Improving local ventilation prediction by accounting for inter-segmental ventilation

2016 ◽  
Vol 87 (5) ◽  
pp. 511-527 ◽  
Author(s):  
Nagham Ismail ◽  
Nesreen Ghaddar ◽  
Kamel Ghali
Keyword(s):  
Wind Velocity ◽  
Ventilation Rate ◽  
Air Permeability ◽  
Statistical Correlation ◽  
Accurate Estimation ◽  
Thermal Manikin ◽  
Tracer Gas ◽  
Local Ventilation ◽  
Wind Velocities ◽  
Ventilation Rates

The inter-segmental ventilation rate at clothing inter-connection of arms and trunk affects the estimation of local ventilation rates of these clothed segments. The accurate estimation of the inter-segmental ventilation rate is based on the integration of a connected clothed cylinders model with a bio-heat model to predict a realistic segmental skin temperature. This integration is validated with experiments on a thermal manikin using the tracer gas method. The results show that accounting for the inter-segmental ventilation rate improves the estimation of the segmental ventilation of the arm and the trunk for different garment apertures at external wind velocities less than 4 m/s. For a wind velocity of 1 m/s, the inter-connection increased the trunk ventilation by up to 12% and heat loss by up to 5.46%. A statistical correlation is established for the inter-segmental ventilation rate in terms of the influencing parameters: air permeability, wind velocity, mean air gap size between skin and clothing, and the upper clothing aperture design. Furthermore, a local ventilation rate correction factor equation is developed as a function of the inter-segmental ventilation rate to correct for local ventilation rates when derived from values of isolated/unconnected clothed segments.

Theoretical and Experimental Estimation of Inter-Segmental Clothing Ventilation and Impact on Human Segmental Heat Losses

2015 ◽  
Author(s):  
Nagham Bilal Ismail ◽  
Nesreen Ghaddar ◽  
Kamel Ghali
Keyword(s):  
Human Body ◽  
Flow Characteristics ◽  
Heat Losses ◽  
The Body ◽  
Thermal Manikin ◽  
Body Parts ◽  
Tracer Gas ◽  
Wind Speeds ◽  
Local Ventilation ◽  
Ventilation Rates

Air exchange between a specific garment and the environment could occur 1) through the fabric with the environment, 2) through garment apertures with the environment, and 3) between local body parts’ microclimates. The first mechanism is related to the fabric properties and the flow characteristics around the human body. The second mechanism is induced by buoyancy and pressure alteration due to external wind. The third mechanism named inter-segmental ventilation occurs between different clothing sections caused by position of apertures, relative wind, fabric permeability and microclimate size of connected clothed segments. The objective of this work is to develop a simplified accurate model that solves coupled momentum, mass and heat balances including buoyancy for the connected clothed upper human body to predict inter-segmental ventilation and assess its impact on the air flow characteristics in the microclimate layer and on local ventilation rates. This model is coupled to the bioheat model to predict the effect of the inter-segmental ventilation on the heat losses from the body and on bringing the thermal comfort. The model is validated by performing an improved experimental method on a thermal manikin using the tracer gas method at different wind speeds for permeable clothing.

Ventilation of Wind-Permeable Clothed Cylinder Subject to Periodic Swinging Motion: Modeling and Experimentation

2008 ◽  
Vol 130 (9) ◽  
Author(s):  
N. Ghaddar ◽  
K. Ghali ◽  
B. Jreije
Keyword(s):  
Cotton Fabric ◽  
Current Model ◽  
Ventilation Rate ◽  
External Pressure ◽  
Motion Modeling ◽  
Tracer Gas ◽  
Wind Speeds ◽  
Air Speed ◽  
Local Thermal Comfort ◽  
Ventilation Rates

Abstract A theoretical and experimental study has been performed to determine the ventilation induced by swinging motion and external wind for a fabric-covered cylinder of finite length representing a limb. The estimated ventilation rates are important in determining local thermal comfort. A model is developed to estimate the external pressure distribution resulting from the relative wind around the swinging clothed cylinder. A mass balance equation of the microclimate air layer is reduced to a pressure equation assuming laminar flow in axial and angular directions and that the air layer is lumped in the radial direction. The ventilation model predicts the total renewal rate during the swinging cycle. A good agreement was found between the predicted ventilation rates at swinging frequencies between 40rpm and 60rpm and measured values from experiments conducted in a controlled environmental chamber (air velocity is less than 0.05m∕s) and in a low speed wind tunnel (for air speed between 2m∕s and 6m∕s) using the tracer gas method to measure the total ventilation rate induced by the swinging motion of a cylinder covered with a cotton fabric for both closed and open aperture cases. A parametric study using the current model is performed on a cotton fabric to study the effect of wind on ventilation rates for a nonmoving clothed limb at wind speeds ranging from 0.5m∕sto8m∕s, the effect of a swinging limb in stagnant air at frequencies up to 80rpm, and the combined effect of wind and swinging motion on the ventilation rate. For a nonmoving limb, ventilation rate increases with external wind. In the absence of wind, the ventilation rate increases with increased swinging frequency.

Experimental Investigation of Ventilation Effectiveness in an Airliner Cabin Mockup

2016 ◽  
Author(s):  
Jignesh A. Patel ◽  
Byron W. Jones ◽  
Mohammad H. Hosni ◽  
Ali Keshavarz
Keyword(s):  
Distribution System ◽  
Ventilation Rate ◽  
Mean Value ◽  
Tracer Gas ◽  
Flight Duration ◽  
Factors Affecting ◽  
Aircraft Cabin ◽  
Local Ventilation ◽  
Effective Ventilation ◽  
Ventilation Effectiveness

Frequent air travel and long flight duration makes the study of airliner cabin environmental quality a topic of utmost importance. Ventilation effectiveness is one of the more crucial factors affecting air quality in any environment. Ventilation effectiveness, along with the overall ventilation rate, is a measure of the ability of the air distribution system to remove internally generated pollutants or contaminants from a given space. Because of the high occupant density in an aircraft cabin, local variations in ventilation are important as a passenger will occupy the same space for the duration of the flight. Poor ventilation in even a small portion of the cabin could impact multiple people for extended time periods. In this study, the local effective ventilation rates and local ventilation effectiveness in an eleven-row, full-scale, Boeing 767 cabin mockup were measured. These measurements were completed at each of the 77 seats in the mockup. Each seat was occupied by a heated mannequin. In order to simulate the thermal load inside the cabin, the mannequins were wrapped with a heating wire to generate approximately 100 W (341 BTU/hour) of heat. Carbon dioxide was used as a tracer gas for the experiments and the tracer gas decay method was employed to calculate the local effective ventilation rate and local ventilation effectiveness. The overall ventilation rate, based on total supply air flow, was approximately 27 air changes per hour. Local ventilation effectiveness ranged from 0.86 to 1.02 with a mean value of 0.94. These ventilation effectiveness values are higher than typically found in other indoor applications and are likely due to the relatively high airspeeds present in the aircraft cabin and the high degree of mixing they provide. The uniformity is also good with no areas of particularly low ventilation effectiveness being identified. No clear patterns with respect to seat location, window versus center versus aisle, were found.

scholarly journals Applying the CO2 concentration decay tracer gas method in long-term monitoring campaigns in occupied homes: identifying appropriate unoccupied periods and decay periods

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Jessica Few ◽  
Clifford A. Elwell
Keyword(s):  
Indoor Air Pollution ◽  
Weather Conditions ◽  
Co2 Concentration ◽  
Ventilation Rate ◽  
Identification Algorithm ◽  
Tracer Gas ◽  
Content Type ◽  
Rate Analysis ◽  
Specific Implementation ◽  
Ventilation Rates

PurposeVentilation is driven by weather conditions, occupant actions and mechanical ventilation, and so can be highly variable. This paper reports on the development of two analysis algorithms designed to facilitate investigation of ventilation in occupied homes over time.Design/methodology/approachThese algorithms facilitate application of the CO2 concentration decay tracer gas technique. The first algorithm identifies occupied periods. The second identifies periods of decaying CO2 concentration which can be assumed to meet the assumptions required for analysis.FindingsThe algorithms were successfully applied in four occupied dwellings, giving over 100 ventilation measurements during a six-month period for three flats. The specific implementation of the decay identification algorithm had important ramifications for the ventilation rates measured, highlighting the importance of interrogating the way that appropriate periods for analysis are identified.Practical implicationsThe analysis algorithms provide robust, reliable and repeatable identification of CO2 decay periods appropriate for ventilation rate analysis. The algorithms were coded in Python, and these have been made available via GitHub. As well as supporting future CO2 tracer gas experiments, the algorithms could be adapted to different purposes, including the use of other tracer gases or exploring occupant exposure to indoor air pollution.Originality/valueEmpirical investigations of ventilation in occupied dwellings rarely aim to investigate the variability of ventilation. This paper reports on analysis methods which can be used to address this gap in the empirical evidence.

scholarly journals Proposing Alternative Solutions to Enhance Natural Ventilation Rates in Residential Buildings in the Cfa Climate Zone of Rasht

2021 ◽  
Vol 13 (2) ◽  
pp. 679
Author(s):  
Roya Aeinehvand ◽  
Amiraslan Darvish ◽  
Abdollah Baghaei Daemei ◽  
Shima Barati ◽  
Asma Jamali ◽  
...  
Keyword(s):  
Natural Ventilation ◽  
Residential Buildings ◽  
Residential Building ◽  
Ventilation Rate ◽  
Humid Climate ◽  
The Sustainable Development ◽  
Passive Strategies ◽  
Development Goals ◽  
Ventilation Rates ◽  
Ventilation Systems

Today, renewable resources and the crucial role of passive strategies in energy efficiency in the building sector toward the sustainable development goals are more indispensable than ever. Natural ventilation has traditionally been considered as one of the most fundamental techniques to decrease energy usage by building dwellers and designers. The main purpose of the present study is to enhance the natural ventilation rates in an existing six-story residential building situated in the humid climate of Rasht during the summertime. On this basis, two types of ventilation systems, the Double-Skin Facade Twin Face System (DSF-TFS) and Single-Sided Wind Tower (SSWT), were simulated through DesignBuilder version 4.5. Then, two types of additional ventilation systems were proposed in order to accelerate the airflow, including four-sided as well as multi-opening wind towers. The wind foldable directions were at about 45 degrees (northwest to southeast). The simulation results show that SSWT could have a better performance than the aforementioned systems by about 38%. Therefore, the multi-opening system was able to enhance the ventilation rate by approximately 10% during the summertime.

scholarly journals Parametric design analysis of elliptical shroud profile

AIMS Energy ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1147-1169
Author(s):  
Salih Nawaf Akour ◽  
◽  
Mahmoud Azmi Abo Mhaisen
Keyword(s):  
Wind Turbine ◽  
Wind Velocity ◽  
Parametric Design ◽  
Large Family ◽  
Design Analysis ◽  
Average Wind ◽  
Wind Velocities ◽  
Inlet Length ◽  
Commercial Software Package ◽  
Exact Shape

<abstract> <p>Parametric design analysis for Eccentric Rotated Ellipsoid (ERE) shroud profile is conducted whereas the design model is validated experimentally. A relation between shroud inlet, length and exit diameter is established, different ratios related to the wind turbine diameter are introduced, and solution for different ERE family curves that passes on the inlet, throat, and exit points is studied. The performance of the ERE shroud is studied under different wind velocities ranging from 5–10 m/s.</p> <p>The method used in creating the shroud profile is by solving the ERE curve equations to generate large family of solutions. The system is modeled as axisymmetric system utilizing commercial software package. The effect of the parameters; shroud length, exit diameter, inlet diameter, turbine position with respect to the shroud throat, and wind velocity are studied. An optimum case for each shroud length, exit diameter and location of the shroud with respect to the wind turbine throat axis are achieved.</p> <p>The simulation results show an increase in the average wind velocity by 1.63 times of the inlet velocity. This leads to a great improvement in the wind turbine output power by 4.3 times of bare turbine. One of the achieved optimum solutions for the shroud curves has been prototyped for experimental validation. The prototype has been manufactured using 3D printing technology which provides high accuracy in building the exact shape of shroud design curve. The results show very good agreement with the experimental results.</p></abstract>

scholarly journals EFFECT OF WIND VELOCITY AND WIND DIRECTION ON THERMAL INSULATION VALUES OF CLOTHING ENSEMBLES BY USING THERMAL MANIKIN

2007 ◽  
Vol 72 (621) ◽  
pp. 23-28 ◽  
Author(s):  
Shinichi WATANABE ◽  
Tetsumi HORIKOSHI ◽  
Tomoya KANEKO ◽  
Yuji UNO ◽  
Jin ISHII ◽  
...  
Keyword(s):  
Wind Velocity ◽  
Thermal Insulation ◽  
Wind Direction ◽  
Thermal Manikin

scholarly journals A comparison between tracer gas and tracer particle techniques in evaluating the efficiency of ventilation in operating theatres

1983 ◽  
Vol 91 (3) ◽  
pp. 509-519 ◽  
Author(s):  
Per-Arne Andersson ◽  
Anna Hambraeus ◽  
Ulla Zettersten ◽  
Bengt Ljungqvist ◽  
Kenneth Neikter ◽  
...  
Keyword(s):  
Tracer Particle ◽  
Ventilation System ◽  
Airborne Bacteria ◽  
Tracer Gas ◽  
Operating Theatres ◽  
Ventilation Rates ◽  
Operation Wound

Operating theatres are ventilated for a number of reasons, one of them being to keep numbers of airborne bacteria low at the operation wound. No matter how air is brought into the room, bacteria are removed by dilution rather than by air currents, because of turbulence caused by heat liberated by people and equipment and by movement in the room (Lidwell & Williams, 1960). With ventilation rates up to 20 air changes/hour, the dilution may differ at different sites in the room depending on the design of its ventilation system.

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