CFD Simulation of the Airflow Distribution Inside Cube-Grow

Cube-Grow was developed by MARDI to promote urban agriculture to the urban population. The product enables urban people to grow their vegetables with limited space. The initial test run of the system shows that the plant growth inside the structure was below expectation. The problem arises due to a lack of airflow or improper ventilation inside the structure. Optimum ventilation or airflow is crucial for plant growth as it enhances evapotranspiration at the leaf area to promote optimum plant growth. Therefore, this study aims to increase the airflow inside the Cube-Grow and find the best location for the air hole. Computational fluid dynamics (CFD) simulation was used in this study the analyse the effect of adding an air hole to the airflow characteristic inside the Cube-Grow. CFD also was used to select the best location to place the air hole. 3 option of air hole location was analysed and the results were compared with the existing design. The initial CFD simulation results were compared with the actual measurement data before it was used for further analysis. The result shows that adding an air hole increases overall airflow inside the Cube-Grow. Option 3 was chosen as the best location for the air hole as it produces a uniform and higher airflow inside the Cube-Grow. The study proved that CFD was able to be used to optimize the design of Cube-Grow before the actual prototype was built.

Investigation of Airflow Distribution and Contamination Control with Different Schemes in an Operating Room

Controlling contamination via proper airflow distribution in an operating room becomes vital to ensure the reliable surgery process. The heating, ventilation, and air conditioning (HVAC) systems significantly influence the operating room environment, including temperature, relative humidity, pressurization, particle counts, filtration, and ventilation rate. A full-scale operating room has been investigated extensively through field measurements and numerical analyses. Computational fluid dynamics (CFD) simulation was conducted and verified with the field measurement data. The simulation was analyzed with three different operating room schemes, including at-rest conditions (case 1), normal operational conditions with personnel (case 2), and actual conditions with personnel inside and some medical equipment blocking the return air (case 3). The concentration decay method was used to evaluate this study. The results revealed that the contamination concentration in case 1 could be diluted quickly with the average value of 404 ppm, whereas the concentration in case 2 slightly increased while performing a surgery with the average value of 420 ppm. The return air grilles in case 3, blocked by obstacles from some medical equipment, resulted in the average concentration value of 474 ppm. Other than that, the contaminant dilution could be obstructed dramatically, which revealed that proper and smooth airflow distribution is essential for contamination control. The ventilation efficiency of case 2 and case 3 dropped around 6% and 17.91% compared to case 1 in the unoccupied and ideal condition. Ventilation efficiency also decreased along with decreasing the air change rate per hour (ACH), while with increasing ACH, the ventilation efficiency in case 3 actually increased, approaching case 2 in the ideal condition.

Performance Analysis of the Ventilation System for a Surgical Operating Room in Egypt: A Case Study of Mataria Teaching Hospital in Cairo

The Design of the ventilation system in a hospital operating room plays a very important role, not only in providing thermal comfort and hygienic environment for the patients or staff, but also to ensure the scavenging of any contaminants or airborne particles in the operating room theatre that might leak from outside to the operating room or emitting from patients’ infections. The present study focuses at airflow distribution, temperature, humidity and velocity profiles in a surgical operating room. An operating room inside the Mataria teaching hospital in Cairo (Egypt) has been chosen for the study. Numerical and experimental studies were carried out, where the room was ventilated through laminar flow diffuser system and 100% fresh air. The air was released by four outlet grills: two grills at a low level of the floor and two grills at a high level of the floor. In this work, two cases are investigated. In case I, the air outlets have been installed on one side of the room (which already exists in the hospital); and in Case II, the air outlets have been installed on two opposite sides (the suggested case). The results showed that the proposed modification (Case II) performed better distribution of ventilation than Case I. Therefore, it is recommended to install air outlets in two different side areas inside the room in order to avoid the accumulation of contaminants.

Effect of Mesh Topologies to Predict Cooling Effect on Evaporative Cooling Duct

This paper examines the effect of different mesh types on a numerical study of evaporative cooling in the chimney. This research is a follow-up study from previous research. The test specimen used is an evaporative chimney design with the addition of a nozzle arrangement in it. The main focus of this research is the study of mesh refinement, namely by applying structured mesh during the simulation process. Three types of mesh with different levels of fineness were used for the specimens. They are coarse ( mesh A), medium (mesh B), and fine (mesh C). In addition to differences in mesh, research was also carried out with variations in the level of relative humidity (RH). The RH levels used are 5, 10, and 15%. Two main parameters of evaporative cooling performance are airflow distribution and temperature drop in the chimney. Method for measuring the distribution of airflow and temperature drop in the chimney by making five planes with different heights. The results showed that the simulation with mesh B produced a good agreement data with previous studies than mesh A and C. The RH level that generated the most optimal cooling is found at 5% RH.

Indoor air quality evaluation in naturally cross-ventilated buildings for education using age of air

Natural ventilation (NV) is a strategy of bioclimatic design to promote hygrothermal comfort and indoor air quality (IAQ). Nowadays, COVID-19 pandemic highlights the review of ventilation standards. In Mexico, the IAQ standard states a minimum of 6 ACH for educational buildings. ACH considers NV as an ideal piston flow and does not provide information of indoor airflow distribution. In this work, new age of air associated parameters are proposed, considering the indoor airflow distribution: the air renovation per hour (ARH) and the renovation parameter R. An isolated educational building located in a rural region is studied. Four window configurations of cross-ventilation are considered. All configurations have one windward window located at bottom. The configurations axial and upward have one leeward window at bottom and top, respectively. While, configurations corner and upward corner have one lateral side window at bottom and top, respectively. A CFD model of the educational building is validated with experiments. The axial configuration has the best performance according to ACH, nevertheless has the worst performance according to ARH and R. The results show that NV evaluation using ACH can lead to wrong decisions. An improvement of NV standard with the age of air associated parameters is recommended.

Simulation study on effects of purifier positions on formaldehyde removal under the condition of vehicle air supply

In order to further improve the interior air quality and comfort of the vehicle, CFD method is used to simulate the different airflow distribution caused by car-mounted air purifiers at different positions. Combined with the change of formaldehyde concentration field in car, the influence of car-mounted air purifiers on the formaldehyde dilution and removal under the condition of air conditioning air supply is analyzed. The simulation results are verified by actual measurement, and the trend of the simulation results is basically consistent with the measured results. When the car air purifier placed in the middle of the car roof, it can effectively dilute and purify the formaldehyde gas in the car, and reduce the concentration of formaldehyde in the breathing area of the driver and passengers. The adsorption and degradation of formaldehyde by the purifier, together with the dilution of formaldehyde by air supply, can improve the air quality in cars more effectively than using only one of the air purification methods.