REYNOLDS NUMBER DEPENDENCE ON THE EFFECT OF AXIAL STRESS ON UNSTEADY POLYVINYL CHLORIDE PIPELINE FLOW

This paper studies the Reynolds number dependence on the effect of axial stress on unsteady pipeline flow. The unsteadiness is caused by sudden and gradual closure of the valve situated at the downstream end of the pipe. The effect generated by the unsteadiness is controlled by varying the Reynolds number (Re). Measurements were taken at different part of the pipe for a full and half closure of the valve at various Reynolds numbers. The pressure head obtained increase as Reynolds number (Re) increases, measurement clearly shows that Reynolds number majorly control the response of the pressure head although other factors like pipe geometry and wave speed which is a function of material properties and working fluid also contribute. Reynolds number control the magnitude but the wavelength of oscillation is unaltered. For all values of Reynolds numbers considered in this study (3750, 4125, 4750, 5250, 6000) with Polyvinyl Chloride (PVC) material used as pipe, its variation caused pressure head to increase, decrease with time until another steady state is reached which make it constant after a particular time for the Reynolds number considered

Examination of Students’ Academic Performance in Selected Mechanical Engineering Courses Prior-to-and-During COVID-19 Era

Advances in Information and Communications Technology (ICT) as well as the present challenges of COVID-19 have led to a new paradigm causing an absolute or partial transition from in-person classroom teaching-learning to online. There is little information available on research efforts that investigated the impact of an online learning approach on the academic performance of students in mechanical engineering-based courses. Therefore, the objective of this paper is the impact study of online learning mode as compared to in-person on academic performance of students in selected mechanical engineering courses in one of the Universities in South Pacific Islands prior-to-and-during COVID-19 Era. Data on grades obtained for 178 students that offered Fluid Mechanics, Thermodynamics, Heat Transfer, and Advanced Thermofluids (FTHA) courses were subjected to descriptive and non-parametric (Mann-Whitney and Kruskal-Wallis) statistical tests. Although descriptive analysis showed that online mode of instruction might influence a better academic performance in FTHA courses in comparison with in-person mode of instruction, the outcome of Mann-Whitney U and Kruskal-Wallis tests at specific p-values and corresponding z-values generally exhibited p-values higher than of 0.05, implying insignificant difference in performance between the two modes of learning investigated. Though the non-parametric statistical test results showed there was no significant difference in academic performance of students when online and in-person modes of learning were used, this, however, does not imply that a difference does not exist at all. Although the difference may be very trivial, descriptive analysis has shown that the online learning mode has at least exhibited better students’ academic performance when compared to in-person. It can be inferred from the foregoing that the online learning mode does not yield a negative response in respect of the performance of students who offered all four mechanical engineering courses. Based on the findings of this study, online is considered a reliable alternative to in-person or at least a suitable complement to in-person in the in-person-online hybrid mode during the ongoing COVID-19 era and other inevitable constraints in the future. Doi: 10.28991/esj-2022-SPER-017 Full Text: PD

Wind energy evaluation for electricity generation using WECS in seven selected locations in Nigeria

This paper statistically examine wind characteristics from seven meteorological stations within the North-West (NW) geo-political region of Nigeria using 36-year (1971–2007) wind speed data measured at 10 m height subjected to 2-parameter Weibull analysis. It is observed that the monthly mean wind speed in this region ranges from 2.64 m/s to 9.83 m/s. The minimum monthly mean wind speed was recorded in Yelwa in the month of November while the maximum value is observed in Katsina in the month of June. The annual wind speeds range from 3.61 m/s in Yelwa to 7.77 m/s in Kano. It is further shown that Sokoto, Katsina and Kano are suitable locations for wind turbine installations with annual mean wind speeds of 7.61, 7.45 and 7.77 m/s, respectively. The results also suggest that Gusau and Zaria should be applicable for wind energy development using taller wind turbine towers due to their respective annual mean speeds and mean power density while Kaduna is considered as marginal. In addition, higher wind speeds were recorded in the morning hours than afternoon periods for this region. A technical electricity generation assessment using four commercial wind turbines were carried out. The results indicate that, while the highest annual power is obtained with Nordex N80–2.5 MWas 14233.53 kW/year in Kano, the lowest is in Yelwa having 618.06 kW/year for Suzlon S52. It is further shown that the highest capacity factor is 64.95% for Suzlon S52–600 kW in Kano while the lowest is 3.82% for Vestas V80–2MW in Yelwa

Magnetic Field Enhancement in Ammonia-Water Absorption Refrigeration Systems

Absorption enhancement has been considered as an effective way of improving coefficient of performance (COP) of refrigeration systems and magnetic enhancement is one of these methods. A model of magnetic field enhancement in ammonia-water absorption systems is presented in this paper. A numerical model using finite difference scheme was developed based on the conservation equations and mass transport relationship. Macroscopic magnetic field force was introduced in the momentum equation. The model was validated using data obtained from the literature. Changes in the physical properties of ammonia solution while absorbing both in the direction of falling film and across its thickness were investigated. The magnetic field was found to have some positive effect on the ammonia-water falling film absorption. The results indicate that absorption performance enhancement increased with magnetic intensity. The COP of simple ammonia solution absorption refrigeration system increased by 1.9% and 3.6% for magnetic induction of 1.4 and 3.0 Tesla respectivel

Performance evaluation of wind turbines for energy generation in Niger Delta, Nigeria

This paper evaluates wind energy potentials of seven selected locations spreading across Niger-Delta region of Nigeria using wind speed data that extend over 9 to 37 years and subjected to 2-parameter Weibull distribution functions. The performance of four wind turbine models ranging from 35 to 500 kW was simulated in all the locations considered. The results show that the performance of all the wind energy conversion systems gave the least energy output values at Ikom. In addition, annual energy output ranged from 4.07 MWh at Ikom to 145.57 MWh at Ogoja with Polaris America (100 kW) and Zeus Energy (500 kW) wind turbines respectively. It was also observed that, irrespective of the site, G-3120 (35 kW) wind turbine has the highest capacity factor among the models considered. Therefore, for wind energy development, G-3120 model or wind turbine with similar rated wind speed would be most suitable in all the locations. The number of inhabitants that can be served by the energy produced using G-3120 turbine in each location was estimated

Generation of a typical meteorological year for north–east, Nigeria

The Finkelstein–Schafer statistical method was applied to analyze a 34-year period (1975–2008) hourly measured weather data which includes global solar radiation, dry bulb temperatures, precipitation, relative humidity and wind speed in order to generate typical meteorological year (TMY) for five locations spreading across north–east zone, Nigeria. The selection criteria are based on solar radiation together with the dry bulb temperature values and representative typical meteorological months (TMMs) were selected by choosing the one with the smallest deviation from the long-term cumulative distribution function. A close-fit agreement is observed between the generated TMY and long-term averages. The TMY generated will be very useful for optimal design and performance evaluation of solar energy conversion systems, heating, ventilation, and air conditioning (HVAC) and other solar energy dependent systems to be located in this part of Nigeri

Solar energy applications and development in Nigeria: Drivers and barriers

In this study,current perspectives of solar energy utilization as a renewable energy option in Nigeria are examined and discussed from the stand point of sustainable development.The country being a world crude oil and natural gas producer,is over-dependent on the seenergy sourcesforelectricitygeneration and otherenergyapplications.Thishascurrentlyputthecountryatariskofimpendingenergycrisesin view ofthefastdiminishingfossilreserves,inadequaterefining capacitytomeetdomesticconsumption and seriouscasesofenergyinsecurityinrestiveregionswhereexploitationsexist.Inspiteofthevast fossil basedenergyreserves,ameagerelectricityproductioncapacitythatisputat4517.6MWasat December 2012isgeneratedtosupporttheeconomyofateemingpopulationofapproximately170 million people.Nigeriaisnaturallyendowedwithabundantdepositofrenewableenergyresourcesof which solarenergyfromtheSun(beingtheworld0s mostabundantandpermanentenergysource)has for decadesbeenenjoyingveryhighlevelutilizationbyruraldwellersforagriculturalprocessingsinthe country.Itisvastlydepositedwithanestimated17,459,215.2millionMJ/day of solar energy falling on the country0s 923,768km2 land area(approximaterangeof12.6MJ/m2/day in the coastal region to about 25.2 MJ/m2/day in the far north). The different applications to which solar resources have been put and the extent of utilization(including details of existing projects)in the country were thoroughly investigated and discussed.The possible motivations for extensive development of solar energy conversion systems in Nigeria area l so discussed and some of the barriers and challenges are presented. Step sand policy measures to over come the barriers and facilitates the utilization of this resource are suggeste

A Typical Meteorological Year Generation Based on NASA Satellite Imagery (GEOS-I) for Sokoto, Nigeria

Energy remains the convergence point of most critical economic, environmental, and developmental issues confronting the wodd at the moment. Clean, efficient, stable, and sustainable energy seiVices are ideal for global prospe1ity. Energy is paramoru!l to achievi11g Nige1ia's Vision 20:2020 needed by the coruttly to be among the top 20 industiialized nations of the world. Lack of energy or its insufficiency in an economy is a potential source of social and economic pove1ty [I]. In general, a larger prop01tion of energy is found to be consumed in buildings in Nigeria as is the case in many countries. There is thus a growing concern about energy consrunp

The effect of climate change on solar radiation in Nigeria

In this study, global solar radiation over Nigeria was simulated under an enhanced atmospheric CO2 level using the International Centre for Theoretical Physics (ICTP) Regional Climate Model version 3 (RegCM3) for the period 1981 to 2100 with ECHAM5 GCM as the lateral boundary conditions. The simulated seasonal global solar radiation bias for the RegCM3 with NIMET and NASA observed datasets in the control period are of similar magnitudes and showed a mixture of persistent positive and negative biases ranging between �10% and 30%. The model generally underestimates solar radiation (biases �10% to �30%) across the whole country in most of the months. In addition, it overestimates radiation (biases +2–30%) over the northern region of the country. Alongside the present climate (1981–2010), three future periods were considered viz: period 1 (2011–2040), period 2 (2041–2070) and period 3 (2071–2100) for the potential future changes. The seasonal potential future changes in period 1 (i.e. potential future changes with respect to 2040) showed a reduction in the range of 0% (North) to 3.27% (South) whereas more reduction in global solar radiation is observed in period 2 (i.e. 2041–2070 minus present climate) having general decrease ranging from 0.11% to 3.39% with the least value in April (Middle-belt) and the largest in the South zone (March). Potential future changes in period 3 (i.e. 2071–2100 minus present climate) is generally characterized with mixed increase and decrease in global solar radiation across the country than the previous two periods (1 and 2). For the annual potential future changes, RegCM3 model predicted a decrease in solar radiation towards the end of the century with more reduction found in the South zone and the least in the North region. Furthermore, future changes in global solar radiation across the zones in all the periods are however found to be insignificant at p 6 0.01

A Typical Meteorological Year Generation Based on NASA Satellite Imagery (GEOS-I) for Sokoto, Nigeria

Computer simulation of buildings and solar energy systems are being used increasingly in energy assessments and design. This paper evaluates the typical meteorological year (TMY) for Sokoto, northwest region, Nigeria, using 23-year hourly weather data including global solar radiation, dew point temperature, mean temperature, maximum temperature, minimum temperature, relative humidity, and wind speed. Filkenstein-Schafer statistical method was utilized for the creation of a TMY for the site. The persistence of mean dry bulb temperature and daily global horizontal radiation on the five candidate months were evaluated. TMY predictions were compared with the 23-year long-term average values and are found to have close agreement and can be used in building energy simulation for comparative energy efficiency study