Academic literature on the topic 'Localized thermal comfort'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Localized thermal comfort.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Localized thermal comfort"
1
Brajkovic, Dragan, Michel B. Ducharme, and John Frim. "Influence of localized auxiliary heating on hand comfort during cold exposure." Journal of Applied Physiology 85, no. 6 (December 1, 1998): 2054–65. http://dx.doi.org/10.1152/jappl.1998.85.6.2054.
Full textAbstract:
There is a need for a hand-heating system that will keep the hands warm during cold exposure without hampering finger dexterity. The purpose of this study was to examine the effects of torso heating on the vasodilative responses and comfort levels of cooled extremities during a 3-h exposure to −15°C air. Subjects were insulated, but their upper extremities were left exposed to the cold ambient air. The effect of heating the torso [torso-heating test (THT)] on hand comfort was compared with a control condition in which no torso heating was applied, but Arctic mitts were worn [control test (CT)]. The results indicate that mean finger temperature, mean finger blood flow, mean toe temperature, mean body skin temperature, body thermal comfort, mean finger thermal comfort, and rate of body heat storage were all significantly ( P< 0.05) higher on average ( n = 6) during THT. Mean body heat flow was significantly ( P < 0.05) lower during THT. There were no significant differences ( P ≥ 0.05) in rectal temperature between CT and THT. Mean unheated body skin temperature and mean unheated body heat flow (both of which did not include the torso area in the calculation of mean body skin temperature and mean body heat flow) were also calculated. There were no significant differences ( P ≥ 0.05) in mean unheated body skin temperature and mean unheated body heat flow between CT and THT. It is concluded that the application of heat to the torso can maintain finger and toe comfort for an extended period of time during cold exposure.
2
Conceição, Eusébio, Ma Inês Conceição, João Gomes, Manuela Lúcio, and Hazim Awbi. "Influence of the Ceiling Mounted Localized Air Distribution System Performance in the Human Body." E3S Web of Conferences 362 (2022): 14002. http://dx.doi.org/10.1051/e3sconf/202236214002.
Full textAbstract:
This work presents a numerical study of the influence of the ceiling mounted localized air distribution system performance in the human thermal behavior. In his study a coupling of the Computational Fluids Dynamics and the Human Thermal Modelling is used to evaluate the thermal comfort, the indoor air quality and the Draught Risk. The input data, of the coupling numerical models, are evaluated in the Building Dynamics Modelling. The virtual chamber geometry is generated using the Computational Aided Design system and the occupants’ geometry is generated using empirical equations, based on occupant height and weight. The ADI (Air Distribution Index) and the ADTI (Air Distribution Turbulence Index), used to evaluate the Heating Ventilating and Air Conditioning system performance, depends of the thermal comfort level, the indoor air quality level, the Draught Risk level, the effectiveness for heat removal, the effectiveness for contaminant removal and the effectiveness for airflow removal. The study is made in a virtual chamber occupied by twelve virtual manikins and equipped with twelve seats, six desks and with a ceiling mounted localized air distribution system. The ceiling mounted localized air distribution system is equipped with an inlet system and an extraction system located above the head level.
3
Conceição, Eusébio, João Gomes, Maria Manuela Lúcio, and Hazim Awbi. "Energy Production of Solar DSF for Ceiling-Mounted Localized Air Distribution Systems in a Virtual Classroom." Buildings 12, no. 4 (April 16, 2022): 495. http://dx.doi.org/10.3390/buildings12040495.
Full textAbstract:
This paper presents an application of energy production in a solar Double Skin Facade (DSF) used in a Heating, Ventilation and Air-Conditioning (HVAC) system for a ceiling-mounted localized air distribution systems in a virtual classroom. In this numerical work, a virtual classroom, an inlet ceiling-mounted localized air distribution system, an exhaust ventilation system, and a DSF system are considered. The numerical simulations consider an integral building thermal response (BTR) and a coupling of an integral human thermal-physiology response (HTR) and differential computational fluid dynamics (CFD). The BTR numerical model calculates, among other parameters, the DSF indoor air temperature and energy production. The HTR numerical model calculates, among other parameters, the human thermal comfort. The CFD numerical model, among other parameters, calculates the indoor air quality. In this study which is performed for winter conditions, the energy produced in the DSF is used for driving the HVAC system. Six different airflow rates are used. The air temperature and energy production in the DSF are also evaluated. The influence of the airflow rate on the HVAC system performance is evaluated by the Air Distribution Index for mid-morning and mid-afternoon conditions. The results show that energy production reduces when the airflow increases and the operating point can be selected using the acceptable levels of thermal comfort and air quality levels or using the maximum Air Distribution Index value. In this study, the application of the thermal comfort and air quality levels criteria demonstrates that the HVAC system uses an optimum airflow rate.
4
Uğursal, Ahmet, and Charles H. Culp. "The effect of temperature, metabolic rate and dynamic localized airflow on thermal comfort." Applied Energy 111 (November 2013): 64–73. http://dx.doi.org/10.1016/j.apenergy.2013.04.014.
Full text
5
KUBO, Hiroko, Norio ISODA, and Takuko YANASE. "EXPERIMENTAL STUDY ON EFFECTS OF LOCALIZED COOL AIRFLOW ON THERMAL COMFORT IN SUMMER CONDITIONS." Journal of Architecture and Planning (Transactions of AIJ) 62, no. 492 (1997): 31–37. http://dx.doi.org/10.3130/aija.62.31_2.
Full text
6
Conceição, Eusébio Z. E., Cristina I. M. Santiago, and Hazim B. Awbi. "Numerical study of different ceiling-mounted air distribution systems for a virtual classroom environment." Indoor and Built Environment 26, no. 10 (July 19, 2016): 1382–96. http://dx.doi.org/10.1177/1420326x16659325.
Full textAbstract:
This paper presents a comparative numerical study of different ceiling-mounted-localized air distribution systems placed above students in a virtual classroom in summer conditions. The influence of four different ceiling-mounted-localized air distribution systems, using vertical descendent jets, on the thermal comfort, local thermal discomfort, and air quality levels was numerically evaluated. The air distribution index, developed previously, was used for non-uniform environment. This index considers the thermal comfort level, air quality level, effectiveness for heat removal, and effectiveness for contaminant removal. Numerical simulations were conducted for a virtual classroom equipped with one of four different ceiling-mounted-localized air distribution systems and with 6 desks, 6 or 12 students, and 2 upper airflow outlets. Inlet air supply temperature of 20 and 24℃ and an outdoor air temperature of 28℃ were used. The simulation results show that the air supply system having a vertical air jet placed at 1.8 m above the floor level (Case III), and with an inlet area of 0.01 m2 and a supply air velocity of 3 m/s would represent the best option in comparison with other air supply methods. In general, the air distribution index value decreases with an increase in inlet air temperature and the number of occupants. The air distribution index values are highest for Case III representing a classroom with 6 or 12 occupants with an inlet air temperature of 20 or 24℃.
7
Conceição, Eusébio, Mª Inês Conceição, Mª Manuela Lúcio, João Gomes, and Hazim Awbi. "Numerical Simulation of the Human Microenvironment Around the Occupants." E3S Web of Conferences 356 (2022): 02049. http://dx.doi.org/10.1051/e3sconf/202235602049.
Full textAbstract:
In this study the numerical simulation of the human microenvironment around the occupants is carried out. This numerical work is made inside a virtual chamber, used as classroom, considers the ceiling mounted localized air distribution systems built with one inlet and one exhaust system. The virtual chamber has twelve chairs, each occupied by a virtual mannequin, and six tables. The software, developed by the authors, considers a differential CFD, an integral Human Thermal Modelling and an integral Building Thermal Modelling numerical model. The inlet and exhaust ventilation systems promote, respectively, a downward airflow and an upward airflow in the occupied zone. The study, made in winter conditions, evaluates the thermal comfort, the indoor air quality, the Draught Risk, the Air Distribution Index and Air Distribution Turbulent Index. The results obtained in this work allow us to infer that the thermal comfort, indoor air quality and Draught Risk are acceptable according to what is proposed in international standards.
8
Oh, Myoung Su, Jae Hwan Ahn, Dong Woo Kim, Dong Soo Jang, and Yongchan Kim. "Thermal comfort and energy saving in a vehicle compartment using a localized air-conditioning system." Applied Energy 133 (November 2014): 14–21. http://dx.doi.org/10.1016/j.apenergy.2014.07.089.
Full text
9
De Turck, Sven, Nathan Van Den Bossche, and Jelle Laverge. "The potential of Personal Conditioning Systems." MATEC Web of Conferences 282 (2019): 02098. http://dx.doi.org/10.1051/matecconf/201928202098.
Full textAbstract:
Traditional HVAC systems provide a uniform indoor climate for the whole building or space, whereas the occupants each have their own comfort preferences. The result is suboptimal comfort for the occupants on the one hand, with at best up to 5 % of dissatisfied, and energy losses due to control on the safe side by the building operators. Personalised conditioning systems (PCS) do not aim to heat, cool or ventilate the space but to deliver the heat, cold and fresh air directly to the occupant. This paper provides a systematic assessment about the energy saving potential and potential comfort gains that can be achieved by implementing localized and personal HVAC systems in home environments. Using the Human Thermal Module software that allows to study the thermal sensation and thermoregulation under transient and asymmetric environmental conditions, the energy saving potential was evaluated in TRNSYS, and for a case study with different user behavior patterns it was shown that comfortable micro-climates can be achieved by means of heated chairs for an air temperature as low as 17°C, and the total annual energy savings amount to 30% in winter conditions and 70% in summer conditions.
10
Su, Chu-Qi, Ze-Zheng Wang, Xun Liu, Xin Xiong, Tao Jiang, and Yi-Ping Wang. "Research on thermal comfort of commercial vehicle and economy of localized air conditioning system with thermoelectric coolers." Energy Reports 8 (November 2022): 795–803. http://dx.doi.org/10.1016/j.egyr.2022.10.153.
Full textDissertations / Theses on the topic "Localized thermal comfort"
1
Arghand, Taha. "Human subjective response to combined radiant and convective cooling by chilled ceiling combined with localized chilled beam." Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-20444.
Full textAbstract:
The aim of the present research is to identify human subjective response (health and comfort) to the micro-thermal environment established by integration of individually controlled localized chilled beam and chilled ceiling (LCBCC) system and to compare its performance with the performance of mixing ventilation combined with chilled ceiling (CCMV).Experiments were carried out in mock-up of an office (4.1 m × 4.0 m × 3.1 m, L× W× H) with one person under two summer temperature conditions (26 °C and 28 °C). To mimic direct solar radiation in the room, five radiative panels on the wall together with electrical sheets on the half of the floor were used. The test room was set-up with two desks, as two workstations, and one laptop on each table. The main workstation (WS1) was located close to the simulated window. The second work station (WS2) was placed in the opposite side of the room. The room was equipped with two types of ventilating and cooling systems. The first system consisted of a localized active chilled beam (LCB) unit together with chilled ceiling (CC) panels. The LCB was installed above the WS1 to create micro-environment around the occupant sitting at the desk. The supply flow rate from the LCB could be adjusted by the occupant within the range of 10 L/s to 13 L/s by means of a desk-mounted knob. The integration of mixing ventilation (MV) system and chilled ceiling panels was the second ventilating and cooling strategy. Twenty- four subjects (12 female and 12 male) were exposed to different indoor environment established by two cooling systems. Each experiment session lasted 120 min and consisted of 30 min acclimatization period and 90 min exposure period. The performance of the systems was identified and compared by physical measurements of the generated environment and the response of the human subjects. The study showed that perceived air quality (PAQ), overall thermal sensation (OTS) acceptability and local thermal sensation (LTS) acceptability clearly improved inside the micro-environment by using LCBCC system. Moreover, at the main workstation, OTS and LTS votes were close to “neutral” thermal sensation (ASHRAE seven point scale) when LCBCC system was used. However, OTS and LTS votes increased to the “slightly warm” side of the scale by applying CCMV system which implied the better cooling performance of the LCBCC system. Acceptability of work environment apparently increased under the room condition generated by LCBCC system. In agreement with human subjective study, the results from physical measurements and thermal manikin study showed that uniform thermal condition was generated all over the room. Air and operative temperature distribution was almost uniform with no difference higher than 1 °C between the measured locations in the room. Thus, both LCBCC and CCMV systems performed equally well outside of the micro-environment region. The use of the chilled ceiling had impact on the airflow interaction in the room and changed the airflow pattern. It can be concluded that the combination of convective and radiative systems can be considered as an efficient strategy to generate acceptable thermal condition in rooms.
2
Choi, Sung In. "Smart Localized Heating Control System With Human Movement Tracking." Master's thesis, Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/407171.
Full textAbstract:
Electrical EngineeringM.S.E.E.
According to the U.S. energy consumption survey in 2012, about 25% of the commercial and 42% of the residential building energy were used for heating. Despite the development of new and more efficient Heating, Ventilation, and Air Conditioning (HVAC) systems over the years, the high energy consumption in heating is still one of the major energy efficiency issues. Studies showed that decreasing HVAC operating temperature set points by 4°F will result in energy savings of 15% or more. Thus, the smart localized heating control (SLHC) system was designed and prototyped to provide localized heat directly to a person so that HVAC can run at a lower temperature set point. SLHC detects human movement and delivers the heat based on the result of the target location estimation and temperature measurement feedback. To detect the human movement, image processing techniques were used; image segmentation, mass center detection, background subtraction using the Mixture of Gaussian model, and human feature detection. In SLHC, a near-infrared heater and a tracking function were used to provide an instant and a direct heat to the person in order to minimize wasting energy. The SLHC system is divided into the sensing and processing (SP) and the heating and regulating (HR) subsystem. The SP’s primary function is to process captured video images and measured temperature data. SP also generates and sends the heater operating signal to HR. HR purposes to control the heater’s direction and power based on the signal. The communication between SP and HR was established through Wi-Fi enabled development platform. The SLHC prototype successfully processed the sensing data and transmitted the control signal. The result shows that it detected human movement and estimated the person’s location in 3D space within 10% margin of error. Also, it delivered the focused heat to the surface of the human body and increased the temperature by 10.0°F in 3 minutes at the distance of 1.5m away from the heater. This cost-effective, wireless, and localized heating system demonstrates the potential to improve energy efficiency in buildings.
Temple University--Theses
3
Ugursal, Ahmet. "Thermal Comfort under Transient Metabolic and Dynamic Localized Airflow Conditions Combined with Neutral and Warm Ambient Temperatures." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8877.
Full textAbstract:
Human thermal environments constitute complex combinations of various interacting thermal factors. The transient and non-uniform nature of those thermal factors further increases the complexity of the thermal comfort problem. The conventional approach to the thermal comfort problem has been simplifying the problem and providing steady thermal environments which would satisfy the majority of the people in a given space. However, several problems emerged with this approach. People became finely tuned to the narrow range of conditions and developed expectations for the same conditions which made them uncomfortable when there were slight deviations from those conditions. Also, the steady approach didn't solve the comfort problem because, in practice, people move between spaces, and thermal conditions such as metabolic rate, surface temperatures, airflow speed and direction vary in a typical day.
A human subject test was designed to determine the transient relationship between the people and their environments. In the first part, thermal perceptions of people were taken during various metabolic rate conditions. In the second and the third parts, transient conditions of different thermal factors were created. Various combinations of airflow frequencies, airflow location around the body, metabolic rate, and room temperatures were tested for their individual and interaction effects of providing thermal comfort. The concept of Localized Dynamic Airflow was proposed in which room airflow was simply redirected to different parts of the body with a varying airflow speed.
Results showed that males and females respond differently to the thermal conditions. The room temperatures they found neutral were significantly different. People‟s thermal comfort during transient metabolic conditions was similar to high metabolic conditions. This heightened response extended into the next ten minutes after the high metabolic conditions ended. Test results suggested that people tolerate higher temperatures during transient environmental conditions. The average response was for comfortable even during the high temperature (83°F) and high metabolic rate (4 met) conditions. Low energy use of the localized dynamic airflow and the increased room temperatures has significant potential for monetary savings.
Book chapters on the topic "Localized thermal comfort"
1
Myat, Aung. "Application of Artificial Intelligence in Air Conditioning Systems." In Recent Updates in HVAC Systems [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.107379.
Full textAbstract:
Urbanization has led to a sharp rise in the demand for power over the past 10 years, alarmingly rising greenhouse gas (GHG) emissions. HVAC (heating, ventilation, and air conditioning) systems account for nearly half of the energy used by buildings, and minimizing the energy use of the HVAC systems is essential. However, the common problems, such as hot spots and cold spots in office spaces, experienced in the building need to be addressed. Therefore, this chapter introduces the application of artificial intelligence proactive control to resolve typical office issues. A demonstration testbed was implemented on the Singapore Institute of Technology (SIT) campus. The experiments were conducted in baseline mode and smart mode. In the case study, two big zones were segregated into 43 micro-zones equipped with smart dampers at each diffuser, allowing a localized set point to improve thermal comfort and eliminate hot and cold spots. It has been observed that the proactive AI control reduces cooling provided to the office by 29 percent and AHU electricity usage by 50 percent, respectively, while keeping the area within thermal comfort range of 23 to 25°C and 50 to 63% relative humidity.
Conference papers on the topic "Localized thermal comfort"
1
Ghaddar, Nesreen, Kamel Ghali, and Alain Makhoul. "Performance of Coaxial Ceiling-Mounted Personalized Ventilator for Comfort and Good Air Quality." In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17814.
Full textAbstract:
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.
2
Kalra, M., M. Bahrami, and C. J. Sparrey. "Effect of Geometry and Blood Flow in Cooling of Upper Leg." In ASME 2013 Conference on Frontiers in Medical Devices: Applications of Computer Modeling and Simulation. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fmd2013-16089.
Full textAbstract:
Systemic hypothermia has been shown to reduce neurological damage in post-cardiac arrest patients. Reducing a patient’s core temperature to 33°C over a period of 24 to 48 hours has been shown to reduce long-term neurological damage by 16% and mortality by 14% [1]. Hypothermia is frequently induced by surface cooling, either with medical devices that circulate coolant in a pad, or ice packs. However, there is a lack of knowledge about the thermal response of tissue to localized cooling. Current thermal models are designed for determining human comfort and have not been evaluated for the targeted low temperatures required for inducing hypothermia. Metabolic heat generation and tissue perfusion rate can significantly change under low temperature, which in turn affects the overall heat flux and cooling rates.
3
Nuckols, Marshall, Jerry Henkener, Jeffrey Chao, Chris Shaffer, and Matthew Swiergosz. "Manned Evaluation of a Prototype Cold Water Diving Garment Using Superinsulation Aerogel Materials." In 25th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/omae2006-92026.
Full textAbstract:
During January 2005, the U. S. Navy Experimental Diving Unit (NEDU) in Panama City, Florida conducted a repeated measures series of twelve test dives, each up to three hours in duration, to compare the thermal performance of a prototype diving garment using a superinsulation aerogel fabric with that of a commercially-available Thinsulate garment worn beneath a commercial dry suit. The thermal benefit of the experimental aerogel garment was determined by statistics describing psychological and physical thermal status data from the aerogel and the commercial Thinsulate garments. All tests were conducted to simulate long-duration cold water conditions in the NEDU test pool, where water temperature was maintained between 1.7 and 4.4 °C (35 and 40 °F). Divers remained immobile while either lying or sitting in chairs on the bottom of the test pool, and they subjectively reported their thermal comfort at 30-minute intervals during each dive. Mean dive durations were found to be approximately 43% longer when divers wore the prototype aerogel garment than when they wore an M400 Thinsulate liner. The prototype aerogel garment also enhanced thermal protection to the fingers and toes, although thermal stress to these body regions still remained the most frequent reason for aborting dives. Future research should include work on localized active heating of the hands and feet to augment the thermal insulation of the prototype aerogel garment.
4
Colvin, David P., and Yvonne G. Bryant. "Protective Clothing Containing Encapsulated Phase Change Materials." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0807.
Full textAbstract:
Abstract Based upon experimental results from numerous Small Business Innovation Research (SBIR) programs for USAF, NASA, NAVY, NSF and USMC, new protective clothing are being developed that provide significant enhancements in thermal storage and comfort using encapsulated phase change material With a paraffinic phase change core and a polymer outer shell whose latent phase change can be designed to occur at a selected temperature, particles of microencapsulated phase material (microPCM) can range from 3–100 microns in diameter and be added to textile fibers, composites, foams, coatings and liquid coolants. Much larger 1–3 mm macroencapsulated phase change material (macroPCM) particles can also be included within clothing to provide significant improvements in breathable thermal cooling under conditions of high humidity. When microPCM particles of 10–50 microns diameter are added to a flexible matrix such as foams, new materials are created that can provide both enhanced thermal storage and insulation within the same thickness. Enhancements of thermal capacitance of textile fibers and foams can reach 10X or 1,000 % compared to unfilled fibers and materials. The resulting clothing can provide greatly enhanced thermal protection in both hot and cold environments with both low bulk and thickness. Firefighters, race drivers, skin divers and snow skiers are discovering significant protective advantages with these new materials. For example, waterproof and breathable arctic gloves have been shown to provide superior protection to commercially-available ski wear that is less susceptible to loss of thermal resistance with localized compression.
5
Kader, Md Faisal, Kang Hyu Goo, Yong-Du Jun, and Kum-Bae Lee. "A Numerical Investigation of Automobile Environment Through Cooling Period and Condensation." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88203.
Full textAbstract:
Understanding the fluid flow and heat transfer characteristics within a vehicle compartment is very important for controlling the effect of major design parameters. Also, adequate visibility through the vehicle windshield over the entire driving period is of paramount practical significance. The numerical solution was done by an operation friendly, fast and accurate CFD code — SC/Tetra with a full scale model of a SM3 car and turbulence was modeled by the standard k-ε equation. Numerical analysis of the three-dimensional model predicts a detailed description of fluid flow and temperature distribution in the passenger compartment and on the inside windshield screen. During the cooling period, the lowest temperature is observed in the lower part of the windshield and in the vicinity of the defroster griller. It was found that the temperature dropped down to a comfortable range almost linearly at the initial stage. The initial period to achieve this comfortable range is dependent on the inlet velocity. Experimental investigations are performed to determine the localized thermal comfort and further validation of the numerical results.
6
Katramiz, Elvire, Nesreen Ghaddar, and Kamel Ghali. "Effect of Intermittent Personalized Ventilation on Coughed Particles Dispersion in an Office Space and Resulting Cross Contamination." In ASME 2021 Heat Transfer Summer Conference collocated with the ASME 2021 15th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/ht2021-60817.
Full textAbstract:
Abstract The transmission of infectious respiratory diseases has been a topic of broad interest for decades. It is largely influenced by the ventilation in the space, especially localized ventilation near the infection source. One energy-friendly ventilation technique that has been extensively investigated in contaminants transmission is Personalized Ventilation (PV), which delivers cool clean air directly towards the breathing zone of the user, procuring acceptable levels of thermal comfort and breathable air quality. However, when used by an infected person, it might amplify the dispersion of the expiratory droplets, increasing the risk of airborne cross-infection. Some PV applications varied the supplied cool clean air intermittently in order to enhance occupants’ thermal comfort and improve energy performance. Such system operation is referred to as Intermitted PV (I-PV). Nonetheless, the effect of such oscillatory jet on airborne diseases dispersion has not been assessed in literature to the authors’ knowledge. In this work, the impact of integrating I-PV with mixed ventilation on cross-contamination is investigated for the case where an infected user is coughing. The I-PV is considered to operate at an average flowrate of 10 l/s, with a minimum of 4 l/s at a typical frequency of 0.94 Hz. The infected person is considered seated in a tandem (i.e. back-to-face) position with respect to a healthy person, located at a distance of 1.5 m and not using PV. This reflects the worst-case scenario where the healthy person is not protected by PV. A validated computational fluid dynamics (CFD) model is used to assess the cross-contamination between the occupants. A comparison between I-PV and steady PV (S-PV) of constant flowrate of 10 l/s is conducted to highlight the influence of I-PV on contaminants dispersion in the space and the resulting exposure level of a healthy occupant. Results showed that the use of I-PV reduced the exposure levels of the healthy occupant in comparison to S-PV.
7
Makhoul, Alain, Kamel Ghali, and Nesreen Ghaddar. "Ceiling-Mounted Fresh Air Personalized Ventilator System for Occupant-Controlled Microenvironment." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-87565.
Full textAbstract:
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.