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Distributed aircraft propulsion has renewed the interest in power-dense, high-efficiency power packs. Ceramic turbomachinery could be a major enabler, although no successful design has been achieve...

Nexus water/energy security is one of the main global challenges for the future generation. Solar distillation (thermal process) represents a sustainable solution to water shortages and energy crisis in the world especially in the Middle East and North Africa region. The technique is based on a evaporation–condensation process via heat delivery through a cylindrical parabolic collector to a thermal energy storage, in the form of sand integrated into the solar still, to maximize water production efficiencies. It is a technically feasible and operational method. Results suggest that the additional solar collector flux has a direct impact on the increase in average sand and seawater temperature particularly over the period between 12 p.m. and 4 p.m. Seawater temperature increases by >26.6%. The energy stored quantity delivered for the distiller basin grows proportionality with the sand temperature, which is depending directly for the solar collector absorber temperature. The difference between the both temperatures defines a decreasing rate of −19%. The daily water production by the hybrid solar distiller is 6.5 l/day, it represents an increase of +91% compared to the traditional concrete solar still production (3.4 l/day), for the same geometry and meteorological conditions. HIGHLIGHTS Renewable energies integration in the seawater distillation process.; Improvement of the water evaporation phenomenon using a parabolic trough solar concentrator.; Solar still efficiency optimization by the thermal energy storage integration.; New design of the greenhouse still flow control principle, materials.; Proved the efficiency of the hybrid still compared to the concrete still in a Mediterranean climate.

Non admixed Natural gas-fuelled diesel engines are usually associated with harsh engine emissions as well as low performances at moderate to high engine loads. However, the use of Moringa biodiesel as additive in hydrogen-compressed natural gas (HCNG) is a viable novel strategy for reducing toxic emissions such as hydrocarbons and nitrogen oxides in CI engines. In this study, five hybrid HCNG–Moringa biodiesel (MB) oil samples labelled A–E were analysed for their abilities to improve the overall performance of a CI engine (Petter PH1W diesel engine). The fuels had a fixed volume by volume hydrogen : carbon ratio of 87:13% respectively, and the HCNG–MB hybrid samples consisted of 0, 5, 7, 10 and 13 %v/v MB for samples A, B, C, D and E, respectively. At higher engine loads (i.e. 58%–100%), the engine performance improved thus giving higher BTEs in the range of 19–33.9% for all the fuel blends relative to the BTE (15.1%–19%) of the unblended HCNG fuel; this confirms the suitability of MB as an additive for improving the brake thermal efficiency of CI engines; there were also reductions in HC, O2, CO2, CO and NOx emissions for all the MB–HCNG fuels relative to the case of the unblended HCNG fuel. At optimum condition, the fuel that gave the best results in terms of the aforementioned engine characteristics is the MB–HCNG fuel blend having 10% MB.

Heating tower heat pumps are increasingly used in subtropical areas due to their frost-free characteristics. The spray heating tower (SHT) solves the fouling problem suffered by the packing heating tower and ensures thermal performance. However, the heat and mass transfer characteristics of SHT have not been fully revealed and the power consumption of SHT is higher than that of packing heating towers. In the present study, the effects of tower height, air temperature, solution concentration/type, and liquid to gas ratio on the thermal performance of SHT were analyzed using a mathematical model. The heat and mass transfer characteristics of SHT with 100% thermal efficiency and/or 100% tower effectiveness were investigated. The results showed that when thermal efficiency approached 100% and liquid to gas mass ratio was 0.28, evaporation and condensation occurred at the bottom and top of the tower, respectively. Based on the parametric analysis results, a parameter design strategy to reduce pump power consumption while ensuring thermal performance was determined, which reconciled the contradiction between power consumption and thermal performance of SHT. The results of this investigation may provide a reference for the design and operation of SHT.

In this study, experiments were carried out in two stages. In the first stage, n-heptane (in 4, 8, 12, 16, and 20% volumes) was added to biodiesel (C0) which was produced from refined cottonseed oil via the transesterification method. The optimal n-heptane ratio was determined to be 8% in volume as a result of engine experiments. In CH8 fuel compared to C0 fuel, there was a 7.52% increase in brake power, 7.84% in engine torque, 2.57% in brake thermal efficiency, and 3.08% decrease in brake specific fuel consumption. When n-heptane additive fuels were analyzed, it was observed that the cylinder pressure in CH8 fuel were higher in all loading cases. The minimum ignition delay at full load was 12.88 o CA in CH8 fuel. When the exhaust emission was analyzed, in n-heptane added fuels compared to C0 fuel in CH8 fuels, there was a 29.99% decrease in CO emissions and a 3.16% decrease in THC emissions. In NO X emissions, there was a 1.18% increase in CH8 fuel and a 1.19% increase in smoke emissions. As a result of the analysis of engine performance and the experimental data regarding emission characteristics, the optimal n-heptane additive fuel was determined to be CH8 fuel. In the second phase of the experiment, an organic based manganese addition (4 ppm, 8 ppm, 12ppm, and 16 ppm) was added to 8% n-heptane additive (CH8) fuel. The optimal experiment results were obtained at a ratio of 12 ppm organic based manganese additive. Compared to CH8 fuel, in CH8Mn12 fuel, brake power increased by 3.42%, engine torque by 7.12%, and brake thermal efficiency by 5.35% while brake-specific fuel consumption decreased by 5.91%. In the evaluation of exhaust emissions, in CH8Mn12 fuel compared to CH8 fuel there was an 8.28% decrease in CO emissions, a 5.54% decrease in THC emissions, and a 3.67% decrease in smoke emissions while there was a 10.67% increase in NO X emissions. Depending on its properties, the additive reacted directly with carbon atoms and caused a serious reduction in emissions.

One feasible solution to reduce the cost of concentrated solar power is to employ a higher temperature and efficiency supercritical carbon dioxide Brayton power cycle. An alternative heat transfer medium and thermal energy storage (TES) system therefore needs to be explored. This work considered a variety of phase change materials (PCMs) and graphite as the storage media in four indirect shell-and-tube storage configurations, including a 3-PCM and 5-PCM cascade storage, a PCM-graphite-PCM hybrid storage and a single graphite storage. The sizing and design of the TES systems were performed by using a dynamic cycling methodology based on a transient 2D numerical model. The cost of those designs were then determined by using an economic model developed inhouse. This work also investigates the impact of some geometric parameters and cost assumptions on the techno-economic performance of the TES system. The analysis suggests a scenario exists whereby a low thermal efficiency storage system which therefore utilises less tube or storage material could be more cost-effective. Overall, the cost of hybrid TES is the lowest among all studied systems, at $26.96/kWht and $21.49/kWht for charging temperature of 720 °C and 750 °C, respectively, followed by the 5-PCM storage at $28.06/kWht and $21.82/kWht, respectively Refereed/Peer-reviewed

The roller kiln is characterized by significant heat losses mainly caused by flue gas and cooling gas accounting for 70%. In this study, four novel power cycles including a basic organic Rankine cycle (BORC), a regenerative organic Rankine cycle (RORC), a Kalina cycle11 (KC11) and a Kalina cycle 34 (KC34) with the parallel double-evaporator (PD) configuration are proposed for dual-level waste heat recovery for a roller kiln. To identify the superiority system, the recommended power cycles are assessed and compared from an integrated thermodynamic and economic perspective. The impacts of the basic operating parameters on net power output, exergy efficiency, electricity production cost and savings to investment ratio are discussed. Meanwhile, the single-, bi- and three-objective optimizations are conducted and the optimal solutions are compared. The results indicated that for the considered optimization models, PDKC34 achieved the highest net power output of 211.06–224.45​ kW and thermal efficiency of 20.02–21.20%, PDBORC had the best economic performance on electricity production cost of 0.0875–0.0932 $/kWh, payback period of 5.709–6.210 year and savings to investment ratio of 2.191–2.335 while PDRORC with R-141b possessed the best exergy efficiency of 45.11–49.17%. On the whole, the four thermodynamic cycles contributed to the best thermodynamic performance in the maximizing net power output model while these had the best economic performance in the minimum EPC model. Besides, the evaporation unit had the highest impact on exergy destruction and total investment cost among all components for the studied optimization models.

In recent years, attentions are focused on the application of cutting-edge reactors to utilize the remarkable virtues such as safety and also higher thermal efficiency. Sodium-cooled fast reactors (SFRs) are midst the promising types of fourth generation reactors for their non-reacting behavior and packed configurations, which are considered as heat source of various thermodynamic systems. Accordingly, nitrogen Brayton cycle could be devised as power conversion system (PCS) of the mentioned sodium cooled reactors, due to its simple arrangement. In present study, proposing the topping system of nitrogen Brayton cycle as a power generation system which is driven by the sodium reactor system, Kalina and heat pump cycles, as bottoming cycles, were designed to increase the performance of the overall system by integration with topping system. Subsequently, energy, exergy and exergoeconomic analyses were carried out to examine the reliability of the proposed system. The results displayed that under operating conditions, thermal efficiency, exergetic efficiency of the proposed system are 34% and 62%, respectively. Furthermore, using the exergy point of view, it was revealed that steam generator heat exchanger, SGHX, is the foremost cause of exergy destruction. Also, in order to attain an inclusive insight over the system, a parametric analysis was conducted. Therefore, investigating the influence of alterations in key features of the overall cycle, several optimum working conditions, such as optimal basic concentration of ammonia in Kalina cycle, optimal turbines (I&II) expansion ratio and low-pressure compressor pressure ratio etc., were derived.

Biodiesel has great potential as an alternative fuel for diesel engines. However, poor low-temperature flow property and high viscosity of biodiesel limit its use in engines. Therefore, alcohol comes into researchers’ eyes as a promising additive for diesel–biodiesel (DB) blends. In this study, the effects of lower and higher alcohol contents with different speeds on combustion and emissions characteristics were investigated in a modified single cylinder diesel engine. The results indicated that the maximum pressure rise rate (MPRR) maintained a consistent drop ratio as speed increased from 1500 rpm to 1800 rpm for the tested fuels. However, B10E10 (10% biodiesel and %10 ethanol by volume) had a big drop, which meant that engine’s power ability had a big loss at high speed. The declining rate with speed decreased for indicated thermal efficiency (ITE) when adding alcohol to diesel–biodiesel blends, especially n-pentanol. Moreover, compared with other tested fuels, B10P10 (10% biodiesel and 10% n-pentanol) had smaller cycle variation and more stable combustion state as speed changed, despite it had the highest coefficient of variation (COV) at 1000 rpm. It can be found that has advantages in combustion stability, and can well reduce the total hydrocarbon (THC) and carbon monoxide (CO) emissions under the condition of medium speed commonly used by vehicle. Overall consideration, using diesel/biodiesel/alcohol ternary fuels may be a better choice for diesel engines.

Cascade solar thermal systems provide a new direction for solar power generation. This paper focuses on the configuration optimization of a cascade solar system in which a Stirling engine array is applied. The array has multiple configurations. To find out the influence of the configuration on the performance of the engine array, five basic connection types were proposed. A Stirling engine model considering various losses and irreversibilities was developed. The model was evaluated by considering the prototype GPU-3 Stirling engine as a case study. Stirling engine array models were developed based on the Stirling engine model. Global efficiency and power of different connection types of Stirling engine arrays with the same hot and cold flows were evaluated. The effects of different factors on the performance of the Stirling engine arrays were considered. The result shows that flow order, the co-current flow or the counter-current flow, has little influence on the engine array performance. The maximum differences of thermal efficiency and output power of different flow orders are 0.39% and 0.70%, respectively. Serial flow connection type is the best for a Stirling engine array to obtain the best performance and adaptability for given heating and cooling fluids.

In the present study, the countermeasures are proposed to minimize the problem on torque and power output performance and exhaust gas emissions of natural gas engine with use of lower calorific gas. An experiment was conducted to identify thermal efficiency and harmful exhaust gas emission characteristics under partial load conditions in order to improve efficient fuel use in engines affected by the introduction of low calorific gases. A countermeasure for coping with emission gas regulations and preventing thermal efficiency deterioration under rated power operating conditions was then presented. An 11 L six-cylinder turbo-charged engine for city buses compliant with the EURO 6 regulation was used in the experiment, and the results obtained using the reference natural gas fuel were compared with those obtained using simulated low calorific gases. Pure methane (CH 4) was also used to investigate the effects of gas composition changes on thermal efficiency and exhaust gas emissions. When N 2 is added or pure CH 4 is used under partial load operating conditions, the combustion rate decreases; consequently, the optimum ignition timing is additionally advanced relative to that obtained when the reference natural gas fuel is used. If the N 2 mixing ratio is increased to a minimum of 4.7% under rated power operating conditions, combustion becomes unstable. Stable operation can be secured by increasing the set base fuel amount, 2.35% and 9.41% for pure CH 4 and 8% N 2 , respectively; however, torque decreases in proportion to the combustion speed of the gas fuel. The strategy of boost pressure control for the torque compensation can minimize the decrease in thermal efficiency.

Solar energy is a widely used green energy resource that is used for drying processes. Through this assessment, the performance of an Indirect Solar Dryer (ISD) with three different cases, namely solar collector - without Thermal Energy Storage (TES), with TES unit having Phase Change Material (PCM) and with TES having fins inserted PCM have been experimentally analyzed during spring and summer seasons for drying Momordica charantia. Totally six experiments were undertaken to compare temperature, drying kinetics, and energy analyses. The initial moisture level of 2 kg of specimen decreased from 1.84 kg of water (92% w. b) to 0.24 kg of water (12% w. b) in 10.5 h utilizing ISD with TES having fins inserted PCM (Test 6). The maximum thermal efficiency achieved about 19.41% on Test 6. Exergy efficiency increased from 8.66% to 79.02% at Test 6. Environmental impacts assessment has revealed that the Energy Payback Time for the ISD was 1.42 years. The CO2 emission, mitigation, and carbon credit gained (Test 6) are 23.88 kg/year, 20.13 tons, and $100.642 to $402.569 for the 35 years’ intended lifespan. The assessment report showed that the device established was a potentially effective commercial drying technique, both in energy utilization and environmental sustainability.

This experimental study investigates the advantage of using Mn–Zn Fe2O4/water ferrofluid subjected to the effect of a non-uniform magnetic field on the thermal efficiency of a fabricated cylindrical solar collector with a receiver in the shape of the helical pipe. Using ASHRAE Standard, this study has investigated the influence of the nanoparticles volume fraction (0.0–1.0%), the mass flow rate of fluid (0.00415–0.033 kg/s), and the produced non-uniform magnetic field by a set of permanent magnets (Br = 0.0–1.2 T) on the collector' thermal efficiency. The results show that for the ferrofluid, the overall thermal efficiency of the collector is increased with the volume fraction augmentation. For the case with the flow rate of 0.033 kg/s and the volume fraction of 1.0%, the maximum collector efficiency enhancement compared with water has been 48.54%. The positive effect of applying the magnetic field predominates at lower flow rates and higher volume fractions. In the case with the flow rate of 0.00415 kg/s and the volume fraction of 1.0%, by applying the magnets with Br = 1.2 T, the collector's maximum efficiency is increased by 26.8% compared with that without a magnetic field.

Palm biodiesel-ethanol blends could be the better automotive fuel over palm biodiesel alone owing to the high oxygen content and high volatility of ethanol. The evaporation and burning characteristics of palm biodiesel with 10%, 20%, and 30% ethanol by volume concentration respectively, were investigated by using the droplet experiment. Rapid bubble growth and bubble explosions during the heating stage were observed to be substantial for the palm biodiesel droplet added with 30% volume of ethanol (BE30). Adding ethanol in palm biodiesel increased the ignition delay and burn-rate constant by up to 38.6% and 23.2%, respectively whereas, the evaporation duration and burning period decreased by up to 20.6% and 22.5%, respectively. Overall, the relatively shorter evaporation duration and higher burn-rate found for the BE30 droplet could promote high thermal efficiency and has the potential to achieve ultra-low carbon monoxide (CO) and unburned hydrocarbons (UHCs) emissions in diesel and gas turbine engines.

Operation safety and efficiency are two main concerns in power plants. It is important to detect the anomalies in power plants, and further judge whether they affect key performance indicators (KPIs), such as the thermal efficiency. These two goals can be achieved by KPI-related nonstationary process monitoring. Although the thermal efficiency cannot be accurately measured online, it can be strongly characterized by some online measurable variables, including the exhaust gas temperature and oxygen content of flue gas. These critical variables closely related to the thermal efficiency are termed as output variables. Inspired from nonstationary common trends between input and output variables in thermal power plants, the output-relevant common trend analysis (OCTA) method is proposed, in this article, to model the input–output relationship. In OCTA, input and output variables are decomposed into nonstationary common trends and stationary residuals, and the model parameters are estimated by solving an optimization problem. It is pointed out that OCTA is a generalized form of partial least squares (PLS). The superior monitoring performance of OCTA is illustrated by case studies on a real power plant in Zhejiang Provincial Energy Group of China. Compared with the other PLS-based recursive algorithms, OCTA can effectively detect the anomalies in power plants and accurately determine whether they have an impact on the thermal efficiency or not.

The popular application of latent heat storage (LHS) units using phase change materials is limited in converting and utilizing renewable energy due to their poor thermal efficiency. To address this deficiency, a tree-shaped fin inspired by nature is employed for the thermal enhancement of vertical LHS units. A three-dimensional mathematical model using the enthalpy-porosity method is developed to comprehensively evaluate the heat charging/discharging process of the new and traditional LHS units, focusing on the role of heat transfer fluid (HTF) direction. The results indicate that tree-shaped fins improve the temperature uniformity and facilitate the melting/solidification rate, which exhibits a preferable advantage that the full melting/solidification duration shortens by 34.5% and 49.2%, and the time-averaged heat storage/release rate augments by 49.4% and 96.4%. Interestingly, natural convection significantly improves the heat charging performance, while the role of natural convection can be considered negligible during discharging processes. Moreover, the HTF temperature seriously affects the performance of LHS units, while the role of HTF flow rate is less prominent. It is found that the upward flow of HTF is beneficial to the heat charging improvement while a downward flow mode facilitates the discharging performance, providing useful advice for practical applications of vertical LHS units.

Photovoltaic Thermal (PVT) systems generate hot water and electricity simultaneously. The grade of thermal energy generated by such PVT systems is low, resulting in limited application. To overcome this challenge, the coupling of the PVT system to a secondary flat plate collector (FPC) has been explored in this work. For the system's performance estimation, a 3-D numerical model has been developed for both glazed and unglazed PVT-FPC collector. Based on the numerical model, PVT collectors have been fabricated, and each is then connected in series to a commercially available FPC collector. Experiments conducted on the fabricated PVT-FPC system showed a close match between simulation and experiments. Further, experiments conducted on the unglazed PVT – FPC collector showed a peak outlet water temperature of 60–63 °C at 30 LPH. For the unglazed PVT collector, the peak electrical and thermal efficiency of 16% and 25% is reported respectively, whereas for the FPC collector, the thermal efficiency of 35% is reported. Compared to an individual unglazed PVT collector, 17 °C higher outlet water temperature is reported for the coupled system. Similarly, for the case of glazed PVT-FPC collector, the peak outlet water temperature reported is 65–67 °C at 30 LPH with 14–15 °C higher outlet water temperature.

A major technical barrier of solar water heating systems for space heating and domestic water usage is the mismatch between the seasonal availability of solar energy and demand loads. The resulting low solar fraction in winter and high risk of overheating in summer reduces the competitiveness of this technology. Aiming to solve this problem, a novel collector module which combines asymmetric compound parabolic reflector with horizontally aligned evacuated tubular absorber is proposed in this paper. The special configuration enables the reflector to realize the seasonal dual function which performs as a concentrator in winter and a shading device in summer. This collector design can achieve high thermal performance during winter when demand is high and lower the efficiency in summer when demand is low. Based on the design principle, a prototype device was fabricated. Its photo-thermal behavior was investigated by the numerical approach as well as the experimental approach under real outdoor conditions on summer and winter days. Both theoretical and experimental results revealed that the prototype device has a high average optical efficiency on clear December days of 0.70, whereas it maintained low average optical efficiency of 0.39 on clear August days. In addition, the daily thermal efficiency remained above 0.5 for a large temperature difference between the fluid and ambient air at 77 K during the testing days around the winter solstice. These results confirmed that this solar unit achieves satisfactory performance in winter and also reduces the overheating risk in summer.

Solid oxide fuel cell combined with heat and power (SOFC-CHP) system is a distributed power generation system with low pollution and high efficiency. In this paper, a 10 kW SOFC-CHP system model using syngas was built in Aspen plus. Key operating parameters, such as steam to fuel ratio, stack temperature, reformer temperature, air flow rate, and air preheating temperature, were analyzed. Optimization was conducted based on the simulation results. Results suggest that higher steam to fuel ratio is beneficial to the electrical efficiency, but it might decrease the gross system efficiency. Higher stack and reformer temperatures contribute to the electrical efficiency, and the optimal operating temperatures of stack and reformer when considering the stack degradation are 750 °C and 700 °C, respectively. The air preheating temperature barely affects the electrical efficiency but affects the thermal efficiency and the gross system efficiency, the recommended value is around 600 °C under the reference condition.

This is a study on the enhancement of the thermal performance of a thermosyphon heat pipe (THP) using the Al2O3 nanoparticle in a mixture of water and Triton X-100 (TX-100) surfactant. The effects ...

The performance of the solar photovoltaic (PV) panel is greatly affected by a rise in operating temperature. A combination of phase change material (PCM) and natural water cooling system for effective thermal management of the PV panel is examined to tackle this issue. Experimentation involved incorporating OM 35 PCM at the tedlar surface of the PV panel and water was allowed to flow from the bottom portion of the PCM chamber. Four different cases considering the direction (bottom to top and top to bottom) and period (continuous and maximum allowable temperature mechanism) of cooling water flow were evaluated and compared with the reference panel. Various parameters such as electrical/thermal efficiency, energy balance and exergy analysis of the PV panel with and without cooling are compared and discussed. Experimentation indicated that the performance of the PV panel augmented due to the incorporation of PCM with natural water circulation. Further, it was identified that the top to bottom continuous water supply cooling technique showed better performance than other cases with an increase in average electricity generation, electrical efficiency, power enhancement percentage, average temperature reduction, maximum overall exergy output and exergy efficiency of 11.92%, 12.4%, 13.54%, 5.4 °C, 26.07% and 8.08% respectively.

Next-generation concentrating solar power (CSP) tower technologies target operating temperatures exceeding 700 °C to increase the thermal-to-electric conversion efficiency. Molten chloride salts are one possible alternative to current commercial molten nitrate salts to enable the higher operating temperature. This paper analyzes the predicted optical, thermal-fluids, and structural performance of traditional external tubular solar receiver configurations applied with a chloride salt heat transfer fluid (HTF) and inlet/outlet temperatures of 500 °C/735 °C, and considers sensitivity analysis and optimization relative to receiver sizing, tube sizing, number of panels, flow circuit configurations, and solar flux concentration under constraints on internal velocity, pressure drop, wall thickness, and required creep-fatigue lifetime. The high temperature conditions increase the significance of inelastic deformation mechanisms such as creep relative to that expected in commercial 565 °C nitrate salt designs. High-temperature creep and creep-fatigue damage in the metal alloy tubes are the key factors that limit allowable solar flux concentration and achievable receiver thermal efficiency at the near-800 °C wall temperature conditions. For a traditional external cylindrical receiver configuration, the design parameters and conditions capable of satisfying all constraints produced, at best, a design point receiver efficiency of 78.2%, or 80.5% when excluding receiver intercept efficiency. Variation in the optimal receiver performance relative to uncertainty in the binding maximum velocity, minimum wall thickness, and minimum lifetime constraints is presented.

This work deals with determination of thermal efficiency of spherical ball roughened collector aligned inclined to flow direction. Roughened collector produces more heat transfer compared to smooth ones but heat transfer augmentation comes at the cost of increased frictional losses. Lesser thermal efficiency of solar air heater has necessitated researchers to focus on its improvement by providing artificial flow modification techniques in the flow field. Laminar sublayer beneath the absorber plate will get disturbed and this helps to increase turbulence level of air. Present work discusses the influence of inclined spherical ball shaped roughness element and improving its thermal performance. Design considerations, geometries used viz. relative roughness pitch 9–18, relative roughness height 0.024–0.040, height-diameter ratio 0.5–2, angle of attack 35°-75°, flow conditions and their influence on turbulence viz. Reynolds no 2500–18500, heat transfer rate, absorber temperature and thermal performance enhancement factor have been thoroughly discussed. Finally concluding remarks and future scope for additional enhancement in performance of solar air heater is proposed. Maximum thermal efficiency for roughened ducts was found as 81% compared to 38% for smooth duct at parameters viz. ‘relative roughness pitch = 12, ‘relative roughness height’ = 0.036, ‘height-diameter ratio’ = 1 and ‘angle of attack’ = 55 at mass flow rate = 0.0319 kg/s.

Novel tri-generation systems are developed to operate in a complete CHP or CCP mode, with having relatively simple configuration to meet a cost-effective design. The system consists of conventional Rankine and ejector refrigeration cycles in which CO2 is used as the environmentally-friendly working media (System I). To enhance performance of the proposed System I, a modification is made by incorporation of an internal heat exchanger to form the System II. Thermoeconomic performance of the systems are evaluated and optimized based on levelized cost of system products. Also, the reliability of the proposed systems are evaluated and discussed. It is found that, the proposed System II has exergy efficiency and levelized product cost of 39.68% and 28.51 $/GJ, for summer application mode. The results also indicated that at optimal operating conditions, System II has lower levelized product cost than System I by 10.4% and 2.3%, besides it has higher exergy efficiency than System I by 11.4% and 4.0%, for summer and winter modes, respectively. However, for winter applications, System I performs better than System II in terms of heating output and thermal efficiency by 97.3% and 34.1%, respectively. The results demonstrated that, the proposed systems offer opportunity of selecting a suitable one depending on the user's energy (power, cold or heat) demand.

The objective of this paper is to investigate the theoretical performance of Parabolic Trough Collector (PTC) using various nanofluids. The theoretical performances are calculated for Al 2 O 3 , graphite, magnetite, SWCNH, CuO, SiO 2 , MWCNT, TiO 2 , Fe 2 O 3 , and ZnO in water nanofluids. The heat transfer equations, thermodynamic properties of nanofluid and pumping power are utilised for the development of novel thermal model. The theoretical thermal efficiency of the PTC is calculated, and the economic viability of the technology is predicted for a range of nanofluid concentration. The results showed that the thermal conductivity increases with the concentration of nanoparticles in the base fluid. Magnetite nanofluid showed the highest thermal efficiency, followed by CuO, MWCNT, ZnO, SWCNH, TiO 2 , Fe 2 O 3 , Al 2 O 3 , graphite, and SiO 2 , respectively. The study reveals that MWCNT at 0.4% concentration is the best-suited nanofluid considering thermal gain and pumping power. Most of the nanofluids achieved optimum efficiency at 0.4% concentration. The influence of mass flow rate on thermal efficiency is evaluated. When the mass flow rate increased from 70 Kg/hr to 90Kg/hr, a 10%-20% efficiency increase is observed. Dispersing nanofluids reduces the levelized cost of energy of large-scale power plants. These findings add to the knowledge of the scientific community aimed explicitly at solar thermal energy technology. The report can also be used as a base to pursue solar thermal projects on an economic basis.

The production of bricks using different fueled systems is an emerging field, and many of the scientific concepts and principles are applied to overcome air pollution and improve the artisan tradition. The environmental problem is the most important, becoming a phenomenon that reaches levels of serious consequences with an irreversible environmental impact. This study aims to determine the outstanding performance of two built coupled brick kilns, enhancing the energy consumption, energy savings, and energy efficiency, through an energy analysis with thermodynamic efficiency, when fuel combustion process occurs during the brick cooking, and reduction of polluting emissions. The highest recorded amounts of energy savings and emission reductions to date suggest that the use of two coupled kilns increases energy efficiency up to 77% instead of a traditional kiln of 60.66%, and 53.83% reduction in combustion gas emissions liberated to the atmosphere. Some results with the system of two kilns obtained are 2.4 times fewer reduction in fuel consumption, 50% fewer cooking time, and higher compressive strength of bricks of 90 kgf/cm2 compared to that obtained from traditional kiln 40 kgf/cm2. The emissions of combustion gas concentrations with the two kilns coupled were reduced: (a) by stoichiometric mass balance: 58.33% CO2, 58.55% SO2, and 52.89% H2O, (b) by analytical composition by using air as an oxidant: 85.12% CO2, 4.7% HC, and 85.11% H2O, instead of steam as an oxidant, (c) average concentration emissions reduction by gas chromatography mass analysis at chimney: 67.3% CO2, 97.7% CO, 97.4% CH4, and 100% SO2.

Passive solar still is the simplest design for distilling seawater by harnessing solar energy. Although it is undeniable that solar still is a promising device to provide an additional freshwater source for global increasing water demand, low thermal efficiency along with daily distillate yield are its major disadvantages. A conventional solar still can produced 2 to 5 L/m2day. Various studies have been carried out to improve passive solar stills in terms of daily productivity, thermal efficiency, and economic effectiveness. Most of the researches that relate to the daily output improvement of passive solar still concentrates on enhancing evaporation or/and condensation processes. While the condensation process is influenced by wind velocity and characteristics of the condensed surface, the evaporation process is mainly affected by the temperature of basin water. Different parameters affect the brackish water temperature such as solar radiation, design parameters (for example water depth, insulators, basin liner absorptivity, reflectors, sun tracking system, etc). The inclined angle of the top cover is suggested to equal the latitude of the experimental place. Moreover, the decrease of water depth was obtained as a good operational parameter, however, the shallow water depth is required additional feed water for ensuring no dry spot existence. Reflectors and sun-tracking systems help solar still absorb as much solar intensity as possible. The internal reflector can enhance daily yield and efficiency of stepped solar still up to 75% and 56% respectively, whereas, passive solar still with the support of a sun-tracking system improved daily yield up to 22%. Despite large efforts to investigate the impact of the different parameters on passive solar distillation, the effect of the basin liner (including appropriate shapes and type of material), needs to be analyzed for improvement in practical utilization. The present work has reviewed the investigation of the solar still performance with various types of basin liner. The review of solar stills has been conducted critically with rectangular basin, fins basin, corrugated basin, wick type, steps shape, and cylindrical shape basin with variety of top cover shapes. The findings from this work conclude that the basin liner with a cylindrical shape had better performance in comparison with other metal types and provides higher freshwater output. Stepped type, inclined, fin absorber, and corrugated shapes had the efficient performance. Further exploration revealed that copper is the best-used material for the productivity of passive solar still.

Heat pipe solar collectors (HPSCs) are heat exchangers that carry heat based on the phase change of the heat pipe working fluid. It is aimed to increase the operating temperature range of solar collectors by changing the phase of the working fluid in the heat pipe at low temperature. For this reason, it has become widespread to use nanofluids obtained by mixing nanosized metal oxides with the base fluid in certain proportions in order to increase both the thermal conductivity of the heat pipe working fluids and to increase the specific heat closures. The main purpose of this study, which was conducted to evaluate the performance of HPSCs, is to increase performance, and an experimental study has been conducted in this direction. For this purpose, an HPSC designed and manufactured was used. Al2O3-water and TiO2-water nanofluids containing 2% nanoparticles were used in order to increase performance in the study. HPSC used in the study consists of 8 heat pipes with a length of 100 cm. The experiments were carried out for pure water and nanofluids, and their efficiency and strength were compared. The highest value of instantaneous efficiency was calculated as 48% when pure water was used as the working fluid, 58% for Al2O3-water nanofluid, and 64% for TiO2-water nanofluid. The instantaneous power obtained using pure water was determined as 135.66 W, 167.96 W for Al2O3-water nanofluid, and 184.03 W for TiO2-water nanofluid. The improvement in efficiency was determined as 20.8% for Al2O3-water nanofluid and 33.3% for TiO2-water nanofluid. Improvement in powers was found to be 23.8% for Al2O3-water nanofluid and 35.6% for TiO2-water nanofluid.

This article is the second part of the research devoted to the exergetic analysis of heat treatment processes of concrete products in heat technology installations. In the first part, the issues of calculating the exergy of a concrete mixture and hardening concrete have been considered, taking into account all the components of the exergy, viz. reaction, concentration and thermomechanical ones. In the present part of the study, exergetic criteria are proposed that make it possible to evaluate the energy efficiency of the operating modes of heat-technological equipment for the heat treatment of concrete products. These include the degree of thermodynamic perfection of a heat-power system, which is used to evaluate the completeness of the use of the exergetic input; thermodynamic efficiency of the system of heat treatment of concrete products in heat technology installations, representing the degree of thermodynamic perfection of the heat power system that is calculated without taking into account all the components of the sum of transit exergies; thermodynamic efficiency of the heat treatment system, taking into account the exergetic efficiency of the system of heat energy production and transportation; the degree of technological perfection that indicates at the portion of the exergy supplied to the heat technology installation for the heat treatment of concrete products is intended to obtain a technological result. To calculate the listed indicators and characteristics, a mathematical apparatus is proposed that takes into account the mass of the concrete product, the specific mass exergy of cement and hardening concrete, the specified degree of hydration of cement in concrete at the end of heat treatment, the exergetic flows supplied to the product in a heat technology installation during its heat treatment, and numerical indicators characterizing the incompleteness of the cement hydration process. The results obtained in this paper are discussed from the viewpoint of their applicability in the selection of heat treatment modes. They can be used in the selection of energy-saving modes of heat-technological equipment for industrial heat treatment of concrete products.

The combination of photovoltaic and photothermal, often abbreviated as PV/T, is a promising approach that has been increasingly studied to improve solar energy conversion efficiencies. In this paper, a low-concentration bifacial PV/T system (LC-BiPV/T) which uses double-axis tracking module and direct-contact glass-channel was built. The electric and thermal performances of this system are studied experimentally. When the series and parallel waterflow configuration is compared, the result shows that the average electric efficiency of the direct contact glass-channel LC-BiPV/T system is 13% and the average thermal efficiency is 48.13% when running at series configuration. When the average electric efficiency is 14.90% and the average thermal efficiency is 58.69% at parallel configuration. In general, the thermal and electric performance of this system are excellent, and the series configuration can further improve both efficiencies of the system. This experimental result can aid on the improvement of future energy-using.

PurposeThe different performance tests were conducted on diesel engine compression ignition (CI) mode and CRDi engine.Design/methodology/approachThe CI engine was suitably modified to CRDi engine with Toroidal re-entrant combustion chamber (TRCC) and was run in dual-fuel (DF) mode. Hydrogen (H2) was supplied at different flow rates during the suction stroke, and 0.22 Kg/h of hydrogen fuel flow rate (HFFR) was found to be optimum. Diesel and biodiesel were used as pilot fuels. The CRDi engine with DF mode was run at various injection pressures, and 900 bar was found to be optimum injection pressure (IP) with 10o before top dead center (bTDC) as fuel injection timing (IT).FindingsThese operating engine conditions increased formation of oxides of nitrogen (NOx), which were reduced by exhaust gas recycle (EGR). With EGR of 15%, CRDi engine resulted in 12.6% lower brake thermal efficiency (BTE), 5.5% lower hydrocarbon (HC), 7.7% lower carbon monoxide (CO), 26% lower NOx at 80% load as compared to the unmodified diesel engine (CI mode).Originality/valueThe current research is an effort to study and evaluate the performance of CRDi engine in DF mode with diesel-H2 and BCPO-H2 fuel combinations with TRCC.

The improvement in performance has been observed by changing the injector nozzle's geometry of the dual-fuel liquid–gas engine. The combined effect of injector parameters and producer gas (PG) derived from the redgram stalk on the performance and emission characteristics of a dual-fuel diesel/Honge Oil Methyl Ester (HOME)-PG operated CI engine has been studied. The injector nozzles with 4, 5, and 6 holes (diameter of 0.2, 0.25, and 0.3 mm) were analyzed. Diesel-PG operation with 4 holes, 0.25 mm diameter nozzle and HOME-PG operation with 6 holes, 0.25 mm diameter nozzle resulted in better performance and lower emissions. Diesel-PG operation has 4.5% higher BTE (brake thermal efficiency) with a 4 hole nozzle and 0.7% higher for a 0.25 mm diameter 6 holes nozzle than HOME-PG operation. The HOME-PG operation results showed that the with an injection opening pressure of 240 bar, 6-hole nozzle, and a diameter of 0.25 mm have an improved BTE of 5.8% with emission levels 15–30% lower than those of other geometries.

The box type solar cooker is a user-friendly solar energy harvesting system suitable for domestic cooking in tropical countries. The benefit of adding aluminum fins to the lids of the cooking vessels in a solar cooker is investigated in this experimental study. Four different cylindrical aluminum cooking vessels that are un-finned and finned vessels with varying fin lengths of 25 mm, 35 mm, and 45 mm are used to heat water—outdoor experiments are conducted for five days each case. For all four configurations, water is observed to attain a peak temperature of 102 °C in a closed system. The maximum temperature range maintained is between 90 °C and 100 °C for about two to 3 h during outdoor testing. The attained thermal efficiency and heat transfer coefficients are 56.03% and 58.54 W/m2°C, respectively, for the 45 mm finned configuration. The boiling point of water is attained in 2 h and 17 min using the cooking vessel with 45 mm fins. The results of the stagnation and sensible heating tests show that the finned cooking vessels have higher thermal performance than the conventional un-finned vessel due to increased heat transfer surface.

Recent research has been focusing on using various media in glazing cavities to minimize heat transfer through translucent elements of buildings. During this study, the thermal efficiency of a Phase change material (RT28HC) glazed unit was experimentally investigated compared with that filled with air in dry arid region. Then, the effect of PCM thicknesses on the thermal efficiency of double-glazing unit (DGU) was investigated using Fluent software including internal temperature, temperature time lag, total transmitted energy, and liquid fraction. The results indicated that the effect of using PCM on room temperature is high. The internal layer's peak temperature time lag in PCM-filled DGU was around 5 h than common DGU. Also, increasing the PCM thickness can effectively improve thermal performance parameters till thickness 30 mm, and more thickness can reverse the variation trend. Hence, these outcomes could contribute to the thermal regulation of highly glazed buildings in dry arid region of Egypt.

The application of tire pyrolysis oil (TPO) as an alternative fuel has attained attention owing to the exponentially raise demand and price of fossil fuels, environmental impacts, and landfilling of the waste tires. Globally, the pyrolysis process has become the leading solution to this problem by converting the waste tires to the TPO. So, this review paper studies the application of TPO in diesel engines related to the purification and physicochemical properties of TPO with their effects on the combustion, performance, and emission characteristics of the fuel. Oxidative desulfurization and catalyst process is the most reliable method to remove the sulfur contents and purified the tire pyrolysis oil. Higher cylinder peak pressure, heat release rate, and ignition delay has been observed and noted its impact on the combustion analysis of the TPO. An increase in brake power, brake thermal efficiency, and lower brake specific fuel consumption have been found in the performance analysis of TPO. In emission analysis literature, mixed trends have been seen in nitrogen oxides and hydrocarbon emission, so in some cases, emission tends to increase, but the opposite direction has also been observed in other cases. Carbon monoxide and carbon dioxide and particulate matter emission are reduced owing to the excess of oxygen shares in TPO. In general, no alteration in the diesel engine is required for a low share of TPO in the TPO-diesel blend. Finally, it is concluded that the studies recommended the TPO-diesel (10%–90%) blend in the engine as an alternative fuel.

In this article, six-lobed absorber tube equipped with combined turbulators was investigated. To enhance the productivity of solar unit, hybrid nanoparticles were added in to working fluid. Helical coil and twisted tape have been employed together. For evaluating the thermal behavior and exergy loss, average solar flux were imposed in boundary condition. Also, variable heat flux was applied to evaluate the thermal efficiency including air gap for solar system. Homogeneous model for hybrid nanomaterial was utilized and outputs were presented to analyze the impact of changing operating fluid. Selecting six-lobed tube instead of circular tube leads to better cooling performance and lower exergy loss. When Re = 10000, convective coefficient augments about 3% while exergy drop declines about 5.198% with using six-lobed tube. Insertion of twisted tape for lower Re leads to augmentation of h by 1.666% and reduction of exergy drop about 1.828%.To scrutinize the influence of width ratio and ( w ˜ ) and revolution number ( n ˜ ) for coil insert, exergy drop and friction factor values in form of bar chart were presented. Velocity augments with rise of both factors and impingement of fluid with wall increases which provides higher pressure drop and lower exergy drop. Exergy loss decreases about 8.671% and 6.286% with augment of n ˜ and w ˜ when Re = 5000. Owing to nice attributes of hybrid nanofluid, not only convective flow augments but also exergy loss reduces by adding such particles. Dispersing nanoparticles can enhance the convective flow about 9.096% and 8.438% for circular tube and six-lobed tube with turbulator, respectively. Also, exergy loss for six-lobed tube with turbulator reduces about 8.562% with adding hybrid nanomaterial. Replacing, six-lobed tube with turbulator instead of circular tube leads to reduction of exergy drop about 17.907% while convective coefficient augments about 12.719%. Augmenting solar irradiation enhances the thermal efficiency about 180.24% and outlet temperature rises from 293.2 K to 293.36 K when Re = 5000.

The use of nuclear reactors is a large studied possible solution for thermochemical water splitting cycles. Nevertheless, there are several problems that have to be solved. One of them is to increase the efficiency of the cycles. Hence, in this paper, a thermal energy optimization of a Sulfur–Iodine nuclear hydrogen production cycle was performed by means a heuristic method with the aim of minimizing the energy targets of the heat exchanger network at different minimum temperature differences. With this method, four different heat exchanger networks are proposed. A reduction of the energy requirements for cooling ranges between 58.9-59.8% and 52.6-53.3% heating, compared to the reference design with no heat exchanger network. With this reduction, the thermal efficiency of the cycle increased in about 10% in average compared to the reference efficiency. This improves the use of thermal energy of the cycle.

This paper deals with analysis of the influence of fuel injection pressure with ternary fuel (diesel + Mahua methyl ester + Pentanol) on the emission, combustion and performance characteristics of a four stroke, single cylinder, common rail direct injection diesel engine working at a constant speed and varying operating scenarios. The usage of ternary fuel raised the NOx emission (12.46 %) value and specific fuel consumption (SFC) with a decrease in the BTE (brake thermal efficiency) which attributes to its properties and combustion characteristics. The combustion process was affected by the physical properties of the blended fuel such as volatility and viscosity and this eventually affected the performance of the engine. The fuel injection pressure is varied from 20 MPa to 50 MPa so that ternary fuel can be properly utilized. The high injection pressure of 50 MPa has better combustion characteristics and higher brake thermal efficiency (4.39 %) value than other injection pressure values. A better mixture is formed due to well atomized spray and as a result, the levels of CO (22.24 %), HC (9.49 %) and smoke (7.5 %) falls with the increase in injection pressure.

Concentrating solar power technology is one of the most promising alternative energy technologies. In recent past, Linear Fresnel Reflector systems have received great attention and novel designs have been proposed keeping in view the objective to enhance its functionality and performance. For achieving the same objective, this study presents a novel concept where a conventional LFR is enclosed in a greenhouse called greenhouse-LFR. It was expected that such an enclosure can: (1) increase the incoming solar radiation, (2) further improve the overall efficiency due to simplified cleaning process and (3) reduce the capital cost for the construction of LFR support system. A complete thermal and optical analysis was presented for modeling and performance evaluation of the solar field of both conventional-LFR and novel greenhouse-LFR. Sets of non-linear equations for each system were solved using Newton-Raphson method. More detailed optical analysis was further performed for conventional-LFR considering the seasonal variations. The results concluded that the greenhouse-LFR is better than the conventional-LFR as it had higher efficiency and useful heat with lesser heat losses. For greenhouse-LFR, the maximum thermal efficiency was 73.2% whereas for conventional-LFR it was 37.2%. Also, there was an average increase of useful heat by 3 times in the month of February and 4.7 times in the month of September. SolTrace™ analysis indicated significant spillage loss when a conventional-LFR was used without a secondary reflector or slight curvature of the mirrors.

A double-pass solar air heater (DPSAH) with shot blasting and winglets in the air passage is a recommended cost-effective design development to enhance thermal performance. Three different absorber plate configurations for DPSAHs were experimentally tested: (a) V-corrugation with shot blasting, (b) V-corrugation with shot blasting and a 4-3 winglet pattern, and (c) V-corrugation with shot blasting with a 3-2 winglet pattern. Furthermore, aluminum winglets were welded to the DPSAH absorber plate to increase the channel turbulence to enhance the heat transfer performance. The pressure drop and thermal performance of the DPSAHs with and without winglets were investigated using meteorological parameters such as ambient temperature, wind speed, solar irradiance, and interior temperature at regular time intervals. V-corrugation with 4-3 winglets has a maximum thermal efficiency and pressure drop of 49.5 % and 230 Pa, respectively, at a mass flow rate of 0.02 m/s. Results showed that the thermal efficiency of V-corrugation with 4-3 winglets was improved by a maximum of 7 % compared with the V-corrugation air heater. Finally, increasing the mass flow rate from 0.01 kg/s to 0.02 kg/s increases the pressure drop by 1.22 times for the V-corrugation and 1.3 times for the V-corrugation with 4-3 winglets. Furthermore, a complete economic study of DPSAHs for India is examined in this article.

The present work focuses on the techno-economic assessment and multi-objective genetic algorithm optimization of small-scale (40 kWth input), solar Organic Rankine Cycle (ORC) systems driven by medium-to-high temperature (up to 210 °C) parabolic dish (PDC) and trough (PTC) collectors. The ORCs are designed to maximize their nominal thermal efficiency for several natural hydrocarbon working fluids. The optimization variables are the solar field area and storage tank capacity, with the goal of minimizing the levelized cost of produced electricity (LCoE) and maximizing the annual solar conversion efficiency. The lowest LCOE (0.34 €/kWh) was obtained in Athens for a high solar field area and low storage tank capacity. Meanwhile, the maximum annual solar conversion efficiencies (10.5–11%) were obtained in northern cities (e.g., Brussels) at lower solar field locations. While PTCs and PDCs result in similar efficiencies, the use of PTCs is more cost-effective. Among the working fluids, Cyclopentane and Cyclohexane exhibited the best performance, owing to their high critical temperatures. Notably, the systems could be more profitable at higher system sizes, as indicated by the 6% LCoE decrease of the solar ORC in Athens when the nominal heat input was increased to 80 kWth.

Compression-ignition (CI) engines can produce higher thermal efficiency (TE) and thus lower carbon dioxide (CO2) emissions than spark-ignition (SI) engines. Unfortunately, the overall fuel economy of CI engine vehicles is limited by their emissions of nitrogen oxides (NOx) and soot, which must be mitigated with costly, resource- and energy-intensive aftertreatment. NOx and soot could also be mitigated by adding premixed gasoline to complement the conventional, non-premixed direct injection (DI) of diesel fuel in CI engines. Several such “dual-fuel” combustion modes have been introduced in recent years, but these modes are usually studied individually at discrete conditions. This paper introduces a mapping system for dual-fuel CI modes that links together several previously studied modes across a continuous two-dimensional diagram. This system includes the conventional diesel combustion (CDC) and conventional dual-fuel (CDF) modes; the well-explored advanced combustion modes of HCCI, RCCI, PCCI, and PPCI; and a previously discovered but relatively unexplored combustion mode that is herein titled “Piston-split Dual-Fuel Combustion” or PDFC. Tests show that dual-fuel CI engines can simultaneously increase TE and lower NOx and/or soot emissions at high loads through the use of Partial HCCI (PHCCI). At low loads, PHCCI is not possible, but either PDFC or RCCI can be used to further improve NOx and/or soot emissions, albeit at slightly lower TE. These results lead to a “partial dual-fuel” multi-mode strategy of PHCCI at high loads and CDC at low loads, linked together by PDFC. Drive cycle simulations show that this strategy, when tuned to balance NOx and soot reductions, can reduce engine-out CO2 emissions by about 1% while reducing NOx and soot by about 20% each with respect to CDC. This increases emissions of unburnt hydrocarbons (UHC), still in a treatable range (2.0 g/kWh) but five times as high as CDC, requiring changes in aftertreatment strategy.

A bubbling humidification-dehumidification (HDH) desalination system directly heated by concentrated sunlight is presented in this work. Sending directly the concentrated sunlight into bubbling humidification chamber can save the circulation pipeline and solar receivers, and reduce the heat loss of the pipeline which simplifies the device's structure and adds its operation reliability. The HDH system consists of a Fresnel lens solar concentrator, a bubbling humidification chamber and a bubbling dehumidification chamber. The operating principle and the structural design of the bubbling chambers are explained. A cylindrical Fresnel lens is used to focus sunlight into the humidification chamber to directly heat the seawater. With air coming out from the perforated wall of the immerged pipe, bubbles will generate underwater to obtain sufficient heat and moisture transfer. Experimental tests under different conditions were carried out to verify the design and study the performance characteristics. The results that the maximum freshwater productivity is about 1.24L/h/m2 when the maximum solar irradiance is 980 W/m2. The accumulated yield can reach 5.61L/d/m2 with an average thermal efficiency about 69% for sunny weather conditions in October in Beijing. Besides, the average thermal efficiency is about 71% under steady-state condition. Compared to some published works, the proposed bubbling HDH desalination system has relatively higher freshwater productivity owing to its effective heat and moisture transfer enhancement by direct solar heating and bubbling. The economic analysis showed that the price of the produced water for the system is about 0.027$/L.

As a rule, the highest permissible sulfur content in the marine fuel must drop below 0.5% from 1 January 2020 for global fleets. As such, ships operating in emission control areas must use low sulfur or non-sulfur fuel to limit sulfur emissions as a source of acid rain. However, that fact has revealed two challenges for the operating fleet: the very high cost of ultra-low sulfur diesel (ULSD) and the installation of the fuel conversion system and the ULSD cooling system. Therefore, a solution that blends ULSD and biodiesel (BO) into a homogeneous fuel with properties equivalent to that of mineral fuels is considered to be significantly effective. In the current work, an advanced ultrasonic energy blending technology has been applied to assist in the production of homogeneous ULSD-BO blends (ULSD, B10, B20, B30, and B50 with blends of coconut oil methyl ester with ULSD of 10%, 20%, 30% and 50% by volume) which is supplied to a small marine diesel engine on a dynamo test bench to evaluate the power and torque characteristics, also to consider the effect of BO fuel on specific fuel consumption exhaust gas temperature and brake thermal efficiency. The use of the ultrasonic mixing system has yielded impressive results for the homogeneous blend of ULSD and BO, which has contributed to improved combustion quality and thermal efficiency. The results have shown that the power, torque, and the exhaust gas temperature, decrease by approximately 9%, 2%, and 4% respectively with regarding the increase of the blended biodiesel rate while the specific fuel consumption and brake thermal efficiency tends to increase of around 6% and 11% with those blending ratios.

An improved evacuated absorber tube (AT) design consisting of a semi-circular tube is proposed for large-aperture parabolic trough concentrator. The absorber tube also contains a flat-plate radiation shield in the vacuum part of the tube in the glass cover. To enhance the heat transfer in the AT, different fins geometries added to the bottom of the AT were analyzed here. Compared to an AT without fins, the thermal efficiency of the tube could be increased from 75.7% to 76.9% with a short and thick fin and to 77.3% with a long and thin fin in the flow velocity range of 0.4–1.5 m/s. The long and thin finned AT shows better enhancement of heat transfer, but the heat transfer performance factor also accounting for frictional losses is higher for short and thick fin. Simultaneously, increasing the number of long and thin fins in the AT would not improve much the heat transfer performance.

In the current study, a passive single-slope solar distillation unit has been proposed. An incorporated condenser has been integrated into the system to promote the condensation rate and hence improve the unit productivity. External fins have been used as a means to enhance the condenser performance further. The system performance has been examined experimentally for seven consecutive summer days in Mashhad city located at 36° 18′56.12″ N latitude and 59° 34′4.66″ E longitude. The unit yield and efficiency have been compared to the corresponding data for a conventional solar still tested in Tehran city. The results reveal that using fins increases the distillate in the condenser by 35%. But, there is only a 5% increase in the total unit productivity due to a reduction in distillate on the glass cover by 8%. Compared to the typical solar still tested in Tehran, up to 92.3 and 86% increase in daily productivity can be achieved using the current still with and without fins, respectively. The thermal efficiency of the currently proposed structure is about double than is it for the traditional solar still. The economic feasibility of the current solar still has been compared to some passive and active designs found in the literature, where it has been found not only efficient but less costly as well. The system without fins is the least expensive with C P L = 0.007 $ / l / m 2 , while the one with fins is slightly more expensive with C P L = 0.0117 $ / l / m 2 but still economically outstanding.

The present study provides an analytical and numerical investigation of the energy and exergy analysis of a v-corrugated solar air heater (VCSAH) integrated with twisted tape insert (TTI). The TTI is placed in the air passages formed by the absorber and backplates. The effect of design parameters such as twisted tape ratio (Y) and the number of channels (N) on the thermo-hydraulic performance is examined for a wide range of Reynolds number (Re) under realistic weather conditions data. The results reveal that as the Y decreases, the thermo-hydraulic efficiency of VCSAH-TTI is first rises to a specific value of Re to reach the peak value, and then drops down. The optimal number of channels that provides maximum thermo-hydraulic efficiency is N = 5 when the TTI is implemented. The maximum thermal and thermo-hydraulic efficiencies of VCSAH-TTI observed are 17.5 and 17%, respectively, compared to the VCSAH without TTI. Besides, the thermal efficiency is directly proportional to the number of channels. At Re = 10,000, the thermal efficiency is found to be 69.3% and 76.7% for N = 4 and N = 14, respectively. The accumulated useful heat gain of the proposed design is 17% higher than VCSAH without TTI.

Low thermal efficiency is one of the main problems in using solar collectors in different fields. In the present study, the effect of using phase change materials (PCM) inside the Flat plate collector (FPC) on the thermal performance and overall drying efficiency of FPC was investigated. Four PCM positions were considered inside of the collector, and the results compared with the collector without PCM. Experimental results implied that specific energy consumption for drying tomato slices is between 11.12 and 9.01 MJ/kg. The drying time of the slices using the collector with PCM at the end section was decreased about 21.87%. Based on the position of PCM, the thermal efficiency of FPC increased by about 5.02%-10.13%. The overall efficiency varied from 21.92% to 25.72% for different PCM positions. CFD simulation of the system was performed by Ansys 2015, and it showed that the thermal performance of the collector could be predicted with good accuracy (R2 > 0.9432). Moreover, the result of evolutionary polynomial regression models applied for each PCM position. It confirmed that outlet temperature and thermal efficiency of collector predicted with acceptable accuracy (R2 > 0.98). Due to the use of PCM at the end section of the collector, a homogeneous drying process, normal temperature, and short drying time resulted. The quality of tomato slices dried by the solar dryer was higher than other positions.

Flat plate solar collector plays a significant role in domestic water heating due to the ease of operation and maintenance. The rmal energy storage with phase change materials is used to store heat energy. The thermal performance of paraffin wax-based multitube latent heat storage with a flat plate solar collector is investigated experimentally. The present work focuses on the fluid flow direction for charging and discharging in a vertical multitube-based thermal storage unit. The charging process took about four hours, with a fluid flow rate of 0.02 kg/s at about 70°C . The flat plate solar collector's thermal efficiency is 56.42% for the fluid flow rate of 0.02 kg/s at the average solar radiation of about 600 W/m 2 . During the discharge process, there was an increase in water temperature by 40°C at a fluid flow rate of 0.01 kg/s in 30 minutes. The 25-liters of water is circulated to discharge the stored heat. The heat storage effectiveness is varied between about 0.4 and 0.75. During the discharge, the flow of water from the center to the periphery showed about a 1.7% higher temperature than that of the water from the periphery to the center. For charging the heat storage, the preferred fluid flow mode is from the periphery to the center. The employment of latent heat storage with a solar collector is beneficial for our thermal needs after sunshine hours.

International audience; This paper deals with photovoltaic-thermal (PV/T) collectors that combine photovoltaic (PV) module and solar thermal (ST) modules to provide heat and electricity simultaneously. The use of a PV/T system not only enhances PV efficiency but also allows to use solar thermal energy for various heating applications. The performance evaluation of the PV/T collectors had been investigated both theoretically and experimentally for the past few years. In this work, we consider a new water-based PV/T configuration by incorporating a tedlar layer and parallel tubes and further investigate its modeling. The aim is to develop a non-linear dynamic model which gives a realistic and reasonable performance of the system. The fundamental equations are determined for the thermal part using a bond graph approach which is a generic and general tool to represent thermal transfers. Simulations are given to highlight the usefulness of the proposed design and its modeling, considering the influence of some external factors (e.g. wind action) and internal geometrical parameters (e.g. insulator thickness). The results indicate that the rise in wind speed can reduce thermal efficiency from 70% to approximately 40%. The results also show that with an increase in insulator thickness, there is a sudden change in outlet temperature but thicknesses of more than 0.14 m is not required as the energy losses become constant. The assessment of the electrical and thermal performance of a PV/T collector is taken into consideration for a sample weather condition of southern France. Further, our results are compared to existing experimental and numerical ones from the literature on alternative PV/Ts design to validate and demonstrate the viability and consistency of our model.