Papers by Keyword: Airflow

Abstract: Leakage in the building envelope may occur airflow as well as its surface. It brings series of adverse consequences, including the flow of diffuse. The airflow building envelope is allowed through a pressure gradient, which is caused by the difference in temperature and wind effects; if necessary a mechanical ventilation system. Article introduces the analysis which was performed on experimental objects of different wind exposition in situ. In this analysis was measured pressure, relative humidity and air temperature in the interior and exterior, for a period of one year. In the conclusion is evaluated the effect of these boundary conditions on the very existence of the airflow through building envelope.

Abstract: The Venturi effect has been defined as the increase in fluid speed or flow rate due to a decrease of the flow section. In the present paper the wind speed conditions in passages between triangular buildings with different distances are studied with Computational Fluid Dynamics (CFD) to investigate the extent to which the Venturi effect is present in the passages. In this paper are considered eight different variants of relative positions of the two high-rise buildings. The variable is a distance between towers. They are investigated maximum wind velocities and the point at which the maximum velocity occurs for each from these variants.

Abstract: Thermal condition of a house is one of the comfort factors. Traditionally, village houses in Malaysia uses corrugated zinc roofing due to economic reason. Considering the thermal conductivities of the material, space under the roof coverage will intent to occur thermal discomfort due to Malaysian ambient temperature. The roof plays an important role to ensure the house is in a state insulated from the hot sun and rain where the zinc roofing will radiated by the sun in noon and yet become the heat source for in-house area. Thermal discomfort will result due to zinc highly heat absorbing material property. The space under the covering will experience significant temperature increase proportional to the amount of supplied heat from sunlight radiated to the zinc roof, and will further be aggravated if ventilation is poor. The purpose of this study is to compare the temperature distribution by two alternatives methods to reduce the temperature inside a zinc-covered house. The main concept of this cooling system is by splashing water throughout the area of the zinc roofing, where heat exchange process will occur upon contact. The process will dissipate heat from the zinc and will increase the water temperature. This research is focusing on the medium (water) re-cooling process by either open water exhausted or radiator system to state that which one will give better heat exchange. Open water exhausted system heated water will then free fall by gravity into a tank through perforated tube as water droplets. To facilitate higher rate of water-cooling, fan will be provided. Another re-cooling system is the radiator system, which use radiator device to cool down the heated water. Radiator use coolant as the medium to exchange the heat from the roof heated water. By the same heat transfer process, the circulated water temperature will be lower where, which will be recirculation back to the roof. Both systems had been compared about the differences of temperature drop distribution which result the better water re-cooling system.

Abstract: The pressure coefficients on duo-pitched roofs of separated buildings are well described by several standards. Nowadays, there are various commercial or non-commercial programs which can predict the pressure coefficients. However, the most accurate method is to perform a wind tunnel test. The aim of this paper is to simulate the airflow over a gable roof with different elevations under ANSYS Fluent 14.0 program. Examined elevations of the gable roof are 5°, 15° and 30°. Classical two equation k-ε turbulence models based on Reynolds Averaged Navier-Stokes (RANS) equations simulation were performed. Performance of each turbulence model with the increasing angel of the roof was compared.

Abstract: It is important to analyze the temperature, airflow field, PMV-PPD index distribution within the passenger compartment to ameliorate the amenity and decrease consumption. A numerical model to assess the thermal comfort taking into account the different air velocity. This paper uses commercial software FLUENT to simulate 3-D temperature, PMV-PPD index distributions and flow field in a compartment passenger. The predicted results basically meet the requirement of thermal comfort except the local temperature around the lower region and the local air velocities around passengers’ head region. When the air-outlet temperature is 20 °C, air-outlet velocity 4 m/s is agreed to the thermal comfort. PMV index are about -0.4-0.6, and PPD index is less than 10%, which is agreed with passenger’s thermal comfort. The predicted values illustrate the uniformity of indoor environment in the occupied zone.

Abstract: Recirculation region behind a fume cupboard sash is the potential contributor to the leakage of the contaminants due to its large size. This is found from the computational fluid dynamics (CFD) simulation of SERVCO fume cupboard using κ-ω turbulence model. For a good fume cupboard, the recirculation zone needs to be minimized while maintaining the flow distribution to all area in the fume cupboard. The opening on the baffle may reduce the recirculation zone which in turn may reduce back flow that is the cause of leakage. In this paper, the effect of shape of baffle openings on flow distributions of a SERVCO fume cupboard will be presented as a result of CFD. The results are presented in terms of velocity vectors Vy (in the direction towards the sash opening) at different cross sections for 4 opening shapes. The opening is found to improve the airflow distribution.

Abstract: The grinding heat directly affected workpiece surface in the grinding process and it might produce some defects such as crack and burn. Meanwhile wear debris generated in the grinding process could easily embed grinding wheel blowhole and caused clogging and passivation. So it was particular important to avoid defects and improve the grinding workpiece surface integrity effectively. This paper established an incompressible turbulent fluid spray model based on the study of the existing airflow and the grinding fluid distribution in the grinding zone. Then according to different grinding fluid supply parameters established the two-phase gas liquid spray flow model by using CFD(computational fluid dynamics), simulated and calculated the model, compared the mass flow rate of the grinding fluid flow field with different spray distances, heights, speeds and spray angles in the grinding zone and determined the most reasonable spraying jet position. At the last, through researching on the workpiece surface integrity experiment, it provided an experimental basis to determine the most suitable spray jet position and verify the rationality of supply parameters selection.

Abstract: Research on Micro air vehicle (MAV) has been carried out by many researchers to gather information in environmental monitoring, security and so on. When the earthquake, fire, smoke take place, it is difficult for human beings to investigate the detail because of dangerous condition. However, MAV has possibility to investigate the detail because MAV can fly freely around. Recently, dragonfly is highly focused by many researchers because dragonfly has high flight performances those are high efficiency flight, unintended acceleration, rapid turn and hovering. In general, these characteristics have root that wing is corrugation shape. We focus on microstructures on wing and its aerodynamic characteristics because there are many unique microstructures. We focused on micro spikes on dragonfly wing. Over three thousands of spikes exist on two sides of wing. The length and shape of spikes are 10 to 100 micron meters and oblique circular cone. It is important to clear the aerodynamic effect of the oblique circular cone. Artificial wing was fabricated by following processes. We fabricated micro spikes utilizing electro polishing. Fabricated micro spikes were set on plate utilizing micro spot bonding. We investigated the flow around the artificial wing and found that the flow around wing was controlled by micro spikes on wing. In this paper, we focused on comb shape of leading edge of wing. Comb shape is fabricated utilizing micro-EDM. We investigate flow characteristics of comb shape.

Abstract: Experimental phonetics development to today has undergone a long and complicated process. The field of study from the acoustic analysis of expansion to the physiological and perceptual field. Speech aerodynamics signal is one of the most important physiological signal language research, plays an important role in human phonation process. Air pressure signal as an important physiological signal, which has great significance to the study of speech physiology, mainly through speech aerodynamics equipment acquisition. In this paper, according to the need of research, established by MATLAB program analysis platform, can be edited on the speech, the airflow and pressure signal is better, which is more suitable for speech research.

Abstract: The air-blast freezer is common freezing technique for shrimps in seafood industry. In many companies encounter with developing this technology for food industry. In this study, Development in effects and behavior of airflow over in pressure chamber of continuous belt air-blast freezer, were investigated by simulating the airflow field by using computational fluid dynamics (CFD). Pattern holes in plenum plate and Modifying shape tunnel were cases study in redesign of development. The average velocity at outlet holes of airflow were determined and the streamline and vector of airflow were analyzed. The effects of redesign could increase the average relative velocity at outlet up 22- 32% compared with the original design.