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.

scholarly journals Investigation of thermal comfort and the nozzle usage behaviour in aircraft cabins

2017 ◽  
Vol 28 (1) ◽  
pp. 118-131 ◽  
Author(s):  
Zhaosong Fang ◽  
Hong Liu ◽  
Baizhan Li ◽  
Andrew Baldwin
Keyword(s):  
Thermal Comfort ◽  
Thermal Environment ◽  
Thermal Sensation ◽  
Ventilation System ◽  
Body Part ◽  
Upper Body ◽  
Body Parts ◽  
Aircraft Cabins ◽  
Minimum Number ◽  
Personal Ventilation

In order to understand passengers’ demand for thermal comfort in aircraft cabins, we carried out a measurement of thermal environment parameters and thermal comfort field survey in an aircraft cabin under cruising at altitude in both summer and winter. The results showed that the air temperature studied was always kept within the range of 25℃ to 28℃ and the relative humidity was maintained within the range of 20% to 35%. The Mean Thermal Sensation Vote (MTSV) of passengers’ back and feet was higher than other local body parts, with lower air movement sensation. The MTSV of passengers in winter was higher than that in summer. Due to the muggy thermal environment, more than 60% of passengers advocated that it was necessary to utilize the personal ventilation system. In their usage of the personal ventilation nozzle, more than half of these passengers chose to cool upper body parts, only a minimum number of passengers opened the nozzle to direct airflow to their head. Therefore, we concluded that the position of the personal ventilation nozzle should be as close to the upper body part of a passenger’s body as possible, making it more convenient and effective to regulate passengers’ thermal comfort.

Influence of sinusoidal airflow and airflow distance on human thermal response to a personalized ventilation system

2016 ◽  
Vol 27 (3) ◽  
pp. 317-330 ◽  
Author(s):  
Yongxin Xie ◽  
Sauchung Fu ◽  
Chili Wu ◽  
Christopher Y.H. Chao
Keyword(s):  
Thermal Comfort ◽  
Thermal Sensation ◽  
Human Subjects ◽  
Ventilation System ◽  
Thermal Response ◽  
Joint Effect ◽  
Experimental Conditions ◽  
Movement Perception ◽  
Air Movement ◽  
Personalized Ventilation

Since the concept of personalized ventilation was introduced in the late 1990s, many studies on thermal comfort have been conducted and a number of parameters identified. In this research, the influence of three parameters, the airflow speed, airflow fluctuating period and a parameter which has drawn less attention in previous studies – the airflow distance between the human subject and the nozzle of the personalized ventilation device on air movement perception, thermal sensation and thermal comfort – are studied. The combinations of fluctuating period and airflow amplitude were selected based on the Power Spectrum Density method. Then 25 human subjects participated in the thermal comfort experiment, each of them underwent 54 tests of different experimental conditions and expressed their thermal feelings by completing the survey questionnaire. Our findings showed that a longer airflow distance could lead to cooler thermal sensation, but not cause any difference in thermal comfort. Changing the fluctuating period of the sinusoidal airflow from 10 s to 60 s did not cause an influence on thermal sensation, but a shorter fluctuating period could result in a higher air movement perception. When dealing with thermal comfort issues, a joint effect with airflow speed and fluctuating period occurs and this should also be considered.

scholarly journals Evaluation of Thermal Comfort in the Traditional Bourgeoisie Houses in Beirut

2020 ◽  
Vol 3 (1) ◽  
pp. p1
Author(s):  
Jad Hammoud ◽  
Elise Abi Rached
Keyword(s):  
Thermal Comfort ◽  
Natural Ventilation ◽  
Heat Waves ◽  
Thermal Environment ◽  
Thermal Sensation ◽  
Residential Buildings ◽  
Ventilation System ◽  
Electricity Consumption ◽  
Comfort Level ◽  
Climate Zones

The increasing of energy demands has considerably increased the requirements for new and traditional buildings in different climate zones. Unprecedented heat waves have increased climate temperature, in particular, in moderate climate zones such as Lebanon. In Beirut, only the residential sector consumes 50% of total electricity consumption. HVAC (Heating, Ventilation and Air conditioning) systems are used to reach acceptable thermal comfort levels in the new residential buildings. In case of the traditional bourgeoisie houses in Beirut, there are no discussions about the use of HVAC systems to achieve the required thermal comfort level. Thus, to reach an acceptable thermal comfort level, these houses which already contain natural ventilation system shall adapt the modern thermal comfort requirements and thermal comfort strategies and technologies where their architectural features and existing materials condition the available solutions. In order to identify the best options within the possible intervention lines (envelopes, passive strategies, equipment, renewable energy systems), it is necessary to perceive the real performance of this type of houses. In this context, the article presents the results of the study of thermal performance and comfort in a three case studies located in Beirut. Detailed field data records collected are analyzed, with a view to identify the indoor thermal environment with respect to outdoor thermal environment in different seasons. Monitoring also included measurement of hygrothermal parameters and surveys of occupant thermal sensation.

Transient Model for Particle Dispersion Generated by High Momentum Respiratory Activities in Spaces Ventilated by Displacement Ventilation System

2015 ◽  
Author(s):  
Carine Hanna Habchi ◽  
Kamel Ghali ◽  
Nesreen Ghaddar
Keyword(s):  
Flow Rate ◽  
Transport Model ◽  
Ventilation System ◽  
Particle Diameter ◽  
Particle Dispersion ◽  
Cross Infection ◽  
Thermal Plume ◽  
Cross Contamination ◽  
Breathing Zone ◽  
Displacement Ventilation

A transient zonal model wit is developed to study particle distribution resulting from transient respiratory activities in spaces ventilated by displacement ventilation system (DV). Two transient sub-models are coupled: a transport model of exhaled particles computing the percentage of generated particles penetrating the infected thermal plume and tracking the exhaled jet propagation, and a transport model predicting particle exchange between the different affected layers and regions. A parametric study was performed to determine the effect of different factors on the risk of cross-infection between the occupants: exhalation velocity, DV flow rate, distance separating the occupants and particle diameter. It was observed that with the increase of the DV flow rate, the ventilation effectiveness increases reducing particle accumulation in the breathing zone. The risk of cross-contamination becomes higher for reduced separating distance between the occupants, and for increased cough velocity, as the momentum of released droplets and their quantity increase. Therefore, it was found that to reduce cross-infection, measures can be considered as avoiding getting close to an infected occupant and covering the mouth during a cough. In addition, assisting DV system by chair fans is expected to reduce cross-contamination by increasing the strength of the rising thermal plumes.

scholarly journals Impact of ventilation system type on indoor thermal environment and human thermal comfort in a ceiling cooling room

2021 ◽  
pp. 277-277
Author(s):  
Xiaozhou Wu ◽  
Genglin Liu ◽  
Jie Gao ◽  
Shuang Wu
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Thermal Environment ◽  
Thermal Sensation ◽  
Ventilation System ◽  
Physical Parameters ◽  
Curtain Wall ◽  
Indoor Thermal Environment ◽  
Human Thermal Comfort ◽  
System Type

A ceiling cooling (CC) system integrated with a mechanical ventilation system is an advanced HVAC system for the modern office building with glass curtain wall. In this paper, considering the influence of heat transfer of external envelope, the indoor thermal environment and human thermal comfort were objectively measured and subjectively evaluated in a ceiling cooling room with mixing ventilation (MV) or underfloor air distribution (UFAD). Indoor physical parameters and human skin temperatures were measured as the chilled ceiling surface temperature and supply air temperature were 17.1?C-17.6?C and 22.2?C - 22.6?C. Simultaneously, 16 subjects (8 males and 8 females) were selected to subjectively evaluate the thermal environment. The results showed that the difference between mean radiant temperature and air temperature in the occupied zone was 0.8?C with CC+MV and 1.2?C with CC+UFAD, and the indoor air velocity was 0.17m/s with CC+MV and 0.13m/s with CC+UFAD. In addition, the calculated and measured thermal sensation votes with CC+MV were all slightly less than those with CC+UFAD. Therefore, ventilation system type had a slight impact on the indoor thermal environment and human thermal comfort in the ceiling cooling room.

scholarly journals Enhancement of Thermal Comfort Inside the Kitchen of Non-Airconditioned Railway Pantry Car

2021 ◽  
Vol 39 (1) ◽  
pp. 275-291
Author(s):  
Md Sarfaraz Alam ◽  
Urmi Ravindra Salve
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Thermal Environment ◽  
Thermal Sensation ◽  
Ventilation System ◽  
Comfort Level ◽  
Air Velocity ◽  
Sustainable Improvement ◽  
Study Results ◽  
Air Ventilation

There are ample literature studies available, focusing on hot-humid built environment, which have achieved an increase in thermal comfort conditions by proper installation of ventilation-systems. The present thermal comfort study has been carried out in the kitchen environment of a non-air-conditioned railway pantry car in Indian Railways. The purpose is to enhance thermal comfort level under the currently applied ventilation system inside the kitchen of pantry car by determining the standard effective temperature (SET) index. During the summer and winter seasons, a field study was carried out to obtain the value of air temperature, globe temperature, relative humidity, and air velocity inside the pantry car for estimation of the SET index. A computational fluid dynamics (CFD) analysis was used to obtain a better-modified case model of the pantry car kitchen for the improvement of thermal comfort. The design interventions for the pantry car kitchen were created, with emphasis on increasing energy efficiency based on low-power consumption air ventilation system. The study results indicated that, modified case-I model has a better ventilation design concept as compare to the existing and other models, which increased the air velocity and significantly decreased the air temperature inside the kitchen of pantry car at all cooking periods. A value of SET (28.6–30℃) was found with a comfortable thermal sensation within all cooking periods, which is better for the pantry car workers. This finding suggests a sustainable improvement in the thermal environment of the "non-air-conditioned" pantry car kitchen in the Indian Railways, which can be applied immediately.

scholarly journals An indoor environment evaluation by gender and age using an advanced personalized ventilation system

2017 ◽  
Vol 38 (5) ◽  
pp. 505-521 ◽  
Author(s):  
Ferenc Kalmár
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Side Effect ◽  
Thermal Sensation ◽  
Ventilation System ◽  
The Other ◽  
Air Velocity ◽  
Personalized Ventilation

In a closed space, appropriate thermal comfort and proper indoor air quality are extremely important in order to obtain the optimal work performance and to avoid health problems of the occupants. Using advanced personalized ventilation systems, different comfort needs can be locally satisfied even in case of warm environments. Thermal sensation and the subjective evaluation of indoor air quality of young and elderly people, men and women respectively, were studied in warm environment using advanced personalized ventilation system combined with total volume ventilation system. Using an advanced personalized ventilation system, 20 m3 h−1 air flow was alternately introduced by three air terminal devices built-in the desk and placed on a horizontal plane at the head level of the sitting subject. Thermal sensation was significantly cooler in case of young women in comparison with the other groups. Odor intensity was evaluated to be significantly lower in case of elderly women in comparison with the other groups. Evaluation of air freshness is in correlation with the general thermal sensation. Variation of the direction of the air velocity vector has a cooling side-effect, which, in warm environments, might be useful in order to improve the thermal comfort sensation. Practical application: From the basic factors that influence the thermal comfort sensation, air velocity is the one and only parameter that must be treated as a vector. The air flow velocity has an important effect on the convective heat quantity released by the human body, but the changes in the air velocity direction have a cooling side-effect. This cooling side-effect should be exploited properly in warm environments by advanced personalized ventilation systems to improve the thermal comfort sensation of the occupants without supplementary energy use.

scholarly journals Can Heart Rate Variability (HRV) Be Used as a Biomarker of Thermal Comfort for Mine Workers?

2021 ◽  
Vol 18 (14) ◽  
pp. 7615
Author(s):  
Guoshan Wu ◽  
Heqing Liu ◽  
Shixian Wu ◽  
Guanglei Liu ◽  
Caihang Liang
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Thermal Comfort ◽  
Thermal Sensation ◽  
Low Frequency ◽  
Predictive Biomarkers ◽  
Strong Negative Correlation ◽  
Significant Difference ◽  
Low Frequency Power ◽  
Mine Workers

This study aimed to determine whether heart rate variability (HRV) can express the thermal comfort of mine workers. Eight subjects ran on a treadmill (5.5 km/h) to simulate heavy labor in three kinds of mining environments (22 °C/90%, 26 °C/90%, 30 °C/90%), respectively. Based on the measured electrocardiogram (ECG) data, the HRV of the subjects was calculated. The results showed that the HRV indices changed obviously under different temperature environments. In the neutral and hot environment, except for the LF, TP and LF/HF, there were significant differences in each index. However, there was no significant difference between the cold and neutral environments. The R-R intervals, the very low-frequency power (VLF), pNN20 and SampEN had strong negative correlation with the thermal sensation of people from sitting to work (ρ < −0.700). These indices may be used as thermal comfort predictive biomarkers of mine workers.

scholarly journals Numerical Investigations of Effect of Indoor Air Quality on Thermal Comfort in Residential Buildings

2014 ◽  
Vol 60 (1) ◽  
pp. 91-121
Author(s):  
M. Krzaczek ◽  
J. Tejchman
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air ◽  
Residential Buildings ◽  
Ventilation System ◽  
Cfd Model ◽  
Inlet Velocity ◽  
Numerical Investigations ◽  
Air Inlet ◽  
System Type

Abstract The influence of the CO2 concentration in a local air zone in naturally ventilated residential houses on the residents’ behaviour was numerically investigated. A numerical two-dimensional CFD model of the indoor zone based on experiments performed by the authors was used. Different resident locations in the fluid domain and different inlet velocities imposed by wind were considered in simulations. The overall thermal comfort and IAQ indices were also calculated. The investigations results show that in contrast to the overall air quality, the local CO2 was strongly dependent upon the resident location, fresh air inlet velocity and ventilation system type.

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.

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