EXPERIMENTAL STUDY OF LPG AND R134a REFRIGERANTS IN VAPOR COMPRESSION REFRIGERATION

Natural refrigerants, such as hydrocarbons, have been renewed in recent years as a result of the environmental problems associated with chlorofluorocarbon (CFC) and hydro-chlorofluorocarbon (HCFC) refrigerants. Due to the depletion of the ozone layer and global warming effects, synthetic refrigerants are being gradually phased out in accordance with the international protocols that aim to protect the environment. A refrigerator designed to work with R134a was used for this experiment, liquefied petroleum gas (LPG) which consists of 60% propane (R290) and 40% butane (R600) was compared with R134a refrigerant in a vapor compression refrigerator with a total volume of 62 L. The experiments were carried out using different charges of 40, 60, 80, and 100 g for R134a and LPG refrigerants, the charges were measured with a digital charging scale. The K-type thermocouples were used to measure the temperatures at the inlet and outlet of the four major components (evaporator, compressor, condenser, and expansion device) of the refrigeration system. The system was instrumented with two pressure gauges at the inlet and outlet of the compressor for measuring the suction and discharge pressures. The results obtained were used to determine the thermodynamic properties of the refrigerants using Refprop, version 9. The results obtained showed that the design temperature and pull-down time set by the International Standard Organisation (ISO) for a refrigerator were achieved with LPG earlier than with R134a. The coefficient of performance (COP) of the system increases by 9.5% and the power consumption is reduced by 12%, when compared with R134a. Therefore, LPG can successfully substitute R134a in domestic refrigerator

Experimental performance of LPG refrigerant charges with varied concentration of TiO2 nano-lubricants in a domestic refrigerator

This article present an experimental investigation of varied mass charges of Liquefied Petroleum Gas (40 g, 50 g, 60 g and 70 g) enhanced with varied TiO2 nanoparticle/mineral oil concentrations (0.2 g/L, 0.4 g/L and 0.6 g/L nanolubricants) in a R134a compressor of a domestic refrigerator. Performance tests investigated at steady state included: pull down time, power consumption, compressor power input, cooling capacity and coefficient of performance (COP). Analysis was based on temperature and pressure readings obtained from appropriate gauges attached to the test rig. Refrigerant property characteristics were obtained using Ref-Prop NIST 9.0 software. Results obtained showed almost equal evaporator air temperatures and reduction in power consumption for all tested nano-lubricant concentrations except at 70 g charge of LPG using 0.6 g/L nano-lubricant. Furthermore, the lowest compressor power input was found to be 21 W and obtained using 70 g of LPG with either of 0.2 g/L or 0.4 g/L nano-lubricants. At 70 g of LPG using 0.6 g/L concentration of nano-lubricant, highest cooling capacity index of 65 W was obtained while the highest COP of 2.8 was obtained with 40 g charge of LPG using 0.4 g/L concentration of nanolubricant. In conclusion, LPG-TiO2 nano-lubricant mixture works safely and efficiently in domestic refrigerators without modification of capillary tube length, but requires adequate optimization

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

Organizational challenges in the adoption of wind energy in Africa

Although fossil fuels uncomplicated are easy to use energy sources, the issues associated with their use are numerous; it affects political, economic, health and environment. The current energy problems result from the way fossil fuels are consumed at an exponential rate, and the world demand of these fuels is expected to go up each year for several decades to come. Renewable energy deployment is steadily growing in Africa, a continent with abundance of resources- wind, water, sun, and biomass. Investing in the long term solutions that these renewable energy sources have to offer would be advantageous and beneficial to all African countries by helping to avoid economic and sustainability problems. These truths show us that the wind can provide a lot of our present and future world energy requirements

Dataset on thermodynamics performance analysis and optimization of a reheat –regenerative steam turbine power plant with feed water heaters

Steam power plants have a considerable potential to meet the growing energy demand, but its dependence on con- ventional fossil fuels has hampered its viability. One of the ways to minimize fuel consumption and upgrade the perfor- mance of a Rankine cycle is by incorporating closed feedwa- ter heaters(FWHs). The datasets contained in this paper are thermodynamic performance analysis carried out on reheat –regenerative steam power plant with FWHs using CyclePad V2.0 software. The thermodynamic performance indices as- sessed are thermal efficiency, network output, heat rate, fuel consumption, boiler efficiency and specific steam consump- tion. Result obtained show that an increase in the number of FWHs decreases the fuel consumption, heat rate, heat re- jected in condenser and heat input to the cycle. This effect invariably can lead to a reduction in operating cost and envi- ronmental impacts

A comparative analysis of the chemical composition and compliance level to established standards of concrete reinforcement steel rods rolled in Nigeria

Nigeria is presently facing the challenges of collapsing buildings and bridges due to substandard materials used as reinforcement products. The increasing use of scraps as feedstock for the production of reinforcing steel bars by steel rolling mill companies has adversely affected the quality of rebars in Nigeria. This research study aimed to appraise the chemical properties of selected brands of steel rebars of Nigeria. Thirty selected brands of rebars were sourced from the six geopolitical zones in Nigeria, and their chemical compositions were analysed for level of compliance with five selected standards (SON, BSI, ASTM, AISI, ISO). The chemical composition test was performed using Optical Light Spectrometric methods. One way analysis of variance (ANOVA) test was performed using SPSS version 20 to examine whether significant differences exist or not in mean chemical composition for the different categories of selected steel rods. Statistical analysis shows a significant difference (P < 0.05) in chemical composition and compliance level between the different types of selected steel rods. The imported steel rods recorded the highest mean (μ = 101.4) in terms of chemical composition and compliance, followed by locally rolled from imported billets (μ = 101.2), TMT steel rods (μ = 101.0), and ordinary steel rods (μ = 100.6). Concerning CEV1 and CEV2, it was observed that all the brands were fully compliant within the maximum permissible ranges given in the local, foreign and international standards except an ordinary steel bar of Brand 16, which has value beyond the specified limits of CEV1. This study also shows that all imported and 77.8% of locally-rolled steel bars are low-carbon steel as specified by the selected standards

Wind resources in North-East geopolitical zone, Nigeria: An assessment of the monthly and seasonal characteristics

This paper evaluates wind speed data of 37 years, 1971-2007 periods measured at 10 m height for five meteorological stations in North-East geo-political zone, Nigeria, namely Bauchi, Nguru, Maiduguri, Yola and Potiskum that have been analyzed statistically to examine the monthly and seasonal variation of the wind characteristics. Wind data at 50 m hub height were obtained by extrapolating the 10 m data using the power law. The results proved Bauchi and Maiduguri to be the best sites among the five locations with monthly mean wind speeds ranging from 3.96 to 7.04 m/s and 4.49 to 6.10 m/s respectively while monthly average power density varies between 61.33-299.88 W/m2 and 63.80-173.70 W/m2 in that order, followed by Potiskum recording monthly mean wind speed ranging from 3.92 to 5.68 m/s coupled with an average power density between 53.82 and 150.84 W/m2 in April and June. A Weibull distribution also gave a better fit than actual data while further investigations revealed higher wind speeds in the morning hours for Nguru, Maiduguri and Potiskum together with equal monthly periods of rainy and wet seasons whereas Bauchi and Yola are windier in the afternoon than morning periods with almost comparable months of rainy and dry seasons. Furthermore, wind availability shows that Maiduguri has wind speed above 4 m/s, 100% of the time in the two seasons while Bauchi, Nguru, Potiskum and Yola have approximately 80 and 100%, 50 and 50%, 75 and 75%, 50 and 50% periods of wind availability above 4 m/s in the dry and rainy seasons respectively.North-East geopolitical zone Mean wind speed Power density Wind energy Nigeria

Assessment of wind energy resources for electricity generation using WECS in North-Central region, Nigeria

This paper presents a statistical analysis of wind characteristics of five locations covering the North-Central (NC) geo-political zone, Nigeria, namely Bida, Minna, Makurdi, Ilorin and Lokoja using Weibull distribution functions on a 36-year (1971-2007) wind speed data at 10 m height collected by the meteorological stations of NIMET in the region. The monthly, seasonal and annual variations were examined while wind speeds at different hub heights were got by extrapolating the 10 m data using the power law. The results from this investigation showed that all the five sites will only be adequate for non-connected electrical and mechanical applications with consideration to their respective annual mean wind speeds of 2.747, 4.289, 4.570, 4.386 and 3.158 m/s and annual average power densities of 16.569, 94.113, 76.399, 71.823 and 26.089 W/m2 for Bida, Minna, Makurdi, Ilorin and Lokoja in that order. Weibull parameters k and c together with the energies for the respective locations were computed while further observation revealed that Bida, Minna, Makurdi and Ilorin are windier in the morning than afternoon periods for many months in a year whereas Lokoja had a windy afternoon. Additionally, four wind turbines De wind 48--600 kW, De wind D6--1250 kW, De wind D7--1500 kW and De wind D8--2000 kW were technically assessed for electricity generation by calculating their respective yearly energy output and capacity factor in all the locations.Weibull distribution Wind energy conversion systems Mean wind speeds Wind energy Nigeria

Economic analysis of wind energy conversion systems using levelized cost of electricity and present value cost methods in Nigeria

Technical electricity generation assessment and economic analysis of six wind energy conversion systems in the categories small, medium, and large (with power ratings of 20, 35, 275, 500, 1,000, and 2,000 kW) were examined in this study. Electricity cost values were estimated based on the levelized cost of electricity (LCOE) and present value cost (PVC) methods for six locations selected across all the geopolitical zones of Nigeria. This was done using wind speed data that span between 25 and 37 years, measured at the height of 10 m. The result showed that the annual average energy output ranges from 2.242 MW h in Uyo with P10-20 turbine to 12,521.55 MW h in Kano using Vestas V80-2 MW wind turbine. Furthermore, of all the selected sites, Kano gave the least costs of electricity production per kilowatt hour with Vestas V80-2 MW model at 67-m hub heights, while the highest is obtained in Uyo with GEV-HP (1 MW) model at 70-m hub heights for the LCOE and PVC height for both the LCOE and PVC methods. In addition, sensitivity of the selected parameters to the levelized cost of electricity was also carried out

Performance modeling of industrial gas turbines with inlet air filtration system

The effect of inlet air filtration on the performance of two industrial gas turbines (GT) is presented. Two GTs were modeled similar to GE LM2500+ and Alstom GT13 E2-2012, using TURBOMATCH and chosen to operate at environmental conditions of Usan offshore oilfield and Maiduguri dessert in Nigeria. The inlet pressure recovered (Precov) from the selected filters used in Usan offshore, and Maiduguri ranged between 98.36≤Precov≤99.51% and 98.67≤Precov≤99.56% respectively. At reduced inlet Precov by 98.36% (1.66 kPa) and, at a temperature above 15 °C (ISA), a reduction of 16.9%, and 7.3% of power output and efficiency was obtained using GT13 E2-2012, while a decrease of 14.8% and 4.7% exist for power output and efficiency with GE LM2500+. In addition, a reduction in mass flow rate of air and fuel under the same condition was between 4.3≤mair≤10.6% and 10.4≤mfuel≤11.5% for GT13 E2-2012 and GE LM2500+, correspondingly. However, the GE LM2500+ was more predisposed to intake pressure drops since it functioned at a higher overall pressure ratio. The results obtained were found worthwhile and could be the basis for filter selection and efficient compressor housing design in the locations concerned