Nazri Kamsah

Assessment of thermal comfort in a naturally ventilated residential terrace house

In hot and humid climates thermal discomfort is a major problem to the occupants of many residential terrace houses especially when they are not equipped with an air-conditioning system. This paper presents a study on an assessment of the level of thermal comfort in a naturally ventilated residential terrace house in Malaysia using computational fluid dynamics (CFD) method. Actual measurements were made to obtain the average air temperature, relative humidity and air flow pattern in various sections of the house. CFD simulations were conducted on a simplified model of the house to predict and visualize the temperature distribution and air flow pattern and its velocity in the house. The level of thermal comfort in the house was found to be well outside the comfort limits as specified by ASHRAE standards.

CFD Simulation of Air Temperature inside a Bus Passenger Compartment

Good ventilation is important for passenger for sufficient supply of fresh air during commuting in a bus. Insufficient fresh air causes feeling of uncomfortable to passenger and affects passenger’s health. Airborne transmission disease, headache and respiratory allergies are the usual health symptoms. This paper presents the CFD study of air flow inside a bus passenger compartment. The objective is to estimate the temperature level at the diffuser, seat and floor locations of the bus passenger compartment. Two conditions of airflow velocity at the supply diffuser were examined, namely 2.7 m/s and 3.1 m/s. A CFD Fluent software was employed to develop and meshed a simplified 3D model of a quarter section of a bus passenger compartment. Air velocity and temperature boundary conditions were prescribed on the model based on the actual data obtained from field measurement. Turbulent flow analyses were carried out using standard k-ε model to visualize the air flow distribution inside the compartment. The results show that the velocity distribution is uniform when the diffuser air velocity is 3.1 m/s. When the diffuser air velocity is 3.1 m/s the air temperature of the seat area was decreased by 0.3°C. The air temperature inside the cabin can be maintained uniform at 23°C when diffuser air velocity was fixed at 3.1 m/s.

Numerical analysis of air-flow and temperature field in a passenger car compartment

This paper presents a numerical study on the temperature field inside a passengers compartment of a Proton Wira saloon car using computational fluid dynamics (CFD) method. The main goal is to investigate the effects of different glazing types applied onto the front and rear windscreens of the car on the distribution of air-temperature inside the passenger compartment in the steady-state conditions. The air-flow condition in the passengers compartment is also investigated. Fluent CFD software was used to develop a three-dimensional symmetrical model of the passengers compartment. Simplified representations of the driver and one rear passenger were incorporated into the CFD model of the passengers compartment. Two types of glazing were considered namely clear insulated laminated tint (CIL) with a shading coefficient of 0.78 and green insulated laminate tint (GIL) with a shading coefficient of 0.5. Results of the CFD analysis were compared with those obtained when the windscreens are made up of clear glass having a shading coefficient of 0.86. Results of the CFD analysis show that for a given glazing material, the temperature of the air around the driver is slightly lower than the air around the rear passenger. Also, the use of GIL glazing material on both the front and rear windscreens significantly reduces the air temperature inside the passengers compartment of the car. This contributes to a better thermal comfort condition to the occupants. Swirling air flow condition occurs in the passenger compartment. The air-flow intensity and velocity are higher along the side wall of the passengers compartment compared to that along the middle section of the compartment. It was also found that the use of glazing materials on both the front and rear windscreen has no significant effects on the air-flow condition inside the passengers compartment of the car.

Development of vapor pressure in FR4-copper composite material during solder reflow process

This paper presents a finite element (FE) methodology for predicting the distribution of vapor pressure in a simple FR4-copper composite material when it is heated up to 215°C. A general purpose finite element software was used to develop a two-dimensional plane strain model of the composite material. FE simulation of transient moisture absorption was performed to predict the distribution of wetness fraction in the material after pre-conditioning at an 85°C/85%RH environment for 15 days. FE simulation of transient moisture desorption was carried out at the peak solder reflow temperature of 215°C to predict new distribution of wetness fraction in the material. The results of the moisture desorption analysis were used to compute the magnitude of vapor pressure in the material and its distribution at 215°C. It was found that the moisture in the material redistributes itself during solder reflow. The moisture concentration in the area close to the FR4-copper interface below the longer copper trace increases during the solder reflow. The magnitude of the vapor pressure in 70% of the FR4 and near the FR4-copper interface below the lower copper trace is closed to the saturation pressure of water vapor at 215°C. The distribution of the vapor pressure in the material is in similar fashion as the new distribution of wetness fraction after the moisture desorption analysis.

Exploring the Potential Use of Adhesion Strength for Coating Analysis

This paper discusses the possibility of the potential use of adhesion strength for coating analysis. Most of the steel structures used in industrial and non-industrial applications are exposed to outdoors weathering conditions. Organic coating typically protects them from corrosion. The maintenance actions can be done efficiently only if there is sufficient information on the accurate condition of it. Therefore, the deterioration of the coating system and its lifetime has to be assessed accurately. Adhesion strength has the potential to be used as a parameter for evaluation. This paper explores the development of these parameters mainly based on fracture mechanics. transformed into a degradation rate. A time series modeling approach was proposed to predict daily degradation. Heutink et al. (6) describe how the maintenance methodology used in the Netherlands was applied to protective paint systems. The lifetime-extending maintenance model, in which deterioration is modeled by a gamma process with expected deterioration non-linear in time, is applied successfully to optimize maintenance of the coating of the Haringvliet storm-surge barrier. Among other deterioration parameters, this paper emphasizes on the adhesive strength taking the advantage of the blister formation and development as a symptom of the coating deterioration.