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The rates of energy that moving vehicles dissipate to road surfaces as well as noise emissions and their propensities for pitting (and hence their repair costs per year) all depend upon the structural properties of these surfaces. Thus, to increase the strength of bituminous concrete (i.e. a typical flexible road-surface) has been one of the major recent aims in highway engineering. The present study explored techniques that will increase these strength properties by modifying the material, using rubber latex, through rubberization and hence, improve the strength of the flexible trafficked surface when in contact with vehicles. At the optimal design asphalt (i.e. bitumen) content of 4.68%, the successive addition of various percentages of the rubber latex produced a design value of 1.65% rubber content, which increased the stability of the roadway from 1595 to 2639 N (i.e. an 65.5% increase) and the density from 2447 to 2520.8 kg/m 3 (i.e. a 3.02% increase). This shows that the addition of rubber latex to bituminous concrete (a flexible road-surface) increased sustainability and the strength (in terms of stability and density). Similarly, the air voids and voids in the mineral aggregate (VMA) were reduced by introducing latex from 4.22% to 3.45% (i.e. a 17.06% reduction) and 16.25% to 13.43% (i.e. an 17.4% reduction), respectively. Whereas, the reduction in voidage volume added strength to the bituminous concrete by increasing its stability and density, the reduction in VMA had no positive impact on the strength properties of the flexible road-surface.

The relationship between changes in the incident rotor-blade angle due to compressor blade profile distortions and the required compressor power is investigated. This was achieved by measuring certain performance characteristics of an operational gas-turbine. Corresponding theoretical predictions were obtained from computer simulations. Graphs plotted from both the measurements and theoretical predictions were compared, and showed significant similarities. Compressor blade profile distortions from the design profile, results in significant increases in the power required by the compressor.

The production of biogas is of growing interest as fossil-fuel reserves decline. However, there exists a dearth of literature on the design considerations that would lead to process optimization in the development of anaerobic digesters aimed at creating useful commodities from the ever-abundant municipal solid-waste. Consequently, this paper provides a synthesis of the key issues and analyses concerning the design of a high-performance anaerobic digester.

This sheller uses abrasion between a rotating shelling-disc and stationary concave compartments to achieve the stripping. A manually-operated handle is used to rotate two shafts, one of which translates rotational motion to become linear motion of a slider crank. The slider pushes the maize cobs into the sheller continually one after another. Though manually operated, the sheller can provide a continuous flow; the kernels being collected via a chute. At a speed of 60 rpm, a shelling effectiveness of 67% was achieved, with a low kernel-breakage factor of 0.090 and a throughput of 6.82 kg/h. For the trial runs, the machine was designed to shell a batch of 100 maize cobs, which were introduced into the feed hopper in one batch, without stopping until all the cobs were stripped via the shelling unit. This design is preferred, because of its rapid operation, low human-energy expenditure, low breakage-factor for the kernels as well as relatively little dust being emitted during shelling; hence leading to a relatively-healthier local atmosphere for the operator. Its wider use is therefore recommended.

Productivity in Nigeria is decreasing: this has adversely affected the average standard-of-living of the population and led to economic hardship. HIV/AIDS, hunger, disease and wars have lowered African productivity and the effectivenesses of public utilities have declined, while unemployment and crime are on the increase. A computer program, which considers the combined concept of partial productivity, total productivity measurement and reliability in order to analyse the effectiveness of a firm, society or nation has been developed. Its predictions have been tested with data from a Nigerian petroleum-product marketing company, namely Rock Oil and Gas Ltd., Aba, Abia State: the management of this business is representative of those of many Nigerian firms. The developed software (see Appendix) can help in identifying the causes of productivity problems, which can so adversely affect the performance of any organisation.

The practice of injecting the flocculation effluent of liquid-phase oil-based drill-cuttings (LP-OBDCs) into the ground is a popular current disposal-option for this type of drilling waste in Nigeria. Unfortunately, this practice leads to environmental degradation because this flocculation effluent contains high concentrations of chromium (Cr6+), which is a heavy-metal pollutant. Consequently, it is recommended that the flocculation effluent be treated in a batch adsorption process, using powdered activated-carbon (PAC) in order to improve the quality of the flocculation effluent before its sub-surface injection. A representative sample of the untreated LP-OBDC was collected from a mud pit close to an oil-well in the Niger Delta region of Nigeria. Initial characterization of the untreated LP-OBDC showed that the concentration of Cr6+ was 5.26 g/m3. Flocculation of the LP-OBDCs was carried out using aluminum sulphate and sodium chloride as coagulant and flocculant, respectively. After flocculation, the Cr6+ was reduced to 5.01 g/m3 (i.e. a 4.75% reduction). The flocculation effluent was then subjected to an activated-carbon batch-adsorption process. At the end of the process, the Cr6+ content was further reduced to 2.77 g/m3 (i.e. a 44.7% reduction), which shows a significant improvement on the quality of the flocculation effluent. The adsorption mechanism of Cr6+ onto the PAC fitted the second-order kinetic model (with R2 = 1.00 approximately) with equilibrium being attained within 60 minutes of contact time. Performance characteristics of the PAC show that the maximum adsorption capacity of the adsorbent at equilibrium is 1.60 mg/g (i.e. a 64.0% adsorption) at the initial chromium-concentration, C0, of 2.50 g/m3. Also, adsorption-capacity data, obtained using the regressed Freudlich’s isotherm ( Q e = 0.768 C e 1 / 1.32 ) , were quite close to the pertinent experimental data (with R2 = 0.981). The adsorption intensity, n, is 1.32, indicating a strongly favourable adsorption, which shows that a large amount of chromium is adsorbed at low concentrations of adsorbate in the flocculation effluent.

Labour costs represent the major portion of the total cost in many industries and activities. This investigation examines a four-day workweek (compared with the current five-day week schedule) for maintenance operations in the Power Holding Company of Nigeria (PHCN). The aim is to reduce maintenance labour-costs, while satisfying increasing demands for higher effectiveness. Changing from the five to a four-day workweek for maintenance personnel at the Afam power-station is predicted to produce savings of 10% of maintenance labour cost without any loss of output or quality of service.

Bio-augmentation has been used as a bio-remediation option for hydrocarbon-contaminated, oily-sludge restoration. This sludge was obtained from the Bonny-Terminal Improvement Project (BTIP) for Bonny Island, near Port Harcourt, Nigeria. Its total hydrocarbon-content (THC) was 69,372 mg/kg of sludge. Three treatment reactors (X, Y and Z) and one control reactor (A) were charged with 1500 g of oily sludge and 250 g of agricultural soil (i.e. an oily sludge to soil ratio of 6:1), the mixture homogenized and allowed to settle for seven days before various CFUs were added to reactors X, Y and Z. Reactor A did not receive any bio-preparation. The agricultural soil served both as a nutrient and a microbe carrier. With regularly scheduled mixing and watering, the THC reduction in the oily sludge varied between 40.7% and 53.2% within two weeks as well as between 63.7% and 84.5% within six weeks of applying the bio-remediation. The CFU counts of the added bio-preparation varied between 1.2 × 12 12 and 3.0 × 10 12 CFU/g of sludge and decreased to 7.0 × 10 11 CFU/g of sludge by the end of the sixth week. The pH of the degrading sludge fluctuated between 6.5 and 7.8 during the same period. When compared with the performance of the indigenous microbes in the control sample, the added bio-preparation evidently increased the THC reduction rate in the oily sludge.

In Port Harcourt metropolis, municipal solid-waste (MSW) is generated and collected in large quantities, but some remains as litter in parts of the municipality. Refuse is mostly buried, but some reckless open-burning ensues, so posing environmental hazards. Waste collected from different receptacles and dumpsites in the city was subjected to analysis: on average, it consisted of 66.6% volatile solids, 13.5% fixed solids, 19.1% liquid and 0.8% other components. The average biodegradability fraction is 0.807, with a carbon-to-nitrogen ratio of 27:1. The energy content of the refuse was 7.25 MJ/kg as collected. These results indicate that such refuse is amenable to several disposal options with less adverse impact on the environment. It is also a source of energy.

The ability to improve continually is desirable. In recent years, the reliabilities of power plants have become increasingly important issues in most developed and developing countries. Reliability, availability, maintainability and supportability (RAMS), as well as risk analysis, have become big issues in the power industries. Major causes of customer dissatisfaction often result from unexpected failures, which have led to unanticipated costs in the Afam thermal power-station. However, with proper integration of RAMS and risk analysis in each maintenance process in the Afam thermal power-station, the frequency of failures can be reduced and their consequences diminished. Taking experiences from the developed world, an approach for the integration of RAMS and risk analysis can be developed as a guide in maintenance policies for the Afam thermal power station. This paper discusses the applications of failure mode effect analysis, failure mode effect and criticality analysis, feedback information, supportive systems and risk analysis, in order to reduce the frequency of failures and maintenance costs.

Domestic cooker-top burners operate at low pressure and low Reynolds numbers. They do not usually have a flue, and are fired with impinging premixed natural-gas/air flames. There are two major considerations in using such burners, namely, poor energy utilization and indoor-air pollution. Because of the large number of cooker-top burners being used, even a slight improvement in thermal performance resulting from a better design will lead to significant reductions of domestic and commercial energy consumptions. In view of the need to raise the thermal performance and to reduce indoor-air pollution, advanced statistical experimental designs have been applied in the present study to evaluate the individual and combined effects of the major cooker-top design parameters. The experimental study was carried out using a 4-factor and 3-level Box–Behnken design-method, utilizing a premixed gas-fired impinging-flame. A cooker-top burner, with circular nozzles with an inner diameter of 3 mm, was used in this experiment. Design parameters of the burner under consideration include Reynolds number, equivalence ratio, nozzle-to-plate distance, and jet-to-jet spacing. Based on an analysis of the experimental data, variations of the thermal efficiency and the carbon monoxide (CO) emission with each of the above mentioned parameters have been reported. Multiple regression models of the thermal efficiency and the CO emissions were obtained in terms of all the major design parameters. Some of the 2-factor interactions on the thermal efficiency and the CO emissions were significant. The findings are important for the designer of a fuel-efficient and environmentally-friendly cooker-top burner.

Reference-beam interferometry (RBI) was applied to study the axisymmetric temperature fields of a small-scale, low Reynolds-number, low-pressure and fuel-rich premixed butane/air circular-flame jet, when it was impinging vertically upwards onto a horizontal copper plate. By maintaining a Reynolds number, Re, of 500 and an equivalence ratio, ϕ, of 1.8, interferograms of the impinging-flame jet were obtained for various nozzle-to-plate-distances. Temperature fields of the flame were then determined using the inverse Abel transformation from the obtained interferograms. Temperatures at several locations were measured experimentally with a T-type thermocouple: they were used as a reference to help in the determination as well as the validation. In the present study, a non-contact method has been successfully developed to measure the temperature fields of a circular impinging gas-fired flame jet.

The economic and political realities of the 1990s forced managers to reverse long-standing organizational cultures in order to reduce costs and energy expenditures in their organisations. For instance, these can be achieved, with respect to maintenance, by replacing a reactive repair-focused attitude by a proactive reliability-focused culture. Thereby far less (i) human effort is expended and (ii) energy would be wasted, both of which lead to increased profitability.

Ground-water contamination resulting from the leakage of crude oil and refined petroleum products during extraction and processing operations is a serious and a growing environmental problem in Nigeria. Consequently, a study of the use of activated carbon (AC) in the clean up was undertaken with the aim of reducing the water contamination to a more acceptable level. In the experiments described, crude-oil contamination of ground water was simulated under laboratory conditions using ground-water samples collected from existing hand-dug wells at Eagle Island, Port Harcourt, Nigeria. Different masses of the absorbent (i.e., activated carbon) were then added to the samples of ground water. The so treated water samples were left to equilibrate for 7 days, after which the total petroleum hydrocarbon (TPH) contents of the samples were measured. Adsorption isotherms were derived for the two forms of activated carbon used, namely granular activated-carbon (GAC) and powdered activated-carbon (PAC). Results of the TPH analyses showed that activated carbon is an excellent means for the stripping-off of the contaminant: there were decreases in contaminant concentration from an initial concentration of 9304.70 mg/l to average final concentrations of 361.00 and 12.37 mg/l, that is, 96% and 99.9% resulting from the same amounts of GAC and PAC applications respectively. The results of this study revealed that the powdered form of AC would be very effective in the remediation of petroleum-hydrocarbon contaminated ground water and its use is therefore recommended.

Experimental studies have been performed to investigate the thermal performances of woks fabricated from materials with different thermal conductivities and surface emissivities. A pre-mixed air/butane flame impinged vertically upwards upon a flat impingement-plate’s (to simulate the wok’s flat-bottom) surface under laminar-flow conditions. The operation parameters of the premixed flame were kept constant (i.e., Reynolds number = 1200; equivalence ratio = 1; and nozzle-to-plate distance = 5). In order to examine the effect of conduction, three materials, namely red brass ( k = 61 W/mK), bronze ( k = 26 W/mK) and stainless steel ( k = 14.9 W/mK), were considered. Because of the lower thermal-conductivity and hence higher conduction–resistance, a significantly lower heat-flux would ensue over the stagnation region for the stainless-steel wok. However, there were no significant differences in the heat-flux distributions in the wall-jet regions for the stainless-steel, bronze and red-brass impingement plates. To examine the effects of radiation, three red-brass impingement plates with surface-emissivities of either 0.1, 0.38 or 0.98 were tested experimentally. Different surface-emissivities have only slight impact, on the heat-flux distributions on the wok’s surface. In addition, there were only insignificant differences in the heat-flux and temperature distributions in the wall-jet regions of the impingement plates fabricated of the same material but with different surface-emissivities.

A swirling flow has been induced in a premixed gas-fired impinging circular flame jet by adding two tangential air flows to the main axial air/fuel flow. The flame jet system was considered to be small-scale and operated under low-pressure, laminar flow conditions. The effects of Reynolds number of the air/butane mixture and nozzle-to-plate distance on the heating performance of the flame were studied and compared with the heat-flux distributions on an impingement plate under different operating conditions. The whole investigation was conducted under the stoichiometric air/fuel condition (i.e., equivalence ratio, Φ = 1) with the Reynolds number being varied from 800 to 1700, and nozzle-to-plate distance being selected between 1.5 and 4.0. The introduction of swirl to small-scale, low-pressure, laminar premixed gas-fired impinging circular flame jets is the method for enhancing their thermal performances. The heat-flux distribution on the impingement plate was more uniform and the flame temperatures essentially higher when compared with a similar flame jet system without induced swirl.

The Bahrain International Circuit (BIC) and complex, at latitude 26.00N and longitude 51.54E, was built in 483 days and cost 150 million US$. The circuit consists of six different individual tracks with a 3.66 km outer track (involving 10 turns) and a 2.55 km inner track (having six turns).The complex has been designed to host a variety of other sporting activities. Fifty thousand spectators, including 10,500 in the main grandstand, can be accommodated simultaneously. State-of-the art on-site media and broadcast facilities are available. The noise level emitted from vehicles on the circuit during the Formula-1 event, on April 4th 2004, was acceptable and caused no physical disturbance to the fans in the VIP lounges or to scholars studying at the University of Bahrain’s Shakeir Campus, which is only 1.5 km away from the circuit. The sound-intensity level (SIL) recorded on the balcony of the VIP lounge was 128 dB(A) and was 80 dB(A) inside the lounge. The calculated SIL immediately outside the lecture halls of the University of Bahrain was 70 dB(A) and 65 dB(A) within them. Thus racing at BIC can proceed without significantly disturbing the academic-learning process. The purchased electricity demand by the BIC complex peaked (at 4.5 MW) during the first Formula-1 event on April 4th 2004. The reverse-osmosis (RO) plant at the BIC provides 1000 m 3 of desalinated water per day for landscape irrigation. Renewable-energy inputs, (i.e., via solar and wind power), at the BIC could be harnessed to generate electricity for water desalination, air conditioning, lighting as well as for irrigation. If the covering of the BIC complex was covered by adhesively fixed modern photovoltaic cells, then ∼1.2 MW of solar electricity could be generated. If two horizontal-axis, at 150 m height above the ground, three 75m bladed, wind turbines were to be installed at the BIC, then the output could reach 4 MW. Furthermore, if 10,000 Jojoba trees (a species renowned for having a low demand for water, needing only five irrigations per year in Bahrain and which remain green throughout the year) are planted near the circuit, then the local micro-climate would be improved with respect to human comfort as well as the local environment becoming cleaner.

Using finite-time thermodynamics, the relations between thermal efficiency, compression and expansion ratios for an ideal naturally-aspirated (air-standard) Miller cycle have been derived. The effect of the temperature-dependent specific heat of the working fluid on the irreversible cycle performance is significant. The conclusions of this investigation are of importance when considering the designs of actual Miller-engines.

A developing society needs to adapt to change and foster creativity. In the pursuit of continual improvement (e.g., reducing fossil-fuel consumption and waste, better service performance, greater availability and improved reliability), implementing wise maintenance-schedules is essential for contemporary organisations. Several studies of a wide range of Nigerian industries indicate that indigenous low availability and low productivity are endemic. The resulting closure of some of these industries has triggered off a realisation of the strategic challenges in maintenance management. In addition, the increasingly-competitive business environment in Nigeria has raised the strategic importance of maintenance functions, especially in organisations with significant investments in physical assets. Five strategic aspects of maintenance management have been identified, namely: maintenance methodology; support processes; organisation and work structuring; comparable culture; and general management policy. Three factors that permeate these dimensions are wise leadership, excellent communications and an understanding of the human factors involved.

Using finite-time thermodynamics, the relations between the power output, thermal efficiency and compression ratio have been derived. The effect of the specific heat of the working fluid, being temperature dependent, on the irreversible cycle performance, is significant. The conclusions obtained in this investigation are in full agreement with those of published studies for other cycles and may be used when considering the designs of actual diesel-engines.

In the Nigerian electric-power industry, maintenance costs over 70% of the total production expenditure. Unplanned downtime has resulted in lost electricity-generation and requires resources to be diverted to get the system running again, i.e., lower profitability occurred. Therefore, the electric-power stations are facing major challenges to shorten downtimes and reduce maintenance costs per MWh of output. In order to improve the maintenance schemes that are implemented, self-assessment of the existing maintenance processes and schedules has to be conducted. Organizations sometimes overlook (i) the need to establish structured ways of prioritizing actions for improvement, (ii) facilitating the sharing of experience, (iii) collecting feedback, (iv) developing good practices and (v) comparing performances against those achieved using a business-excellence model. Hence a maintenance audit of the Afam power-station has been conducted and the station’s performance compared with existing international best standards. Weaknesses became apparent in the existing maintenance systems and remedial strategies are suggested.

The aim of this investigation is to be able to diagnose gas-path faults in gas turbines by minimising the differences between the observed and simulated data for the engine’s behaviour. The simulated data are generated using a known set of faults as the input to the engine-behaviour aero-thermo model and an appropriate objective function is minimised to yield the best solution to the problem. The application of evolution strategy (ES) in the search for this minimum is an effective, flexible, robust and reliable way of solving engine-diagnostics problems. Adopting this approach leads to a considerable reduction in the overall time taken to obtain a convergent solution when compared with that required using a simple genetic-based algorithm.

Original article can be found at: http://www.sciencedirect.com/science/journal/03062619 Copyright Elsevier Ltd. DOI: 10.1016/j.apenergy.2004.02.002 [Full text of this article is not available in the UHRA]

Today's economic climate requires that each industry aims at achieving maximum production capability, while minimizing capital investment e.g. in the maintenance function. This means finding ways to maximize equipment reliability and up-time and extend plant and equipment life through cost-effective maintenance. This paper surveys the performance of gas-turbine plants in Afam thermal-power station. The findings show that the financial impact of lost generation (through non-availability) exceeded within a few years, the initial purchase price of the power plants and associated equipment.

A computer-simulation model of the behaviour of a photovoltaic (PV) gas-turbine hybrid system, with a compressed-air store, is developed in order to evaluate its performance as well as predict the total energy-conversion efficiency and the incurred costs under various operating conditions. This integrated PV and gas-turbine hybrid plant produces approximately 140% more power per unit of fuel consumed compared with corresponding conventional gas-turbine plants. In addition, lower rates of pollutant emissions to the atmosphere per kWh of electricity generated are achieved.

The ability to assess faults in a system, while it is operating, requires an appropriate set of measurements. Engine availability can be increased if the faults can be detected, isolated and assessed, so enabling an optimised shutdown of the plant for maintenance to ensue. Depending on the engine-power-setting parameter, the measurements required to diagnose the faults along the gas path of a gas-turbine vary. This study used a non-linear gas-path analysis (NLGPA) model to predict the required instrumentation set, which can be optimised with respect to the number and type of sensors and their locations for the considered engine-faults. A thermodynamic model of the behaviour of a 2-shaft engine is used as a case study. Redundancy in the sensor set is shown to be unnecessary.

Performances of eight configurations of a ventilated room are predicted. The flows exhibit increasingly three-dimensional tendencies as the proportion of wall occupied by the supply and extract vents is reduced. For all of the cases studied, short-circuiting of the air-flow is predicted. Using the concept of the air-exchange effectiveness alone, as a comparative indicator of ventilation performance, is questionable.

Ignorance of mesh dependency can sometimes be an embarrassment in numerical calculations. Mesh structures need to be developed to eradicate mesh dependency without compromising the finite computing resource and/or incurring large computational expense. For the inexperienced, mesh deployment often degenerates into a time-consuming iterative procedure. To understand mesh influences, different mesh-structures have been applied to two simple, yet typical, room–air–ventilation configurations. The predictions, using various mesh regimes, have been compared with a datum result set: marks have been awarded according to the closeness of comparison to mesh-independent predictions. This mark, i.e. the ‘Mesh Independence Number’ (MIN), is a numerical indicator of the closeness to achieving a mesh in-dependent solution. A relationship for the MIN versus number of nodes is presented together with relationships for the average values of the air-velocity components. In many instances, high correlation-coefficients are established which suggests that this MIN methodology could reduce the need for iterative time-consuming mesh-dependency studies.

Sensor failures are a major cause of concern in engine-performance monitoring as they can result in false alarms and, in some cases, lead to the condemnation of a non-offending component or section of the engine. This condition has the potential to increase engine downtime and thus incur higher operational costs. The fact that more than a single sensor could be faulty simultaneously should also not be overlooked. In this paper, we present a set of neural networks, modularly designed to diagnose and quantify single and dual-sensor faults in a two-shaft stationary gas-turbine. A further outcome of the analysis is the restructuring of the faulty data to a fault-free form through the filtering out of noise and bias. This restructured data can be used to perform sensor-based calculations accurately. The engine chosen for this analysis is thermodynamically similar in performance to the Rolls Royce (RR) Avon. The data used to train the networks were derived from a non-linear aero-thermodynamic model of the engine's behaviour. The results obtained show the good prospects for the use of this technique.

Space-and-water heating in the commercial sector is achieved in Jordan primarily by the combustion of fossil fuels, and so contributes significantly to air pollution and the build-up of carbon dioxide in the atmosphere. The results of a recent survey were used to evaluate the energy demands of the commercial and public-service buildings. In sequence of decreasing popularity, diesel fuel, kerosene and LPG are the main sources of energy for space heating. Unfortunately unvented combustion-appliances, e.g. portable kerosene and LPG stoves, are too often still employed for this purpose in unclassified hotels, some clinics and health centres as well as retail shops. These stoves emit high rates of combustion by-products that result in excessive pollution, in enclosed spaces, of toxic gases such as carbon monoxide. Electricity consumption is relatively high due to the excessive lighting-demands and the use of air-conditioning and ventilation systems to compensate for the dry climate and high temperatures during summer. Due to the lack of available information about the energy-consumption performances of commercial buildings, detailed energy audits should be conducted with the aim of identifying the most applicable energy-effective measures. However, preliminary estimates showed that about 50×10 3 toe of the annual consumption in Jordan can be saved with little investment: the corresponding annual CO 2 emissions reduction would be approximately 160×10 3 tonnes.

A two-storey, four-bedroomed, flat-roofed detached house, with a plan area of 115 m2 and a total floor area of 240 m2, has been designed and its behaviour simulated using a thermal-analysis computer system (TAS). The aim was to reduce the purchased-energy consumption, during both the heating and cooling seasons, required to achieve the thermal comfort of the occupants within the building. The conclusions from this simulation analysis were implemented when constructing a four-bedroomed house in Sarih, Jordan (32.6 °N, 35.9 °E and 616 m above sea level). The thermal performance of this four-bedroomed house has been measured and the resulting experimental data corroborated the simulation predictions. During construction, the building evolved somewhat from the theoretical design investigated. The actual performance achieved is far superior to that of the typical nominally-similar sized, house commonly found in Jordan.

An evaporator's time-constant ( t c ) equation has been developed as part of a mathematical model describing the time-dependent behaviour of a refrigeration system. The magnitudes of the evaporator's t c were approximately 2 and 5 s, respectively for 100 and 50% loads imposed on the refrigerator. As a result of a step change in the inlet's water-temperature, the magnitudes of both t c and the two-phase heat-transfer coefficient ( f tp ) for the refrigerant system were altered. Although a step decrease in the inlet-water's temperature led to large increase in t c, the system's behaviour stabilized quickly because f tp had also increased significantly. The predictions of this investigation showed that such an analysis is highly sensitive to the accuracy of the equations used to calculate both t c and f tp and this makes the experimental verification of this model desirable.

In this paper, the drying behavior of two Jordanian oil shales was investigated using three different techniques: a thermogravimetric analyser (TGA), direct solar insolation, and a convection drying furnace. The weight losses and drying rates of the samples were measured gravimetrically. It was noticed that the drying rate falls off at a specific temperature of approximately 120 ∘C, and becomes zero beyond this temperature. For both types of examined oil shales, the surface-moisture loss is proportional to the drying temperature: the higher the temperature the more of free-water can be driven-off.

Too often, in the last 50 years, the energy-thrift lessons of vernacular architecture have been forgotten or ignored. In the Middle East, many recently-designed commercial buildings, with large areas of glazing, incur excessively high electricity-demands to provide energy for the required air-conditioning plant. One way of reducing the magnitude of this demand is through better window design. For this purpose, a new form of triple-glazed window is proposed to facilitate achieving improved thermal comfort within buildings, while simultaneously reducing the expenditures on purchased energy.

In 1995, Jordan's annual emissions of greenhouse gases (GHGs) were approximately 13.8×10 6 tonnes, of which fossil-fuel combustion contributed more than 85%. It is likely that CO 2 emissions, from energy operations, will rise to about 20×10 6 tonnes in the year 2010, when the energy consumption will be twice that in 1995. There are many viable CO 2 -mitigation measures identified for the energy sector, some of these can be considered as attractive opportunities. However, their implementation requires the removal of certain obstacles, such as the lack of awareness, lenient energy pricing policies and lack of access to appropriate technology.

An experimental investigation has been conducted to study the steady-state forced-convection heat-transfer characteristics of the hydrodynamic fully-developed turbulent flow in air-cooled horizontal equilateral triangular ducts (i.e. of 60° apex angle), which were each fabricated with the same length of 2.4 m and hydraulic diameter of 0.44 m. The inner surfaces of the triangular ducts were roughened by a milling process, shaping process or fixing uniformly-spaced parallel square ribs orthogonal to the mean air flow. The average surface roughness of the inner surfaces, which were produced by milling and shaping processes, were 3.0 and 11.5 μm, respectively. The square-sectioned ribs, adopted to produce the roughened surface, had different protrusions of 6.35, 9.525 and 12.7 mm, and the uniform separation between the centre lines of two successive ribs was kept constant at 57.15 mm. Both the triangular ducts and the square ribs were fabricated out of duralumin. The experiments were performed with the hydraulic-diameter based Reynolds numbers ranging from 4000 to 15000. The entire inner wall of the duct was heated uniformly, while its outer surfaces were thermally well insulated. By comparing the heat-transfer performances with those of a smooth triangular duct (i.e. average inner-surface roughness of less than 1.0 μm) having the same geometry, it was found that forced convection was enhanced by the roughened surfaces. In addition, a much enhanced forced convection was obtained by fixing uniformly-spaced parallel square ribs, rather than by fabricating random roughness on its inner surfaces by machining. However, the heat-transfer enhancement was not proportional to the rib size; the maximum forced convection heat-transfer augmentation was obtained using the smallest (i.e. 6.35 mm) ribs of those tested. Non-dimensional expressions for the determination of the steady-state heat-transfer coefficient of the equilateral triangular ducts, which were fabricated with the various kinds of artificial inner-surface roughness, were also developed.

Using the energy-and-power evaluation program (ENPEP), which is a simulation-model, detailed predictions for the primary and final energy consumptions, electricity demands and generation-capability expansion plans, during the period 2000–2015, in Jordan, have been computed. Also, based on the Government's published policies and plans, greenhouse-gas (GHG) emissions emanating from the electricity sector and the associated proposed mitigation measures are discussed briefly. The future use of natural gas as a fuel, as a substitute for heavy fuel oil and diesel fuel, is recommended. Renewable energy technologies should be promoted, especially in proven applications, such as water heating and pumping, where their economics are attractive. Other actions, such as reducing losses in the generation system as well as the transmission and distribution networks will contribute positively to CO2-emissions mitigation in Jordan.

This paper presents some insights into the prime problems of energy and related environmental issues as well as urbanisation in Jordan. The country has very limited natural resources: water is scarce; arable land is limited; and fossil-fuel sources are few. Moreover, the population is increasing rapidly. Hence, problems are arising. During the last 30 years, the country has experienced vast changes in its infrastructure with respect to the housing, urbanisation, commerce, agriculture and industry. Such developments have led to increasing demographic stresses: unemployment has increased and poverty is experienced by more than half of the population. The pressures have resulted in a high percentage of the population moving from rural to urban areas and so society is becoming less self-sufficient. At present, energy consumption in the residential sector accounts for about one quarter of the kingdom's fuel consumption. Kerosene, bottled LPG, diesel fuel and electricity are the main forms of energy used by households, but kerosene is still the dominant fuel because about 83% of households depend on it for space and water heating. The use of open fires and/or portable stoves has led to an increasing number of people being killed each year by suffocation or suffering health problems due to the inhalation of fumes and gaseous pollutants. Thus a national plan to achieve energy thrift and protect the environment, as well as accomplish the more rational utilisation of the limited natural resources available, is urgently needed and should be enacted soon.

Steady-state heat-transfers from pin-fin arrays have been investigated experimentally for staggered and in-line arrangements of the pin fins, which were orthogonal to the mean air-flow. For the applied conditions, the optimal spacings of the fins in the span-wise and stream-wise directions have been determined. The dependences of the Nusselt number upon the Reynolds number and pin-fin pitch (in both directions) have been deduced.

The requirements imposed upon advanced short take‐off and vertical landing (ASTOVL) aircraft give rise to challenging demands on their propulsion systems. One possible approach is to have a high‐performance turbofan of traditional design and an additional, but separate, fan to provide a major part of the lift during the take‐off and landing manoeuvres. For such a design, there are several quite‐different choices of layout for providing the power to drive the remote fan by means of the core engine. These include shaft‐driven and bleed‐driven options. The choice will depend on the anatomy and required thermodynamic‐performance of the whole system. In this paper, several pertinent alternative engine‐designs are discussed. Four of these, based on a high‐performance low‐bypass‐ratio core engine, are studied in detail and their behaviours compared. Prima facie, the preferred choice is the engine with the shaft‐driven fan. A slightly less acceptable choice is the high‐pressure turbine exit‐bleed driven remote‐fan.

For the present experiments, such a pond was located at JUST, i.e. at 32°N latitude. Its walls were inclined at 45° to the horizontal. The pond was built of galvanized steel (1.44 mm thick) with a circular surface area and total depth of 1 m2 and 500 mm, respectively. The effects of the solar-pond's depth and its water's salinity on the store's temperature distributions were determined experimentally and compared with theoretical predictions. A dimensional analysis was carried out to show the effect of the mini solar-pond's size on its thermal behaviour.

In this article the results of measurements of the rate of evolution of carbon monoxide, hydrogen, and hydrocarbon gases during gasification, using a continuous-feed fluidized bed reactor, from Jordanian oil shales are reported. The influences of the bed temperature (750 - 950°C) with CO2 as the fluidizing gas on the quality and quantity of produced fuel gas were investigated. It was found that there was a nearly linear increase in the product gas volume as a function of temperature, reaching ~ 300 Nm3 (i.e., 330 kg) per tonne of dry raw shale and the gross calorific value ranged from 15 to 23 MJ kg with CO and H2 being the major constituents. In order to determine the gasification kinetics, subsequent experiments were carried out, employing a thermogravimetric analyzer under similar conditions as applied to the fluidized bed reactor. Gasification of the investigated shales was found to comply with first-order kinetics within the limits of experimental error. Decreasing the particle size resulted in a hig...

Energy-consumption guides (ECGs), produced by the UK Government agencies ETSU and BRECSU under the DETR's Energy-Efficiency Best-Practice Programme, have been examined. The aim was to assess and, if possible, improve the methodologies used for the production of ECGs, and in particular to ensure (i) the conclusions are statistically valid; (ii) each presentation appeals to its appropriate target audience; and, in each instance, (iii) ease of information extraction is facilitated. In the course of the study, several ECGs were considered, together with their consultants' reports and the answers to pertinent survey questionnaires. The problems with these ECGs fell into three categories — the use of inappropriate indicators and/or sample populations for energy benchmarking; errors in calculations presented in the guides; and mistakes, ambiguities and other weaknesses in the published text. These problems, although detected in relatively few ECGs, were due to inadequate quality-control and/or a lack of appropriate technical review of the documents before publication. The aim throughout this investigation was to develop a more coherent strategy in order for authors and editors, of future Guides, to present only the facts relevant to the needs of each intended category of user in a persuasive, clear and simple manner.

Two oil shale samples from two different deposits in Jordan have been non-isothermally pyrolysed using a thermogravimetric analyser (TGA). The controlling parameters studied were the final pyrolysis temperature (up to 900°C) and the influence of the heating rate (from 20 to 50 K min −1 ) as well as type of purge gas (N 2 or CO 2 ) employed on the process of thermal degradation of the shale sample. The integral method was used in the analysis of TGA data in order to determine the pyrolysis kinetics. The main region of the sample's weight loss, arising from the conversion of organic matter to oil and gas, occurred within the temperature range 200°C to 600°C. The magnitude of the total weight loss was mainly dependent on the final temperature, as well as, to a lesser extent, on the heating rate employed. The rates of decomposition of the Ellujjun and Sultani oil shales changed significantly at a critical temperature of ∼305±15°C.

Trying to achieve the optimal utilisation of oil shale resources, and the production of a more environmentally acceptable fuel, as well as a solid waste with a low a sulphur content, thereby reducing acidic leachates, has led to this investigation. In this article, the influences of the bed temperature and the choice of fluidising gas on the quality and quantity of the produced fuel gas, using a continuous feed fluidised bed reactor, were investigated. The composition and calorific value of the generated gas were determined. There was a nearly linear increase in the amount of fuel gas produced as a function of temperature, reaching ∼350 kg per 103 kg of dry raw shale and the gross calorific value ranged from 15 to 23 MJ·kg−1 with CO and H2 being the major constituents. Subsequent experiments were carried out, employing a thermogravimetric analyser under similar conditions as applied to the fluidised bed reactor. Gasification of the investigated shales complied with first-order kinetics within the limits of experimental error and the activation energy and temperature at which maximum reactivity rate occurred decreased slightly as the shale particle size was reduced.

In this paper, the influences of particle size, grade and pyrolysis temperature on the oil yield have been evaluated in a laboratory scale reactor. Five categories of particle sizes from two different oil shale samples were pyrolyzed by employing a fixed bed retorting system. The reactor and the oil shale sample were heated at a constant rate and nitrogen gas was used to purge the sample, continuously, in order to remove the pyrolysis products from the reactor as well as to reduce secondary reactions. The liquid products were condensed and collected in a series of cold glass-traps and the off-gases analysed for their hydrocarbon and non-hydrocarbon species. Subsequent experiments were carried out, employing a thermogravimetric analyser, using only the four smallest particle sizes under similar conditions as applied to the fixed bed retort. The activation energy was determined by using the integral method. The pyrolysis of the investigated shales was found to comply with first-order kinetics within the limits of experimental error. Increasing the particle size resulted in a small rise in the liquid oil yield, but simultaneously the total gaseous production was decreased.

Augmenting the heat transfer rates in the internal flow passages of several components of a gas turbine, such as the turbine blades, vanes and combustor walls is an important pre-requisite for maintaining their structural integrity. This is particularly paramount when higher turbine inlet temperatures and pressure ratios are utilised for enhancing the thermal efficiencies of the gas turbine plant. In this study, the heat transfer enhancement, which can be achieved by longitudinal ribs in a variable geometry duct, has been examined. With the base of the ribs maintained at a constant temperature, it was observed that the optimal rib spacing, which corresponded to the maximum heat transfer from the ribs, was a strong function of the rib height to length ratio and the Reynolds number but relatively insensitive to the amount of clearance above the ribs. A design correlation is proposed which shows the distribution of this optimal rib spacing for a wide range of rib geometrical and operational conditions. Comparisons of the longitudinal ribs with pin fin arrays indicated that at rib height to length ratios of ⩾0.24, higher heat transfers can be achieved with the longitudinal ribs. The frictional characteristics of the longitudinal ribs is comparable to those of circular pin fins. Measurements of the local heat transfer coefficient for the rib surfaces indicate that it is highly non-uniform along the rib height and length and also significantly influenced by the amount of clearance above the ribs. For all the cases examined, it was observed that developing flow conditions (thermally and hydrodynamically) were prevalent within the longitudinal rib channels.

Two Jordanian oil-shale samples have been pyrolysed and gasified, non-isothermally, using a thermogravimetric analyser. The controlling parameters studied were the final temperature and influence of particle size as well as the heating rate employed during the process of thermal degradation of the oil-shale sample. The integral method was used in the analysis of weight-loss data to determine the pyrolysis and gasification kinetics. Within experimental error, a slightly greater weight loss occurred during the devolitlization phase when carbon dioxide was used instead of nitrogen to purge the system. The magnitude of the weight loss was dependent on the final temperature, as well as, to a lesser extent, on the heating rate employed. Increasing the latter resulted in the reaction ensuing at higher temperatures. Gasification and pyrolysis of the investigated shales complied with first-order kinetics: the activation energy and temperature at which the maximum reactivity rate occurred decreased slightly as the shale-particle size was reduced.

Air, land and water impacts for a proposed commercial-sized oil-shale integrated tri-generation system (OSITGS) are predicted. A preliminary analysis of the processes incurred was conducted to determine the nature and expected rates of various effluent streams emerging from the OSITGS. Mining and the processing of the oil-shale will significantly disturb the environment, as a result of pollution by dust particles and ash derived from the oil-shale as well as various gaseous emissions from the proposed development. However, it is likely that solid-waste handling (including ultimate disposal) as well as land-use impacts will be of greater concern than emissions to the atmosphere from the proposed oil-shale operations. Preliminary predictions indicate that the proposed integrated process will be financially attractive, as well as an environmentally-acceptable technique for producing synthetic (liquid and gaseous) fuels and electricity from oil-shale, compared with conventional utilisation methods. But significant information gaps exist, so inhibiting the making of accurate environmental assessments concerning the behaviour of the OSITGS at this time.