obtain equivalent thermal comfort conditions and achieve higher breathing air quality (45% ventilation effectiveness at 10 L/s.person fresh air flow rate) compared to conventional mixed air systems with the privilege of the occupant being able to control his own microclimate.

scholarly journals Investigating the In-Flow Characteristics of Multi-Operation Conditions of Cross-Flow Fan in Air Conditioning Systems

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 959
Author(s):  
Weijie Zhang ◽  
Jianping Yuan ◽  
Qiaorui Si ◽  
Yanxia Fu
Keyword(s):  
Pressure Distribution ◽  
Flow Rate ◽  
Total Pressure ◽  
Air Conditioning ◽  
Pressure Pulsation ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Operating Conditions ◽  
Aerodynamic Noise ◽  
Cross Flow Fan

Cross-flow fans are widely used in numerous applications such as low-pressure ventilation, household appliances, laser instruments, and air-conditioning equipment. Cross-flow fans have superior characteristics, including simple structure, small size, stable airflow, high dynamic pressure coefficient, and low noise. In the present study, numerical simulation and experimental research were carried out to study the unique secondary flow and eccentric vortex flow characteristics of the internal flow field in multi-operating conditions. To this end the vorticity and the circumferential pressure distribution in the air duct are obtained based on the performed experiments and the correlation between spectral characteristics of multiple operating conditions and the inflow state is established. The obtained results show that when the area of the airflow passage decreases while the area of the eccentric vortex area gradually increases, then the airflow of the cross-flow fan decreases, the outlet expands, and the flow pattern uniformity reduces. It was found that wakes form in the vicinity of the blade and the tail of the volute tongue, which generate pressure pulsation, and aerodynamic noise. The pressure distribution along the inner circumference shows that the total minimum pressure appears in the eccentric vortex near the volute tongue and the volute returns near the zone. Moreover, it was found that the total pressure near the eccentric vortex is significantly smaller than that of the main flow zone. As the flow rate decreases, the pressure pulsation amplitude of the eccentric vortex region significantly increases, while the static and total pressure pulsation amplitudes are gradually increased. Close to the eccentric vortex on the inner side of the blade in the volute tongue area, total pressure is low, total pressure on the outside of the blade is not affected, and pressure difference between the inner and outer sides is large. When the flow rate of the cross-flow fan is 0.4 Qd, there is no obvious peak at the harmonic frequency of the blade passage frequency. This shows that the aerodynamic noise is caused by the main unstable flow.

Numerical and experimental investigation on the air flow characteristics of heating, ventilation, and air-conditioning module for a small electric vehicle

2019 ◽  
Vol 234 (6) ◽  
pp. 1597-1609
Author(s):  
Kang Li ◽  
Hao Gao ◽  
Peng Jia ◽  
Lin Su ◽  
Yidong Fang ◽  
...  
Keyword(s):  
Heat Pump ◽  
Flow Rate ◽  
Air Conditioning ◽  
Air Flow ◽  
Flow Characteristics ◽  
Cold Climate ◽  
Airflow Rate ◽  
Positive Temperature ◽  
Air Flow Rate ◽  
Pump System

In electrical vehicles, replacing positive temperature coefficient heater as heat source with an air source heat pump could improve the driving range and decrease energy consumption in cold climate. Design of the heating, ventilation, and air-conditioning module for heat pump system has a significant influence on its performance in each working mode. A newly designed heat pump heating, ventilation, and air-conditioning module was introduced in this paper. The air flow characteristics of the heat pump heating, ventilation, and air-conditioning module in four working modes were analyzed, and the air flow rate and wind resistance were obtained by numerical simulation. Experiments were also conducted for validating its airflow rate in each working mode. Results of these experiments show that some unfavorable phenomena such as flow maldistribution and vortex inside the heat pump heating, ventilation, and air-conditioning module exist, which could lead to insufficient utilization of the heat exchange area of heat exchangers and the generation of aerodynamic noise. Furthermore, the air flow rate of the original heating, ventilation, and air-conditioning module was also measured for comparison, and the designed heat pump heating, ventilation, and air-conditioning module shows nearly 15–20% decrease in each working mode.

Performance of Mixing Ventilation System Coupled With Dynamic Personalized Ventilator for Thermal Comfort

2017 ◽  
Author(s):  
Douaa Al-Assaad ◽  
Nesreen Ghaddar ◽  
Kamel Ghali
Keyword(s):  
Thermal Comfort ◽  
Flow Rate ◽  
Thermal Sensation ◽  
Ventilation System ◽  
Low Frequency ◽  
Temperature Fields ◽  
Upper Body ◽  
Breathing Zone ◽  
Cfd Model ◽  
Mean Flow

This study optimizes the performance of a mixing ventilation system coupled with a personalized ventilator that emits a cool sinusoidal horizontal airflow jet towards the occupant upper body in order to achieve good overall thermal comfort and good air quality in the occupant breathing zone. A transient 3-D computational fluid dynamics (CFD) model coupled with a transient bio-heat model was deployed to predict airflow and temperature fields in the space and around the occupant as well as segmental skin temperature profiles for local and overall thermal sensation and comfort analysis. Simulations were performed using the CFD model to determine the airflow optimal supply frequency, mean flow rate and amplitude at room temperature of 25 °C and PV jet temperature of 22 °C. The system also showed, that when increasing frequency at fixed mean flow rate, thermal comfort increased from by 15.2 %. However when increasing mean flow rate at a fixed frequency, thermal comfort dropped at the low frequency of 0.3 Hz but remained acceptable at the higher frequency of 0.5 Hz.

Performance of Coaxial Ceiling-Mounted Personalized Ventilator for Comfort and Good Air Quality

2013 ◽  
Author(s):  
Nesreen Ghaddar ◽  
Kamel Ghali ◽  
Alain Makhoul
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Cooling System ◽  
Office Building ◽  
Airflow Rate ◽  
Breathing Zone ◽  
Cfd Model ◽  
Air Conditioning System ◽  
Occupant Comfort ◽  
Intake Fractions

The aim of this work is to study the performance of a novel ceiling mounted coaxial personalized ventilator that can be used as an add on to the conventional ceiling diffuser in providing the thermal comfort and air quality needs to occupants in office building. A detailed 3D CFD model is coupled to a bioheat model to improve prediction of the microenvironment conditions around the human and the associated local and overall thermal comfort. Extensive simulations were performed to assess the effect of nozzle supply temperature and flow rate on the performance of the cooling system and on occupant comfort. The localized air conditioning system reduced the energy consumption by up to 34% when compared with conventional mixing systems providing the same level of thermal comfort. The proposed system also achieved high air quality in the occupant breathing zone with 45% ventilation effectiveness at fresh airflow rate of 10 L/s/person and attained 2°C between the occupant’s comfortable microenvironment and the rest of the space. In addition, the canopy of the angled diffuser was effective in reducing the migration of particles from the macroclimate to the microclimate region and low intake fractions of 1.90×10−4 were achieved.

Rising Importance of Organosulfur Species for Aerosol Properties and Future Air Quality

2019 ◽  
Author(s):  
Matthieu Riva ◽  
Yuzhi Chen ◽  
Zhang, Yue ◽  
Ziying Lei ◽  
Nicole Olson ◽  
...  
Keyword(s):  
Air Quality ◽  
Physicochemical Properties ◽  
Phase State ◽  
Global Climate ◽  
Field Measurements ◽  
Organic Aerosol ◽  
Organic Sulfate ◽  
Isoprene Oxidation ◽  
Aerosol Properties ◽  
Inorganic Sulfate

<div>Acid-driven multiphase chemistry of isoprene epoxydiols (IEPOX), a key isoprene oxidation product, with inorganic sulfate aerosol yields substantial amounts of secondary organic aerosol (SOA) through the formation of organosulfur. The extent and implications of inorganic-to-organic sulfate conversion, however, are unknown. Herein, we reveal that extensive consumption of inorganic sulfate occurs, which increases with the IEPOX-to-inorganic sulfate ratio (IEPOX:Sulf<sub>inorg</sub>), as determined by laboratory and field measurements. We further demonstrate that organosulfur greatly modifies critical aerosol properties, such as acidity, morphology, viscosity, and phase state. These new mechanistic insights reveal that changes in SO<sub>2</sub> emissions, especially in isoprene-dominated environments, will significantly alter biogenic SOA physicochemical properties. Consequently, IEPOX:Sulf<sub>inorg</sub> will play a central role in understanding historical climate and determining future impacts of biogenic SOA on global climate and air quality.</div>

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.

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

scholarly journals Design and Fabrication of a Novel Window-Type Convection Device

2020 ◽  
Vol 11 (1) ◽  
pp. 267
Author(s):  
Han-Tang Lin ◽  
Yunn-Horng Guu ◽  
Wei-Hsuan Hsu
Keyword(s):  
Energy Consumption ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Energy Demand ◽  
Air Entrainment ◽  
Wind Speeds ◽  
Digit Series ◽  
Slit Size ◽  
Deflector Plate

Global warming, climate change, and ever-increasing energy demand are among the pressing challenges currently facing humanity. Particularly, indoor air conditioning, a major source of energy consumption, requires immediate improvement to prevent energy crises. In this study, various airfoil profiles were applied to create a window-type convection device that entrains air to improve convection between indoor and outdoor airflows and adjust the indoor temperature. How the geometric structure of the convection device affects its air entrainment performance was investigated on the basis of various airfoil profiles and outlet slit sizes of the airflow multiplier. The airfoil profiles were designed according to the 4-digit series developed by the National Advisory Committee for Aeronautics. The results revealed that airfoil thickness, airfoil camber, and air outlet slit size affected the mass flow rate of the convection device. Overall, the mass flow rate at the outlet of the convection device was more than 10 times greater than at the inlet, demonstrating the potential of the device to improve air convection. To validate these simulated results, the wind-deflector plate was processed using the NACA4424 airfoil with a 1.2 mm slit, and various operating voltages were applied to the convection device to measure the resulting wind speeds and calculate the corresponding mass flow rates. The experimental and simulated results were similar, with a mean error of <7%, indicating that the airfoil-shaped wind-deflector plate substantially improved air entrainment of the convection device to the goal of reduced energy consumption and carbon emissions.

scholarly journals Sediment Transport and Water Flow Resistance in Alluvial River Channels: Modified Model of Transport of Non-Uniform Grain-Size Sediments

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2038
Author(s):  
Gennady Gladkov ◽  
Michał Habel ◽  
Zygmunt Babiński ◽  
Pakhom Belyakov
Keyword(s):  
Sediment Transport ◽  
Water Flow ◽  
Transport Model ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Field Investigation ◽  
Empirical Modeling ◽  
River Channels ◽  
Channel Deformations ◽  
East European

The paper presents recommendations for using the results obtained in sediment transport simulation and modeling of channel deformations in rivers. This work relates to the issues of empirical modeling of the water flow characteristics in natural riverbeds with a movable bottom (alluvial channels) which are extremely complex. The study shows that in the simulation of sediment transport and calculation of channel deformations in the rivers, it is expedient to use the calculation dependences of Chézy’s coefficient for assessing the roughness of the bottom sediment mixture, or the dependences of the form based on the field investigation data. Three models are most commonly used and based on the original formulas of Meyer-Peter and Müller (1948), Einstein (1950) and van Rijn (1984). This work deals with assessing the hydraulic resistance of the channel and improving the river sediment transport model in a simulation of riverbed transformation on the basis of previous research to verify it based on 296 field measurements on the Central-East European lowland rivers. The performed test calculations show that the modified van Rijn formula gives the best results from all the considered variants.

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