scholarly journals Application of passengers’ thermoregulation integral model used in the evaluation of thermal comfort in vehicles compartment equipped with internal curtains

2021 ◽  
Vol 321 ◽  
pp. 03008
Author(s):  
Eusébio Conceição ◽  
João Gomes ◽  
M. Manuela Lúcio ◽  
M. Inês Conceição ◽  
André Ramos ◽  
...  
Keyword(s):  
Numerical Model ◽  
Thermal Comfort ◽  
Numerical Study ◽  
Numerical Models ◽  
Thermal Response ◽  
Grid Generation ◽  
The Body ◽  
Comfort Level ◽  
Integral Model ◽  
Shading Devices

This work evaluates the passengers thermal comfort level inside a vehicles compartment. The numerical study, made in winter conditions, consider a bus indoor environment equipped with internal curtains, internal seats, lateral panels, ceiling, floor and occupied by 52 passengers. The numerical model considers the passengers and vehicle grid generation, passengers body and clothing thermal response and passengers thermal comfort level. The grid generation is used to evaluate the view factors and Mean Radiant Temperature that the passengers are subjected. In this calculus the passengers and the vehicles surfaces shading devices are considered. The thermal response numerical models consider the energy and mass balance integral equations. The thermal comfort evaluation considers the heat produced inside the body and the heat exchange between the body and the environment. The human body numerical model considers also the thermoregulatory system to control the temperature. The numerical model is used to evaluate the thermal comfort level that seated passengers are subjected in a bus equipped with asymmetrical warm curtains. Three Cases studies were developed: the first one considers the temperature curtains equal to the indoor bus surfaces, while the other two consider higher temperatures values. All Cases are thermally comfortable according to the standards.

Numerical study of flow pattern around lateral intake in a curved channel

2019 ◽  
Vol 30 (11) ◽  
pp. 1950083 ◽  
Author(s):  
Hossien Montaseri ◽  
Hossein Asiaei ◽  
Abdolhossein Baghlani ◽  
Pourya Omidvar
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Flow Pattern ◽  
Numerical Study ◽  
Numerical Models ◽  
Three Dimensional ◽  
Curved Channel ◽  
Channel Bend ◽  
Outer Bank ◽  
Center Region

This paper deals with numerical study of flow field in a channel bend in presence of a lateral intake using three-dimensional numerical model SSIIM2. The effects of bend on the structure of the flow around the intake are investigated and compared with the experimental data. The tests are carried out in a U-shaped channel bend with a lateral intake. The intake is located at the outer bank of an 180∘ bend at position 115∘ with 45∘ diversion angle and the experimental data can be used to calibrate and validate numerical models. The results show that both the center-region and outer-bank cross-stream circulations are observed in the experiments while only the former is captured by the numerical model due to the limitations of the turbulence model. In the curved channel after the intake, both experimental and numerical results show another type of bi-cellular circulations in which clockwise center-region circulations and counterclockwise circulations near the inner bank and the free surface (inner-bank circulations) are captured. The study shows that the numerical model very satisfactorily predicts streamlines, velocity field and flow pattern in the channel and in vicinity of the intake. Investigation of flow pattern around lateral intake in channel bends shows that contrary to the case of flow diversion in straight channels, the width of the dividing stream surface near water surface level is greater than that of near bed level. Finally, the effects of position and diversion angle of the lateral intake, discharge ratio and upstream Froude number on the flow pattern are investigated.

Numerical study of different ceiling-mounted air distribution systems for a virtual classroom environment

2016 ◽  
Vol 26 (10) ◽  
pp. 1382-1396 ◽  
Author(s):  
Eusébio Z. E. Conceição ◽  
Cristina I. M. Santiago ◽  
Hazim B. Awbi
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Air Temperature ◽  
Distribution Systems ◽  
Numerical Study ◽  
Virtual Classroom ◽  
Comfort Level ◽  
Air Distribution ◽  
Air Supply ◽  
Distribution Index

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℃.

scholarly journals Comparative Study of a Clean Technology Based on DSF Use in Occupied Buildings for Improving Comfort in Winter

2021 ◽  
Vol 3 (2) ◽  
pp. 311-334
Author(s):  
Eusébio Conceição ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Maria Inês Conceição ◽  
Hazim Awbi
Keyword(s):  
Air Quality ◽  
Comparative Study ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Thermal Response ◽  
Clean Technology ◽  
Comfort Level ◽  
Airflow Rate ◽  
Winter Conditions

This paper presents a comparative study of a clean technology based on a DSF (double skin facade) used in winter conditions in the occupied buildings comfort improvement, namely the thermal comfort and air quality. The performance of a solar DSF system, the building’s thermal response, the internal thermal comfort and the internal air quality are evaluated. In this study, a DSF system, an air transport system and a HVAC (heating, ventilating and air conditioning) system based on mixing ventilation are used. The study considers a virtual chamber occupied by eight persons and equipped, in the outside environment, by three DSFs. A new horary pre-programming control methodology is developed and applied when the airflow rate is constant and the number of DSFs to operate is variable, when the airflow rate is variable and the number of DSFs to operate is constant and when the airflow rate is variable and the number of DSFs to operate is variable. This work uses a numerical model that simulates the integral building thermal behavior and an integral human thermal response. The internal air, provided by a mixing ventilating system, is warmed using the DSF system. The air temperature inside the DSF system and the virtual chamber, the thermal comfort level using the PMV index, the internal air quality using the carbon dioxide concentration and the uncomfortable hours are calculated for winter conditions. The results obtained show that the energy produced in the DSF, using solar radiation, guarantees acceptable thermal comfort conditions in the morning and in the afternoon. The indoor air quality obtained at the breathing level is acceptable. It is found that the airflow rate to be used is more decisive than the DSF operating methodology. However, when a solution is chosen that combines a ventilation rate with the number of DSF to operate, both variables throughout the day can obtain simultaneously better results for indoor air quality and thermal comfort according to the standards.

Shading devices applied to sun control in occupied spaces in summer conditions

2021 ◽  
pp. 127-139
Author(s):  
Eusébio Conceição ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Hazim Awbi
Keyword(s):  
Thermal Comfort ◽  
Dynamic Simulation ◽  
Ventilation System ◽  
Simulation Software ◽  
Comfort Level ◽  
Or Groups ◽  
Shading Devices ◽  
Heat Exchanges ◽  
Shading Device ◽  
Made In

This work presents a study of a numerical building dynamic simulation in the development of a horizontal shading device passive solution applied in a university canteen. The used building dynamic simulation software, that simulates simultaneously a building or groups of buildings with complex topologies, in transient conditions, considers the solar radiation, the HVAC system, glass radiative proprieties, radiative heat exchanges, thermal solutions, thermal comfort of occupants, indoor air quality, among others properties. The development of efficient external horizontal shading devices is made by a numerical model that uses the sun's trajectory and its position in relation to the windows where it falls. The canteen is constituted by three levels and is divided in 37 spaces. In the numerical simulation, 100 transparent surfaces and 773 opaque surfaces are considered. Special attention is given in the students’ main canteen, professors’ main canteen, specialized canteen and university bar. The simulation is made, in summer conditions, considered the selected spaces without and with horizontal shading devices placed above their windows. In the simulation, the occupancy and the implemented ventilation system are considered. Regarding to the obtained results the use of horizontal shading devices can reduce the air temperature range and improve the thermal comfort level that the occupants are subjected in some of the analyzed spaces.

Evaluation of comfort levels in office space equipped with HVAC system based in personalized ventilation system using energy produced in DSF systems

2020 ◽  
pp. 65-74
Author(s):  
Eusébio Conceição ◽  
Mª Inês Conceição ◽  
Mª Manuela Lúcio ◽  
João Gomes ◽  
Hazim Awbi
Keyword(s):  
Air Quality ◽  
Numerical Model ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Numerical Study ◽  
Ventilation System ◽  
Airflow Rate ◽  
Hvac System ◽  
Personalized Ventilation

In this study the numerical simulation of a Heating, Ventilating and Air Conditioning (HVAC) system, based in a personalized ventilation system, installed in an occupied office desk is made. The energy is produced in a Dual Skin Facades (DSF) system installed in the outdoor environment. The personalized ventilation system, placed above and below the writing area, installed in the desk central area. The office desk is occupied by eight virtual manikins. The numerical simulation is made in a winter typical day. This numerical study considers a coupling of a differential numerical model and an integral numerical model. The differential numerical model simulates the Computational Fluids Dynamics (CFD), evaluates the air velocity, air temperature, turbulence intensity and carbon dioxide concentration and calculates the indoor air quality. The integral numerical model simulates the Multi-Node Human Thermo-physiology Model, evaluates the tissue, blood and clothing temperatures distribution and calculates the thermal comfort level. The HVAC system, based on a DSF system, is built using three DSF unities, is equipped with internal venetian blinds. Each one, installed in a virtual chamber, is turned to south. The personalized ventilation system, made with eight upper and eight lower air terminal devices, is installed in the desk central area. On each table top two upper and two lower air terminal devices are considered in the left and right manikin area, while on each side of the table two upper and two lower air terminal devices are placed between the manikins. The office desk is occupied by eight virtual manikins, one sitting on each table top and three sitting on each side of the meeting table. In this numerical study, carried out in winter conditions, the occupants’ clothing level is 1 clo. In these situations a typical activity level of 1.2 met is considered. The evolution of indoor environmental conditions, in the DSF and in the office room, are calculated during a full winter typical day. The thermal comfort, the indoor air quality, the effectiveness for heat removal, the effectiveness for contaminant removal and the Air Distribution Index (ADI), are evaluated. In accordance with the obtained results the thermal comfort levels increase when the air renovation rate increases and the indoor air quality level increases when the air renovation rate increases. However, the ADI is quite constant when the inlet airflow rate increases, because the thermal comfort number decreases when the inlet airflow rate increases and the air quality number increases when the inlet airflow rate increases.

scholarly journals Coupling of differential CFD and integral human thermophysiology numerical models applied in indoor ventilated spaces

2021 ◽  
Vol 321 ◽  
pp. 03002
Author(s):  
Eusébio Conceição ◽  
João Gomes ◽  
M. Manuela Lúcio ◽  
M. Inês Conceição ◽  
André Ramos ◽  
...  
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Numerical Models ◽  
Exhaust System ◽  
Comfort Level ◽  
Experimental Chamber ◽  
Airflow Rate ◽  
Inlet System ◽  
Computer Fluid Dynamics ◽  
Air Diffusion

This work presents the development of the coupling of differential Computer Fluid Dynamics and integral human thermo-physiology numerical models applied in indoor ventilated spaces. The study is performed in a virtual chamber, similar to an existing experimental chamber, with dimensions of 4.50×2.55×2.50 m3. The chamber, occupied with twelve virtual manikins, is equipped with six tables, twelve chairs, one exhaust system and one inlet system, based on confluents jets system. In the exhaust system, they are considered six air ducts, located above the head level, connected to the ceiling area. The inlet system, based in four vertical ducts, with 0.15 m diameter, located on the corners of the chamber, is equipped with consecutive holes, that promotes horizontal jets near the wall. The results demonstrate that when the airflow rate increases the air quality number increases, the thermal comfort number decreases, and the Air Diffusion Index increases slightly. The predicted percentage of dissatisfied index values show that the thermal comfort level of occupants is acceptable, the dioxide carbon concentration values show that the indoor air quality is near the acceptable value and the Draught Risk is acceptable.

Combined Experimental and Numerical Study for Multiple Microchannel Heat Transfer System

2010 ◽  
Author(s):  
Jingru Zhang ◽  
Yogesh Jaluria ◽  
Tiantian Zhang ◽  
Li Jia
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Steady State ◽  
Numerical Model ◽  
Initial Conditions ◽  
Numerical Study ◽  
Numerical Models ◽  
Three Dimensional ◽  
Variation Versus ◽  
Heat Transfer System

Multiple microchannel heat sinks for potential use for electronic chip cooling are studied experimentally and numerically to characterize their thermal performance. The numerical simulation is driven by experimental data, which are obtained concurrently, to obtain realistic, accurate and validated numerical models. The ultimate goal is to design and optimize thermal systems. The experimental setup was established and liquid flow in the multiple microchannels was studied under different flow rates and heat influx. The temperature variation versus time was recorded by thermocouples, from which the time needed to reach steady state was determined. Temperature variations under steady state conditions were compared with three-dimensional steady state numerical simulation for the same boundary and initial conditions. The experimental data served as input parameters for the validation of the numerical model. In case of discrepancy, the numerical model was improved. A fairly good agreement between the experimental and simulation results was obtained. The numerical model also served to provide input that could be employed to improve and modify the experimental arrangement.

Spin reversal of the rattleback: theory and experiment

1988 ◽  
Vol 418 (1854) ◽  
pp. 165-197 ◽  
Keyword(s):  
Numerical Model ◽  
Numerical Models ◽  
Spin Model ◽  
The Body ◽  
Past Century ◽  
Spin Direction ◽  
The Past ◽  
Spin Reversal ◽  
Observed Behaviour ◽  
Theory And Experiment

The behaviour of a top known variously as the rattleback, celt or wobblestone is studied. When spun on a flat, smooth, horizontal surface, self-induced oscillations about a horizontal axis eventually consume the initial spin energy; once the spinning has ceased, the oscillations decay and the body spins in the opposite direction. Many rattlebacks seem to be spin biased, reversing spin direction only once and only if the initial spin has the proper sense; others reverse readily from either initial spin direction. Analysis and simulation papers appearing over the past century have attempted, respectively, to explain and qualitatively predict the top’s possible behaviours, and to reconcile observed behaviour with various numerical models. In this work, the two broad theories proposed to explain the spin bias, one which neglects slipping and dissipation and one which incorporates these effects, are critically investigated by several means. The validity of the no-slip assumption is questioned. A numerical model which allows for aerodynamic effects and dry friction due to spinning and slipping is developed. The complicated equations of the numerical model are simplified by analysing the transfer of energy between the spin and oscillations. A comprehensive explanation of the behaviour based on this simplified spin model and the realistic limits of the no-slip motion is proposed. Finally, the predictions of the ‘complete’ numerical model and the simplified model are compared with experimental data.

A Numerical Study of the Influence of Different Factors on Mechanical Characterization of Tumors via a 2D Tactile Sensor

2018 ◽  
Author(s):  
Nathan Abshier ◽  
Cristina Genoese-Zerbi ◽  
James Jobe ◽  
Kylee Kohl ◽  
Charles Tison ◽  
...  
Keyword(s):  
Numerical Model ◽  
Indentation Depth ◽  
Reference Model ◽  
Numerical Study ◽  
Numerical Models ◽  
Tactile Sensor ◽  
Tissue Stiffness ◽  
Tissue Surface ◽  
Curved Substrate ◽  
Stiffness Distribution

This paper presents a numerical study of the influence of different factors on tumor detection via a 2D tactile sensor. The 2D tactile sensor entails a polydimethylsiloxane (PDMS) microstructure embedded with a 3 × 3 sensing-plate/transducer array. By pressing the sensor against a tissue region with a predefined indentation depth pattern, the tissue stiffness distribution is extracted from the measured slopes of the deflections of the sensing-plate array versus the indentation depth. In this work, we numerically investigate the influence of curved tissue surface, curved substrate and tissue viscoelasticity on the measured sensor deflection distribution, which is representative of the tissue stiffness distribution. A set of numerical models are created in COMSOL Multiphysics to investigate the influence of the above-mentioned factors separately. A purely elastic numerical model with a flat substrate and a flat tissue surface is created as the reference model. Two other numerical models are created with one having a curved surface and the other having a curved substrate. The same tumor is embedded in these three models. Given the same 2D sensor, how the measured sensor deflection distribution is affected by different curved surfaces and curved substrates is compared with the results from the reference model. The three tumor parameters (elasticity, size and depth) are also varied for their influence on the measured results. A separate viscoelastic numerical model is created to study how the time-dependent behavior of a tumor varies with its viscoelasticity. This model provides the guidance on tailoring the testing parameters in a pre-defined indentation protocol for quantitatively maximizing the difference in viscoelasticity among different tumors.

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