Alireza Zolfaghari

University of Birjand · Department of Mechanical Engineering (Birjand)

Thermal response of the human cutaneous thermoreceptors depends statically upon temperature and dynamically on the temperature change rate at the depth of the thermoreceptors. Therefore, it is very important to estimate the time-dependent thermoreceptors temperature with a good accuracy. On the other hand, the temperature distribution in skin tissu...

In the standard thermal sensation models such as Fanger's and Gagge's models, the clothing system is simulated as an overall insulation covering the whole body. But under actual conditions, some segments of body are bare and other parts are covered by clothing. In addition, there is a significant difference between thermal sensation of the bare and...

Radiant floor heating systems are usually designed in such a way that the sedentary persons feel thermal neutrality. On the other hand, in most of eastern countries, people traditionally tend to directly sit or sleep on the floor. This could arise some limitations in using of the floor heating systems in the countries with such eastern lifestyle. T...

About 20 years ago, Ring and de Dear [Ring JW, de Dear R. Temperature transients: A model for heat diffusion through the skin, thermoreceptor response and thermal sensation. Indoor Air 1991; 1(4):448–56] introduced a thermal response index (R) for evaluating the cutaneous thermoreceptor response and thermal sensation. Although the mentioned index p...

So far, all of the thermal sensation models have been developed on the basis of energy balance equations for each compartment of the human body. But, the human body feels thermal environment by response of cutaneous thermoreceptors, not by balance of energy. Therefore, the mentioned models are not in conformity with the physiology of thermal sensat...

سیستم‏های تهویه مطبوع را می‏توان به دو گروه غیر وزشی و وزشی (مستقیم و غیر مستقیم) تقسیم نمود. در هر یک از سیستم‏های تهویه ذکر شده همواره امکان بروز شرایطی ناخوشایند همچون کوران و یا سرمایش موضعی در افرادی که در فاصله نامناسبی با سیستم تهویه قرار دارند، بواسطه وزش وجود دارد. در اکثر اوقات بخش‏ های فاقد پوشش بدن همچون دست‏ ها و سر تحت تاثیر وزش ناخوش...

Interaction effects between the inlet Reynolds number (250≤ Rei ≤ 3000) and the heat flux of the impingement wall (0.5 ≤ qʹʹ ≤ 20 kW/m2) was investigated in a vertical self-excited oscillating jet confined by a heated cavity. The results revealed that some high amounts of qʹʹ stop oscillating flow. Thus, this study developed a new prediction method...

In this paper, the characteristics of oscillatory flow have been numerically investigated in the isothermal closed cavity of self-excited oscillating twin jets for several nozzle spacing-to-width ratios, 0 ≤ S/e ≤ 12, and volumetric flowrates of Q = 0.04, 0.08, and 0.12 m3/s. The results showed that in 0 ≤ S/e ≤ 6.5 two jets merge at a short distan...

The purpose of new and hybrid ventilation approaches is to provide better conditions such as occupants' pleasure modification, indoor air quality, air pollutants reduction, productivity enhancement, and energy minimization. Confluent jet ventilation is a hybrid ventilation strategy to overcome the limitations of mixing and displacement ventilation....

Confluent jets issuing from different apertures in the same plane flow in parallel directions then at a certain distance downstream they coalesce and move as a single jet. Achieving proper thermal comfort involves considering the sensation of sensitive segments. So, confluent jet ventilation, as a new energy-efficient ventilation system providing h...

Nowadays, as people spend more time indoors, it is crucial to provide comfortable conditions. This can be achieved by using proper air conditioning systems for various environments. The Confluent Jets Ventilation (CJV) system is a HVAC system that can provide occupants with high indoor air quality. The present study conducts an experiment to assess...

The ability of personalized ventilation as an energy-efficient system, in providing an acceptable indoor environment was analyzed in a modeled office building. For this purpose, three criteria including thermal sensation/comfort, air quality, and energy saving were investigated. Based on thermal sensitivities and preferences differences between var...

Over the past few decades, there has been a heightened recognition of the significance of air quality, comfort, productivity, and health in built environments. As a result, there has been a rise in the need for improved thermal comfort, air quality, and flexible ventilation systems. This research focuses on the analysis of a modeled presentation ro...

Non-uniformity in environmental conditions can affect the occupants’ satisfaction. However, under non-uniform conditions, overall thermal comfort depends on local thermal sensation. This complexity has led researchers to develop several multi-segmental models to predict the local temperature and thermal sensation. The multi-segmental and individual...

Background Many studies have shown some relationships between thermal perception (including thermal sensation and thermal comfort) and human physiological parameters, such as brain signals. However, further research is still needed on how these parameters can help recognize the state of a human’s personal thermal perception. Objective This study a...

Carpeting is one of the most efficient approaches to provide both the acoustic and thermal insulation, and improve the comfort of building inhabitants. In the current research work, the acoustic and thermal properties of handmade carpets as one of the commonly used textile products in several countries, especially in Middle-East countries, have bee...

The present study aimed to investigate the effects of air inlet location and flow characteristics on the performance of a personalized ventilation system. For this purpose, a near-body personalized ventilation system is numerically simulated in an office room with the presence of a thermal manikin. Three air inlet arrangements (in front of the feet...

Thermal energy storage systems can reduce the need for energy during peak demand times. In this system, energy is stored during non-peak times and is used during peak demand times. In this research, the performance of the energy storage system in connection with the cooling tower as a sole cooling source of radiant ceiling system has been assessed....

In this study, the effect of foot wearing on local and overall thermal sensation has been experimentally investigated under a personalized ventilation system in an office. Accordingly, the overall and local sensation of occupants for two arrangements of diffusers (desktop and under the desk) and two different clothing (A: conventional office clothi...

Over centuries different elements have been developed in architectures for ensuring adequate natural ventilation in residential units. This study assesses the different components of an ancient windmill in Sistan, Iran, on the structure's indoor air quality (IAQ) enhancement. Several climatic scenarios have been defined by the wind analysis of Sist...

In this study, a class of GPU-based corrected explicit-implicit domain decomposition schemes (GCEIDD) is proposed to accelerate the solution of convection-dominated diffusion problems on GPUs. All of these methods take advantage of the fractional steps and corrected explicit-implicit domain decomposition techniques. In each sweep, the domain is dec...

Thermoregulatory models based on thermoreceptors have attracted the attention of researchers in recent years due to their conformity with the basis of human thermal perception. For this reason, various models have been presented such as STB, ITB, MSTB and JOSTB. In the present study and in continuation of previous studies, an individual multi-segme...

A self-excited oscillating jet can be naturally produced by discharging a plane jet into a rectangular cavity due to pressure effects and without a need for external aid. In recent years, the self-oscillatory jet in non-isothermal conditions has attracted research interests because of its wide range of industrial applications. Therefore, the curren...

Over centuries different elements have been developed in architectures for ensuring adequate natural ventilation in residential units. This study assesses the different components of an ancient windmill in Sistan, Iran, on the structure's indoor air quality (IAQ) enhancement. Several climatic scenarios have been defined by the wind analysis of Sist...

Modeling body’s circulatory system with many vessels and capillaries and its effects on the body thermal conditions is complex. many thermoregulatory models have tried to model the effect of the circulatory system with simplistic and inaccurate assumptions. The MSTB model considers the blood as a node with specific heat capacity and constant temper...

Outdoor thermal comfort is an important factor in designing urban spaces influencing outdoor activities, social interactions, tourism, wellbeing, and health. Focusing on seasonal differences, this study investigates the thermal comfort conditions and the actual thermal sensation of subjects , and attempts to calibrate the scale of subjects' thermal...

In recent years, non-isothermal jets have received much attention due to their wide range of applications in the industry. The present work concentrates on comparing the buoyancy mediating effects on the performance and oscillating behavior of horizontal and vertical self-excited jets. To this aim, the oscillating behavior and performance character...

By considering the importance of providing proper indoor environment conditions for occupants and also due to energy costs, one of the solutions for indoor local air-conditioning is Personalized Ventilation System (PVS). In this paper, the occupants’ thermal sensation was experimentally studied for body segments that are mostly affected by the PVS....

One of the common local thermal discomforts that happen in an indoor environment is draught. Because of the importance of draught, many studies have been carried out to develop equations to calculate the draught rate. But because these equations are obtained from experimental tests in narrow experimental windows, their accuracy under wider environm...

In this study, the flow pattern, temperature distribution and thermal comfort index have been experimentally investigated in a room with personalized confluent jets ventilation (CJV) system for different diffusers’ heights of 30 and 160cm from the floor and for two inlet temperatures of 16 and 24°C and three different inlet angles of 0, 22.5 and 45...

In this research, it has been tried to experimentally investigate the effect of a personalized ventilation system on airflow and temperature distribution in a room for two inlet air temperatures (24 and 32°C) and two different arrangements of the inlet diffusers (desk-mounted and under-desk air terminals). The results showed that the penetration de...

By considering the importance of providing proper indoor environment conditions for occupants and also due to energy costs, one of the solutions for indoor local air-conditioning is Personalized Ventilation System (PVS). In this paper, the occupants' thermal sensation was experimentally studied for body segments that are mostly affected by the PVS....

One of the common local thermal discomforts that happen in an indoor environment is draught. Because of the importance of draught, many studies have been carried out to develop equations to calculate the draught rate. But because these equations are obtained from experimental tests in narrow experimental windows, their accuracy under wider environm...

In recent years, the use of personalized ventilation systems has increased to locally provide the occupants’thermal comfort. The personalized ventilation systems, despite their advantages such as energy saving and high controllability, may cause local and overal thermal dissatisfaction due to localized and non-uniform flow on the body segments. On...

One of the main concerns about the performance of the Under-Floor Air Distribution (UFAD) systems is the possibility of occurring local thermal discomfort such as draught and vertical temperature difference. In the present study, in order to investigate the occupants’ local discomfort, the distributions of air temperature, velocity and turbulence i...

In the present study, a new alternating direction explicit-implicit domain decomposition approach is proposed by combining the alternating direction implicit method with the explicit-implicit domain decomposition method. The method is used for solving the two-dimensional conduction heat transfer equation on a graphics processing unit. In this metho...

In recent years, the applications of under-floor air distribution (UFAD) systems have commonly increased for ventilation of office buildings. In the present study, the effects of inlet cooling air temperature from the diffusers of under-floor air distribution system have been experimentally investigated on the occupants’ local thermal sensation. In...

Providing thermal comfort conditions in sleeping environment can significantly affect the occupants' health. So, the parameters of the air conditioning system must be properly set to satisfy thermal comfort criteria for persons with different physiological characteristics. In the present study, a task/ambient air conditioning system is modeled and...

In swimming pools with spectators’ stand, due to differences in skin wetness, metabolic rates and clothing type of the swimmers and spectators, providing thermal comfort conditions for all residents is very difficult. Accordingly, a reasonable idea to provide the mentioned different comfort conditions is using the air curtain to aerodynamically sep...

This paper presents an experimental study that evaluated the effects of three different non-uniform types of clothing ensembles (Type A: short-sleeve shirt, T-shirt underwear, men’s briefs, straight trousers, socks, shoes; Type B: long-sleeve shirt, T-shirt underwear, men’s briefs, straight trousers; and Type C: long-sleeve shirt, men’s briefs, str...

One of the optimal systems for proper ventilation of the environment and creating favorable thermal comfort conditions for occupants is personalized systems. These systems are known for their ability to determine the speed, direction, and flowrate that distribute fresh and clean air near people. In this study, the thermal comfort and the thermal se...

The objective of the present study was to investigate the effect of swirl angle on the distribution and deposition of contaminant particles in a chamber with swirl diffuser in an under-floor air distribution (UFAD) system. In the desired model, the analysis of flow field and particle distribution for swirling diffusers at four angles 30°, 45°, 60°,...

In recent years, the modeling of human thermal sensation based on thermoreceptors response has attracted the attention of many researchers. However, the biological tissues does not usually follow the principles of Fourier heat transfer. So, the present research aims to develop a new predictive index for a thermal comfort model based on cutaneous th...

The paper presents a numerical study on an impingement cooling system which employs a self-excited oscillating air jet discharging into a confined space. The effect of nozzle width was examined on the flow structure and heat transfer at different inlet flow rates and impinging distances. The unsteady incompressible flow was solved by the finite vol...

The paper presents a numerical study on an impingement cooling system which employs a self-excited oscillating air jet discharging into a confined space. The effect of nozzle width was examined on the flow structure and heat transfer at different inlet flow rates and impinging distances. The unsteady incompressible flow was solved by the finite vol...

In the present study, an efficient GPU-based corrected explicit–implicit domain decomposition scheme is proposed to accelerate fractional steps solvers. Implicit time advancement in fractional steps solvers leads to several independent tri-diagonal systems. In the present method, by decomposing the domain and predicting the solution at the interfac...

Nowadays,most people spend their time in the interior spaces.Therefore,particulate pollutants in these spaces are serious threat to the health of human.Hence,the investigation on distribution and deposition of particle pollutants in indoor spaces is important for assessing indoor air quality.Due to the wide use of fan coils in interior spaces for c...

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In recent years, Personalized Ventilation (PV) systems have been applied in several indoor spaces, such as offices, theatre halls, vehicle cabins, airplanes and so on. The personalized ventilation systems have several advantages such as low energy consumption, and high air quality in the breathing zone. On the other hand, acceptability of air movem...

Oscillatory flow can be observed in the presence of one and also two self-excited jets issuing into a cavity. Until now no investigation has been done on a double-inlet self-excited jet. In the present work, the characteristics of the oscillatory flow caused by a double-inlet jet in a rectangular cavity are studied and compared with those of a sing...

Thermal comfort and indoor air quality in the built environments are important issues that affect the occupants' health and performance. Confluent Jets Ventilation (CJV) system is a new HVAC system that can reduce the energy consumption by performing a high indoor air quality for the occupants. This paper presents an experimental evaluation of an i...

Particle pollutants in the indoor environment are a serious threat to human health. Therefore, it is necessary to recognition, investigation, and controls of the distribution of these particles in the indoor environment. In the present research, the effect of air inlet angle of swirling diffusers in UFAD systems has been investigated on micron part...

Providing thermal comfort conditions for vehicle occupants, especially public transport is a complicated issue due to the density of population and non-uniformity in individual and environmental conditions. So, an important evidence of individual non-uniformity is the variety in passengers' wearing; e.g. in many cases, some passengers have a higher...

Reducing the harmful effects of urban heat islands is one of the major challenges for researchers that require heat modulation strategies to create sustainable cities. One of the most important principles of open space design is to consider thermal comfort in order to improve the quality of space and to satisfy people. This study tries to improve...

Oscillatory flow in a rectangular cavity may occur in the presence of a turbulent jet due to Coanda effect or non-uniformities in pressure. In the present research, the numerical simulation was carried out by the finite-volume based tool OpenFOAM code to investigate the influence of non-isothermal conditions on the frequency and amplitude in the os...

In the present study, a combined method of ADI and CEIDD (ADI-CEIDD) is proposed. In this method, the number of independent tridiagonal systems are more than the ADI method and this allows for more parallelism. Compared with the parallel methods for tridiagonal system of equation the present method does not add any significant overhead to the ADI a...

Air movement acceptability plays an important role in the occupants' comfort under HVAC. In the present study, we aimed to investigate the air movement acceptability in two different arrangements of UFAD diffusers at three different inlet air temperature of 12, 16 and 20°C. The first arrangement (Case 1) is about the conditions that the UFAD diffus...

استفاده از سیستم‌های تهویه انفرادی به‌ویژه در ساختمان‌ها از موضوعات جدیدی است که امروزه به‌دلیل کارایی مناسب آن‌ها در کاهش مصرف انرژی و ایجاد شرایط بهتر آسایش حرارتی، به آن پرداخته می‌شود. در تحقیق حاضر، میزان مصرف انرژی یک سیستم سرمایش انفرادی مستقر در یک اتاق، با در نظر گرفتن قید آسایش حرارتی مورد ارزیابی قرار گرفته و با سیستم سرمایش غیر انفرادی...

In non-uniform environments, different body parts may experience different ranges of physical/environmental parameters. Therefore, to assess the overall thermal sensation in non-uniform environments, the local temperature/thermal sensation of various body parts should be calculated. The local temperature/thermal sensation based on cutaneous thermor...

آسايش حرارتي حالتي ذهني است که ميزان رضايت فرد از شرایط حرارتی محيط را بيان مي‌کند. قضاوت دربارة آسايش حرارتي فرايند پيچيده‌اي است که تحت تأثير عوامل فيزيکي، فيزيولوژيکي و روانشناختي قرار دارد. تحقیقات انجام شده در زمینه بررسی احساس و آسایش حرارتی، شامل مطالعات تحلیلی، مطالعات آزمايشگاهي و تدوين استانداردها مي‌باشد. در رویکرد تحلیلی از طریق معادلات...

هدف این تحقیق بررسی عملکرد یک سیستم سرمایش انفرادی در محیطی اداری برای فراهم آوردن شرایط آسایش حرارتی کارکنان در فصل گرم سال می¬باشد. بدین منظور یک محیط اداری با سیستم سرمایش انفرادی مدل¬سازی شده و دمای ورودی به-گونه¬ای انتخاب شده است که میزان میانگین رای فرد برابر 0.5 شود. از طرفی پاسخ حرارتی بخش¬های مختلف بدن افراد به¬دلیل یکسان نبودن نوع پوشش و...

بررسی توزیع ذرات آلاینده در داخل اتوبوس به عنوان یکی از وسایل نقلیه پرکاربرد که دارای تراکم بالای جمعیت است، به منظور بررسی کیفیت هوای داخل از اهمیت فراوانی برخوردار است. سیستم تهویه اختلاطی بالاسری و جابه‏جایی کفی، دو سیستم تهویه متداول مورد استفاده در اتوبوس‏ها هستند که در پژوهش حاضر به مقایسه این دو سیستم از نقطه نظر پراکندگی و دفع آلاینده‏های ذ...

از میان کاربرد¬¬¬¬های حرارتی انرژی خورشیدی، سیستم¬های ترکیبی گرمايش خورشیدی، به دليل فن¬آوری نسبتا ساده¬ ومزيت¬هاي اقتصادی در مقایسه با سایر سيستم¬هاي خورشید¬ي، بیشتر مورد توجه قرار گرفته¬اند. دلیل ارجحیت این سیستم¬ها در تامین آب گرم و گرمایش خورشیدی، نیاز به سطح دمای متوسط بوده که این دما با استفاده از کلکتور صفحه تخت و با هزینه کمتر نسبت به سایر...

In the warm season, the performance of double skin facades has a significant dependence on the façade design details and climatic conditions. On the other hand, using the double skin facades can increase the building cooling load. In order to eliminate this problem, two different approaches have attracted the intrest of engineers: solar energy stor...

In dense occupancy spaces, providing the proper conditions especially as indoor air quality is very important. On the other hand, in most air distribution systems, the ventilation performance and energy saving parameters are greatly influenced by the arrangements of supply diffuser positions. Therefore, in this study, the effects of supply diffuser...

The freezing process and the rate of cooling in biological tissues have a strong effect on the formation of ice crystals which eventually play an important role in tissue’s cells survival during freezing. The goal of this study is to investigate the harmful effects of severe coldness and tissue behavior in freezing conditions using non-Fourier heat...