Effects of Cross Level Air Interaction within Multilevel Underground Carparks on Indoor Air Quality

Ventilation for underground carparks is critical to indoor air quality (IAQ) due to carbon monoxide (CO) emissions from cars. The IAQ within a multi-level underground carpark of a shopping mall has been investigated using computational fluid dynamics (CFD) model based on ANSYS-FLUENT (18.1) software. The effects of car engines types, porosity of supply and exhaust air louvers and ventilation flow rates on IAQ were examined. A mesh sensitivity study was conducted and the CFD model was validated against the fully mixed mathematical formulations of IAQ with a maximum difference in values of 1.5 ppm and an error of 3.4%. The results showed that the ventilation system must be operated at ACH value of more than 2.7 in order to meet the required CO concentration of 50 ppm within the carpark and should be based on running cars within each level rather than the parking capacity of each level. Porosity of louvers affected air flow distribution between parking levels and led to higher dilution of CO. Therefore, modelling a multilevel underground carpark requires closer attention to cross level interaction across Ramps which could affect the CO concentration within a given level

Effects of Coating Materials as a Cleaning Agent on the Performance of Poly-Crystal PV Panels

Hot and arid areas are considered a harsh environment when it comes to cleaning photovoltaic (PV) modules. Minimizing the panel tilt angle makes it evident that dust and other substances such as airborne dirt (both organic and inorganic) and bird droppings can build up over time and impact the amount of electricity generated by a module. The current study aims to find the most effective and optimum cleaning technique/material based on cleaning performance of the PV panel. The effects of different easy-to-clean materials on the performance of poly crystalline silicon type PV modules were experimentally investigated. As there is no specific recommended material to clean solar panels, the cell surface was coated with different types of easy-to-clean materials available in the Jordanian local market. The cleaning materials utilized were: Crystal glass coating type AJJL-CSS, jiajialy nano energy saving & anti UV solution, GIE (Galsilk 7, isopropanol, ethanol, water), TGIE (TiO2, Galsilk 7, isopropanol, ethanol, water), sodium hexa meta phosphate, and NanoUltra. Results from temperature measurements and output voltage of coated cells showed that all coating materials were able to reduce the cell temperature in different scales. The jiajialy nano energy saving & anti UV solution provided the best cooling effect, while the GIE and TGIE showed good results, too. Output voltage of cells coated with GIE and TGIE materials was the highest

Natural ventilation of residential building Atrium under fire scenario

A residential block consists of two buildings connected via an Atrium is common nowadays because they could provide attractive, environment controlled and naturally lit spaces. The purpose of the current study is to undertake a performance based assessment of the proposed ventilation strategy and justify the performance through the use of computation fluid dynamics (CFD) approach. The three dimensional study utilized two available CFD packages: CFD ACE + for natural ventilation simulations and Fire Dynamic Simulator (FDS) for fire simulations. Four different louver opening areas were examined to see their effect on air speed and temperature of air within the Atrium. Another five scenarios were examined with the existence of fire within the Atrium. Results showed that the natural ventilation solution is dependent on ambient conditions outside the Atrium. Therefore, operable louvres are recommended to be fully closed under extreme weathers and to have it fully opened at an outdoor temperature of 19 °C–27 °C. In the case of a fire being ignited within the Atrium, it is found that the location of the fire has a significant impact on the air quality within the Atrium. It is found that when the fire is located in the open void area to the east of the Atrium, a simple ventilating strategy is capable of providing the required ventilating capacity to maintain the Atrium safe for evacuating the occupants. When the fire is located at the lifts and stairs area, however, the ventilation strategy requires a more sensitive approach. It is found that the natural ventilation approach failed in extracting the smoke out of the Atrium (Lifts lobby) unlike when the fire was located in the void area. However, the air temperature within the Atrium is found to meet the design requirements of lower than 60 °C

Effect of Down Stand Depth Variation on Atriums Upper Balconies Smoke Contamination

In case of fire in an atrium, smoke produced is recognized as one of the major hazards for the occupants because of open spaces present in an atrium. The effect of varying the down stand depth at fire compartment on smoke contamination in upper balconies of an atrium has been investigated in this paper. Correlation to predict the smoke contamination in upper balconies of an atrium in the presence of 0.5 m deep down stand structure has also been developed. This correlation is compared with correlations developed for 1 m deep down stand and without down stand structure by past research. The comparison results showed that when the depth of down stand structure increase, smoke contamination in upper balconies of an atrium also increases. The results also showed that smoke contamination in upper balconies of an atrium decreases when the ratio of w/d increases. The comparison of correlations from 1 m and 0.5 m deep down stand showed that the difference in smoke contamination increases when w/d < 3. By comparing the correlations from 0.5 m deep down stand and no down stand, there is very small difference in smoke contamination from both case but it is applicable for w/d < 3

Energy Performance and CO2 Emissions of HVAC Systems in Commercial Buildings

Energy performance of buildings has attracted much attention among building physicists and engineers worldwide. The effects of building heating; ventilation; and air conditioning (HVAC) systems’ design upgrade on the building energy performance are the focus of the current study. The adopted HVAC system consisted of chilled ceiling and chilled beam systems served by a centrifugal water chiller. An energy simulation study was undertaken in accordance with the national Australian built environment rating system-rules for collecting and using data. A three-dimensional simulation study was carried out utilizing the virtual environment-integrated environmental solutions software. Results from the current study have shown the importance of utilizing energy-efficient HVAC systems and HVAC strategies for achieving a high building energy star rating. Recommended strategies in order to achieve the nominated star rating; as predicted by the simulation analysis; were presented. Moreover; the effects of solar radiation inside the building atrium were significant; which cannot be overcome by simply installing a low shading coefficient glazing type at the atrium skylight. In addition to providing chilled ceiling technology; a high efficiency chiller and low energy lighting; it is recommended that the building be well tuned during the commissioning period. The current approach could be extended to accommodate higher energy ratings of commercial buildings at different locations worldwide

Computer Simulation Investigation on the Effect of Channelled and Unchannelled Screens on Smoke Contamination in Atriums Upper Balconies

This paper performed the effect of installing channel screen on smoke contamination in the presence of 0.5 m deep down stand in a fire compartment. The results are then compared with smoke contamination occurrence when the channel screens were removed. The results showed that there will be 96% increase in upper balconies smoke contamination in an atrium when no channel screens at fire compartment opening are used. This work provides new correlation obtained from numerical study which can predict the smoke contamination height in upper balconies of the atrium in the presence of 0.5 m down stand and no channel screens. The proposed correlation will be useful design tool for building designer to design safe shopping malls (atrium)

Computer Simulation Investigation on the Effect of Channelled and Unchannelled Screens on Smoke Contamination in Atriums Upper Balconies

This paper performed the effect of installing channel screen on smoke contamination in the presence of 0.5 m deep down stand in a fire compartment. The results are then compared with smoke contamination occurrence when the channel screens were removed. The results showed that there will be 96% increase in upper balconies smoke contamination in an atrium when no channel screens at fire compartment opening are used. This work provides new correlation obtained from numerical study which can predict the smoke contamination height in upper balconies of the atrium in the presence of 0.5 m down stand and no channel screens. The proposed correlation will be useful design tool for building designer to design safe shopping malls (atrium)

Numerical investigation on the thermal performance of perforated and non-perforated twisted fins at different twisting angles

The present study numerically investigated the effect of variations in the twisting angle and perimeter of diamond-shaped perforation on the heat transfer of twisted fin heat sinks. The study showed a possible configuration of a heat sink design, aiming to improve heat transfer and the hydrothermal performance factor (HTPF). ANSYS/FLUENT computational fluid dynamics software was used to perform the simulations, and the Reynolds-averaged Navier–Stokes-based k−ε turbulence model was used. Results revealed that a maximum of 46 % enhancement in the Nusselt number and a 25 % increase in (HTPF) could be attained with a twisting angle of 540° in comparison with conventional cylindrical fins. Furthermore, the variation in perforation perimeter at a twisting angle of 540° resulted in a maximum of 28 % enhancement in the Nusselt value and a 36 % enhancement in HTPF in comparison with the twisted fins with no perforations. Therefore, this configuration is recommended as the optimal heat sink configuration

Effect of Induced Vibration on the Blood Flow Properties in a Mechanical Aortic Valve

The effect of induced vibration on velocity distribution for the blood flow in the bileaflet mechanical heart valves conveying blood was investigated in this study. The bileaflet valve was simulated as an orifice. The induced vibration is due to the pulsed blood flow in the artery. Results presented in this study were performed using CFD FLUENT software. This analysis is based on the non-linear numerical solution by using a finite-element method, for the system of governing partial differential equations (continuity, momentum) of Navier - Stokes equation of blood flow through the orifice. It has been found that as the flow through the orifice increased, the vibration at the orifice inlet increased. For steady state conditions, at Reynolds number 50 the recorded frequency was 20Hz. When the Reynolds number increased to 100 due to the increase in the blood flow the recorded frequency increased to 30Hz. The increase in frequency may result in damaging the blood red cells and platelets which subsequently results in increasing the blood clogging downstream of the orifice

Numerical Investigation of the Effect of Square and Sinusoidal Waves Vibration Parameters on Heat Sink Forced Convective Heat Transfer Enhancement

Among numerous electronic cooling methods, a vibrating heat sink using sinusoidal wave vibration effectively enhances the heat transfer by disturbing the thermal boundary layer. However, sinusoidal wave vibration has reached its limits in enhancing heat transfer. The present study utilizes a new square wave-shaped vibration and numerically investigates the thermal performance of a heat sink subjected to sinusoidal and square waves vibration. It is found that using the square wave vibration is more beneficial to the thermal performance of the heat sink than the sinusoidal wave. The sudden impulsive motion of square wave vibration induces a higher randomness of the airflow profile and recirculation zones than the sinusoidal wave, causing the air flow to impinge directly into the fin surfaces, and further enhances the heat transfer. Furthermore, increasing the frequency and amplitude leads to a higher heat transfer enhancement. Moreover, square wave vibration achieves a 25% increase in Nusselt values compared to the nonvibrating fins and it is 11% higher than the Nusselt number recorded by the sinusoidal vibration. Consequently, Reynolds number values can be reduced by 42.2% to achieve the Nusselt number values of nonvibrating fins, potentially reducing the cooling system or fin size. This reduction may contribute to solving the challenges of electronic systems compactness