seyed alireza zolfaghari

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.

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.

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.

Nowadays, the building ventilation is an essential process, due to need of improving the air quality and thermal comfort conditions for occupants. Providing the mentioned conditions is more complex for crowded and larger spaces. In this study, the effects of air change rate per hour (ACH) on thermal comfort, indoor air quality and energy consumption in an amphitheater with under floor air distribution system have been investigated by using the computational fluid dynamics and Open Foam numerical solver. For this issue, an amphitheater with 50 occupants has been modeled under the conditions that the air inlet diffusers located in front of seats. Also, the air change rate per hour is assumed to be 5, 10 and 15. For better comparison between the results, inlet air temperature is controlled until the mean of thermal comfort index (TSENS) in the occupied zone equals to zero. The results indicate that for air change rates of 15, 10 in comparison with ACH of 5, the CO2 concentrations in the occupied zone are respectively reduced about 36 and 46 percent and so the indoor air quality is improved. On the other hand, the energy consumption is increased about 28 and 69 percent, respectively. Also, based on the results, by increasing the ACH rate, the draft local discomfort is significantly increased and can be reached at the amount of 15%.

The aim of this study is to compare the performance of floor displacement and overhead mixing ventilation systems in providing the thermal comfort conditions for bus passengers. For this reason, the flow and energy have been numerically simulated inside a Scania 4212 bus with its 45 passengers. In the case of displacement ventilation, the inlet diffusers have been located under the seats at the floor and for mixing ventilation mode, the inlet diffusers have been established overhead of passengers. In both cases, as mentioned in ASHRAE standard for public transportation, the inlet air rate of 5 lit/s has been provided for each passenger and the inlet air temperature has been controlled until the predicted mean vote index is within the allowable range of thermal comfort standards. In displacement ventilation because of locating the inlet diffusers on the floor and the buoyancy effects, the air temperature in foot region is about 18C, which is lower than other parts of body and vertical temperature difference in overhead mixing ventilation occurred less than floor displacement ventilation and the temperature difference between foot and head region is only 2C. In overhead mixing ventilation, air temperature near the head is about 24C while in floor displacement ventilation the temperature is about 26C that is not in neutral zone. The results of 65-nodes thermal comfort model indicate that the temperature difference between skin neutral temperatures of each segment in floor displacement mode is higher than overhead mixing ventilation

Thermal sensation evaluation of occupants in a dense occupancy space can be an effective step for designing ventilation systems of these environments. In a dense occupancy environment, because of the presence of a large population and also differences in personal parameters such as age, gender, clothing, weight, and body mass index, providing the appropriate thermal comfort conditions is complicated. In this study, the individual characteristics effects on thermal comfort conditions of occupants in a dense occupancy environment is investigated by individualized three-node model. For this issue, a dense occupancy environment with displacement ventilation and inlet air diffusers on the floor is modeled and thermal sensation index for occupants who seated in middle row has been analyzed. Based on the results, the women are more sensitive than men under cold conditions. Also, effects of mass body index on thermal sensation are significantly noticeable. Compared with a healthy person, the thinner people have a cold sensation and fatter ones feel warmer. For example, in the mentioned case, difference between thermal sensation index of thin woman and obese man is 0.42 for the bare parts of the body, indicating noticeable effects on thermal sensation.

Investigation on thermal comfort in a public transport has a significant impact on the satisfaction of this environment. Therefore, in this study, the thermal comfort conditions in a bus was investigated and among the different factors affecting on the thermal comfort in this space, the shape and the location of the inlet valves are studied in order to achieve optimum thermal comfort index for seated people. Hence, three different inlet valves with the same area and the same inlet air velocity was considered; circular cross-sections under each seat, rectangular valves on the floor and rectangular valves on the body and at the height of 0.2 meters from the floor. The results show that in order to achieve the optimal thermal comfort index, temperatures for circular air inlet must be 24.0
̊ C, for rectangular valves on the floor must be 20.1
̊ C and for the rectangular valve of the body must be 21.6
̊ C. These results suggest that the use of circular air inlet in the cooling system is more economical. To evaluate the effect of height on the thermal comfort index, the difference of the index was calculated with the height of 0.1 and 1.1 meters for three different inlet valves. The results show that by the use of rectangular valve on the body, the distribution of thermal conditions on the body of the passengers will be more uniform.

Differences in the persons’ individual parameters such as age, gender, weight, height and basal metabolic rate have a significant effect on the human body thermoregulation. Therefore, using the human thermal models that developed on the basis of large humanity population cannot lead to accurate results for specific individuals. Because, the individual parameters have not been considered in standard thermal comfort models and also available individual and local models are so complicated in applications; nowadays, the necessity of developing a simple and accurate individualized model is felt. In this study, some physiological parameters such as: body fat percentage, subcutaneous fat layer thickness, body heat capacity coefficient and tissue conductive resistances have been modeled from readily-available external measurement of individuals and these parameters are incorporated into three node-model algorithm structure to predict individual variations in thermal response between individuals. Three-node thermal comfort model is based on Gagge’s standard model that has been accurately estimated thermal sensation of the bare and clothed parts of the body. The model has been verified against the analytical and experimental results where a good agreement was found. In conclusion, the results indicate that the mean error in prediction of skin temperature is decreased from 1.2℃ for three-node model to 0.4℃ for the new individual model.

Due to high humidity, high air temperature and hazardous compounds including chlorine indoor swimming pools are called as ýunhealthy environment. Therefore, the pollutants’ concentration, relative humidity and thermal comfort conditions must be ýsimultaneously considered in designing the air conditioning systems of indoor swimming pools. In this study, a new approach has been ýpresented for concurrent modeling of water evaporation mechanism, chlorine concentration level, occupants’ thermal sensation and ýtemperature and velocity fields in a championship-size indoor swimming pool. In this regard, a new algorithm has been developed in ýorder to apply adaptive boundary conditions at water-air interface in the pool. In the mentioned pool, the air enters the environment ýthrough a linear ceiling diffuser at temperature of 35°C, relative humidity of 30% and air exchange rate of 4 times per hour. The results ýshow that the distribution of temperature, relative humidity and concentration of chlorine contaminant are significantly depending on the ýheight from the water surface. So, the volumetric average of relative humidity from the floor to 0.5m height is about 62%; while the ývolumetric average of relative humidity in the occupied zone is about 50%. Moreover, results indicate that in the distance of floor to 0.5m ýheight, the mean value of chlorine’s concentration is about 60% larger than its mean value in the occupied zone. Also, the temperature ýfield and distribution of thermal comfort index are significantly dependent to the height.ý

In the present study, the effect of high temperature radiant heaters’ arrangement on providing appropriate and uniform thermal conditions under asymmetric flow field have been investigated in an industrial environment. For this reason, a sample industrial environment with one inlet and outlet opening has been considered with two different types of high temperature radiant heaters’ arrangement: single radiant heater and couple radiant heaters. For the mentioned conditions, continuity equation, momentum equations, energy equation and radiative transfer equations have been solved by OpenFoam numerical solver. Also energy consumption has been evaluated in the present study. The results show that in presence of asymmetric flow field, using couple high temperature radiant heaters in comparison with single radiant heater causes more uniform temperature distribution and decrease about 10 degrees of Celsius in maximum temperature of floor. Also, this can cause to decrease about 35 percent in floor temperature distribution deviation from the average appropriate temperature (27 degrees of Celsius). Moreover, the results indicate that utilizing couple high temperature radiant heaters leads to increase in energy consumption about 10 percent in comparison with single radiant heater.

General Purpose Graphics Processing Unite (GPGPU) allows the user to utilize GPU for general computing purposes. Using these processors can cause a great speedup in numerical calculations. Several studies have been performed to investigate the advantages of using the GPGPU in numerical calculations including solving tridiagonal set of equations. The main focus of the mentioned studies was on improving parallel methods for example CR and PCR algorithms. Although these algorithms are consistent with GPU architecture, they have higher arithmetic complexity compared with serial Thomas algorithm and also they have limitations in dimensions of the equations’ set. Therefore, in the present study, according to the advantages of Thomas algorithm compared with the parallel algorithms, a novel method entitled checkerboard Thomas has been developed to accommodate Thomas algorithm for running on GPU. This method has been used for solving 2D steady heat conduction problem and the results show an increase in the solution precision compared to Thomas and PCR algorithms. Also the results indicate that the new algorithm can cause to computing speedup between 5.7 to 22.2x, compared with Thomas algorithm. Furthermore, results show that the new method is about 2x faster than PCR algorithm. Also it has been seen that speed decrement for uncoalesced access to global memory is 42.7% in minimum and 81.9% in maximum for 128×128 and 1024×1024 grid size, respectively.

Under the critical thermal conditions, the human body cannot adapt itself to the environment by using physiological thermoregulatory mechanisms. Under these conditions, using the protective clothing is one of the effective ways to protect the human body against the thermal injuries. Therefore, in the present study, the effect of using Phase Change Materials (PCMs) on the performance of firefighters’ protective clothing has been numerically investigated under the critical scorching conditions. The main contribution of this study is the simultaneous modeling of a PCM based protective clothing with physical and physiological mechanisms of the human body. For this purpose, a multi-layer protective clothing with a PCM layer has been considered and its thermal performance has been investigated under scorching conditions for three different arrangements of the layers. The results show that the middle layer of protective clothing is the best position for implementing the PCM. Also, and is the best melting temperature for the mentioned PCM is about 40˚C. Moreover, the results indicate that using the PCMs in protective clothing can increase the thermal tolerating time from 300 seconds (for non-PCM protective clothing) up to 900 seconds, under the scorching conditions.

In this research, the effects of flow rate and temperature of supply air on the performance of a bed-based task/ambient air conditioning system (TAC) have been investigated. For this reason, a bed-based task/ambient air conditioning system including a bed, a supply air inlet on the top of the occupant's head and a return air outlet under the bed have been considered and for the mentioned conditions, the equations of flow, energy and thermal comfort have been solved by OpenFoam numerical solver. Also, the thermal comfort conditions, local thermal discomfort and energy utilization coefficient have been evaluated in the present study. The results show that the performance of the mentioned system significantly depends on the supply air temperature and flow rate. So that, the low supply air flow rates may cause non-uniform temperature and velocity distributions and this leads to unpleasant thermal comfort conditions. Also, in order to achieve the benefits of TAC systems, using of high supply air flow rates must be avoided because in high flow rates a wide area of the room is affected by supply air instead of the bed zone. Also, the results indicate that the energy utilization coefficient decreases with supply air flow rate increment. Therefore, this coefficient has reached to less than 1.5 in 120 lit/s air flow rate that demonstrate the low advantage of using TAC systems in high supply air flow rates.

Nowadays, using the double skin facades has attracted the attention of many engineers because of its significant effects on the buildings’ energy consumption. The previous researches have shown that the double skin facades have an appropriate thermal performance in the cold season. However, using double skin façade may lead to increase the building’s energy demand in the warm season. Therefore, in the recent years, the idea of using double skin facades with phase change materials (PCM) 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 phase change material 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 20% in cold months of the year; it can lead to increase the summer cooling load about 4.6%. However, by using double skin façades with the phase change material glazing, the building’s energy consumption in cold and warm seasons may decrease about 40% and 26%, respectively.

In this study, the effects of discharge angle from an air curtain’s jet have been investigated on aerodynamic sealing of a room with positive pressure ventilation system. For this reason, the modeling of flow, heat transfer and species diffusion has been performed by using OpenFoam® numerical solver. The results show that the jet discharge angle has significant effects on the distribution of parameters such as temperature, concentration of pollutants and occupants’ thermal sensation index. So, by varying the jet discharge angle from +10 (towards the indoor space) to -10 (towards the outdoor space), the average temperature difference between two spaces is reduced to 2.5°C. Also, the mentioned varying in discharge angle causes a significant reduction in the mean concentration of pollutants at the indoor space, from 25ppm to 5ppm. On the other hand, the results indicated that for the discharge angle of -10, the average of occupant’s thermal sensation index is shifting to the cool feeling. Therefore, the mentioned discharge angle can reduce the impacts of outdoor warm conditions on the indoor’s. In other words, the discharge angle of -10 demonstrates the best performance of the air curtain device in thermal and aerodynamic separating of two indoor and outdoor spaces.

Although,the physical activity in the cold condition causes the body temperature to rise,it can be a significant factor in the occurrence of thermal discomfort due to increase in the perspiration rate and water gathering in the fabric.Moreover,the accumulated water at the inner side of the clothing can cause a difficulty in the skin respiration. So, the amount of accumulated water and interior surface wetness are important indices for evaluating the suitability of clothing for winter activity. The aim of this study is to determine the amount of accumulated water in various arrangements of multi-layer clothing assemblies containing of three bathing layers of Polyester and Viscose in a very cold environment (with -20C temperature).For this reason,the clothing has been modeled as a porous media with multi-phases and multi-species flow by considering the sorption and condensation phenomena.Also,the implicit finite volume numerical method has been used for discretizing and solving the governing equations.The results show that locating the non-absorbing polyester fabric at the layer adjacent to the skin causes the wetness to decrease at this region. Also, locating the polyester at the outer layer can help to maintain the clothing temperature at the proper conditions.Also,the results indicate that using the viscose fabric as the middle layer leads to decrease in the water content value at the center of clothing. Therefore, the “polyester-viscose-polyester” arrangement can properly remove the perspiratory moisture from the skin to environment, with the minimum of inner water content index (0.02) and maximum inner surface temperature(33C) and average clothing temperature(16.1C).

Nowadays، the baseboard heating systems have attracted the attention of many HVAC engineers because of its uniform temperature distribution and low feed water temperature. Despite this، the uniformity of indoor thermal conditions can be disturbed by some parameters such as exterior walls and air infiltration from window gaps. Therefore، the main goal of this study is to investigate the effects of air infiltration from window gaps on the performance of baseboard system and occupants’ thermal conditions. For this reason، a room has been considered under the terms of “ASHRAE-140 standard/Case 600” and climatic conditions of Tehran with winter outdoor design temperature of -10C. Also، the heat power on the baseboard panel has been set as much as the average of occupants’ thermal dissatisfaction index stays within the allowable range (lower than 10%). The results show that the heating baseboard system can provide the appropriate thermal conditions for sitting occupants with average panel temperature of 43C. In spite of this، the distribution of occupants’ dissatisfaction index near the floor is not uniform. The results indicate that the air infiltration can cause to increase the thermal dissatisfaction index up to 40% in the floor region.

Generally, most of the human thermal response models are dependent upon a narrow range of personal/environmental parameters. In other words, the effects of other parameters such as eating foods are not considered in these models. On the other hand, previous studies have indicated that the overall thermal condition of the body can be significantly affected by eating cold or hot foods. In the present study, the time-dependent thermal response of the human body is simulated with considering the effect of eating hot/cold food. This simulation is performed by adding an extra term to Gagge’s transient model. In this study, three thermal conditions of the human body (hot, neutral and cold) are considered and the effects of eating hot/cold food are investigated under the mentioned conditions. Results indicate that the effects of eating hot or cold food are not negligible during the eating time and also in a period of time after that. At the neutral condition, the human thermal sensation is more sensitive to hot food than to cold ones. Eating hot food changes the body thermal sensation from neutral to hot. But, eating cold food would not make significant changes in the thermal sensation of the body. Results also show that cold food changes the body core temperature more than hot food. While hot food influences the skin temperature significantly.