Journal of Advanced Research in Fluid Mechanics and Thermal Sciences

Cooling Period Strategies in an Intermittent Usage Building: A Case Study of a Mosque in the Tropical Climate of Malaysia

Sun, 10 Nov 2024 00:00:00 +0700

Mosques are used five times a day according to the prayer schedule, which follows the sun's position. Indoor thermal conditions in air-conditioned mosques are maintained with a cooling time pattern that follows prayer times. Therefore, an effective air conditioning operating strategy is needed for energy efficiency. This study aims to investigate the effect of air conditioning intermittent operation time strategies on the energy usage of a mosque. It involves reducing the cooling period before prayer time and swapping active air conditioning periods from pre-prayer calls to post-prayer in the base case. Field measurements in Universiti Teknologi Malaysia – Kuala Lumpur (UTMKL) mosque and simulation using DesignBuilder software were conducted to predict annual specific energy consumption. The results indicate a reduction in specific energy consumption of 5% by operating the air conditioning 10 minutes before the call to prayer. Shifting the pre-prayer call-post prayer cooling period results in an insignificant reduction in energy consumption of 0.3-0.6%; however, it can accommodate extended periods of comfortable conditions for people who perform prayers outside of congregational prayers on time. Furthermore, the results indicate that the cooling period after the prayer time affects the cooling load of the following prayer. This study provides information for architects, engineers, and other stakeholders towards improving energy consumption in religious buildings with intermittent occupancy.

Development of Friction Factor-Generalized Equation for Multi-Shapes Microchannel

Sun, 10 Nov 2024 00:00:00 +0700

The major goal of this research is to use computational fluid dynamics, CFD to derive a generalized friction factor formula for a smooth micro-size channel in a laminar flow regime. Based on the number of channel sides and the Reynolds number value, this generated formula can be used to precisely calculate the friction factor. The microchannel shapes are correlated to the friction factor constant as a function of the number of channel sides, N, starting from infinity for a circular microchannel, down to 3 numbers of N, for a triangular microchannel. The following microchannel shapes with a constant hydraulic diameter of 104 µm are selected, which are triangle, square, pentagon, hexagonal, octagonal, decagon, and circle. The developed equation works for a fully developed laminar flow range up to Reynolds number of 2000. Moreover, the current work results are further compared with the previous results of microchannels for verification within acceptable value of 0.07% to 0.48%.

Droplet Evolution and Stability of Water-in-Biodiesel Emulsion with Biosurfactant

Asghar Ali Ghoto, Abd. Rashid Abd. Aziz, Mhadi A. Ismael — Sun, 10 Nov 2024 00:00:00 +0700

Use of an alternative water-in-diesel emulsion (WiDE) fuel instead of pure diesel in a diesel engine reduces emissions and environmental pollution. However, as time passes, water from the emulsified fuel separates. Emulsion stability is affected by the amount of water, type of surfactant, and emulsion technique. Since biodiesel and biosurfactants are environmentally friendly as compared to pure diesel and chemical surfactants, biodiesel-emulsified fuel can reduce emissions, improve combustion, and improve engine performance. Water-in-diesel droplets split into tiny droplets during secondary atomization, which is believed to be caused by microexplosions. In this study, the effect of biosurfactant on the stability and microscopic behaviour of water-in-biodiesel emulsion (WiBDE) fuel were examined. A mixture of B10 biodiesel, 5% water, and a mixture of surfactant (63% lecithin and 37% TWEEN 85 (0.5–3%)) was emulsified for 20 minutes by using a magnetic stirrer at 1500 rpm. Six WiBDE fuel samples were observed for 10 days, and the microscopic behaviour of fuel droplets was examined. The evolution of droplets leading to micro-explosions was captured at 200 °C, 300 °C, and 400 °C. WiBDE-5, having a 2.5% surfactant concentration, is highly stable and reduces the time of micro-explosion of droplets, which can improve combustion and engine performance.

Rice Bran Oil as Emerging Green Fuels: Exploration on Combustion Behaviours of Single Cylinder Diesel Engine (Light-Duty Engine)

Sun, 10 Nov 2024 00:00:00 +0700

In the current work, an experiment was conducted to examine the combustion properties of a single cylinder compression ignition direct ignition engine fuelled with rice bran oil at different engine loads. The investigation focused on the analysis of cylinder pressure and exhaust gas temperature as key factors in combustion. The fuel blends utilized in this study consist of various proportions of diesel and rice bran oil, including 100% pure diesel (RBO00), a blend of 25% rice bran oil and 75% pure diesel (RBO25), a blend of 50% rice bran oil and 50% pure diesel (RBO50), a blend of 75% rice bran oil and 25% pure diesel (RBO75), and 100% rice bran oil (RBO100). Comparisons are made between the results of an experiment using rice bran oil (RBO25, RBO50, RBO75, and RBO100) and a diesel engine (RBO00). RBO00 exhibits a greater heat output per unit mass compared to RBO25, RBO50, RBO75, and RBO100 blends because of the highest value of calorific value (CV) among others blends. Consequently, RBO00 demonstrated a higher measurement of exhaust gas temperature (EGT). One further contributing factor was the increased exhaust gas temperature (EGT), which led to an extended ignition delay, resulting in a lengthier fuel combustion process and the egress of combustion gas from the combustion chamber at higher temperatures. RBO100 achieved the highest cylinder pressure in both 50 % and 100 % engine load settings. The RBO100 blends fuel successfully achieved the optimal cylinder pressure in both 50 % and 100 % engine load conditions. The cylinder pressure for RBO00 (pure diesel) was the lowest at both half and full loads. The observed decrease in peak pressure can be attributed to the decreased cetane number (CN) and oxygen concentration found in RBO00 in comparison to the mixed fuels of RBOs. This will affect the completion of combustion such as wear and tear for the cylinder and piston. Under both 50 % and 100 % engine load condition, the cylinder pressure for RBO00 (pure diesel) was the lowest. In summary, rice bran oil showed superior combustion behaviour compared to pure diesel, and the mixture blends RBO75 and RBO100 can be thought of as ideal in terms of exhaust gas temperature and cylinder pressure.

Performance Analysis of V-trough Solar Water Heater using Curve Shaped Riser Tubes

Channaveerayya, Gowreesh Subramanya, Nare Sreenivasalu Reddy — Sun, 10 Nov 2024 00:00:00 +0700

An experimental study has been carried out in a V-trough solar water heating system (SWHS) equipped with curve shaped riser tubes (CSRT). By adding CSRT, the performance of the V-trough SWHS has improved. Experiments were carried out at different mass flow rates and different pitch values CSRT. Due to incorporation of reflector and shape of riser tubes leads to better efficiency and performance of the collector. In comparison to a plain tube CSRT offers better thermal performance. The results obtained indicate that curve shaped riser tubes have a larger frictional factor and Nusselt number than the plain riser tubes. As compared to the plain tube, the rise in Nusselt number is 41.04% and 49.43% at 100mm pitch, corresponding to a Reynolds number of 5500 and 14500 respectively.

Study on the Effect of Intake Air Temperature towards RCCI Mode Engine of Performance and Emission

Sun, 10 Nov 2024 00:00:00 +0700

Significant progress has been made in the field of research pertaining to combustion engines to lower emissions such as nitrogen oxide (NOx) and carbon monoxide (CO). In recent years, the relative control compression ignition (RCCI) engine has been created to minimize emissions of nitrogen oxides (NOx). This research examines the influence of the intake air temperature has on RCCI-mode engines’ performance and emissions. A modified single-cylinder diesel engine was used to investigate the effects of changing intake air temperature and Primary Reference Fuel (PRF) over a spectrum of engine loads. The result shows that a higher air intake temperature for the RCCI strategy improved the performance of the RCCI engine, especially on fuel mixtures of B0 and PRF40, without comparing to a single fuel strategy, and reduced the amount of NOx emissions in the trade-off between UHC and CO compared to a single fuel strategy. In the not-too-distant future, one of our goals is to do more research on the influence that fuel octane has on port injection rate while maintaining the same values and parameters.

Experimental Study on Heat Transfer Characteristics of a ⊥-shaped Oscillating Heat Pipe Used in the Battery Thermal Management System

Sun, 10 Nov 2024 00:00:00 +0700

This paper introduces a ⊥-shaped oscillating heat pipe (OHP) with the purpose of improving the volumetric utilization of the battery thermal management system (BTMS) for electric vehicles. Distinguished from standard OHP structures, the evaporator and condenser sections of the ⊥-shaped OHP are oriented vertically in spatial arrangement. Experimental investigations were conducted on two types of ⊥-shaped OHPs and a standard OHP, employing filling ratios from 13.1% to 32.6%, working fluid mixtures of acetone with methanol, ethanol, and water, and thermal loads from 10 to 100W. The results indicate that all the OHPs with an acetone filling ratio of 19.6% exhibit minimum thermal resistance at 30W. When employing mixed working fluids, the acetone-ethanol and acetone-methanol combinations display the least and most temperature fluctuations, respectively. The OHP with mixed working fluids achieves no more improved thermal performance than the use of acetone. As the heating power increases, the operational stability of the ⊥-type OHP improves, however, the trend is opposite for the R-⊥-type OHP. In comparison to the standard OHP, the ⊥-type OHP demonstrates stronger oscillation stability at 100W and achieves a 3.3°C lower maximum temperature on the heat collector plate.

Analytical and Numerical Approaches to Optimize the Air Vents Location of Office Space at Different Surrounding Conditions

Sun, 10 Nov 2024 00:00:00 +0700

Optimization becomes an essential tool in all aspects of life. Air entrances and exits locations in any building are one of them that need to be optimized to reduce the energy consumption. Hence, a numerical and analytical investigations of two Models were performed to a teaching assistantship (TA’s) office. The original office design (Model 1) has all the hot and cold air inlets beside the air outlet in the mid-position of the room ceiling. The suggested model of the office (Model 2) is designed by putting the cold air inlet in the middle of the ceiling, whereas the hot air inlet in the middle of the floor close to the widow of the office. The air outlet was kept in the middle of the room ceiling. These models analysed as a function of the ambient temperatures in the 21st of four months (December, March, June, and September) within the periods 9:00, 12:00, and 16:00 h. For more validation, the comparison between the analytical and numerical results of Model 2 is validated with a maximum variation of about 7%. In addition, the analytical room temperature results of Model 1 are higher than Model 2 by 10.3%. Finally, the best average comfortable temperature for humans had been discovered in Model 2 for all cases around 23 ˚C with a maximum error percentage of less than 10%.

Passive Control of Base Pressure and the Flow Development in a Duct with Sudden Expansion at Sonic Mach Number

Sun, 10 Nov 2024 00:00:00 +0700

The primary purpose of this research is to investigate the effectiveness of rib as a passive control to control the flow development around the circular duct at different levels of expansion using Computational Fluid Dynamics (CFD). The nozzle pressure ratio (NPR), rib size, and rib orientation were considered in this research. The L/D ratio is from 3 to 5; the simulated NPRs were 1.5, 2, 3, 4, and 5. The rib was designed with a quarter circular shape to see the method's effectiveness. The focus was on the duct’s base pressure and wall pressure. The results show that the rib size and orientation strongly influenced the base pressure. The base pressure for the model with rib keeps increasing while the base pressure for the model with plain duct shows opposite results as the NPR increases. The base wall's pressure was not affected by nozzle pressure ratio only. Still, other characteristics, such as rib size and orientation, are significant in manipulating the result. However, the rib does not adversely impact the flow in the duct.

Investigation of the Influence of Bulbous Bow on the Wake Field and Power Demand

Alaaeldeen Mohamed Elhadad, Ahmed Mokhtar Abo El-Ela, Mohamed Mostafa Hussien — Sun, 10 Nov 2024 00:00:00 +0700

Ship resistance is one of the main factors affecting the ship's design and the selection of her propulsion system. Propeller designers must accurately estimate the wake field in waves behind the ship in order to create effective propeller geometry under actual operating circumstances. In this study, various bulbous bow shapes of the DTMB 5415-51 surface combatant were numerically investigated using a CFD method. The aim of the study is the evaluation of the impact of the bulbous bow shape variation not only on the ship resistance but also on the wake field as well as on the propulsion performance. Three-dimensional URANS numerical flow simulations of combatant ship were applied and systematically altered bow shapes in calm water and waves were carried out. For the validation of the numerical simulations, three alternative mesh sizes for Froude numbers ranging from 0.10 to 0.40 are considered; results are compared with those of the towing tank in terms of wave field, resistance coefficients, and propulsive efficiency. The results show a considerably different hydrodynamic characteristics for different bow shapes.

Application of Response Surface Methodology (RSM) for Optimizing the Food Grade Bio Lubricant

Sun, 10 Nov 2024 00:00:00 +0700

With growing global concerns about the production of environmentally friendly lubricants, efforts to develop vegetable oil-based alternatives to mineral oil-based lubricants are gaining growth. However, the properties of vegetable oil-based lubricants such as poor low-temperature behaviour, low oxidative stability and poor thermal stability are concerning for industrial gear lubricant applications. Although the number of researches of using vegetable oil-based as an alternative lubricant, the scientific research for industrial gear oil application have not been studied adequately. As a result, the purpose of this study is to investigate the friction coefficient and wear rate of the blended oil using a pin-on-disc test experiment and then compare it to food grade oil, with the hope that the findings will assist the food industry in improving their machinery. Response Surface Methodology (RSM), a Box- Behnken Design approach, has been employed to optimize the lubricant characterization based on the results. The effects of three independent variables—load, speed, and additive concentration—on the coefficient of friction and wear rate have been investigated in this study. The number of tests has been reduced to 15 using this RSM methodology. At the speed of 600 RPM, 30 N load and 30% concentration concluded the lowest predicted wear rate was -38.1986 m3 /m. These results showed that blending palm oil with gear oil can increase the development of biodegradable and environment-friendly lubricants without concerns about downgrading the tribological performance.

Modelling for Climate Adaptation in Urban Drain Design with Orifice Flow Restrictor

Sun, 10 Nov 2024 00:00:00 +0700

Due to the increasing stormwater runoff in urban areas, stormwater infrastructure requires modification to address the flash flooding issues. Occurrences of floodwater overflowing the urban drain have urged drainage engineers to re-look its design. Conventionally, the urban drain is designed to free flow following the provided drain slope. This paper is challenging the old design by introducing orifices into the drain. The lesser-known stormwater characteristics restricted by orifices in open drains were investigated. In this case, twenty-four units of terrace houses were selected as the study area with special attention to the 170 m front drain with a dimension of 0.5 m x 0.55 m. The drain was inserted with one to three orifices of 0.45 m diameter separating the drain into one or more compartments. Three scenarios were formulated, namely S1 with one orifice plate at 170 m, S2 with two orifice plates at 86 and 170 m, and S3 with three orifices at 50, 110 and 170 m, from the starting point. Storm Water Management Model version 5.0 (SWMM5) was utilized to simulate and represent the unique characteristics of the three scenarios subjected to a 5-minute, 10-year average recurrent interval design storm. The analysis found that S1 had similar patterns with the existing condition and therefore, was insignificant. However, S2 and S3 demonstrated improved regulation of flow and water level along the drain. Between the two scenarios, S3 repeatedly displayed the most stable patterns, for example, S3 had a tight range of water levels between 0.30-0.34 m (compared to existing condition with fluctuating water levels between 0.32-0.50 m) and a tight range of flows between 0.01-0.08 m³/s (compared to existing condition with wider range of flows between 0.01-0.18 m³/s). The flows in S3 were reduced by half by introducing these series of orifices. These results point to an important finding that orifices were not worsening flood flushing in open drain but capable to regulate the flow and water level better than existing condition without any orifice. The capability of orifices to lower water levels allowing more spaces within the drain channel to accommodate climate-induced floodwater.

The Analysis of Building Thermal Comfort based on Air Flow Pattern by using SIMSCALE Simulation

Apif Miptahul Hajji, Whildan Yusriawan, Dian Ariestadi, Huang Yue — Sun, 10 Nov 2024 00:00:00 +0700

Thermal condition is one of the most important elements of comfort, which can affect people’s activities and working circumstances. Thermal comfort in a room can be controlled by improving the quality of ventilation and designing air flow. This study aims to determine the thermal comfort of a building by using simulation. The data used are building design specification, air temperature, and air flow pattern. The simulation input variables are the 3D model of the room design, maximum and average air temperatures and average air flow velocity values. The expected simulation output are air temperature contour data and air flow patterns. These two values of output are then compared with Indonesia’s national standard SNI 03-6572-2001 and subjective reactions to determine comfort in the rooms. The results show that based on the air temperature contour, the wider the room the air temperature tends to be in a comfortable condition. It also shows that the ratio of the opening area to the floor area can influence the cooling of the air temperature in the room. Based on the flow pattern air, openings facing each other in a room will improve air circulation and it is influenced by the ratio of the area of the opening to the area of the room. The research results show that air temperature contours and air flow patterns can be a reference for determining thermal comfort in a room. Regarding the output of simulation, it is recommended that the energy savings calculations need to be carried out to find out how much impact the building's natural ventilation performance has on electrical energy use.

Diagnosing the Process of Forming Biofuel Combustion Mixtures in Diesel Engines by a Program to Compute Spray Volume

Mai Duc Nghia, Ho Duc Tuan — Sun, 10 Nov 2024 00:00:00 +0700

A diesel engine's injection and combustion mixture formation process are essential; it determines the engine's economic, technical, and environmental criteria. When the engine uses biofuel, fuel parameters such as viscosity, density, and surface tension affect the above process. Each engine using a specific fuel type will have to adjust injection parameters such as injection pressure and timing to ensure the injection process and formation of a homogeneous air-fuel mixture. Therefore, through the spray structure, it is possible to diagnose the process of combustion mixture formation, thereby making adjustments to the fuel injection system that will improve engine performance and reduce emissions of toxic exhaust gases. In this study, the article presents the content of building a program to compute spray volume using Matlab software. Through the spray volume, quickly diagnose the process of forming the biofuel-air mixture in the diesel engine combustion chamber, thereby determining the appropriate fuel injection system adjustment. Results of simulation and experimental research on 4CHE Yanmar engines installed on fishing vessels with fuel types DO, B5, B10, and B15 show that the B15 fuel mixture when used for the engine needs to be increased injection pressure is about 10% higher than DO fuel injection pressure.

Performance and Emission Analysis of a CI Engine Fueled with Preheated Neem Straight Vegetable Oil-Diesel Blend at Various Compression Ratios

Gaffar Gulab Momin, Narayan Lal Jain, Bholu Kumar — Sun, 10 Nov 2024 00:00:00 +0700

The twin crisis, fast depletion of limited conventional fuel and environment degradation due to these fuels created a dire need to search for clean, green and sustainable alternatives to conventional fuels. Neem vegetable oil may be an alternative of conventional petroleum fuels due to its abundant availability in India and comparable physical and chemical properties. In the present study, performance and emission characteristics of VCR diesel Engine were observed using preheated and blended straight Neem oil. Initially experimentation was carried out to optimize the neem oil blend at engine optimize conditions which was given by manufacturer but this part is not considered in this research paper. Optimize Neem oil blend B30 (30% Neem oil and 70% Diesel) was used as fuel in the current study. Heat exchanger was design and developed to preheat the blended Neem oil up to 90 to 100 °C using engine exhaust gases. This temperature is sufficient to bring viscosity of blended Neem oil about viscosity of diesel. Performance emission characteristics of diesel engine were evaluated at compression ratios 18, 19, 20, 21 and 22. It was observed that at compression ratio 22, brake thermal efficiency of the engine was found optimum 34.99% using preheated optimum blend B30 which was higher than other compression ratios, diesel (1.64%) and unheated optimized same blend (5.07%). Less emission was observed for pre heated optimized blend B-30 as compared to other compression ratios, diesel and optimized same blend. Smoke opacity, CO, HC, NOx emissions at CR 22 for preheated NOB30 observed lowest 33%, 0.15%, 20 PPM and 340 PPM at full load condition.

Investigation of Vibrational Response of Bio-Lubricants and SAE40 for Journal Bearing Application

Sun, 10 Nov 2024 00:00:00 +0700

Amidst the burgeoning landscape of contemporary industrial growth, journal bearings have become integral components extensively employed across diverse rotating machinery. The intricate dynamics of journal bearings, particularly the robust nonlinear characteristics manifesting in the oil film pressure, constitute a focal point in this study. The research endeavours involve designing a journal bearing test rig (JBTR) to unravel the dynamic properties of journal bearings through a series of experimental trials. The operational speed for the analysis is set to 900 rpm and 1200 rpm to simulate low and high speed operations. The test sample includes conventional lubricants, SAE40 and bio-lubricants, palm olein, soybean and rapeseed oil. The bio-lubricants are compared to SAE40 to validate its vibrational response. The static characteristics (viscosity, eccentricity ratio, attitude angle) which represent the operational factors are also presented. A thorough analysis of the influences of bearing load, eccentric mass and rotational speed on dynamic characteristics yields nuanced insights and specific findings. Journal bearings, essential machine components facilitating relative movement among working parts, bear the dual role of load distribution and preservation of positional stability. Vibrational diagnostics, tantamount to the meticulous scrutiny of vibrational parameters, emerges as a pivotal technique for the comprehensive diagnostics of critical machinery in industrial plants. Earlier studies underscore the significance of bearing issues, attributing approximately 40% of machine failures to such concerns. Consequently, researchers actively discern the causative factors of bearing damage and pioneering innovative techniques for detecting destructive bearing issues. The experimental result from JBTR showcase the capabilities of bio-lubricants during operations yielding results such that, at 900 rpm the velocity reactions is at 14% average difference compared to SAE 40, displacement value at 1% and 46% average percentage diffenrence at 25%. While at 1200 rpm, the velocity value also shows at 14% differences compared to SAE40,displacement percentage at 25% and acceleration percentage difference of 44%. The initial hypothesis may suggest a probable applications of bio-lubricants within rolling bearings system.