Journal of Engineering Science

CFD Analysis on HVAC System Functionality in an Amphitheater

M M Rahman, M M Hasan — Mon, 29 Jan 2024 00:00:00 +0000

Heating, Ventilation and Air conditioning (HVAC) is an important part of residential structures such as single-family homes, apartment buildings, hotels and medium to large industrial and office buildings such as skyscrapers and hospitals, on ships, submarines and in marine environments.This paper investigates the characteristics of the performance HVAC system at “KUET auditorium” regarded as amphitheater for various internal and external conditions. A 2D model of the longitudinal section of the auditorium was drawn by using ANSYS-Fluent software in Design Modeler, for simulating the various functionality of the HVAC system for both summer & winter seasons. In this research, both the indoor & external conditions of KUET auditorium were considered, having the entire spectacle of hall is occupied by people. The main aim of this study was to observe the air temperature, air velocity and relative humidity for each case. The results are represented comparatively as graphs and spectra for various mass flow rates and indoor-outdoor temperatures. It was observed that the HVAC system provided sufficient human comfort conditions in terms of air flow and relative humidty recommended by (American Society of Heating, Refrigerating and Air Conditioing Engineers) AHRAE in the amphitheater for both the summer and winter season.

Journal of Engineering Science 14(2), 2023, 01-14

Hazardous Free and Natural Colorization of Blended Fabric Utilizing Coffee with The Attainment of Acceptable Functional Properties

Mon, 29 Jan 2024 00:00:00 +0000

In this study, blended fabric like 65% polyester 33% rayon 2% spandex was naturally dyed utilizing coffee with maintaining of all the quality parameters. In the coffee-dyed fabric, carcinogenic element like formaldehyde was not detected. The bursting strength of the fabric was unchanged after dyeing and the fabric composition was identically tantamount. The color levelness of the dyed fabric was satisfactory and the color fastness to washing rating was 4-5. Colorfastness to perspiration in both acid and alkali medium was excellent containing a rating of 4-5. The naturally dyed fabric was able to hinder the microbial effect, and the entire dyeing procedure was convenient. Due to the absence of detrimental elements, the coffee-dyed fabric could be utilized to prepare hygienic garments items; baby wears products. The main function of this article is to enhance the functional properties of traditional fabric which is improving with the utilization of natural ingredients.

Journal of Engineering Science 14(2), 2023, 15-20

Development of an IoT-Based Automatic Remote Health Monitoring System

Pallab Kumar Nandi, Tahmida Tabassum, Mohiuddin Ahmad — Mon, 29 Jan 2024 00:00:00 +0000

A well-planned health monitoring system is essential for the modern health center, and a portable remote health monitoring system with many intellectual features is becoming a great improvement in healthcare arrangements. The proposed system includes various micro-electronics medical devices and applications that come through network-connected devices and help to monitor patients' real-time medical data. In this paper, the patient's health condition has been monitored by using the four types of major health parameters temperature sensor, heart pulse rate sensor, blood pressure sensor module, and blood oxygen (SpO2) sensor. All the sensor nodes are connected to the Raspberry Pi-based embedded system. The real-time health data are recorded, stored, and transmitted to the doctor via the internet with the help of a Raspberry Pi-based embedded system and IoT server. The system will benefit the patient from remote areas with quick diagnosis, remote observation, home observation, and a medical data storage system.

Journal of Engineering Science 14(2), 2023, 21-30

Mixed Convection in Ferrofluids Vertical Layer with Inclined Magnetic Field

Md Habibur Rahman, Mst Lovly Khatun , Sushmita Mondal — Mon, 29 Jan 2024 00:00:00 +0000

In this article, the flow characteristics and linear stability of mixed convection in a ferrofluid layer are investigated. The fluid layer is positioned between two vertically oriented and differently heated nonmagnetic plates under an inclined magnetic field with non-zero gravity. This study involves the patterns of fluid motion, heat transfer, and the effects of the inclined magnetic field with gravitational action. The objective of this article is to analyze the flow characteristics of smaller Prandtl number of fluid and figure out the significant comparisons with larger Prandtl numbers of fluids. The characteristic of every instability mode is examined for a fluid having a different Prandtl number than the one that was previously investigated. The influence of buoyancy effects undergoes a notable transformation, shifting from a destabilizing role in flows dominated by gravity to a stabilizing role in flows characterized by stronger magnetic effects. It is found that in both normal and oblique magnetic fields, the basic flow evolves into a state of greater stability, and wave propagation is faster with lower Prandtl numbers of fluids than with larger Prandtl numbers of fluids.

Journal of Engineering Science 14(2), 2023, 31-45

An IoT-based Smart Doorbell System for Mitigating Stealth Attacks

Martins Osifeko, Godswill Iroegbu, Ayodeji Okubanjo — Mon, 29 Jan 2024 00:00:00 +0000

The need for smart doorbell systems has increased in recent times. This is due to the general tendency for burglars to use stealth when breaking into homes and businesses. Also, visitors are known to spend time searching for doorbells around the house. Thus, to address this problem, this paper presents a smart doorbell system that detects human presence at the door and automatically notifies the homeowner. The system consists of a microcontroller, ultrasonic sensor, GSM module, and software. When a human presence is detected within the configured range of 1 to 70cm, the ultrasonic sensor sends a signal to the microcontroller, which in turn sends a command to the GSM module to notify the homeowner. The performance of the system was tested using various parameters with results showing that the device can detect human presence within the range of 1-80cm.

Journal of Engineering Science 14(2), 2023, 47-58

A Study on the Heat Wave Conditions over Bangladesh During 1990 - 2019

Mon, 29 Jan 2024 00:00:00 +0000

When temperature exceed 36 degrees with a large area and linger for minimum three or more days can be considered as heat wave (HW). In the Pre-monsoon, the sun ray drops down on the ‘Thar’ desert (India) and the foothill of the Himalayas vertically, the area makes a hot-tempered zone. That is why, these regions produce a trough of low and there is a possibility to advect temperature towards Bangladesh. The south/south westerly wind carries a high amount of moisture over Bangladesh. The heat capacity of moisture is higher than that of dry air. Solar insulation, temperature advection and moisture incursion are three main phenomena that are responsible for HW condition. Veering is also responsible for especially severe and very severe HW conditions. The present study is accompanying with all category’s frequency of heat wave days (HWD) and HW for the Pre-monsoon (March to May) over most of the stations (34) of Bangladesh for the period 1990-2019. Microsoft excel, Surfer and Arc GIS software have been used for data calculation, however, linear trend analysis and Mann-Kendall test have been used to draw the trend of HW frequency. The highest numbers of HWD are found in Jashore (30.9 days) of all types of events whereas the highest frequencies of HW are found in Rajshahi (4.2333) during pre-monsoon season. The lowest numbers of frequency of HWD and HW, both are found at Chattogram. April is the hottest month in Bangladesh. On the basis of frequency of HWD, the obtained highest hot places are Jashore, Chuadanga, Rajshahi, Ishurdi and Satkhira. while in Kutubdia and Teknaf, no HW is found at all. Among 30 years, 2014 is found the hottest year and 2018 is the recorded lowest hot year. By Mann-Kendall test, the HW trend of M. Court, Mongla, Patuakhali and Chandpur have indicated positive significant value, and Mymensing station has given only negative significant value. From spatial distribution, it shows the hottest areas which are south western and middle-western parts of Bangladesh.

Journal of Engineering Science 14(2), 2023, 59-67

Manganese Oxide Based Core@Shell Nanoparticles and Its Application in Aqueous Zinc-Ion Battery

Mon, 29 Jan 2024 00:00:00 +0000

In this study, MnO₂ as well as core@shell type MnO₂@Ag material were prepared through the versatile reverse micelle route. FTIR absorption band at 522 cm^-1 was ascribed to the Mn-O stretching mode, demonstrating the presence of a Mn-O bond inside the MnO₂ structure. XRD was used to determine the crystalline structure of the prepared samples. Peaks at 2θ = 12.7°, 18.1°, 28.8°, 37.5°, 42.1°, 49.9°, 56.2°, and 60.3° matched the α-MnO₂ diffraction peaks nicely. The spherical shape of the produced MnO₂ and MnO₂@Ag compounds was observed in FESEM. The results of the histogram show that MnO2@Ag particles are marginally smaller than MnO2 particles. The electrochemical assessment of the generated cathode materials for aqueous zinc-ion battery (AZIB) CR-2032 was conducted using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and battery charge-discharge (BCD) techniques.

Journal of Engineering Science 14(2), 2023, 69-77

Parametric Optimization and Efficiency Assessment of Horizontal Earth Water Pipe Heat Exchanger (EWPHE) in the Context of Bangladesh

Mon, 29 Jan 2024 00:00:00 +0000

This study aimed to evaluate the efficiency of the Earth Water Pipe Heat Exchanger (EWPHE) system in Bangladesh through simulation and experimental work carried out at Joypurhat in Bangladesh during the coldest period of the year, January. Additionally, the study sought to establish the method for selecting optimal installation parameters of EWPHE to increase performance and efficiency. A simulation model was made in the TRNSYS (v16.0) platform to determine the optimum values of design parameters. The simulation was run by altering its operating parameters, such as the rate of water flow, length of the pipe, built materials of the pipe, and the diameter of the underground pipeline. According to the findings, pipe burial can be done to a depth of 3.5 meters to achieve optimal output. The results of comparing four distinct materials, namely GI, Steel, PVC, and HDPE, show that these materials' characteristics do not significantly affect how well the systems perform. Additionally, as the water flow rate is increased, it is shown that the EWPHE performance is declining. According to the simulation results, it is concluded that a pipe with a length of 50 meters would be sufficient in the proposed EWPHE system to reach an average temperature decrease from 35 °C to 27 °C. Subsequently, in the field experiment, the EWPHE system had an average efficacy of 55% throughout January, which is quite promising.

Journal of Engineering Science 14(2), 2023, 79-88

Steam Boilers in Ready-Made Garments Industry in Bangladesh: Existing Scenario and Scope for Development

Mon, 29 Jan 2024 00:00:00 +0000

Bangladesh's Ready-Made Garments (RMG) industry, historically prone to hazards including boiler explosions with numerous fatalities, has prompted the RMG Sustainability Council (RSC) to initiate boiler safety inspections. This study addresses the lack of empirical data on boiler operations in RMG factories, focusing on operational scenarios, risk factors, and remediation strategies. Conducted from March 2021 to March 2023, structured visual inspections across 1386 RMG factories assessed 2204 boilers. Key findings reveal that 34.99% of factories predominantly use a single boiler, 91.24% of boilers are government-registered, and the majority are imported (63.29%) with a steam generation capacity below 1,000 kg/hr (59.75%). Additionally, 63.11% were manufactured between 2010 and 2019, 79.63% burn fossil fuels, 54.60% are vertically oriented, and 82% use softened feedwater. The study also identifies 32 external risk factors across 11 categories, providing insights for decision-makers to enhance boiler operation safety and sustainability. By leveraging this inspection data, the research aims to bridge the empirical gap and offer a comprehensive understanding of the existing challenges in RMG boiler operations.

Journal of Engineering Science 14(2), 2023, 89-105

Measuring Compact Development Potential of an Emerging Urban Area: A Case of Savar

Md Muktadir Rahman — Mon, 29 Jan 2024 00:00:00 +0000

Compact development is an urban development policy aimed at promoting high density mixed used city to improve city’s environmental condition. Savar is a fast-growing outer urban area of the capital Dhaka, which is growing through rapid urbanization in the recent decade. As enormous population growth causing the capital city to expand beyond city boundary, Rajdhani Unnayan Kartripakkha (RAJUK), the Capital Development Authority of the Government of Bangladesh has identified Savar as one of the five outer urban areas in the Regional Development Plan (RDP) known as Dhaka Structure Plan (2016-2035) for promoting compact development where various activities of the capital city will shift to minimize the congestion of the core city. For successful implementation of this strategy a careful investigation of the existing spatial structure of these areas is essential for guiding future urban development. Therefore, this study aims to evaluate the potential of these proposed urban areas to accommodate their future growth in a compact manner focusing on Savar, an established urban area of the Dhaka Metropolitan Region. For assessing the compact development potential of Savar, this paper analyzed six indicators of two major aspects of urban form, population and land use pattern using Geographical Information System (GIS). The results of this study revealed that the growth pattern of Savar is still not compact and efficient planning mechanism should be devised for its future growth in a sustainable manner. The findings of this study will help policymakers, planners, architects and development authorities in policymaking, planning and designing a more sustainable and efficient urban area through compact urban development at intra-urban level.

Journal of Engineering Science 14(2), 2023, 107-125

Impact of Climate Change on Precipitation and Temperature Changes in the Northwest Region of Bangladesh Using SDSM: A Comparison of CanESM2 and HadCM3 Models

Md Masud Rana, Sajal Kumar Adhikary — Mon, 29 Jan 2024 00:00:00 +0000

Assessment of climate change-induced precipitation and temperature changes is crucial for the adaptive and sustainable management of water resources in a country. The objective of this study is to explore the impact of climate change on future precipitation and temperature changes in the northwest region of Bangladesh using the statistical downscaling model (SDSM). In this study, Rajshahi station is taken as the case study area, and two widely applied general circulation models (GCMs), namely the Canadian Earth System Model (CanESM2) and the Hadley Center Coupled Model (HadCM3), are used for the climate change analysis. The results demonstrate that after bias correction, the CanESM2-based downscaling model performs better compared to the HadCM3-based downscaling model. The bias-corrected models for both GCMs are then employed for the projection of future precipitation and temperatures for the 2040s and 2090s, considering climate change scenarios. The precipitation trend is found to be negative for both GCMs in all scenarios. Considering the worst climate change scenarios for both GCMs (i.e., the RCP8.5 scenario in the CanESM2 and the A2 scenario in the HadCM3), the mean annual precipitation will be decreased by 9.3% and 4.5% in the 2040s and 12.1% and 4.1% in the 2090s. Furthermore, the mean annual maximum temperature will be increased by 0.233°C and 0.245°C in the 2040s and 0.468°C and 0.633°C in the 2090s, whereas the mean annual minimum temperature will be increased by 0.394°C and 0.188°C in the 2040s and 0.394°C and 0.357°C in the 2090s. Thus, the current study comes to the conclusion that decreased precipitation and increased temperatures will have an effect on the water resources in the study region, leading to a reduction in the overall supply of surface water and groundwater storage. It is expected that the study findings will help water managers and policymakers in developing a framework for sustainable and adaptive water management in the face of climate change.

Journal of Engineering Science 14(2), 2023, 127-136

Effects of Heat Generation and Chemical Reaction on Time-Dependent MHD Natural Convective Transport Past in a Vertical Perforated Sheet

Md Abu Bkar Pk — Mon, 29 Jan 2024 00:00:00 +0000

This investigation focused on the impacts of heat production and chemical reaction on time-dependent MHD-free convective transport via a vertical permeable sheet. The ODEs are obtained by transforming the governing PDEs using similarity transformations. With the assistance of MATLAB software, the shooting technique is utilized to numerically resolve the non-dimensional governing equations with boundary conditions. The role of emerging non-dimensional parameters or numbers like the Schmidt number , heat generation parameter (Q), Prandtl number , and chemical reaction parameter (Kr) on fluid temperature, velocity, and concentration were discussed within the boundary layer. The results show that temperature and fluid motion are improved by raising the heat generating parameters. On the contrary, as the chemical reaction value goes up, the fluid velocity and concentration do as well.

Journal of Engineering Science 14(2), 2023, 137-144

Micro-Characterization of Recycled Concrete Aggregate

Muhaiminul Islam Alim, Kazi ABM Mohiuddin — Mon, 29 Jan 2024 00:00:00 +0000

Recycled concrete aggregate (RCA) is generated by crushing and processing concrete waste from demolition and construction activities, thereby reducing the environmental burden associated with disposing of concrete debris. The use of RCA in concrete production helps to alleviate the depletion of natural resources, as it serves as a substitute for traditional coarse and fine aggregates. This study identifies the microstructural aspects of RCA concrete, employing advanced techniques like scanning electron microscope (SEM) imaging with energydispersive spectroscopy (EDS) to analyze the microstructure and chemical composition of recycled concrete. The detailed microstructural analysis is anticipated to elucidate how the RCA content influences the interfacial transition zone, bond strength, and overall concrete performance. RCA exhibits a unique microstructure due to the presence of attached old mortar, which can influence the overall performance of RCA concrete. This study also explores the utilization of 100% RCA in preparing recycled concrete, comparing it with old and ordinary new concrete. The focus is on microstructural properties, hydration products, and the Interfacial Transition Zone (ITZ) between cement paste and aggregates. Samples were collected from a 47-year-old building, separating aggregates into different grades. Recycled coarse aggregates and recycled fine aggregates were obtained, and natural aggregates were collected. Concrete mixes for recycled and natural concrete were designed for a test strength of C30. Concrete cylinders were tested for compressive strength at 7, 28, and 90 days. Old concrete exhibited a dense microstructure with well-formed C-S-H gels, contributing to its superior strength. Recycled concrete, however, showed a wider and less dense ITZ, resulting in a more porous microstructure. EDS spectra confirmed C-S-H gel as the primary hydration product in all mixes, with the Ca/Si ratio varying, indicating complexity in hydrated product formation. The research highlights differences in microstructural and chemical characteristics among old concrete, ordinary new concrete, and recycled concrete. The wider ITZ and more porous microstructure in recycled concrete contribute to reduced strength. These findings provide insights into sustainable construction practices, promoting the use of recycled materials and addressing environmental challenges in the construction industry. As the construction industry continues to embrace sustainability, further research into the properties, performance, and best practices for incorporating RCA into concrete will play a pivotal role in advancing eco-friendly construction methodologies.

Journal of Engineering Science 14(2), 2023, 145-155