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Air pollution is a major environmental risk to health. The new building normally has a facing problem with indoor air pollutant. New construction materials and furniture will contribute higher contaminants compared to old materials. The effect of indoor air pollutants can result in human health problems, discomfort and reduces their productivity. The purpose of this present work is to experimental study the indoor air pollution status regarding carbon dioxide, carbon monoxide, volatile organic compounds, and formaldehyde concentration in an administration office at the new building faculty of mechanical engineering in Johor Bahru, Malaysia. The contaminants concentration values are investigated through field measurements and then compared to the limits stated in the Occupational Safety and Health Act standard. The field measurement of contaminant concentration level was conducted at the intersect plane between the vertical plane at the center of the air conditioning diffuser and the horizontal plane at 1.2 m from the floor. The contaminant concentration readings were taken at 6 locations inside the office. The data were conducted during actual working conditions. The reading of contaminants concentration is taken in 30 minutes. One minute is equal to one number of samples. It was found that only the formaldehyde concentration is exceeding the maximum limit.

Heating, ventilation, air-conditioning (HVAC) duct system for an automotive has a complex geometry due to space constraints in the engine compartment. This could reduce air pressure inside the duct, decreasing the airflow velocity at the HVAC outlets, and correspond to the intended value prescribed by design. Higher air velocity at the ventilation outlets is desirable to promote thermal comfort in the passenger cabin. This study aims to enhance the airflow velocity and uniformity at each duct outlet by varying outlet geometry and duct elbow angles using the computational fluid dynamics (CFD) method. A typical HVAC duct of a C-segment car has been chosen as the case study. Steady-state parametric flow analyses were conducted to determine the duct geometry that would significantly improve the airflow uniformity and velocity at the duct outlets. It was found that a combination of circular outlets with a 65° elbow angle results in the best improvement in the airflow velocity distribution inside the duct. It was also found that the airflow velocity at the outlets increases between 4% to 9% compared to the baseline design. The air velocity difference between all outlets is around 1.3%, which can be considered negligibly small.

The present study aims to examine the effects of medical staff’s turning movements on the number of particles falling onto the patient. A simplified computational fluid dynamics (CFD) model of the ...

This article presents the results of a numerical study to examine the transport of particles in an operating room equipped with an Econoclean ventilation system. Its aims are to reduce the number of particles falling onto the operating table. A simplified CFD model of the operating room was developed and validated based on the measured air velocity distribution. An SST k-ω turbulent flow model was used to simulate the airflow, while a discrete phase model was used to simulate the movement of the airborne particles. The effects of the standing posture of the surgical staff on the settlement of the particles on the operating table were examined. Results show that under the present ventilation system, when the surgical staff bend forward at an angle of 45°, the number of airborne particles that tend to fall onto the operating table increased by 1.4-fold. Adding an exhaust grille to the operating room does not have any significant effects on the distribution of the airborne particles. However, when a larger air supply diffuser is also used, the number of airborne particles that settled on the operating table was reduced 4-fold. More airborne particles are transported towards the exhaust grilles, and more airborne particles accumulate below the operating table. The present study shows that the usage of large air supply diffuser in the operating room is capable of reducing the number of airborne particles fall onto the operating table. Also, it enhances the efficiency of airborne particle removal.

Thermal comfort is the human subject perceived satisfaction to the environmental condition. The human comfort level is affected by skin temperature. Currently to determine the human skin temperature by using human experiment in a controlled environment. However, the experiment is very rigorous and exhaustive. This study was conducted to predict human skin temperature under comfort level with using the finite element method and the bioheat equation. The bioheat equation is used to predict the initial value of human skin temperature with the influence of the metabolic heat generation and the blood perfusion. It is discovered the skin temperature of the human subject experiment fluctuates. However, the result obtained from the model remains unchanged until the simulation ends. The predicted results from the model were well in agreement with the experimental results with an acceptable error of 1.05%.

Many large confined spaces in tropical countries employ a combination of natural ventilation and mechanical fans for space cooling purposes. However, due to low wind velocity and an inability of mechanical fans to remove warm air, this cooling method is not capable of providing a satisfactory thermal comfort to the occupants. This study aims to find out a simple strategy for improving the thermal comfort inside a mosque building in Malaysia. Field measurements were first carried out to acquire the airflow velocity, air temperature, relative humidity and mean radiant temperature inside the mosque, for a duration of one-year. These data were then used to calculate two thermal comfort indices namely predicted mean vote (PMV) and predicted the percentage of dissatisfied (PPD). A computational fluid dynamic (CFD) method was employed to predict airflow and temperature distributions and to examine the effects of installing exhaust fans on the thermal comfort condition inside the mosque. Parametric flow analyses were conducted to find out the arrangement of the exhaust fans that would produce highest improvement in the PMV and PPD thermal comfort indices. It was found that, under the present ventilation condition, both PMV and PPD values at the selected locations inside the mosque exceed the respective upper limits as recommended in the ASHRAE Standard-55, indicating that the thermal comfort inside the mosque is extremely hot. Results of parametric flow analyses show that installing ten exhaust fans with a 1-m diameter at the south-side wall, at the height of 6 m from the floor, has a potential of reducing the PMV index by 75–95% and the PPD index by 87–91%. This translates into a vast improvement in the thermal comfort inside the mosque building. Keywords: Large confined space, CFD flow simulation, Thermal comfort, Predicted Mean Vote (PMV), Predicted Percentage of Dissatisfied (PPD), Exhaust fan

In educational facilities, good and healthy indoor air quality is critical to ensure students’ focus and academic activities can be carried out efficiently. The goal of this study was to evaluate the link between indoor air quality level with sick building syndrome and health complaints among occupants. A cross-sectional study was conducted which involved 513 occupants. A modified MM040Na questionnaire was used in this study. Occupants’ workspaces were monitored for indoor air quality. The score obtained from the questionnaire and environmental factors were tested using statistical analyses incorporating test of differences namely Chi–Square, t-test, and non-parametric analysis. Logistic regression was conducted to evaluate relationship between exposure and occupants’ complaint. Results shows that some indoor air pollutants (carbon dioxide, formaldehyde, and particulate matter) are related to overall sick building syndrome (Odd Ratio, OR=1.348, 2.493, 1.958 respectively). General score of sick building syndrome (SBS) shows significant relationship with air motion (OR=2.220) and air flow (OR=2.515). Mucosal score of SBS suggest exposure risk towards indoor factors namely formaldehyde (OR=2.799), while dermal effect was associated from the exposure of Particulate (OR=2.88), carbon dioxide (OR=4.000), and air flow (OR=2.679). In educational environments, indoor contaminants have an impact on reported symptoms.

A ceiling fan is a commonly used mechanical device for promoting airflow inside an enclosed space, for thermal comfort purposes. However, it is difficult to clean and maintain, noisy and sometimes can be dangerous to occupants. Recently, a high-volume low-speed fan (HVLS) was introduced as an alternative device to provide better air movement at a lower energy cost. This study aims to compare the distribution of airflow velocity produced by a single HVLS fan and that produced by two ceiling fans inside a room, using computational fluid dynamic (CFD) method. Two simplified models of two similar rooms were developed using commercial CFD software. One is furnished with an HVLS fan and the other with two ceiling fans. Steady-state flow simulations were performed on the CFD models using a Spalart-Allmaras turbulence airflow model and adopting a moving reference frame (MRF) technique. The CFD models were validated based on experimental data obtained from the literature. It was found that for a single HVLS fan operating at a rotational speed of 140 RPM, the average airflow velocity on a horizontal plane at 1.1 m height from the floor is around 0.87 m/s. This value falls within the range stated in the ASHRAE-55 standard for good thermal comfort. For the room furnished with two ceiling fans operating at the same rotational speed, the average airflow velocity on the similar horizontal plane is around 0.19 m/s, which is outside the limit specified in the ASHRAE-55 standard. But when the two ceiling fans were operated at a rotational speed of 300 RPM, the average airflow velocity on the plane increases to 0.42 m/s, which satisfies the ASHRAE Standard-55 requirement. These findings suggest that a single HVLS fan would provide a more desirable air movement inside a confined space thereby would promote a much better feeling of thermal comfort to the occupants, as compared to the use of two ceiling fans operating at a much higher rotational speed.

Firefighting is a life-threatening situation, they are exposed to extreme heat fire and explosion. Burn injury is the most common injury occur in firefighting. The firefighters are enforced to used personal protective clothing to protect them against fire. The purpose of the study is to assess the effectiveness of fire fighter’s personal protective clothing by utilizing heat transfer model in finite element analysis. The model applied bioheat equation to solve heat transfer through living tissue at muscle area with consideration of metabolic heat generation and blood profusion. The validation of the heat transfer model was performed by comparing the predicted and measured skin temperatures with an acceptable error of less than 20%. The study found the skin temperature increases significantly with the heat flux intensities. The heat flux of 1200W/m2 causes to skin temperature 38.3°C. Skin temperature will gradually rise at t = 0 second and approaches it’s steady at t =198 seconds. The maximum air gap thickness reduces the heat stress effect. The reduction of 1 mm air gap thickness contributes to an increment of 0.2°C of the skin temperature.

Solid desiccant air dehumidifier systems are widely used to supply dry air for many industrial processes. As humid atmospheric air flows through the system, the water vapor in the air is adsorbed by the desiccant material, resulting in dry air leaving the system. A numerical solution has become the preferred choice for determining the performance criteria of desiccant materials. The aim of this study is to determine the moisture removal capacity (MRC), dehumidification effectiveness (?DW), and thermal effectiveness (?th) of a solid desiccant wheel material using a numerical method. A representative three-dimensional model of an air channel enclosed with desiccant material was developed and meshed using triangular elements. Flow simulations were carried out under a transient condition. The model was validated by comparing the simulation results for moisture content and air temperature at the outlet of the air channel with similar results using experimental data obtained from the literature. The relative errors for the desorption process were found to be 0.14% for air temperature and 3.7% for air humidity. For the adsorption process, they were around 3.2 and 0.01%, respectively. These figures indicate that the numerical model has an excellent ability to estimate the desiccant material performance. It was also found that at any given regeneration temperature, silica gel-CaCl2 has the highest MRC, dehumidification effectiveness, and thermal effectiveness compared to silica gel B and Zeolite 13X.

Ventilation system in a bus is employed to provide good indoor air quality and thermal comfort for passengers. Poor ventilation system will increase the concentration level of air contaminants which could affect the passenger’s health. The presence mixing ventilation system used in many buses is not efficient in removing the air contaminants from the passenger compartments. This article presents a study on the effects of using different ventilation setups on the concentration level of gases and particulate matters inside a passenger compartment of a university’s shuttle bus. The goal is to find a suitable layout of the air supply diffusers and air return grilles that would lower the concentration level of contaminants inside the passenger compartment. Field measurements were carried out to quantify the concentration of gases (carbon monoxide, carbon dioxide and formaldehyde) and particulate matters (PM1, PM2.5 and PM10). The measurements were done at the front section of the bus compartment, close to the front door. The data were acquired in the morning, afternoon and evening hours during a clear and sunny day. The bus travelled along an in-campus road with no passengers. A simplified three-dimensional model of the bus compartment was developed using computational fluid dynamics software. Flow analyses were carried out to predict distribution of gases and particulate matters concentration. The concentrations of carbon dioxide, carbon monoxide, formaldehyde and particulate matters obtained from the field measurements were used as boundary conditions and for validating the computational model. A parametric study was carried out to identify a suitable layout of air supply diffusers and air return grilles that would lower the concentration level of the air contaminants. Two types of ventilation systems were considered namely a displacement ventilation and an underfloor air distribution. Results show that the underfloor air distribution system is more effective in reducing the concentration level of gases and particulate matters inside the passenger compartment compared to the displacement ventilation system.

This paper presents the friction loss model of a novel double chamber rotary sleeve air compressor (DCRSC) concept. The compressor mechanism is similar to that of rotary compressor whereby the novelty transpires in the instalment of two rotating sleeves and a secured vane that has one end fixed to an outer sleeve and the other end to a rotor, respectively. This Part II of the paper series presents the friction losses analysis of the compressor. Thermodynamic and leakage losses models were respectively presented in Part I and Part III of this paper series. The primary aim of this paper is to formulate and analyse the friction loss model at the radial and axial contact regions of DCRSC at different rotational speed. The variations of the mechanical power and efficiency were evaluated based on the adiabatic, polytropic and isothermal thermodynamic principles as illustrated in Part I of this paper series. Considering the design simplicity of cylindrical shaped components, at maximum rotational speed of 1500 rpm, the DCRSC mechanical efficiencies are 72.43%, 66.2% and 59% when air undergoes adiabatic, polytropic and isothermal compression process, respectively. it is believed that the DCRSC is well suited for compressed air systems and air-conditioning applications.

This paper introduces a novel double chamber rotary sleeve compressor (DCRSC) concept. The compression mechanism is basically that of a rotary motion whereby the novelty lies in the usage of a rotating sleeves and a non-sliding vane that has one end fixed to a rotor and the other fixed end to an outer rotating sleeve. The main goal of this paper is to describe the compression processes of air as the working fluid and reveals the variations of pressure, temperature, mass and compression power inside the compressor working chambers at different rotational speed. Friction and leakage model of the proposed compressor are evaluated in Part II and Part III of this paper series. The compressor was theoretically analysed based on three thermodynamic compression approaches namely: adiabatic, polytropic and isothermal approaches. According to the thermodynamic simulation, a 171 cm3.rev−1 DCRSC can deliver a 15.4 m3.h−1 of compressed air at 9.3 bar, 6.8 bar and 4.9 bar when air undergoes adiabatic, polytropic and isothermal compression processes, respectively. The DCRSC compression mechanism shows a potential capabilities of a new compressor concept and to be well suited for the air conditioning and compressed air systems articles must contain an abstract.

This paper presents comprehensive leakage model of a novel double chamber rotary sleeve air compressor (DCRSC). The compressor mechanism is that of a rotary motion whereby the novelty lies in the usage of two rotating sleeves and a secured vane that has one end fixed to an outer sleeve and the other end to a rotor, respectively. The thermodynamic model and friction model of the DCRSC are respectively presented in Part I and Part II of this paper series. The main goal of this study is to formulate and analyse the internal leakage losses at different rotational speed. Dynamic clearance at the contact regions between the high-pressure and low-pressure chambers were made clear. The variations of the internal leakage rate and volumetric efficiency for three compression approaches namely: adiabatic, polytropic and isothermal compression processes were evaluated. At maximum rotational speed of 1500 rpm, the DCRSC volumetric efficiencies are 53.1%, 69.4% and 98% when air undergoes adiabatic, polytropic and isothermal compression process, respectively. The internal leakage losses can effectively be minimized by selecting the right lubricant and reducing the assembly clearances of the rotating parts that defines the compression chambers.

During a surgical procedure, each of the medical staffs would have different postures. Supporting medical staff such as anaesthesiologist would stand in upright condition with straighten-forearm, while medical staff that is performing surgical procedures is in bent-forearm posture. The positioning of forearm might interrupt the air supplies from the ceiling-mounted diffuser, that serves to remove the airborne particles from the surgical zone. Consequently, the movement of particles in the surgical zone is affected, and the tendency of particles to fall onto the patient’s wound is increased. This situation could elevate the chances of a patient contracting surgical site infections and could increase the risk of death. The present study aims to examine the effects of medical staff’s forearm posture on the number of particles falling onto the patient. A simplified computational fluid dynamics (CFD) model of the operating room was developed and validated based on the published data. An RNG k-ε turbulence model based on the Reynolds-Averaged Navier-Stokes (RANS) equations was used to simulate the airflow, while a discrete phase model was used to simulate the movement of the airborne particles. Results show that bent-forearm of medical staff obstructed the downward airflow to remove the particles released by the medical staff. Approximately 37 particles/m3 accumulated in the chest region of the medical staff. A high particle accumulation is also observed at the gap between the staff’s legs due to the stagnant airflow.

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.

The issue of global warming has triggered more critical issues, and today’s refrigerants with high global warming potential (GWP) are facing the challenges of being phased out. According to 2014 Assessment Report of the Refrigeration, Air-Conditioning and Heat Pumps Technical Options Committee (RTOC Assessment Report 2014), the R410A has GWP of 2100 and is widely used in residential air-conditioning and heat pump systems. Currently, in the market, the potential refrigerant that can be used to replace R410A in the air-conditioning system is R32. The purpose of this project is to create a new refrigerant mixture using low GWP refrigerant as a base that can replace for R410A in an air-cooled split air conditioner. Simulation works have been developed using Refprop software to simulate the refrigeration cycle with the operating conditions of the air-cooled split air conditioner, in the tropical region. The chosen cycle was an ideal vapour compression cycle with the evaporating and condensing temperatures of 5 °C and 47 °C, respectively. Through this study, two potential refrigerants mixture was found to be suitable to replace the R410A. The two refrigerant mixtures, R32/R1234ze and R32/R600a, both based on R32, were found to have similar thermodynamic properties as the R410A. They were found to be able to produce the coefficient of performance (COP) very close to the R410A when used in an air-cooled split air-conditioning system. Hence, the use of this refrigerants will avoid significant modifications on the present air-conditioning system configurations. Refrigerant R32/R1234ze has the potential to reduce the GWP of R410A by 70 % while refrigerant R32/R600a by 73 %. At the end of the equipment lifespan, refrigerant R32/R1234ze would reduce the direct of Total Equivalent Warming Impact (TEWI) by 23 % while refrigerant R32/R600a by 20 %.in constructing both.

In this study, ANN model for a standard air-conditioning system for a passenger car was developed to predict the cooling capacity, compressor power input and the coefficient of performance (COP) of the automotive air-conditioning (AAC) system. This paper describes the development of an experimental rig for generating the required data. The experimental rig was operated at steady-state conditions while varying the compressor speed, air temperature at evaporator inlet, air temperature at condenser inlet and air velocity at evaporator inlet. Using these data, the network using Lavenberg–Marquardt (LM) variant was optimized for 4–3–3 (neurons in input–hidden–output layers) configuration. The developed ANN model for the AAC system shows good performance with an error index in the range of 0.65–1.65%, mean square error (MSE) between 1.09 × 10 −5 and 9.05 × 10 −5 and the root mean square error (RMSE) in the range of 0.33–0.95%. Moreover, the correlation which relates the predicted outputs of the ANN model to the experimental results has a high coefficient in predicting the AAC system performance.

This article presents an investigation on the effects of using ventilation fans on the air temperature inside a car passenger compartment when the car is parked under the sun. It was found from a measurement that the air temperature inside the passenger compartment could raise up to 48°C. Computational fluid dynamics method was used to develop model of the compartment and carry out flow simulations to predict the air temperature distribution at 1 pm for two conditions: without ventilation fans and with ventilation fans. The effects of fan location, number of fans used and fan airflow velocity were examined. Results of flow simulations show that a 17% temperature reduction was achieved when two ventilation fans with airflow velocity of 2.84 m/s were placed at the rear deck. When three fans were used, an additional 3.4% temperature reduction was attained. Placing two ventilation fans at the middle of the roof also reduced the air temperature by 17%. When four fans were used a further 4.8% temperature reduction was achieved. Increasing the airflow velocity at the four fans placed at the roof, from 2.84 m/s to 15.67 m/s, caused only a small reduction in the air temperature inside the passenger compartment

There has been an increasing demand for renewable energy in order to create a sustainable society as the non-renewable energies such as fossil fuel resources are limited. Modern wind turbines claim that they have a high efficiency in term of wind energy extraction. However, there are still having losses due to tip vortex causing to a reduction in performance. Motivated by this reason, this research aims at exploring the possibility to increase the performance of low speed small-scaled horizontal axis wind turbine with various tip devices using Computational Fluid Dynamics (CFD). Four wind turbine blades with different tip devices which consist of sword tip, swept tip, upwind winglet and downwind winglet are compared with wind turbine blade without tip device in term of CP. The application of tip device can significantly reduce induced tip vortex and improve wind turbine performance. For TSR below than 4, adding a sword tip increases CP about 7.3%, swept tip increases CP about 9.1%, upwind winglet increases CP about 1.8% and downwind winglet increases CP about 3.2%. It is observed that the best tip device for low wind speed application is swept tip as it give the highest performance increment compared to without tip device.

The presence of moisture in the air along with temperature has a long term and devastating effect on man and material. One way to create a low humidity environment is by using a solid desiccant wheel system. In the present work, an experimental analysis has been carried out under steady-state conditions to investigate the effects of different operating parameters on a solid desiccant wheel system performances. An experimental rig consists of an FFB300 air dehumidifier system was constructed. A parametric investigation was carried out to examine the effects of the reactivation air inlet temperature and process air outlet velocity on the thermal effectiveness, dehumidification efficiency, and moisture removal rate of the desiccant wheel system. The analysis shows that both thermal effectiveness and dehumidification efficiency decrease with the increase of the reactivation air inlet temperature, by 2.5 % and 43 %, respectively. Likewise, when the process air outlet velocity increases both performances criteria reduce by 10 % and 28 %, respectively. The moisture removal rate increases significantly by 30 % as the reactivation air inlet temperature increases. However, the process air outlet velocity has no significant effect on the moisture removal rate.

A combined natural ventilation and mechanical fans are commonly used to cool the interior space inside the mosques in Malaysia. This article presents a study on thermal comfort in the Al-Jawahir Mosque, located in Johor Bahru, Malaysia. The objective is to assess the thermal comfort inside the mosque under the present ventilation system by determining the Predicted Mean Vote (PMV) and the Predicted Percentage of Dissatisfied (PPD). These values were then compared to the limits stated in the ASHRAE Standard-55. It was found that the PMV varies from 1.68 to 2.26 while the PPD varies from 61% to 87%. These show that the condition inside the mosque is quite warm. Computational fluid dynamics (CFD) method was used to carry out flow simulations, to identify a suitable strategy to improve the thermal comfort inside the mosque. Results of CFD simulations show that installing four exhaust fans above the windows on the west-side wall of the mosque is the most effective strategy to improve the thermal comfort inside the mosque. Both the PMV and PPD values can potentially be reduced by more than 60%.

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.

Passengers commuting with buses are exposed to indoor air that contains contaminants such as particulate matters (PM). These contaminants could affect the passenger’s health in long and short term durations. Depending on the size of the particles, a respiratory allergy and airborne transmission could affect the passenger’s health. This article presents a field measurement to assess the airborne particles concentration of particulate matters inside a passenger bus compartment. The data collections were done at the front, middle and rear sections of the compartment, at a height of 1.1 m from the floor. The field measurements were carried outfrom 7.30 AM to 9.00 AM, 1.30 PM to 2.30 PM and from 4.15 PM to 5.00 PMwhich are the peak hours periods. A HPC300 handheld particles counter was used to measure the concentrations of PM1, PM2.5 and PM10. The results show that the concentrations of PM1, PM2.5 and PM10 were significantly high during the afternoon and evening hours. Also, the concentrations of PM1, PM2.5 and PM10 were higher at the front section of the passenger compartment compared to the middle and rear sections. It was also found that the peak hour periods, ventilation setting, infiltration, boarding and unboarding of passengers are among the factor that would increase the concentrations of PM1, PM2.5 and PM10 particles inside the passenger compartment.

A bus compartment requires a good ventilation system to provide sufficient fresh air and a uniform air flow to passengers. This article presents a numerical study using CFD method to investigate the effects of using different ventilation setups on the air flow velocity and temperature distributions inside a passenger bus. Fluent software was used to develop a simplified three-dimensional model of a quarter section of a bus passenger compartment. Turbulent flow simulation was carried out based on a standard k-epsilon model to predict the distributions of air temperature and velocity inside the passenger compartment. The effects of two ventilation setups, namely mixing and displacement ventilations on the air temperature and air flow velocity distribution were also examined. Results of CFD simulations show that the displacement ventilation setup results in more uniform distribution of air flow velocity and air temperature inside the bus passenger compartment.

In a hospital operating room, adequate air flow and cleanliness are crucial to protect the patient from surgical site infection (SSI) during a procedure. The probability of the patient to get the infection is related to the concentration of bacteria carrying particles inside the room. This paper presents a field measurement study to quantify the concentration of particulate matters (PM) in a hospital operating room which complies with the ISO Class 7 requirements. The operating room was equipped with High Efficiency Particulate Air (HEPA) filters and a vertical laminar air flow (LAF) system. The measurements were conducted at three height levels from the floor namely 1.2 m, 1.8 m and 2.4 m. The data was logged at a rest condition, in accordance to the ISO 14644-1 requirements. A HPC300 particle counter was used to measure the concentrations of particulate matters namely PM0.5, PM1 and PM5. The results show that the concentrations of all particulate matters were higher at the height level of 1.2 m compared to other height levels. The concentration of PM0.5 was relatively higher than PM1 and PM5 in the vicinity of operating table.

This article presents a study to estimate the potential saving in annual operating cost of a hypothetical greenhouse used for planting strawberry, in Johor Bahru, Malaysia. The greenhouse needs to be maintained at a constant temperature of 20°C at all time. The goal of this study is to select a suitable TES system that can save the annual cost of electricity usage to meet the cooling load requirement of the greenhouse, based on a 24 hours operating duration and local electricity tariff. Comparison is made with the annual cost for running a conventional air-conditioning (AC) system to meet the cooling requirement. The cooling load requirement of the greenhouse dictates the capacity and size of the potential TES systems, which was estimated based on the highest total annual cooling load. Three TES system operating arrangements were considered in this study: TES full storage combined with AC systems, TES full storage and TES partial storage. Among these three arrangements, the TES full storage was found to have the highest an annual cost saving of about RM 58,990 compared to the cost of using the conventional AC system alone. This represents about 68 % of annual operating cost saving, which is considered very significant.

Air distribution systems inside a bus compartment are important for providing healthy and comfortable environment for passengers. Lack of ventilation inside the bus passenger compartment causes an increase level of air contaminants concentration. Particulate matters and carbon monoxide are indoor air contaminants which can affect the passenger’s health such as respiratory problem and lung cancer. This article reports the results of a CFD simulation on transport of carbon monoxide and particulate matter 1 inside a passenger compartment of a university’s shuttle bus. Fluent CFD software was used to develop a simplified three-dimensional model of the bus passenger compartment. Flow analysis was carried out using RNG k-e turbulent model for air flow, discrete phase and species transport for the air contaminants. Four variations of ventilation system namely two mixing ventilation types, combined mixing with displacement ventilation and combined mixing ventilation with underfloor air distribution was examined. The CFD simulation results show that the use of the combined mixing and displacement ventilation and also the combined mixing and underfloor ventilation types are capable of reducing the concentration of carbon monoxide and particulate matter 1 inside the bus passenger compartment by 81% and 54%, respectively.

The use of fracture mechanics outside the area of mechanics, including materials science, is evidence that the concept is capable of handling failures involving almost any types of crack propagations. This paper outlines the simple method on how to use fracture mechanics concepts in coating study by using a concrete example that is easy to follow. The example presented here is the use of fracture mechanics to develop equation governing the blister propagation using the concept pioneered by Sih, the SED concept. Despite being simple, the method gives excellently good agreement with those available solutions derived by other methods.

Two-dimensional modeling to compute plastic zone in front of a crack in a compact tension specimen of a multiphase material was published previously. This paper is the continuation of it, using the same concept, but in three dimensions. The heart of this study is to develop a simulation method to predict the effect of microstructural morphology in multiphase steel in three dimensions utilizing commercial software. The object of the model, multiphase of ferrite and martensite, is known to benefit its fatigue performance by its high toughness yet maintains the high tensile properties due to controlled microstructure. Multiphase steel having a microstructure consisting of polygonal ferrite and martensite has received a great deal of attention due to their useful combination of high strength, high work hardening rate, and ductility. From the fracture mechanics point of view, the key to its fatigue performance is the large plastic zone size in front of the crack. In this research, a sub-modeling technique is used, by using three-dimensional modeling of cube with variation of ferrite fraction as local models. The global model, a compact tension specimen, is treated as a homogeneous material. The results show strong correlation and similarity with that of two-dimensional model. The analysis result shows the variation of the plastic zone sizes as the ferrite fraction varies and saturates at about 60% ferrite fraction.

More and more components subjected to dynamic high stress loading are heat treated to get multiphase microstructure as their final products, instead of conventional tempered martensite. It is gaining popularity due its manufacturing benefits, including the elimination of the tempering process, and its better fatigue performance. Multiphase of ferrite and martensite benefits its fatigue performance by its high toughness yet maintains the high tensile properties due to controlled microstructure. The plastic zone size in front of the crack is the key to fatigue performance. In this research, a multiphase (polygonal ferrite and martensite) microstructure was developed. Manipulation method to use commercial software to calculate the plastic zone size in front of a crack is presented. Two-dimensional modeling of squares having variation of ferrite fraction was used as local models. The shape of the ferrites was derived from actual microstructure of multiphase material. These local models were put in front of the CT specimen in a global model. The analysis result shows the variation of the plastic zone sizes as the ferrite fraction varies and saturates at about 65% ferrite fraction.

Problem statement: There are two types of implant fixation in hip joint replacement-cemented and cementless. The cemented types are, in general, more popular due to concerns of possible inability of cementless implants achieving maximum primary stability for bone integration. The concern is more significant in cases where there are major losses of cancellous bone stock and thinning of the trabeculae due to osteoporosis. Approach: Three Computed Tomography (CT) images of human hip joints were obtained from a hospital. The first patient showed osteoporotic condition based on DEXA scan of the bone. The second was registered for total hip replacement due to significant deterioration of the cartilage covering the bone ends. The third dataset was from a patient with no reported skeletal diseases and was used as control. Three dimensional models of the femora were reconstructed from the CT images and hip arthroplasty using cementless stem was simulated. Finite element method was used to analyze the stability of the implant through a specialized algorithm to measure micromotion at the bone-implant interface. Bone properties were assigned on an element-by element basis and loads simulating stair climbing were used. Results: Hip stems fixed in the control and osteoarthritic femoral model showed minimum interface micromotion. For the osteoporotic bone there is a progressive reduction in surface area feasible for bone in growth. Conclusion/Recommendations: Bone quality affects the stability of femoral components used in hip replacement and therefore the bone-implant integration potential. Cementless hip stem should not be used in patients with osteoporotic condition as the deterioration of bone tissues lead to an increase in interface micromotion.

Problem statement: The design of hip prostheses has evolved over time due to various complications found after hip replacement surgery. The currently commercially available cementless femoral stems can be categorized into one of three major types, straight cylindrical, tapered rectangular and anatomical. Each type proposes a unique concept to achieve primary stability-a major requirement for bone healing process. Virtual analyses have been made on individual implants, but comparison between the three major types is required to determine the strength and weaknesses of the design concepts. Approach: Three types of implants were modeled in three dimensions-the straight cylindrical, rectangular taper and anatomical. The size of the three implants was carefully designed to fit and fill the canal of a femur reconstructed from a computed tomography image dataset. Hip arthroplasty was simulated virtually by inserting the hip stem into the femoral canal. Finite element method was used in conjunction with a specialized sub-routine to measure micromotion at the bone-implant interface under loads simulating physiological walking and stair-climbing. Another sub-routine was used to assign bone properties based on the grayscale values of the CT image. Results: All the three types of cementless hip stems were found to be stable under both walking and stair climbing activities. Large micromotion values concentrated around the proximal and distal part of the stems. Conclusion/Recommendations: The three major types of hip stems were compared in this study and all of them were found to be stable after simulated physiological activities.

Room-temperature scanning probe microscopy was used to generate out-of-plane deformation maps around Cu vias and polyimide mesas in single-level Cu–polyimide damascene interconnect structures subjected to a room-temperature to 350 °C thermal cycle. The deformation maps are obtained by taking the difference between the images obtained before and after thermal processing. The deformation of the Cu is shown to be highly heterogeneous on the submicrometer scale. Direct evidence of Cu–Ta interfacial sliding, Cu–Cu grain boundary sliding, and diffusion creep is presented. The direction of Cu–Ta sliding is shown to depend on polyimide mesa size. A hot-stage atomic force microscope was used to show that hillock/extrusion growth occurs at temperatures between 130 and 180 °C. We propose that this hillock/extrusion growth is correlated with dips in stress–temperature plots for blanket, uncapped Cu films in the same temperature range and that the absence of dips for nitride-capped Cu films is due to suppression of the hillock/extrusion growth.

The finite element method was used to estimate the stresses in single level, 1 μm thick Cu-dielectric interconnect line arrays with Ta liners resulting from heating from 20°C to 400°C assuming that the structure was stress free at 20°C. Benzocyclobutene (BCB) and SiO2 were chosen to represent typical polymer and ceramic dielectric materials being evaluated for Cu damascene interconnect structures. Experimentally observed Cu-Ta and Cu-Cu interfacial sliding was incorporated into the model using a 1 nm thick creep element that was calibrated to match the predictions of a classical diffusion-accommodated sliding model. The effect of Cu-Ta and Cu-Cu interfacial sliding was evaluated by comparing the relaxed and unrelaxed stresses. The effect of line width-to-thickness (w/t) ratio and Ta liner thickness on the shear, normal, and Ta liner-plane stresses at the Cu-Ta-dielectric interface was investigated because this interface is a likely failure site.

Desiccant wheels are used as an air dehumidifier in air-conditioning and industrial applications. Desiccant wheel performance determines the size and cost of the whole system. A good desiccant wheel is one that saves energy usage. This article presents an experimental investigation on the effects of varying the regeneration air temperature, viz., 50, 60 and 70°C, on desiccant wheel performance. Three performance criteria were considered, namely condition of process outlet air, dehumidifier efficiencies and dehumidification rate. Two kinds of efficiency of the desiccant wheel dehumidifier were examined, namely thermal and dehumidification efficiency. Results of the experiments show that increasing the regeneration air temperature increases the dry bulb temperature of the process outlet air. However the moisture content of the process outlet air is reduced. The dehumidification efficiency of the desiccant wheel decreases with increasing regeneration air temperature, i.e., 46.7, 45.8 and 45.3 % for 50, 60 and 70°C, respectively. In contrast, the dehumidification rate increases with an increase in the regeneration air temperature, namely 32.6, 37.1 and 40.2 g/h for 50, 60 and 70°C, respectively.

Lacking of stability known to be as one of the principal factors contributes to loosening of hip prosthesis. Initial stability of the hip prosthesis related with the magnitude of relative displacement at the femoral bone-prosthesis interface. The present study aimed to investigate the effect hole as additional features on the initial stability. 3D finite element model of femur and prosthesis developed based on CT dataset of a Malaysian patient. Simulations of normal walking condition performed on the models to investigate the relative displacement between the bone and prosthesis interface. The simulations results report that additional hole as a feature on the proximal region of prosthesis, produce highest relative displacement at the proximal region on the medial side.

Analisis haba di dalam struktur pandu gelombang optik telah dijalankan untuk mengkaji taburan suhu keratan rentas apabila dipanaskan dengan elemen pemanas. Persamaan umum haba diprogramkan menggunakan kaedah berangka pembezaan terhingga. Perbezaan keputusan yang ketara telah diperoleh apabila nilai keberaliran haba yang berbeza bagi setiap elemen pandu gelombang dan mekanisma konveksi ke persekitaran dipertimbangkan. Kata kunci: Kesan termo–optik, analisis terma, kaedah pembezaan terhingga A thermal analysis in optical waveguides structure is simulated in order to predict the temperature distribution over the waveguide cross–section, when heated by a heating element. A steady state heat equation is solved by using finite difference numerical method. It is observed that by applying different value of thermal conductivities for each waveguide element and further application of convection mechanism to the ambient, obvious differences with other researchers’ work are recorded. Key words: Thermo–optic effect, thermal analysis, finite difference method

This paper presents a numerical study on the temperature field inside a passenger's 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 passenger's compartment is also investigated. Fluent CFD software was used to develop a three-dimensional symmetrical model of the passenger's compartment. Simplified representations of the driver and one rear passenger were incorporated into the CFD model of the passenger's 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 passenger's 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 passenger's 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 passenger's compartment of the car.

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.

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.

Progressive materials damage process in solder joint under cyclic shear deformation is examined in this study. A 3-D finite element model of a single reflowed SAC405 solder specimen is developed for this purpose. Cyclic relative displacement cycles between zero and 1.0 mm at displacement ramp rate of 2.0 mm/sec. is applied in the direction parallel to the solder/pad interface. Strain rate-dependent response of the solder is modeled using unified inelastic strain equations (Anand's model) with optimized model parameters for SAC405 solder. Damage initiation is characterized by the inelastic hysteresis energy per stabilized cycle, ΔW. Elastic stiffness of the solder is then degraded progressively using prescribed damage evolution rule. Results show that extensive inelastic strain accumulation is confined to small selected edge regions near the solder/pad interface. The calculated slow inelastic strain rates in the range of 0.24 to 0.29 sec−1 resulted in bulk solder fatigue failure. In the predominantly tensile stress region near the solder/pad interface, inelastic shear strain range parallel to and stress range normal to the interface plane has the greatest magnitude. The inelastic hysteresis energy or work per stabilized cycle has demonstrated to be a better parameter over accumulated inelastic strain per cycle for describing low cycle fatigue failure of solder joints.

This study examines evolution characteristics of inelastic strains and materials damage in Sn-4Ag-0.5Cu (SAC405) solder joints of a BGA package under cyclic mechanical stressing. For this purpose, a finite element model of the assembly under four-point bend test set-up is employed. Strain rate-dependent response of the solder is represented by Anand model. Progressive damage in the solder joint is described using continuum damage model. Results show that the critical solder joint is the one located at the corner of the BGA package. In this critical solder joint, both high stress and inelastic strain are localized in a small edge region at the solder/IMC interface at the board side of the assembly. The different inelastic strain rates experienced by the critical solder joint during fatigue cycles correspond to the distinct damage initiation stage, crack propagation stage and the final fast fracture of the solder joint. Damage initiation life covers nearly half of the total fatigue lives of the critical solder.

In this study, cohesive damage zone model is evaluated and employed to model solder/intermetallics (IMC) interface crack initiation and propagation in solder interconnects. Interface materials damage is quantified in terms of stress-to-strength ratios of orthogonal components in a quadratic failure criterion along with a mixed-mode displacement formulation for crack initiation event. Subsequent crack propagation is predicted based on fracture energy considerations. The mechanics of solder/IMC interface decohesion is examined through finite element modeling of a typical solder ball shear test. The 3D model consists of Sn40Pb solder, Ni3Sn4 intermetallics and Ni layers, copper substrate and a rigid shear tool. Unified inelastic strain theory describes the strain rate- and temperature-dependent response of the solder. The strength and work of fracture of the bi-material interface are derived from load-displacement data of solder ball pull tests and ball shear tests. The quasi-static solder ball shear test of reflowed solder sample is simulated at 30°C with a prescribed displacement rate of 0.01 mm/sec. Results show that complex stresses developed on the interface plane due to applied shear and induced bending effects by the shear tool clearance. A nonlinear damage evolution is predicted at each interface material point during the test. Stresses in the "fractured" material points diminish as the crack front progresses. The progression of damage indicates a straight crack front for the brittle solder/IMC interface fracture, as observed experimentally. The corresponding fractographic analysis on the sheared interface indicates that the crack initiated and propagated along the bi-material solder/IMC interface.