سیدعلی رضا ذوالفقاری

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. Since the performance of the cooling tower depends on the environmental conditions, the performance of the cited cooling system has been investigated in different climate zones. The performance of this system has been evaluated in four cities of Tehran, Shiraz, Tabriz and Bandar Abbas, which are representative of temperate and humid, hot and dry, cold and hot and humid climates respectively. The results presented that by storing the chilled water which is produced by the cooling tower in non-peak hours and using this water in peak hours, the maximum COP of the cooling system could increase to 8.5, 14, 12 and 10 in cities of Tehran, Shiraz, Tabriz and Bandar Abbas, respectively. Furthermore, it can be seen that after implementation of the mentioned cooling system, the chilled water temperature of radiant ceiling system is at least 2 to 3°C lower than the temperature of the water which is provided by the tower in majority of occupant attendance hours, especially during peak demand times. The results indicated that the proposed cooling system in Tehran with a temperate climate is able to provide thermal comfort conditions in 90% of attendance times.

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, in front of the abdomen, in front of the face) were modeled, two air temperatures (16 and 20℃) and two air velocities (1 and 2m/s) were assigned to each arrangement. Finally, airflow temperature distribution, velocity distribution, and the overall and local temperature and thermal sensation of different body segments are determined. In some cases, by changing the air inlet placement from the front of the feet to the abdomen and head, the whole-body thermal sensation is cooled by 0.54 and 0.6 units, respectively. In all cases, hands and head felt cooler than the wholebody thermal sensation, which shows that the bareness of a segment has a significant effect on its feeling in personalized ventilation systems. Unlike the foot, the head is an effective local segment for non-uniform cooling purposes in warm conditions, and due to its effect on the whole-body thermal sensation, cooling the head would be an effective way to reduce energy consumption.

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 clothing with thermal resistance of 0.58clo and B: similar clothing without shoes and socks) and three different inlet temperatures (16, 24 and 32°C) have been evaluated. The results showed that the feet wearing has a significant effect on the thermal sensation. In addition, the lack of coverage of the foot area increases the deviations between the sensations of various parts of the body. So, that the difference between the sensation of various segments under the conditions of using clothing A and the desktop arrangement for the diffusers is about 0.5; while this amount in the conditions of under the desk diffusers and using clothing B reaches about twice and the value of 1. Also, the results showed that if the inlet temperature is 16°C or occupants are not used the foot wearing, thermal dissatisfaction cannot be prevented.

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-segment thermoregulatory bioheat (IMTB) model has been introduced which can evaluate the temperature of various segments of the body by considering the effects of individual parameters such as height, weight, age and gender. In this study, the body is subdivided into 17 segments, 3 layers and the blood circulatory system consists of arteries, veins and superficial veins. Also, the effects of individual parameters on physiological parameters, thermoregulatory mechanisms and heat transfer of the body have been investigated. Finally, the performance of the new model in predicting local and mean skin temperature was validated against different experimental data. The results indicate that by considering the individual parameters, the new model can precisely predict the local skin temperature with mean absolute error of 0.4℃.

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 temperature depends on the overall body thermal conditions. This assumption can lead to significant errors in estimating the some organs temperature. Therefore, a JOSTB model has been introduced by the approach of modifying the blood circulatory system. In this model, the body is divided into 17 segments and 3 layers and blood flow in the organs with arteries in the core of each segment is considered. The heat and mass transfer and the localized Pennes equations in different segments have been used to determine tissue temperature. Comparing JOSTB results with MSTB and experimental results show that JOSTB accurately predicts the body temperature. The average errors for the local skin temperature in the wide range of operative temperatures (10-50 ) are equal to 2.3  and 1.1   for MSTB and JOSTB.

In this research, it has been tried to experimentally investigate the the effect of personalized ventilation system on air flow 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 depth of heat and momentum due to the inlet diffuseres were not the same; So that the effect of inlet diffusers’ temperature on the room temperature distribution is significant up to a distance of about 60 cm. However, the effect of inlet velocity is noticeable up to a distance of about 110 cm. As a result, the occupants’ thermal sensations up to about one meter from the inlet diffusers will be affected by the inlet conditions. Also, the results indicated that the draught dissatisfaction along with the diffusers’ centerline is significant to a distance of about 180 cm. Also, based on the results, the air velocity and turbulence intensity are the two main factors in determining the draught dissatisfaction in the personalized ventilation system and due to the rapid thermal mixing of inlet air with the room air, the effect of inlet temperature on the draught dissatisfaction is not significant.

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 degrees. The results showed that the above cases can be significantly affected by changing in location of inlet diffuser. So that by placing the inlet diffuser at a height of 160 cm, the occupants’ upper body is strongly affected by the flow and the maximum air velocity in this region, depending on the change of inlet flow angle from zero to 45 degrees, can respectively reach about 1.5 to 1 m/s and this causes the draught dissatisfaction in the occupants’ upper body. However, by placing the diffuser under the desk and at a height of 30cm, the most dissatisfaction caused by draught occurs in the legs and feet. Finally, it can be concluded that the draught dissatisfaction is the most important factor that can limit the use of personalized confluent jets ventilation system.

One of the concerns about the operation of underfloor air distribution systems is the occurrence of local thermal discomfort such as draught and vertical air temperature difference. In the present study, to investigate these discomfort parameters in a room with the mentioned system, the temperature, mean velocity and turbulence intensity for vertical and horizontal supply air diffuser with 16 and 20°C inlet temperatures were evaluated. These parameters were measured at 0, 30 and 60cm distances from the center of diffuser of the underfloor air distribution system at 8 different heights from the floor. Also, by using the Fanger model, thermal sensation, percentage of thermal discomfort and the percentage of thermal discomfort caused by the draught were determined. The results indicated that the amount of thermal discomfort in a room with an underfloor air distribution system is significantly dependent on supply air direction (horizontal/vertical) and, distance from the inlet diffusers. Also, the results showed that by using proper diffusers, while subjects’ thermal comfort maintains constant, the supply air temperature can be increased from 16 to 20 °C, which is a major step towards reducing energy consumption.

In the present study, the new ADI-CEIDD approach is proposed by combining the ADI method with the explicit-implicit domain decomposition method. The method is used for solving the two-dimensional conduction heat transfer equation on GPU .In this method, an explicit numerical scheme is used to predict values at inner boundaries and an implicit scheme based on the ADI method is used to solve the sub-domains. Then, an implicit scheme is used to correct the values on the inner boundary. The present method increases the number of independent sets of equations and enables more threads to occupy the device. Numerical experiments are done to investigate the accuracy and speed of the method. The results show that the ADI-CEIDD can achieve a speedup of 1.3 to 2.6 times compared to the ADI method. By increasing the number of subdomains from 2 to 32, the speed of the proposed method is increased up to 1.6 times and the accuracy decreases. Although the error of the presented method is higher than the ADI method, numerical experiments show high stability of the ADI-CEIDD. Furthermore, the results show that the ADI-CEIDD method is more advantageous to problems with coarse grid. By increasing the grid size from 256 * 256 to 512 * 512, the value of the Sp decreases from 2.4 to 1.7.

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 the experiments, the inlet air temperature is controlled at 12°C, 16°C and 20°C, and the inlet velocity is kept constant. Also, the room thermal conditions have been controlled at the mean temperature of 24±0.5°C and mean relative humidity of 25±2%. During the experiment, 8 healthy male subjects with common office clothing and metabolic rate were exposed to an under-floor air distribution system for 30 min and their thermal sensation and satisfaction were assessed on the basis of thermal comfort standards. Based on the results, the head and chest thermal sensations are not significantly depended on inlet temperature. But, by decreasing the inlet temperature, the thermal sensation and satisfaction of hands and feet are decreased. Moreover, the results indicated that the overall body thermal sensation is significantly depended on the sensation of the body parts with extreme thermal conditions. Also, the results show that the feeling of air movement can be increased during the time; so, the subjects reported about 75% draught discomfort after 30 min exposure to under-floor air distribution system.

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 (TAC) system is modeled and the effect of gender and body mass index on thermal sensation has been analysed by individualized three-node model. Results show that although Gagge standard model predict pleasant thermal comfort condition, thermal sensation index varies from -0.63 to 0.66 based on individualized three-node model, and in some cases exceed the thermal comfort region. Moreover, healthy and fat people have a warm sensation in clothed parts of the body and thin people, especially women, have a cold sensation in bare parts of the body. Also, based on the results women compared with men, and thin people compared with obese people feel colder. By changing BMI, thermal sensation index can change up to 0.36, which is very significant in the assessment of thermal comfort.

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 separate the pool hall and the spectators’ stand. In these conditions,it is possible to use two different ventilation systems for these two parts. In the present study, an Olympic-size swimming pool with the spectators’ stand is modeled and distribution of velocity, temperature, relative humidity and chlorine concentration have been determined.Also, the results have been analyzed in both cases: using air curtain and without air curtain. The results show that the air curtain can significantly reduce the influence of chlorine pollutants on the spectators section, so the concentration of chlorine at spectators’ stand with the air curtain is about 0.00016 mg/m3 less than the case without air curtain.In this study,65 multi node local thermal comfort model has been used to determine the thermal comfort of individuals.In case with the air curtain, the standard deviation of thermal comfort index for first to third rows are 0.26, 0.25, and 0.28 respectively; and in the absence of air curtain, for first to third rows thermal comfort quantities the standard deviation of thermal comfort index for first to third rows are 0.33, 0.39 and 0.35, respectively.These results indicate that using the air curtain can leads the thermal sensation to be more favorable and more uniform.

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 thermoreceptors achieved by using non-Fourier heat transfer in biological tissue. The mentioned index is in conformity with the ASHRAE standard thermal sensation scale. The present model considers the concept of non-Fourier heat transfer to describe heat transfer in biological tissue. Since biological tissues consist of complicated and nonhomogeneous structure, it is important to describe the process of heat transfer in these tissues by non-Fourier heat transfer equation. The new index has been verified by extensive comparisons with the experimental and analytical results under steady-state and transient conditions where a good agreement was found. Results show that the new index can predict the thermal sensation with mean absolute errors of 0.32 and 0.49 under steady-state and transient conditions, respectively.

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 cooling and heating,in this article the effect of fancoil airflow velocity on the concentration of micron particles of1,10and100microns in the breathing zone of seating(0.9 to 1/1meter) and standing(1.5to1.7meters)people has been studied.For this purpose,by using the computational fluid dynamics and the solver package developed by the authors in OpenFoam,the particle concentration is investigated in a room with a fancoil airflow velocity at1.5and3 m/s.The results show that large particles(100 microns)have a small effect on air quality and settle down after10seconds,in the other hand the smaller particles(10and1micron)have a major impact on ventilation conditions and they settle down after more time(about800seconds).The results indicate that the fan coil velocity increases,also the results show that more particles are filtered by the filter in the fancoil by increasing fancoil velocity and the percentage of particles deposited on the floor reduced.For example,for10microns particles,by increasing fan coil velocity from1.5to3m/s,the percentage of particles deposited on the floor is reduced from26%to17%.

Particle pollutants in indoor environment are a serious threat for human health. Therefore, it seems necessary to recognize and control the distribution of these particles. In the present study, the effect of air inlet angle of swirling diffusers in UFAD systems has been investigated on micron particles pattern distribution by considering the thermal comfort condition. For evaluating the flow and particle distribution, OpenFoam developed solver by the Eulerian-Lagrangian method and for two node model are used for predicting the flow and thermal conditions. Inlet angles are set in three cases: 30, 45 and 60. Based on the results, in all three cases, the TSENS index is in the comfort zone. But, by changing the inlet angle from 30 to 60, the vertical temperature difference can be reduced about 1 . The results showed that at inlet angle 30 and 60, the percentage of particles exited with 2.5 micrometers diameter were 32% and 55% of the total particles. In other words, increasing the inlet angle can leads to exit more amount of any size of particles from the room. In addition, by increasing particles size, larger particles removed faster from the breathing zone, and smaller particles will remain longer time in the air. In other words, smaller particles have a greater impact on the indoor air quality.

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 level of clothing and some have less. In this study, we tried to evaluate the impact of non-uniformity in bus passengers' wearing on the local and overall thermal sensation under mixing and displacement ventilation systems. Based on the results, displacement ventilation system has shown a better performance in providing uniform conditions. In the mixing ventilation, the maximum thermal sensation vote is about 1.1, however it is about 0.4 under the displacement ventilation system. As well, the results show that using short sleeves instead of long ones can decrease about 2.5°C in the hands skin temperature and also about 0.1 and 0.4 in overall thermal sensation index, respectively under displacement and mixing ventilation systems. This also shows that the sensitivity level of short sleeves subjects is higher in the mixing ventilation system than in the displacement ventilation system.

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 storage and preventing the solar radiation from entering the building by using shading devices. Therefore, in the recent years, the idea of using double skin facades with plants has been proposed in order to decrease the summer energy consumption of buildings. In this study, a thermal performance analysis has been performed by considering a high-rise building with the plants double skin façade in Tehran climatic conditions. The results indicate that although using the ordinary double skin façades can decrease the building’s energy consumption up to 24.3% in cold months of the year; it can lead to increase the summer cooling load about 18.3%. However, by using double skin façades with the plants, the building’s energy consumption in cold and warm seasons may decrease about 21.4% and 22.5%, respectively.

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 positions on thermal comfort, indoor air quality and energy consumption in an amphitheater have been investigated. For this issue, a small amphitheater with 50 occupants has been modeled under the conditions that the linear air inlet diffusers located in four situations. The results indicate that the displacement ventilation can provide the proper conditions. However, by changing the location of supply diffuser positions, IAQ and occupants comfort can be improved. For example, for the inlet diffusers are located vertically on the floor, relative ventilation effectiveness is improved about 20% and CO2concentration is decreased about10% in comparison with the other cases.

In the indoor swimming pools, due to the presence of people with different individual characteristics, it is important to design an air conditioning system which can provide thermal comfort conditions for the occupants. Since the differences in the persons’ individual parameters such as gender and body composition, it is required to study the effect of these parameters on the thermal comfort in swimming pools. On the other hand, the location of the air inlet diffuser is one of the effective factors affecting the thermal comfort conditions. In this study, by using the individual 3-node thermal comfort model, the effect of individual parameters on the thermal sensation of people in an indoor swimming pool has been evaluated. The results show that women are more sensitive than men to the cold conditions. In addition, it can be seen that BMI has a significant impact on people thermal sensation. So, thin people are colder thermal sensation than those with healthy physical fitness, and overweight people have a warmer sensation. Based on the results, with the change in body mass index, the index of the thermal sensation can change up to 0.4 units. This is very important in the evaluation of thermal comfort.

General Purpose Graphics Processing Unite (GPGPU) allows the user to utilize GPU for general computing purposes. Using these processors can cause a significant speedup in numerical calculation for solving CFD problems. Several studies have been performed to investigate the advantages of using the GPGPU in numerical calculations including solving tridiagonal set of equations. In 2016, Checkerboard method introduced for solving tridiagonal set of equations in ADI solvers. In this method each set of equations is divided in to several smaller independent set of equations. Then each one of them will be solved by Thomas algorithm in checkerboard style. In addition to the participation of many threads, in this method it is possible to store the information of each set of equation in shared memory. In the present research, according to consideration around using shared memory, a strategy for using this memory in checkerboard Thomas method has been offered. Results shows that utilizing shared memory has been caused to computing speedup between 1.2x to 1.6x, compared with utilizing global memory. Also, it was found that bank conflict causes to decrease the speed from 10.9% to 18.8% in checkerboard Thomas method.

Improving thermal comfort in vehicles, especially in public transport due to design constraints in locating inlet diffusers, overpopulation and difference condition for passengers, is always faced with many challenges. In this paper, the effect of thermal asymmetry on the sensation of passenger inside a bus with overhead mixing ventilation system in three different air distribution patterns is studied by using the 65-nodes thermal comfort model. Moreover, the inlet air temperature has been set at the value which can maintain the passengers’ predicted mean votes within the allowable range. Also, the Airpak solver has been utilized for solving the flow and energy equations; and a numerical code has been developed for solving the local thermal comfort equations. The results show that under thermal asymmetry conditions, it is necessary to use an asymmetric air distribution in order to provide more uniform thermal sensation for the passengers. In this case, air temperature of the head segment is about 22℃ which is less about 2℃ in symmetric flow pattern. The results of 65-nodes model show that using an asymmetrical distribution pattern in the mixing ventilation system improving its performance and under the mentioned conditions, the skin temperature is closer to neutral skin temperature.

The application of personalized ventilation systems, particularly in the buildings, is one of the new topics that today presented to it, because of their proper performance in reducing energy consumption and creating better thermal comfort conditions. In the current study, the energy consumption of a personalized cooling system installed in a room, considering the constraint of thermal comfort, was evaluated and compared with a non-personalized cooling system. The dimensions of the room equal to 4×3×2.7 m3 and includes a return air outlet (for both personalized and non-personalized situations), a supply air inlet in a non-personalized situation, two air inlets for personalized ventilation, table, chair and an approximate model of a human. OpenFOAM numerical solver was used for the calculation and solving the governing equations. Results indicate that in the status of the use of the personalized cooling system, Predicted Mean Vote (PMV) changes in the presence of the person is much higher than the status of the use of the non-personalized cooling system. The local thermal discomfort parameter stemming from draught is within allowed range (less than %20) for a personalized cooling system, excluding of in velocity of 2 m/s and temperature of 21.1 °C. The other important result is that the energy consumption of the personalized cooling system reported much less than the non-personalized cooling system so that energy saving was achieved in about 50 percent. In personalized cooling mode, desired conditions of thermal comfort and minimum energy consumption obtained only at the velocity of 1 m/s and temperature of 20.5 °C among the cases investigated

In the present study, the effect of simultaneous utilizing of atrium and green roof on the energy consumption of a college dormitory has been evaluated under three different climatic conditions of Iran, including Tehran, Tabriz, and Bandar Abbas. Therefore, four different construction designs on the basis of using atrium and green roof has been considerd for a college dormitory. Results indicate that only in the cold climate of Tabriz, the atrium could decrease the annular energy consumption. However, the atrium may cause to increase the annual load in Bandar Abbas. On the other hand, the results show that the green roof technology demonstrates the best performance in hot climate of Bandar Abbas with aboat 8% reduction in annual energy consumption. However, the green roof can cause the annual energy consumption to decrease about 7% and 3% in Tehran and Tabriz climatic conditions, respectively.

The present study investigates the thermal response of individuals whose forearms were subjected to severe cold stimulation and how it is influenced by the personal and physiological characteristics. So, the hands’ transient thermal responses of 89 individuals (male) was observed by thermography imaging technique. Then, statistical analysis was employed to establish an experimental relationships to estimate the thermal response time of the subjects with different individual and physiological conditions. The results showed that among the 9 individual and physiological parameters (age, vascular fat, muscle percentage, fat percentage, body mass index, systolic blood pressure, diastolic blood pressure, heart rate and fasting time), only four independent parameters including internal fat, body mass index, systolic blood pressure and fasting time are significant related to the response time. Also, using multivariate linear regression, a relationship was developed to estimate the thermal response time of the subjects against cold stimulation. This relationship indicates that the response time of the obese can be up to 20% higher than that of the lean subjects. In addition, the results shows that for each one hour after the last meal, the thermal response of the body is slower about 1%.