The most important problems that must be solved and improved in ventilation research are indoor air quality and thermal comfort. The Iraqi climate is characterized by being very hot and dry, so fresh cold air must be provided to the occupants of offices, factories, workshops and others to improve thermal comfort and increase their efficiency. This study focused on improving the quality of inhaled air by using two types of ventilation systems (mixing and displacement ventilation) in combined with a personal ventilation system. This study was a set of numerical tests that were conducted to predict the temperature distribution, air movement and speed inside a closed office room subject to the Iraqi climate in terms of weather conditions. This numerical study was carried out using (AIRPAK3.0.16) which is used to solve turbulence equations, Naiver stock, energy equations, and use of (FVM). A thermally isolated room was simulated with a personal ventilation system that supplies air at temperatures from 21 to 23 °C for case I (personal and mixing) and supplies air at a temperature from 18 to 20 °C for case II (personal and displacement) the air velocity for both cases was 0.6 m/s. It was found that there was a positive effect of the personal ventilation system in both cases, but its effect was more pronounced in the first case, through numerical calculations for each of the effectiveness of heat removal (εt) and air distribution performance index (ADPI), where (74.361) and (1.549) were found for the first case, and (68.321) and (1.71) for the second case.

In this study, indoor air quality and thermal comfort were investigated for two persons sitting inside an office room of dimensions (3×2.5×2.5m). The office room is equipped with personal ventilation systems positioned 50 cm from the person's face. These systems are characterized by the ability to change the rates of airflow (ATD). Experimental studies and results were conducted on a thermal manikin that simulates the human body in a sitting position, and the results are compared with CFD analysis using the k-epsilon and the RNG turbulent models. The experimental study focused on measuring the speed and temperature of the air in different areas inside the room, as well as measuring it around the thermal manikin and in the breathing zone. In the numerical analysis, the thermal comfort and the indoor air quality and the detailed airflow around the occupants were evaluated using CFD analysis. It has been found that the use of personal ventilation systems increases thermal comfort and indoor air quality. It was found that by maintaining the temperature of the supply air from the personal ventilation system and increasing the speed of the air supply, this leads to a decrease in the temperature of the breathing air, an increase in the quality of the inhaled air, as well as a lowering of the person's temperature.

Abstract:Illnesses of many indoor air quality problems occur in office room. Ventilation is one way to control the contaminant transport and to provide better indoor air quality with in the office. In the evaluation of indoor air quality, CO 2 concentration is regarded as a good indicator to estimate the air quality level and to assess the performance of a mechanical ventilation system used by many designers, So the CO 2 concentration was used as the tracer gas in this study, also the humans respiration taken into account as CO 2 sources were the rate of production of carbon dioxide (CO 2 ) by human respiration. Experimental measurement and computational fluid dynamics (CFD) simulation methods were applied. The results from this study show that the floor-supply displacement ventilation can improve indoor air quality because the pollutant concentration in the breathing zone is lower than that of mixing system and the risk of cross contamination can be effectively reduced. Nevertheless, the indoor spaces with floor-supply displacement ventilation might have a higher risk of discomfort, because of high temperature stratification between the ankle and head levels when compared to traditional mixing ventilation. The results indicated that the contaminant distribution in a mechanically ventilated office room need to be studied individually according to different cases.

Good indoor air quality and ideal thermal comfort are very important indicators for the comfort of occupant’s space. The Iraqi climate is hot dry in summer, so the use of air conditioners is indispensable. This work focuses on solving the IAQ problems in office room environments, and it evaluated a new principle of ventilation which is combined personal and mixing ventilation systems. Personal and mixing ventilation system can provide individual control of indoor climate. The airflow motion and distribution of temperature investigated numerically with the best flow rate from combined system. CFD study is used for simulation the indoor airflow and temperature distribution by using (AIRPAK3.0.16) for solving the turbulence equations, Naiver-Stocks, energy equations, and using (FVM). The Renormalization Group RNG K-Ɛ turbulence model was used for simulation this study cases, the airflow rate from ATD was 5 l/s and 10 l/s. For mixing ventilation supply temperature of 17°C and The temperature of the supplied air from the personal ventilation system ranges from (17 to 23) °C, it was found that if using personal ventilation system at airflow rate of 10 l / s it would improve the quality of the inhaled air present in the breathing zone. The personal and mixing ventilation system provides good human thermal comfort based on the values of effectiveness temperature (Ɛt) and air distribution performance index (ADPI) which give (1.241) and (63.226%) respectively. The increased airflow rate from (ATD) leads to a decrease in the temperature in the breathing zone, this increases the human thermal comfort of the occupants inside the room.

The main goal of the paper is to study the effect of adding a new type of ventilation device, which is personal ventilation to displacement ventilation, and know its effect on heat removal and how to reach thermal comfort for humans. Experiments were practically conducted inside a thermally insulated room with full-scale of dimensions (3 ϗ 1.75 ϗ 3) m. The results of the experimental work are used to validate the CFD simulations. The RNG k-e model is utilized to simulate the cases for predicting indoor airflows. The displacement ventilation supply temperature is close to 18°C and the flow velocity of 0.25 m/s. As for the personal ventilation, the flow rates 5l/s and 10l/s were taken with a temperature close to where the air was drawn (at height 0.4 m). It was concluded that adding personal ventilation improved air quality and thermal comfort, and it was also concluded that a flow rate of 10 l/s gave better efficiency for the device to function in terms of air distribution performance index and effectiveness of temperature (e.t) which about 71% and 1.8 respectively.