Exergy, Performance And Environmental Impact Analysis Of Compression Refrigeration Systems

Major concern in refrigeration hinges largely on energy conservation, environmental safety and efficient cooling system. The concept of quality of useful energy which invariably leads to energy conservation is naturally related to exergy. This study therefore experimentally conducts exergy, performance and environmental impact analysis of compression refrigeration systems using R134a, R410a and R407c, refrigerants. The experiment was performed using a modified exiting R134a refrigerating system. The refrigerator was built with Scroll compressor, 48m3 evaporator space, 1m throttle length and 0.2mm array of rods in the condensing unit coupled with thermocouple K attached at the various components and a digital 10^-3 accuracy weighing scale for charging refrigerant in the required grams. The results show that for 100 grams charge of the refrigerants, the exergetic efficiency, coefficient of performance (COP) and the degree of environmentally friendliness of each of the refrigerants are of order R410a > R407c,> R134a and for 80 grams charge of the refrigerants, the order of performance is R410a > R134a> R407c. While for 60 grams charge of the refrigerants, the exergetic efficiency, coefficient of performance and the degree of environmentally friendliness of each of the refrigerants are of order R407c> R410a > R134a, that of 40 grams charge of the refrigerants is of order R134a> R407c> R410a. The study therefore established that irrespective of the grams charge values of the investigated refrigerants used, R410a is the best, closely followed by R134a and lastly R407c

Gender pay gap in salary bands among employees in the formal sector of South Africa

Orientation: The gender pay gap is a worldwide challenge that has persisted despite political will and interventions. Comparably qualified women performing similar work as men continue to earn less. There are conflicting views in the literature regarding the status of the gender pay gap. Research purpose: The purpose of the study was to determine status of the gender pay gap among employees in the same salary band and to establish whether men and women receive similar pay for similar work in the study population. Motivation for study: The status of the gender pay gap would establish the progress made towards closing the gap and guide necessary adjustments to interventions. Research approach/design and method: A quantitative analysis was conducted on the pay information of 217 902 employees collected in a survey from over 700 companies, across 10 job families and 6 industries. Main findings: Men’s pay was consistently higher than that of women in all salary bands except at the 75th and 95th percentile in sub-bands B-lower and B-upper and 25th percentile in sub-band E-upper. The gender pay gap ranged from 8% in band A to 27.1% in sub-band F-upper. The gaps observed in the salary bands were statistically significant (p < 0.0001) except in sub-band E-upper, F-lower and F-upper, indicating convergence towards similar pay for similar work at senior to top management levels. Women were under-represented in all salary bands with the lowest presence in band F, especially sub-band F-upper. Gender, race, job family and industry have a significant effect on income earned in the study sample. Practical/managerial implications: Government’s efforts seemed to have produced minimal results as women are represented in all job families, industries and salary bands. The pay of men and women in senior and top management levels was similar. However, more still needs to be done to achieve the 50% target representation of women in senior management and close the gap at all levels. Contribution/value-add: The number of women at management levels is still very low when compared to their male counterparts. However, the gender pay gap in senior to top management positions are converging towards similar pay for work of similar value

Evidence of Heavy Metals Distribution in Placenta in Association with Residual Levels in Some Dams’ Organs from Bodija abattoir, Oyo State, Nigeria

Heavy metals have been known to be causing serious detrimental effect on the health of livestock and human populace in general. However, little study had been carried out on the ability of heavy metal to cross placental barrier, which has already been bio-accumulated in the dam. Therefore, this study aimed at showing the evidence of placental barrier crossing by selected heavy metals. The study was carried out in Bodija abattoir, Ibadan, Oyo-state, Nigeria, located on latitude 70020N, longitude 3005E. A cross-sectional study design was adopted and lasted for 6 weeks. Samples were collected from kidney cortices, apical lobe of dam’s liver and a portion of fetal placenta. 12 sample each from liver, kidney and the placenta which were analyzed using Atomic Absorption Spectrophotometer (AAS). Results were subjected to descriptive statistics, t-test and correlation using SPSS17.0 package.From this study cadmium (Cd) and lead (Pb) residues were not found in the samples, while chromium (Cr) was found in all the samples (100% prevalence) and the total prevalence for the heavy metals in the study was 33.4%. The mean chromium (Cr) residual values in placenta, kidney and liver were 0.89±0.66mg/kg, 1.32±0.94mg/kg and 1.00±0.87 mg/kg respectively. The correlation between chromium (Cr) in the dam’s kidney and placenta was 0.3, while for the dam’s liver and placenta was 0.6.  In comparison with permissible limit, the residual level in kidney 1.32±0.94, liver 1.00±0.87 and placenta 0.89±0.66, were within the permissible limit. The study revealed that chromium (Cr) residue was a major challenge in the organs sampled. Liver of the dam had the highest level of bioaccumulation and stronger correlation in the distribution to the placenta. It is therefore recommended that attention should be paid on the disposal of chromium (Cr) residues on the grazing floor where the bulk of the residues were from. Keywords: Heavy metals, Liver, Kidney, Placenta and cattle

Uncertain pasts and risk-sensitive futures in sub-Saharan urban transformation

This chapter explores the status and the scope for transition of risk- sensitive and transformative urban development in diverse cities of sub-Saharan Africa. Sub-Saharan Africa is important because of its large proportions of urban populations with high vulnerability and growing exposure to risks. High rates of urban growth pose increasing risks as we go into the future, yet there is also opportunity to reduce risk through integrating risk management into development. However, this opportunity space is often constrained by limited capacities to plan and manage the rapid urbanisation process, particularly in informal settlements. Limited capacities to prevent processes of risk accumulation pose threats to poverty reduction and sustainable development. In this context, there is an increasingly urgent need for squarely recognising and addressing the underlying vulnerabilities of urban populations and their root causes. Transitioning towards such sustainable urban pathways will require the strengthening of capacities and accountability of city authorities and broader governance systems, both formal and informal

Prevalence of malnutrition and vitamin A deficiency in Nigerian preschool children subsisting on high intakes of carotenes

The prevalence of malnutrition and vitamin A deficiency was determined in 204 preschool children of both sexes aged 3–57 months. The children were recruited from 2 rural communities of Atakumosa Local Government Area of Osun State in South West Nigeria. Dietary vitamin A intake was estimated from frequency of consumption of locally available vitamin A containing food items. Vitamin A status of the children was assessed from concentration of retinol in plasma. Nutritional status was assessed from height and weight compared with international reference standards. The results indicate widespread malnutrition among the children. The prevalence of stunting (low height for age) was 60.8% while prevalence of wasting (low weight for height) was 7.4% and of underweight (low weight for age) 27.5%. Dietary vitamin A intake appeared to be adequate in the children. Intake of vitamin A is predominantly from plant sources. At least 43% of the children consumed the carotene rich red palm oil 6 or more times per week in contrast to less than 1% who consumed eggs or milk for 6 or more times per week. Vitamin A deficiency was low in the children. Only 11.3% of the children had plasma retinol concentration <0.70µmol/L. The results indicate that childhood malnutrition of public health magnitude can coexist with adequate dietary vitamin A intakes or vitamin A status

Experimental Performance of the Energetic Characteristics of a Domestic Refrigerator with Al2O3 Nanolubricant and LPG Refrigerant

This paper studies the experimental performance of the energetic characteristics of a slightly modified domestic refrigerator infused with nano-lubricant containing different concentrations of Al2O3 (at 0, 0.2, 0.4 and 0.6 g/L) with liquefied petroleum gas (LPG) charge of 40g. Parameters investigated were power consumption, cooling capacity, coefficient of performance (COP), discharge temperature, volumetric refrigerating capacity (VRC) and pressure ratio. The findings showed that when the nano-based lubricants were compared with pure oil, the power at 0.6g/L concentration, gave the best performance of 67.01W, at different time over 180 minutes’ periods. The discharge pressure of the system when compared to pure-oil at 0.6g/L concentrations exhibited acceptable value of 616. 33kPa. For the cabinet temperature, it was seen that the 0.6g/L had the lowest recorded temperature of -8.7ºC after 180 minutes. With the coefficient of performance, the 0.2g/L concentration had the highest average performance of 2.239 at 180 minutes. The highest average performance of 174.225 kW over 180 minutes was found as the refrigerating capacity at 02.g/L concentration. The nano-lubricant can be concluded to work safely in the refrigerator but better optimization in nano-application will still be needed for better results

COMPARATIVE ANALYSIS OF THE EXERGETIC PERFORMANCE OF A HOUSEHOLD REFRIGERATOR USING R134a AND R600a

The coefficient of performance (COP) and exergetic performance of a household refrigerator was investigated using R134a in comparison with the performance of R600a. The coefficient of performance, exergy efficiency, and the efficiency defect in the four major components were investigated. The results showed that the COP of R600a was 10.3% higher than that of R134a, a higher exergy efficiency of 42.8% was obtained using R600a at evaporator temperature of–10 C. Generally, R600a performed better than R134a in terms of COP, exergy efficiency, and the efficiency defect in a household refrigeration system

A spectrum of methods for a spectrum of risk: Generating evidence to understand and reduce urban risk in sub-Saharan Africa

Many African towns and cities face a range of hazards, which can best be described as representing a “spectrum of risk” of events that can cause death, illness or injury, and impoverishment. Yet despite the growing numbers of people living in African urban centres, the extent and relative severity of these different risks is poorly understood. This paper provides a rationale for using a spectrum of methods to address this spectrum of risk, and demonstrates the utility of mixed‐methods approaches in planning for resilience. It describes activities undertaken in a wide‐ranging multi‐country programme of research, which use multiple approaches to gather empirical data on risk, in order to build a stronger evidence base and provide a more solid base for planning and investment. It concludes that methods need to be chosen in regard to social, political economic, biophysical and hydrogeological context, while also recognising the different levels of complexity and institutional capacity in different urban centres. The paper concludes that as well as the importance of taking individual contexts into account, there are underlying methodological principles – based on multidisciplinary expertise and multi‐faceted and collaborative research endeavours – that can inform a range of related approaches to understanding urban risk in sub‐Saharan Africa and break the cycle of risk accumulation

Photovoltaic performance prediction in Northern Nigeria using generated typical meteorological year dataset

Relevant meteorological files are needed by simulation software to assess the energy performances of buildings or efficiency of renewable energy systems. This paper adopts the Sandia method to generate typical meteorological year (TMY), using a 35-year hourly measured meteorological dataset from four stations in the northern region of Nigeria. The cumulative distribution function (CDF) for each year was compared with that of the long-term composite of all the years in the period for the seven major weather indices made up of relative humidity, wind speed, minimum temperature, global solar radiation, precipitation, mean temperature and maximum temperature. The 12 typical meteorological months (TMMs) selected from the different years were used for formulation of a TMY for the zone. In addition, performance assessment of a 72-cell polycrystalline solar PV module using the generated TMY and long-term (LT) values was also conducted. Two statistical indicators, the mean percentage error and the root mean square error, were adopted to evaluate the performance of each TMY with the LT mean, and also that of the PV energy system. Findings show that the TMMs are evenly spread within the data periods across the sites while closest fit between the long-term mean and TMY are obtained with the global solar radiation followed by the mean temperature in all the sites especially in Bida and Minna. From the energy system analysis carried out, it was found that TMY data are able to predict the performance of the PV system to within 5% of the LT data

Towards risk-sensitive and transformative urban development in sub Saharan Africa

Risk-sensitive urban development is required to reduce accumulated risk and to better consider risk when planning new developments. To deliver a sustainable city for all requires a more frank and comprehensive focus on procedure: On who makes decisions, under which frameworks, based upon what kind of data or knowledge, and with what degree and direction of accountability? Acting on these procedural questions is the promise of transformative urban development. This paper explores the status of risk sensitive and transformative urban development and the scope for transition towards these components of sustainability in urban sub-Saharan Africa through the lens of diverse city cases: Karonga (Malawi), Ibadan (Nigeria), Niamey (Niger) and Nairobi (Kenya). The paper draws from a 3-year research and capacity building programme called Urban Africa: Risk Knowledge that aims to address gaps in data, understandings and capacity to break cycles of risk accumulation. A common analytical framework is presented to help identify blockages and opportunities for transition towards a risk-sensitive and transformative urban development. This framework is then illustrated through each city in turn and a concluding discussion reflects on city observations to draw out recommendations for city level and wider action and research partnerships