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A promising ventilation strategy is an effective measure to enhance indoor air quality and protect the patients against healthcare-acquired infection. The Computational Fluid Dynamics (CFD) model represents a patient ward that was constructed using Computer-Aided Design (CAD) software. The simulated results were verified and validated based on the published data. A Renormalization Group (RNG) k-epsilon model based on the Eulerian approach was used to simulate the airflow turbulence, while a discrete phase model (DPM) based on the Lagrangian approach was used to predict the dispersion of airborne particles. This study examined four cases of ventilation strategies, with varying ventilation rates, positioning of supply air diffusers, and location of exhaust grilles. This study revealed that the installation of air curtain jet coupled with a ceiling-mounted air supply diffuser (case 3) above the patient-occupying zone has the highest wiping efficiency against the infectious particles. The utilization of ventilation strategy in case 3 managed to reduce the particle by approximately 3.3 times as compared to the baseline case. The study outcome also suggested that the exhaust grilles should be placed on the upper wall, to ensure a proper mixing of fresh air in the entire patient ward.

Universiti Tun Hussein Onn Malaysia (UTHM) elibrary is in the hot and humid tropical climate of Malaysia and has a distinctive feature of a circular courtyard and semi-outdoor spaces for practical public spaces and energy saving. This study was conducted on the ground level of the library which consists of an open terrace consisting of a cafeteria, a garden in the circular courtyard, and an air-conditioned seminar room. This study aimed to compare the thermal comfort condition of these spaces through physical and subjective measurements. Physical measurement was conducted for air temperature, relative humidity, air velocity and mean radiant temperature at the two selected sampling points on each investigated area positioned at 0.6 meters from the floor. Data were collected for three days in each area during two periods of time; 9 to 11 am and 2 to 4 pm. Subjective measurements were also collected through the distributed questionnaire to 150 respondents to determine the thermal sensation votes (TSV) of each investigated area. Calculations based on physical measurement showed the thermal comfort for both the cafeteria and garden were within 90% thermal comfort acceptability limit. PMV value for the air-conditioned seminar room was -0.45 with a PPD value of 9.03%. Both results complied with the ASHRAE 55 Standards for the acceptable condition for both naturally and air-conditioned spaces. The regression analysis showed that the comfort air temperature range based on the human response method for semi-outdoor spaces and indoor spaces were 24.8 0C to 29.0 0C and 20 0C to 23.5 0C respectively. The PMV regression analysis showed that the comfort air temperature range for indoor space was 22.4 0C to 23.5 0C. Results of the study showed that respondents perceived a higher comfort temperature range in the courtyard and cafeteria compared to indoor air-conditioned spaces, but still within the recommended range of ASHRAE 55 standard. The results of the study concluded that semi-outdoor places can potentially be designed as practical public spaces for comfortable and sustainable spaces.

Poor indoor air quality (IAQ) has developed a positive relationship with human health risks. Recently, research findings reported that the pollution level of indoor air could be 2 – 5 times higher than the outdoor air. In some studies, the poor IAQ could reach up to 100 times or more in a natural/ mechanical ventilated building. IAQ depends heavily on the ambient air quality and pollutants/ contaminants produced by household activities. Poor IAQ could lead to various health issues, i.e., asthma, lung cancer, dizziness, fatigue, headaches, etc. One of the possible solutions to overcome the poor IAQ problem is the utilisation of indoor botanical to improve the IAQ. The phytoremediation of botanical is an affordable and environmentally friendly approach to purify the polluted indoor air. Although there is no established recommendation for determining the best indoor botanical in improving the IAQ, many studies have revealed the ability of specific indoor botanicals to remove pollutants/ contaminants. This paper presents the bibliometric analysis and short review based on 79 publications issued in 2011 – 2021. Those articles were extracted from the Web of Science database. Based on the analysis, the number of publications has increased significantly starting from the year 2017. Indoor Air was identified as one of the top productive journals for this research topic.

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.

The flow and heat transfer over a modulated surface in the form of triangular protrusions using MWCNTs-TiO2 nanohybrids were investigated, and its results are detailed in this paper. The nanomaterials were functionalized and prepared at weight concentrations of 0.025%-wt., 0.05%-wt., 0.075%-wt., and 0.1%-wt., then had its morphology elucidated using the high-resolution transmission electron microscopy (HR-TEM), field emission transmission electron microscopy (FE-SEM), and Energy Dispersive X-Ray Analysis (EDX). The mixture's thermophysical properties at 303 K were determined and utilized in the investigation's numerical aspect. A steady-state 2D analysis of flow over a modulated surface was solved in ANSYS-FLUENT with turbulent flow at 5000 ≤ Re ≤ 15,000. The model was validated using the Dittus-Boelter Eq., and its average error was 9.840%. The heat transfer was enhanced by 13.181%, 18.056%, 22.033% and 26.107% for nanoparticles' weight concentrations of 0.025%-wt., 0.05%-wt., 0.075%-wt., and 0.1%-wt., respectively. The water flow and MWCNTs-TiO2 nanohybrids' turbulent kinetic energy, pressure, velocity, turbulence intensity contours, and velocity vectors were determined, and correlations were formed from the results to predict the average Nusselt number for the DW and MWCNTs-TiO2 as a function of the nanoparticles' weight concentrations.

Mono, hybrid, and ternary nanofluids were tested inside the plain and twisted-tape pipes using k-omega shear stress transport turbulence models. The Reynolds number was 5,000 ≤ Re ≤ 15,000, and thermophysical properties were calculated under the condition of 303 K. Single nanofluids (Al2O3/distilled water [DW], SiO2/DW, and ZnO/DW), hybrid nanofluids (SiO2 + Al2O3/DW, SiO2 + ZnO/DW, and ZnO + Al2O3/DW) in the mixture ratio of 80:20, and ternary nanofluids (SiO2 + Al2O3 + ZnO/DW) in the mixture ratio of 60:20:20 were estimated in different volumetric concentrations (1, 2, 3, and 4%). The twisted pipe had a higher outlet temperature than the plain pipe, while SiO2/DW had a lower T out value with 310.933 K (plain pipe) and 313.842 K (twisted pipe) at Re = 9,000. The thermal system gained better energy using ZnO/DW with 6178.060 W (plain pipe) and 8426.474 W (twisted pipe). Furthermore, using SiO2/DW at Re = 9,000, heat transfer improved by 18.017% (plain pipe) and 21.007% (twisted pipe). At Re = 900, the pressure in plain and twisted pipes employing SiO2/DW reduced by 167.114 and 166.994%, respectively. In general, the thermohydraulic performance of DW and nanofluids was superior to one. Meanwhile, with Re = 15,000, DW had a higher value of η Thermohydraulic = 1.678.

Graphical abstract In this study, a systematic procedure for establishing the relationship between particulate matter (PM) and microbial counts in four operating rooms (ORs) was developed. The ORs are located in a private hospital on the western coast of Peninsular Malaysia. The objective of developing the systematic procedure is to ensure that the correlation between the PMs and microbial counts are valid. Each of the procedures is conducted based on the ISO, IEST, and NEBB standards. The procedures involved verifying the operating parameters are air change rate, room differential pressure, relative humidity, and air temperature. Upon verifying that the OR parameters are in the recommended operating range, the measurements of the PMs and sampling of the microbes were conducted. The TSI 9510-02 particle counter was used to measure three different sizes of PMs: PM 0.5, PM 5, and PM 10. The MAS-100ECO air sampler was used to quantify the microbial counts. The present study confirms that PM 0.5 does not have an apparent positive correlation with the microbial count. However, the evident correlation of 7% and 15% were identified for both PM 5 and PM 10, respectively. Therefore, it is suggested that frequent monitoring of both PM 5 and PM 10 should be practised in an OR before each surgical procedure. This correlation approach could provide an instantaneous estimation of the microbial counts present in the OR.

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 ...

The present study examines the effect of medical staff's turning movements on particle concentration in the surgical zone and settlement on the patient under single large diffuser (SLD) ventilation. A computational domain representing the operating room (OR) was constructed using computer-aided design (CAD) software. The airflow and particle models were validated against the published data before conducting the case studies. The airflow in the OR was simulated using an RNG k-ε turbulence model, while the dispersion of the particles was simulated using a discrete phase model based on the Lagrangian approach. A user-defined function (UDF) code was written and compiled in the simulation software to describe the medical staff member's turning movements. In this study, three cases were examined: baseline, SLD 1, and SLD 2, with the air supply areas of 4.3 m

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.

The effects of using aqueous nanofluids with the presence of Pentaethylene Glycol-Treated Graphene Nanoplatelets as the working fluids on the thermal performance of flat-plate solar collectors (FPSCs) were investigated experimentally. Water-based nanofluids were prepared with the concentrations of 0.025, 0.05, 0.075, and 0.1 wt%. Then the thermophysical properties were measured. Experimental setup and a MATLAB program were used to study the thermal performance of FPSCs-based nanofluids. The fluid inlet temperatures used in this study were 303, 313, and 323 K, and the flow rates were 0.00833, 0.01667, and 0.025 kg/s. Meanwhile, 500, 750 and 1000 W/m2 were set for the heat flux intensities. As the weight concentration was increased, thermal conductivity, dynamic viscosity, and density also improved, while specific heat decreased. The efficiency of FPSC increased as the flow rate and heat flux intensity were increased. However, the efficiency of FPSC decreased when the temperature of the fluid inlet was increased. Compared to water, the FPSC efficiency recorded an increase of up to 10.7%, 11.1%, and 13.3% for PEG-GNP nanofluids at different mass flow rates. Finally, the regression model was developed through MATLAB to predict the thermal efficiency coefficients of FPSC.

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%.

Thermal comfort is the human subject perceive satisfaction to the work environment. The thermal comfort need to be achieve towards productive working environment. The comfort level of the subject is affected by the human skin temperature. To assess the skin temperature with the sorrounding by conducting human experiment in the climatic chamber. It is rigorous and complex experiment.This study was developed to predict human skin temperature in comfort level with the finite element method and the bioheat equation. The bioheat equation is a consideration of metabolic heat generation and the blood perfusion to solve heat transfer of the living tissue. It is to determine the skin temperature focussing at the human arm. From the study, it is found that the predicted skin temperature value were in well agreement with the experimental results. The percentage error insignificant with acceptable error of 1.05%.

Burn injury is one of the most common injury among firefighters. Moisture comes from perspiration or hose spray absorbed in the personal protective clothing and steam burn injury occur with continuous heat exposure. The heat transfer from the heat flux is enhanced due to transformation material properties that holds high thermal conductivity and heat conductivity. Finite element method is used to predict steam burn injury among firefighters. The model is developed in 1dimensional cylinderical quarter geometry representing the human limb. It is discovered the skin temperature 10°C increases with wet material than dry material. The pain threshold at the lower arm of wet material condition is formed 40second rapidly compare to dry material condition. The first degree burn occur at t=9.5second sooner than the dry condition t=25second. The skin temperature increases with the wet material resulting severe skin burn. It is found that the wet personal protective clothing had compromised its thermal protection. Therefore, firefighters will experience high risk of thermal hazard.

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.

Flat-plate solar collectors are one of the cleanest and most efficient heating systems available. Studies on the presence of covalently functionalized graphene (Gr) suspended in distilled water as operating fluids inside an indoor flat-plate solar collector (FPSC) were experimentally and theoretically performed. These examinations were conducted under different testing conditions namely 0.025 wt.%, 0.05 wt.%, 0.075 wt.%, and 0.1 wt.%, 0.5, 1, and 1.5 kg/min, 30, 40, and 50 °C, and 500, 750, and 1000 W/m2. Various techniques were used to characterize the functionalized nanofluids’ stability and morphological properties namely UV/Vis spectrophotometry, EDX analysis with a Scanning Electron Microscope (SEM), zeta potential, and nanoparticle size. The results showed that the collected heat improved as the percentage of GrNPs and the fluid mass flow rates increased, although it decreased as the reduced temperature coefficient increased, whereas the maximum increase in collector efficiency at higher concentration was 13% and 12.5% compared with distilled water at 0.025 kg/s. Finally, a new correlation was developed for the base fluid and nanofluids’ thermal efficiency as a function of dropped temperature parameter and weight concentration with 2.758% and 4.232% maximum deviations.

A flat plate solar collector (FPSC) was analytically studied, with functionalized graphene nanoplatelets (f-GNPs) as its working fluid. Four samples (wt % nanofluids) were prepared in different base fluids such as ethylene glycol (EG), distilled water (DW):EG (70:30), and DW:EG (50:50). Experimental results (via DW) were used to verify the effectiveness of the analytical model. Some of the operating conditions were taken into account in this research, including temperatures, power, and mass flow rates. Experimental techniques were used to elucidate the modified nanofluids’ physicochemical properties, such as its particle sizes, stability, and morphology, involving electron microscopes (EMs), UV–VIS, and X-ray techniques. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were applied to test the thermal analysis. The findings confirmed that the use of f-GNPs nanofluids enhanced the performance of the FPSC relative to the use of base fluids for all testing conditions. The maximum enhancement of the collector’s effectiveness at a mass flow rate of 1.5 kg min−1 and a weight concentration of 0.1 wt %, increased to 12.69%, 12.60%, and 12.62% in the case of EG, DW:EG (70:30), and DW:EG (50:50), respectively. The results also confirmed an improvement in both the heat gain (FR(τα)) and heat loss (FRUL) coefficients for the f-GNPs nanofluid.

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.

Flat plate solar collectors (FPSCs) have gotten a lot of attention in the last decade because of their ease of installation and design. The current study focused on numerical aspects of a three-dimensional (3D) inclined tube-on-absorbing sheet solar collector. The numerical model was considered to work under a conjugated laminar mixed convection heat transfer mechanism in the range of 100 ≤ Re ≤ 1300. CuO/H2O nanofluids were used as the working fluids. The impact of different parameters on the thermal efficiency of the current FPSC, including inlet temperature, nanoparticle size, volume concentration, and various copper oxide morphologies, on the heat transfer, thermodynamics, thermal, and economic performance, was studied. According to simulation results, the solar collector using distilled water (DW) under 293 K performed better in terms of heat transfer and energy efficiency than those using 303 K and 313 K. In comparison to other sizes and volume concentrations, nanosphere nanofluids with 20 nm and 4% showed higher hydrothermal performance characteristics. Nanoplatelets-shaped CuO nanofluids illustrated the higher values for pressure drop, heat transfer, energy gain, energy efficiency, and lower values for surface plate temperature and outlet temperature, followed by nanocylinders, nanoblades, nanobricks, and nanospheres, respectively. The economic performance indicators recommended that nanobricks CuO nanofluids with 1% volume fraction were the best fluid replacement for water in solar collector applications.

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.

Among different sources of renewable energy, solar energy is widely used almost exclusively because of its ease of availability and its lowest environmental effects. The most commonly used solar collectors are the flat plate solar collectors (FPSCs). However, they are less powerful (low capacity to convert solar energy to thermal energy). It is possible to classify the use of nanofluid on FPSCs as an efficient way to boost the solar collectors’ performance. In this paper, studies on metal oxides, non-metal oxides, solid metals, semiconductor nanomaterials, carbon nanostructured, and nanocomposite nanofluids used as heat transfer fluids (HTFs) within FPSCs are examined sequentially. Various parameters affecting the FPSC’s thermal efficiency, such as nanoparticle type, nanoparticle concentration, nanoparticle size/shape, solar radiance, and mass flow rate, are extensively analyzed. Studies have also compared various types of single nanofluids or mixture nanofluids with FPSCs under the same operating conditions. It is found that the use of carbon-based nanofluids compared to metal oxides of nanofluids under the same conditions has resulted in a major improvement in the energetic and exergetic performance of the FPSC. Furthermore, the reviewed research revealed that there is a tremendous opportunity to achieve the commercial application of carbon-based nanofluid FPSC. The obstacles and opportunities for further study are also highlighted.

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.

A covalent functionalization approach was utilized for the preparation of highly dispersed pentaethylene glycol-thermally treated graphene-water as the absorbing material inside a flat-plate solar collector. Four mass fractions of nanofluids were prepared (0.025, 0.05, 0.075, and 0.1 wt% pentaethylene glycol-thermally treated graphene-water). Graphene nanoparticles were characterized by energy dispersive X-ray analysis with a scanning electron microscope. Measurements of the thermophysical properties were subsequently carried out for the nanosuspensions. The raw investigation data were collected from an indoor flat-plate solar collector test setup. The experimental procedure included different sets of variables such as input temperatures of 303, 313, and 323 K; fluid mass flow rate of 0.00833, 0.01667, and 0.025 kg s−1; and heat flow density of 500, 750, and 1000 W m−2. The thermophysical tests of pentaethylene glycol-thermally treated graphene-water nanofluids showed a proportional increase against weight concentrations, while the specific heat power was reduced. The tests showed an increment in energy efficiency by increasing the fluid mass flow rate and heat input. By comparison, the thermal efficiency decreased with the increasing temperature of the fluid supply. Relative to the base fluid, the energy efficiency of pentaethylene glycol-thermally treated graphene/water-based flat-plate solar collector increased to 10.6%, 11%, and 13.1% at the three fluid mass flow rates. In conclusion, an exponential form was used to derive the thermal effectiveness of flat-plate solar collector based on the experimental data.

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.

In this paper, a nonlinear autoregressive neural network with exogenous inputs (NARX) is proposed to model the dynamic behaviour of an automotive air conditioning (AAC) system equipped with a variable speed compressor. Two popular network architectures of artificial neural network namely multilayer perceptron (MLP) and radial basis network (RBN) are adopted to simulate the transient cabin temperature under random modulation of compressor speed. The input and output data required for the system identification are collected from an experimental bench made up of the original components of an AAC system. Optimization of network structure is conducted for the respective network architecture to study the effect of model structures on the model predictive performance. One-Step-Ahead (OSA) and Model Predicted Output (MPO) prediction tests are used to validate and verify the model. Investigation results show that NARX model with the investigated network architectures can be a powerful tool in identifying the nonlinear AAC system. However, a comparison between them signifies the advantage of MLP model over RBN model in term of network complexity, generalization capability and robustness against the presence of noise in the training data. The identified model of the AAC system can be used for further implementation in a model based intelligent control of an AAC system equipped with a variable speed compressor.

In this paper, a Model Predictive Controller (MPC) using an online trained artificial neural network (ANN) as the nonlinear plant model is implemented for an automotive air conditioning (AAC) system equipped with a variable speed compressor (VSC). The training scheme using Levenberg–Marquardt algorithm and sliding stack window technique is incorporated to train the ANN model in real time so that the time varying dynamics of the AAC system can be captured throughout the control process. The ANN model is initially identified offline using the training and testing data obtained from the experimental AAC system. Validation of the neural network is performed using one-step-ahead and 10-steps-ahead prediction tests. Subsequently, several experimental tests are carried out on the AAC test bench to verify the capability of the proposed controller in tracking set point changes and rejecting disturbances. In order to show the advantages of incorporating an online trained ANN in the proposed controller, comparative assessment is performed between the proposed adaptive controller and two other control schemes, namely a MPC using an offline trained ANN model and a conventional PID controller. The experimental results signify the superiority of the proposed control scheme in terms of reference tracking as well as disturbance rejection due to its adaptation capability in capturing the real time AAC system behaviour over the wide range of operation conditions.

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.