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The increase in energy consumption within modern societies in addition to expiration of fossil resources are two vital factors which compel the world to alter dangerously, while construction industry around the world consumes 25%-40% of energy in different countries. Above all postindustrial era causes the increase in number of employees as well as bureaus. As a result, the amount of energy consumption and also the quality of indoor offices has always been one of the main concerns of architects. Several studies represent that the thermal discomfort is the most common complaint in offices. The thermal aspect of indoor buildings, not only provides comfort for the residents, but also brings saving in energy, health, productivity, and also a significant morale improvement of the staff. Since most complaints of indoor environment are caused by failure in providing the adequate thermal comfort, researches concentrated on several offices around the world suggest that indoor quality of such buildings is about average; in which many are dissatisfied about their workplace and while many are suffering from building-related illnesses that negatively affect the productivity, duration of working and having economic consequences for those countries. The requisite of thermal comfort within the indoor environment is the existence of thermal comfort standards. These standards define indoor thermal comfort zone according to the physical and personal indexes. The most important international standards are ISO7730 and ASHRAE 55. Nowadays, various models are introduced for appraising thermal comfort within different standards of thermal comfort. According to ASHRAE Standard 55 (2010) thermal comfort is defined as "condition of mind that expresses satisfaction with the thermal environment". Therefore thermal comfort contains different physical and psychological aspects, which means several factors are in effect for this purpose. Thermal comfort is related to four controllable factors namely air temperature, radiant temperature, air speed and as well as humidity. thermal comfort also is influenced by three additional factors: activity, clothing and personal expectations. As mentioned above, there are several standards for thermal comfort in the world. The most important ones are international standards ASHRAE 55 (North America) and ISO 7730 (Europe). These standards congruous the theoretical analysis of heat exchange of the human body and gathering information regarding the climate chamber. These standards are appropriate for stationary and homogeneous conditions which are not suitable and hence not much used in the real world. This fact is evident by the disparity between the predicted thermal comfort by these standards and the real sense of human comfort in different places. These standards specify comfort zones in which a large percentage of people perceive the environment thermally acceptable by certain personal criteria. According to these standards, acceptable thermal zone is defined based on satisfaction of at least 80% of the occupants. In other words, performing within the provided criterion of this standard does not mean the 100% satisfaction, as if it is difficult to satisfy everybody due to personal differences. It is to be mentioned that personal control of thermal environment or personal compatibility (by clothing or activity) also increases the satisfaction level. Considering the complexities of defining thermal comfort, several models are represented which are allied to the physical and psychological parameters as the physiological ones. Two forthcoming models are available for appraisal of thermal comfort: PMV model; which explains individuals' response to the thermal comfort in the physiology of the heat transfer. This model evaluates the indoor environments and constitutes the current thermal comfort standards. According to the aforementioned standards, environmental thermal conditions must be maintained homogeneously. Therefore, PMV model is not appropriate for appraising inert thermal sense in places like residential buildings which are not thermally homogeneous and have different thermal zones. However regarding several capacities of this model, many studies have been accomplished in order to adjust this model for such buildings by implementing some changes. The other model named 'adaptive' explains individuals' response to the thermal comfort considering behavioral, psychological and physiological aspects. The thermal comfort standards define the thermal environment conditions of residents based on data obtained by climate chamber experiments. Therefore, consequently, there are problems for using these standards and also thermal comfort models for those who are living in different climates. That is to say regions with different climatic conditions may need different levels of satisfaction parameters through these standards. In other words, due to different climates, cultures, and etc.,the thermal satisfaction conditions differ in different places. Hence, many countries all over the world have conducted field studies to introduce the most favorable thermal conditions that fit their location best. The lack of essential standards for determination of thermal satisfaction limits in office buildings in Iran, results in employees’ thermal dissatisfaction and overall performance reduction. This study uses field methods for measuring environmental variables (temperature and humidity) and also leading inventory (n=328). Kermanshah city is chosen as a case study. Since this city lacks a dominant type of office buildings and the only common aspect of such buildings is indoor offices, thus this feature is considered to choose the samples. To develop the questionnaire, that of ASHRAE 55 (2010) is used, however according to type of the research and the questions cover, some related questions are added. Moreover, answers are adjusted in seven scales in order to be analyzable using available scales of thermal comfort standards such as 7-point scale of ASHRAE. According to results, 81.7% of whole 328 respondents and 65.5% are satisfiedwithtemperature and humidity respectively. Adapting these results to ASHRAE 55, it is concluded that most staff are satisfied in their work place however the results are the opposite about the humidity. To determine suitable range of temperature and relative humidity in order to define comfort zone in offices in Kermanshah, measured data using FLUKE AIR METER are opposed to the results about temperature and humidity (questionnaire). Data analysis using SPSS represents that neutral temperature range through offices in this city is 20-26 centigrade and low relative humidity is about 19%.

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In the present study variation of air relative humidity at the inlet and outlet of a cabinet dryer as well as drying kinetic of pear fruit in thin layer were studied.  The experiments were conducted at three temperature levels of 40, 50 and 60^oC and three air velocity levels of 0.5, 1 and 1.5 m/s. It was observed that the difference between input and output air relative humidity increased when drying temperature was increased. This difference followed declining trend at the same level of drying temperature when air velocity was increased. If drying at lower air temperature and higher velocity is desired, for optimum use of energy, a closed loop drying method is appropriate. Otherwise, increasing in air temperature and decreasing in air velocity is recommended. Eight mathematical models were fitted on drying data and the best one was selected according to coefficient of determination (R²) and Chi-square (χ²) statistics for 70 percent of data. The model then validated by statistics of root mean square of error (RMSE), mean bias of error (MBE) and mean relative error (ARE) for 30 percent of remaining data. The approximation of diffusion model with highest R² (0.998), and lowest χ² (0.0001), RMSE (0.01), MBE (0.0008) and ARE (5.2%) was found an appropriate model for estimating the kinetics of thin layer drying of pear cubes drying in a cabinet dryer.  

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Ventilation is essential to provide a smoke-free path for safe passenger evacuation and effective rescue services in case of a tunnel fire. The critical ventilation velocity, VC, is defined as the minimum velocity which creates this safe passage by preventing smoke from spreading upstream in tunnels. This research discusses smoke flow control in tunnels with a focus on the important parameters affecting critical velocity. Critical velocity values are evaluated for different heat release rates and results show good compliance with model-scale experiments. The study is extended to investigate effects of fire source blockage ratio and lateral location, tunnel slope and ventilation air relative humidity on the behavior of critical velocity. Results show a drop in VC about equal to blockage ratio occurs in presence of fire source blockage. Investigation of critical velocity in sloped tunnels illustrates that for each %1 increment in negative slope, 2.5% higher ventilation is required. Results also show that air relative humidity does not have significant effect. However, fire lateral location impacts critical ventilation velocity in such a way that about 10-20% higher airflow is necessary to suppress smoke in a near-wall fire in comparison with a middle-tunnel fire.

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Reactant gases should be humidified before entering a polymer electrolyte membrane (PEM) fuel cell stack. Humidification of the gases can be performed by a membrane humidifier. In the present study, an analytical model has been proposed to investigate the performance of a water-gas membrane humidifier which is used in the fuel cell systems. At first, a set of nonlinear equations was obtained by applying the mass and energy conservation laws on the gas side of the humidifier. The temperature and the humidity ratio of the outlet gases from the humidifier are the unknowns of these nonlinear equations. The proposed model can evaluate the performance of the humidifier based on the temperature and relative humidity of the outlet gases from the humidifier. The effects of different parameters like: gas flow rate, channel's length and depth, temperature and pressure of the inlet gases on the performance of the humidifier were studied by the developed model. The results show that the channel depth does not have an effect on the temperature and humidity of the humidified outlet gases. In addition, increasing the channel length causes an increase on the dew point of the outlet gases but the relative humidity of the dry inlet gas does not have a noticeable effect on the dew point of the outlet gases. Increasing the temperature of the inlet gases cannot improve the humidifier performance, considerably. The results of the model show that increasing the inlet pressure and using less air flow improve the humidifier performance.

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In this study, the relative humidity of the gases in the PEM fuel cell was changed and its effect on electro-osmotic flow was investigated. ‎By changing the humidity on both sides of the fuel cell and using the water balance equations, the values of the electro-osmotic flow, ‎electro-osmotic coefficient and net drag in different humidity levels were found. Results showed that variations of the electro-osmotic ‎flow changed linearly by anode and cathode humidity to the special humidity and after that not much variation was seen. In addition, the ‎results revealed that humidity change at anode had more desirable effect than the cathode. For example, at 70% anode humidity and 35% ‎cathode humidity with the current of 5A, the value of electro-osmotic flow was obtained as 2.66639E-06 mol/cm2.s, while in the former ‎‎35% and the latter 70% with the same current, this value was recorded as 2.56418E-06 mol/cm2.s. In addition, results showed that the‎‏ ‏variations of the electro-osmotic coefficient changed linearly by humidity. It was determined the current change of fuel cell has not so ‎effect on the curves of electro-osmotic coefficient. The electro-osmotic coefficients varied between 0.636001 and 1.632476, which were ‎in a good agreement with the values obtained in other related papers. In addition, the variations of the net drag in respect of humidity were ‎investigated, too. It was determined that the net drag changed linearly by the cathode humidity with positive slope, but its variations by ‎the anode humidity were linearly with negative slope.‎

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To investigate the effect of relative humidity percentage on heat transfer and distribution of droplets in the condensation phenomenon, a test device with the ability to provide and control different environmental conditions was made, and therefore, the hydrophilic (copper) and hydrophobic (Teflon coating on copper) surfaces were measured under controlled environmental conditions. In all the tests, the inlet air flow rate, inlet air temperature, air temperature reaching the test surface, water temperature, water surface height, and test surface temperature were kept constant at specific values using PID control. Each test's relative humidity values of 80, 88, and 96% have been determined and controlled. The results of the transient investigation of heat transfer show that it takes time for the condensation phenomenon to occur, and the higher the surface hydrophilicity and relative humidity, the shorter this time will be. Also, the average heat transfer for 60 minutes was calculated. It showed that the average heat transfer coefficient increases with increasing humidity. Under the same environmental conditions, the heat transfer coefficient on hydrophilic surfaces is higher than on hydrophobic ones. In the graphical analysis of the droplet size, it has been observed that the most oversized droplets on hydrophilic surfaces at relative humidities of 88 and 96% are in the hydraulic diameter range of 0.35 to 0.4, and on hydrophobic surfaces are at relative humidities of 80 and 88% in the hydraulic diameter range of 0.2 to 0.25 mm.