4 research outputs found
Estimation of global solar radiation using empirical models
The dearth of solar radiation data availability has necessitated the development of several mathematical
models for estimating global solar radiation (GSR) of regions using the readily available meteorological data of the
region. This study was centered on estimating the GSR of the Ihiala region in Sub-Saharan Africa using empirical
models. For the last ten years, meteorological data from the Nigerian Meteorological Agency (NIMET) were used.
The sunshine-based equation, temperature-based equation, and multivariate polynomial equations were the empirical
models employed to estimate the GSR of the region. The performance of the seven models was determined using
statistical measures. From the results obtained, the seven models had their respective P-values all less than 5 %
significant level for a confidence interval of 95 %. Thereby attesting their suitability for GSR estimation of the region
is needed. Also, from the other statistical tools employed, the considered multivariate model had better estimation
performance than the other models. Therefore, the considered multivariate model is suitable for estimating the GSR
of the Ihiala region in Sub-Saharan Africa
Determination of a suitable retrofit of R-134A using refrigerant blends of R290 and R600 aided by an optimization technique
The effect of the hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC) refrigerants on the
environment through the attack of its halogen contents-chlorine and fluorine, on the ozone layer and the toxic nature
of such refrigerants, has paid the attention of researchers to work towards getting suitable alternatives using
hydrocarbons (HC) or its blends with HFC refrigerants. This study was centered on getting a suitable retrofit of R134A with a good coefficient of performance (COP) and low global warming potential (GWP) using the blends of R290 and R-600 HCs for use in refrigeration systems. An experimental testing rig was developed by assembling
various measuring devices to the operational points of a vapor compression refrigerator. A mixture design was
developed using the simplex lattice design (SLD) of design expert software 11.0. The response variables considered
were COP and GWP. The experimental design was meticulously followed using 1kg for each refrigerant run, and the
temperature and pressure values at the operating points were noted. From the results obtained, blend A had the
highest COP of 2.5 and the highest GWP value of 3.93. Blend D had the lowest value of C.O.P. of 1.33, while blend
B had the lowest value of GWP of 3.51. Also, the optimal blend was achieved at a mixture factor of 59% R-290a and
41% R-600. The response values obtained at this optimal mixture level were COP-2.05182 and GWP β 3.59.
Therefore, the optimal blend obtained would be a better retrofit to R-134a and could be used in refrigeration systems