Development Of A Mathematical Model To Predict Thermal Performance And Cost Effectiveness Of Solar Air Heaters

Energy is a subject of vital importance because of our great dependence on them in all aspects of life including social, economy and even in defence. In Malaysia the analyses of solar radiation at several main towns show that solar radiation has potential for drying purpose. This research is concerned with developing an internet-based mathematical model which is able to predict the thermal performance and cost effectiveness for different types of solar air heaters. The data and knowledge collected from published sources on solar collectors, literature review and the field survey along with personal communications in the solar energy field is used to develop an internet based mathematical model given the code name Mathematical Modeling for Solar Air Heaters (MMSAH). This Mathematical Model incorporates knowledge and able to calculate the parameters required to predict the thermal efficiency and the cost effectiveness of solar air heaters. These parameters are absorber plate temperature, the temperature of the transport fluid inside the duct flow,the output temperature and the overall heat loss coefficient. It also can calculate the fan power consumption to obtain the net energy gain which is required in the cost effectiveness calculation. The solution procedure is performed for flat and V-groove absorber in single and double flow mode, with and without porous media. The thermal performance was determined over a wide range of operating conditions. The optimum operating parameters with respect to the efficiency, outlet temperature and cost effectiveness have been determined. For mass flow rate it lies in the range of 0.025 to 0.045 kg/s, for channel flow depth the recommended ranges are 0.025 to 0.035 m for flat plate collector, 0.06 to 0.08 m for V-groove absorber and 0.04 to 0.055 m for lower duct in double flow double duct solar air heater. The optimum collector length for reasonable thermal performance and minimum annual cost per unit thermal energy gain was found to be between 1 and 3 m. For flat plate collector type it is found that the system thermal efficiency increases by 10-12% in double flow mode without porous media than single flow. An increase of 18% after using porous media in the lower channel than the single flow. For V-groove absorber type it is found that the double flow mode is 4-5% more efficient than the single flow mode. Observation shows that using the porous media in double flow increase the air heater efficiency by more than 7% efficient than the air heater in single mode and a further 2-3% in double flow mode without porous media. It is found that the annual cost of the collector in the double duct double pass flat plate collector with porous media is higher than the annual cost of the collector in double duct double pass flat plate collector without porous media and that is a consequence of using the porous media in which increase the pressure drop lead to increase in annual running cost. However the cost of solar energy (cost-benefit ratio); the annual cost of the collector/the annual thermal energy gain in double flow duct double duct flat plate collector with porous media is less than the cost of solar energy in double flow duct double duct flat plate collector without porous media due to the higher useful energy gained from using porous media which subsequently increase the heat transfer area. Also it is found that the cost-benefit ratio was affected by the flow depth. The developed program is capable of handling Malaysian ambient conditions, collector characteristics, and material thermal properties. The criteria for solar collector in Malaysia were used as the input in the program to simulate the performance of the solar air heaters. To assess the accuracy of the developed program, the mathematical model was validated by comparing its output with experimental results. The comparison conducted showed a similar agreement with maximum error of 5%. The technique seems to be promising since a great correlation has been obtained between the experimental and the predicted results (97.5% < R2 < 99.76% and P < 0.001)

The Effects of Exchange Rate Changes on Trade Balance in Sudan

One of the primary economic objectives of most developing countries is to improve their trade balance. Economists have suggested that trade deficit can be reduced through currency devaluation. This study attempts to determine the effects of devaluation on the trade balance of Sudan and the pass-through effects on Sudan's major export prices by employing Vector Error Correction Model (VECM). The results from the study suggest that the elasticities of import demand with respect to the price ratio of imports relative to domestic price and domestic income are high, while that of the real effective exchange rate is low. The elasticities of export demand with respect to price ratio of exports relative to foreign price, foreign income and real effective exchange rate are high. In particular, the export demand for cotton and gum arabic are elastic with respect to the exchange rate and the foreign price. For the trade balance, it is found that the elasticities of trade balance with respect to domestic income, foreign income and real effective exchange rate are all elastic. The sum of the long-run elasticities of demand of exports and imports with respect to their respective prices is greater than one and therefore the Marshall-Lerner condition is satisfied suggesting that devaluation could be a useful policy to improve the balance of payments. The findings of the study also indicate that there is a significant long-run relationship between the real effective exchange rate and trade balance indicating that devaluation could improve the trade balance in the long-run. The results of pass-through of the export prices of cotton is complete suggesting that Sudan is likely to be a price-taker in international market and therefore. devaluation of Sudanese pound will increase the demand for the export of cotton in the long-run. The pass-through for gum arabic is incomplete suggesting that Sudan is likely to be a price-maker in international market and the devaluation of the Sudanese pound may have little impact on the export demand for gum arabic in the long-run

Mitigation of Lightning Hazards at the More Sensitive Points in Wind Farms Using Ant-Colony Optimization Technique

The lightning energy can be very harmfull to the wind turbine farm components. This paper attempts to evaluate the overvoltages at the sensitive points in wind farm, using ATP-EMTP package program. Four cases were performed; a) the transient voltage distribution in the insulating layer of the control line, b) the transient voltage on the control equipment, c) the coupling voltage between the tower and the control, and, d) the transient voltage distribution in the wind turbine WT generator, boast transformers and grid. These cases were performed under different lightning current conditions and at conventional design and proper design of grounding system. The results show that the ground potential rise (GPR) is reduced with using the proper design of wind turbine ground system, but the induced voltage at the control system will not affected. This work determines the optimum location of wind turbine at the areas of maximum lightning incidence. Ant colony optimization (ACO) technique is implemented to find the optimum wind farm location. This work enhances the protection strategy of the wind farms against lightning stroke

Electrochemical Performance of Grids of Lead-acid Batteries made from Pb-0.8%Ca-1.1%Sn Alloys Containing Cu, As and Sb Impurities in the presence of phosphoric acid

Electrochemical performance of grids of lead-acid Batteries manufactured from Pb-0.8%Ca-1.1%Sn alloys containing Cu, As and Sb impurities at 0.1 wt% level were studied in 4.0 M H2SO4 without and with 0.4 M H3PO4. The presence of impurities in the alloy or addition of H3PO4 was found to suppress the corrosion rate. H3PO4 increased the rates of both hydrogen and oxygen evolution reactions at high overpotentials for all alloys. Except for Cu-containing alloy, H3PO4 had a slight positive effect on PbO2 formation.The self-discharge of PbO2 under polarization or opencircuitconditions increased in the presence of H3PO4 but the positive grid corrosion decreased, except for the As-containing alloy. Impurity-containing alloys showed significantly lower self-discharge rate in the presence of H3PO4 than in its absence. Impedance measurement was able to detect and quantify the formation of the highly insulating inner PbO layer beneath the outer PbSO4 layer and its transformation to the conducting PbO2, during the oxidation of alloys under constant current conditions.H3PO4 significantly enhanced the formation of PbO in thepresence of impurities, especially Sb

Time Series Analysis of Nyala Rainfall Using ARIMA Method

This paper presents linear stochastic models known as multiplicative seasonal autoregressive integrated moving average model (SARIMA).The model is used to simulate monthly rainfall in Nyala station, Sudan. For the analysis, monthly rainfall data for the years 1971–2010 were used. The seasonality observed in Auto Correlation Function(ACF) and Partial Auto Correlation Function(PACF) plots of monthly rainfall data was removed using first order seasonal differencing prior to the development of the SARIMA model. Interestingly, the SARIMA (0,0,0)x(0,1,1)12 model developed was found to be most suitable for simulating monthly rainfall over Nyala station. This model is considered appropriate to forecast the monthly rainfall to assist decision makers to establish priorities for water demand, storage, distribution and disaster management

The issue of methodology adopted by Mustafa Abdel-Raziq and its effects

This academic thesis deals with the issue of methodology as used by Muṣṭafā Abdel-Rāziq (1885 - 1947). It is an issue that represents the essence of his academic philosophical thought. Muṣṭafā Abdel-Rāziq is considered one of the leading religious reformists, and he was the faithful disciple of f Muḥammad ʿAbdū, the second founder of this trend with Jamāl al- Dīn al-Afghanī. Muṣṭafā Abdel-Rāziq added a dimension of more breadth and accuracy by expanding on the contemporary range of general thought transforming it to an academic specialist thought. Abdel-Rāziq is the founder of the current academic discipline. This foundation is based primarily on his new theory about the philosophical creativity in Islamic Civilization He considered al manhaj al uṣūli or the methodology of uṣūl al fiqh a science that was always subject to classification within the religious legitimate sciences which makes it the focus of this philosophical creativity

Efectos de la incubación in vitro con jalea real sobre las características del semen bovino descongelado

Cryopreserved bovine semen is generally considered to have lower fertility compared to fresh semen. The reduction arises from both a lower post–thaw viability and a possible sublethal dysfunction of the surviving sperm population. The present study was conducted to observe the effect of royal jelly (RJ) on motility, viability and acrosome integrity of spermatozoa during post–thaw incubation. Frozen–thawed semen samples were washed and incubated at 37°C in Tris buffer containing 0.1, 0.2, 0.3, 0.4, 0.5% RJ or none (control). Sperm motility, viability and acrosomal integrity were assessed at 0, 0.5, 1, 1.5 and 2 h. The percentages of sperm motility, viability and intact acrosome were higher in Tris buffer containing 0.4% RJ compared to control (p &lt; 0.05). After 2 h of incubation the percentages of motility, viability and intact acrosome of spermatozoa, respectively, were 52.3; 52.5 and 19.8% in 0.4% RJ containing buffer. Results indicate that the addition of 0.4% RJ in the incubation media was able to maintain better quality and longevity of spermatozoa. Royal jelly may be used as a semen extender to improve sperm quality and fertility.El semen bovino criopreservado generalmente es considerado de menor poder fertilizante comparado con el semen fresco. Tal reducción abarca tanto una más baja viabilidad post–descongelado como una posible disfunción subletal de la población de espermatozoides sobrevivientes. El presente estudio fue realizado para determinar el efecto de la jalea real (JR) sobre la motilidad, viabilidad e integridad acrosomal de espermatozoides durante la etapa de incubación post–descongelado. Las muestras de semen congelado–descongelado se lavaron e incubaron a 37°C en buffer Tris conteniendo JR en proporción de 0,1; 0,2; 0,3; 0,4; 0,5% o ninguna (control). La motilidad y la viabilidad espermáticas, así como la integridad acrosomal, fueron evaluadas a las 0; 0,5; 1; 1,5 y 2 h. Comparados con los controles, los porcentajes de motilidad, viabilidad e integridad acrosomal fueron más altos en los espermatozoides incubados en Tris conteniendo 0,4% de JR (p &lt; 0,05). Después de 2 h de incubación, los porcentajes de motilidad, viabilidad e integridad acrosomal de los espermatozoides fueron respectivamente de 52,3; 52,5 y 19,8% en el buffer que contenía JR al 0,4%. Los resultados indican que la adición de 0,4% de JR en los medios de incubación fue capaz de mantener la buena calidad y longevidad de los espermatozoides. La jalea real puede ser usada como aditivo seminal para mejorar la viabilidad y fertilidad de los espermatozoides