•The thermal performance of curved fins heat sink in natural convection is studied.•The overall thermal efficiency of the proposed fins is around 98%.•The suggested fins provide a mass reduction up ...to 59%.•Curved fin heat sinks improve the heat transfer coefficient by 12.52%.•The air gap between the fins is the most important factor affecting heat sink performance.
This work is an extensive numerical study of the heat dissipation and cooling of a heat- generating vertical base using corrugated fins. The overall objective is to improve the heat transfer performance for passive heat sink applications. Three-dimensional numerical simulations were performed using FLUENT; the mass conservation equation, Navier–Stokes equations and the energy equation were solved using a finite volume approach. Various geometrical configurations were considered, where the aspect ratio of the thickness (AR) for corrugated fins was adopted as the key variable for improving heat transfer performance. The applied heat flux is in the range 811.55 to 4674.56W/m2. The results for the corrugated fins were compared to those for the conventional plate fins in terms of fluid flow, temperatures, heat transfer coefficients and weights. The results show that the proposed finned heat sinks can improve the heat transfer coefficient by up to 12.52% compared to the reference-finned plate. Additionally, the curved fin design can reduce the unit weight and thus the material use by up to 59% compared with the conventional fin design. Finally, the overall thermal efficiency of the proposed fins is around98%. The proposed design presents a suitable solution for industrial applications where the mass of the heat sink substrate is significant.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Double-pipe heat exchanger with helically baffled annulus.•CFD study of heat transfer and pressure drop characteristics.•Performance comparison in turbulent and laminar flow regime.
In this paper, ...the design and thermo-hydraulic performance of a double pipe heat exchanger with helical baffles in the annulus side, are investigated numerically. Three-dimensional computational fluid dynamics (CFD) model, using the software FLUENT, have been performed to investigate the annulus side fluid flow, heat transfer coefficient and pressure drop for different configurations. A numerical analysis is conducted for different values of Reynolds number and baffle spacing (0.025–0.1m). The numerical model was first validated for a simple double pipe heat exchanger by comparison with empirical correlations. The model was then used to investigate the helical baffles effects. The results obtained for a helically baffled annulus side provide enhanced heat transfer performance and high-pressure drop compared to the simple double-pipe exchangers. Thermal performance and high-pressure drop is an increasing function of baffle spacing and Re. In addition, empirical correlations expressing the results were developed based on curve fitting.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
Improving the thermal performance of cooling systems is crucial for energy and raw material savings, increasing the thermal ratings, and extending the work life of various equipment. This paper aims ...to provide a comprehensive review of experimental and numerical research on natural convection heat transfer and fluid flow in heat sinks. This review presents the characteristics and capabilities of various feasible cooling strategies, including new methods and advanced solutions. The many research that have paid attention to the parametric study of the geometry of the heat sink are extensively discussed Key parameters with a significant impact on the heat sink’s design and performance are thoroughly discussed, including the effects of operating conditions and geometric parameters of working fluids (i.e., effect of magnetic field, use of nanofluids, etc.), and the use of phase change materials. Correlations for estimating natural convection heat transfer rates as a relation of key parameters (spacing, height, orientations) are provided and detailed. Finally, the study highlights the important points and research gaps to provide better insight and valuable guidance for researchers who intend to study, improve, or optimize any type of heat sink for different applications.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Protected crop production is rapidly expanding in the Mediterranean Basin, and particularly in Morocco. Increased local and overseas demand for these products led to a rapid development in greenhouse ...usage encouraged by government policies. The aim of this study is to investigate key design parameters that affect the thermal behavior and the heating/cooling energy need of a greenhouse situated in Agadir (Morocco). The parameters include the cladding material characteristics, shape, orientation, and air change rate. The greenhouse is modeled by a developed thermal model using TRNSYS software. The model considers the presence of the plants inside the greenhouse by adding the heat and humidity gain into the heat and water balance of the greenhouse using an evapotranspiration sub-model. The effect of evapotranspiration on the greenhouse thermal behavior was also examined in this study. A validation of the current TRNSYS simulation and evapotranspiration model was made using previous studies from the literature, and the comparison showed fair agreement. The relative error of the annually heating demand obtained by this model is 1.66%, and the evapotranspiration model used in this study shows relative deviation less than 6.5%. The results of this study indicate that the East-West greenhouse orientation is the optimum orientation as it can reduce the annual cost of air-conditioning of the greenhouse by 9.28% compared to North-South orientation. Quonset shape is the optimum greenhouse shape in Morocco as it can save 14.44% of annual cost of air-conditioning instead of the Even-span shape.
Agitated vessels (or mechanically stirred reactors) are heat exchange devices that are most widely used in many chemical and biochemical process industries, such as anaerobic digestion process. The ...mixing and heat transfer performances in these vessels are of crucial importance for increasing the energy efficiency in both batch and continuous processes. In this paper, a series of experiments were conducted to investigate heat transfer performance in agitated vessels for various configurations. In fact, this study examines the effects of heat transfer geometry (wall jacket and helical coils), heating power, and stirring speed, on the heating performance of two stirred fluids—water alone and a mixture of water and food waste. The experiments were conducted using a jacketed insulation tank with a helical coil and a propeller agitator. In each experiment, a transient method, based on measuring the temperature dependency on time, and solving the unsteady enthalpy balance, was used to determine the overall heat transfer coefficients between the agitated fluid and the heating surface. Finally, an extensive analysis of the reduced data was conducted based on temperature, heating time, heat transfer rate, heat transfer coefficient, and thermal resistance. The main finding was that the presence of food waste in agitated vessels reduces the heat rate of the agitated fluid with an average of 18.13% and 49.51%, respectively, for the case of JHX and CHX, and creates additional fouling, which further limits the heat transfer.
A Review: Ventilated Double-skin Façades Lahayrech, Safaa; Siroux, Monica; El Maakoul, Anas ...
IOP Conference Series: Earth and Environmental Science,
07/2022, Volume:
1050, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract
In the aim of reducing the effect of climate change on the environment, multiple energy efficient solutions have been developed in all energy-consuming sectors around the world, especially ...smart building design strategies in the building sector. One of these technologies are Ventilated Double-Skin Façades (VDFs), which use the thermal interaction between the external environment and the internal space of a building in order to reduce its heating or cooling loads and thus reduce the greenhouse gas emissions. They also offer multiple other benefits, depending on several parameters, including improving the building’s thermal and acoustic insulation, and providing natural ventilation and exposure to daylight. The goal of this paper is to provide a review of the available research on VDFs in literature, namely their thermal behavior, the parameters that influence it, and the main criteria used to categorize VDFs.
•Techno-economic and environmental feasibility assessment of AD plants in Morocco.•Three energy scenarios were studied, where produced biogas is exploited differently.•The optimal energy scenario is ...dependent on the cities’ number of inhabitants.•Capital cost and biogas volume have the biggest impact on the plants’ profitability.•Energy production in the designed AD plants can greatly reduce pollution in Morocco.
Developing countries face major challenges related to energy management and environment preservation, which have sparked interest in anaerobic digestion. Therefore, this study evaluates the techno-economic and environmental feasibility of anaerobic co-digestion plants in four Moroccan cities (i.e., Casablanca, Agadir, Temara, and Essaouira). These plants treat the organic fraction of municipal solid waste and sewage sludge under different energy scenarios. The considered scenarios involve burning the entire volume of the produced biogas in combined heat and power (CHP) units for electricity and heat co-generation (scenario 1), combusting a fraction of the biogas to meet the plants’ energy needs and upgrading the rest into biomethane (scenario 2), and upgrading all of the biogas into biomethane while satisfying the plants’ electric and thermal needs through electricity purchase and solar thermal systems (scenario 3). The economic evaluation results indicate that the AD plants in very large Moroccan cities (e.g., Casablanca) can be financially feasible only if scenario 3 is adopted, with an internal rate of return (IRR) of 10.14%. Concerning large, midsized, and small Moroccan cities (e.g., Agadir, Temara, and Essaouira, respectively), scenario 2 is the most economically viable, with IRR values of 13.85%, 13.64%, and 12.18%, respectively. Furthermore, the sensitivity analysis shows that the capital cost and biogas volume have the biggest impact on the profitability of the considered AD plants. From an ecological standpoint, findings show that scenario 1 is the most environmentally friendly for all the considered cities, followed by scenarios 2 and 3 (1.95, 2.02, and 2.30 kg CO2-eq/m3biogas, respectively). Additionally, using biogas as a fuel for energy production has been shown to reduce the emitted greenhouse gases by up to 37% compared to coal and by 24% compared to oil.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
This paper provides an updated literature review about greenhouse systems and helps to identify the most preferable characteristics of a greenhouse for diverse climates and operating conditions. Data ...on appropriate properties of the covering materials and comparisons of several cladding materials were extensively discussed. The selection process of the greenhouse shape and orientation for different climates is presented, and comparisons between several shapes and orientations are made. This paper also examines the existing thermal models and simulation tools used to optimize the thermal operating conditions of the greenhouse. Furthermore, many recent studies are presented where greenhouses are combined with several systems to provide a favorable microclimate for crops, under extreme, tropical and subtropical climates. Finally, other applications such as greenhouse dryers and seawater greenhouse desalination are also discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The thermal performance of a new heat sink design is presented and discussed.•The proposed geometry offers a reduction in mass up to 47% compared to plate fin.•The influence of the ripples is ...amplified when the heating power is high.•The mass specific heat transfer coefficients are improved in range of 78–112.5%.
In the present work, a new fin shape is proposed to improve the convective heat transfer in heat sinks and to reduce their weight. The problem under consideration is a natural convection with air as the working fluid. Three-dimensional numerical simulations are carried out using FLUENT 19.0, to solve the continuity, momentum, turbulence, and energy equations to predict the flow and temperature field for different fins on a vertical base. Five configurations of rippling fins are considered with two aspect ratios and different heat flux inputs. The numerical results are compared to previous data available in the literature for a vertical rectangular finned plate (reference case) to validate the model. For each configuration, the heat sink temperature field and the natural convection driven air flow are discussed. The heat flux is varied from 519.396Wm2 to 4674.565Wm2. The overall thermal performance is characterized by the heat dissipation rate per unit mass. By comparison to conventional rectangular fin, the proposed fin geometry can reduce the temperature at the heat sink base by up to 18.35 K, increase the mass specific heat transfer coefficient by up to 101.41%, and decreases the thermal resistance by 9.81%. Within the scope of this study. The case with one ripple provides the best thermal performance. The results also showed that, the flow and heat transfer enhancements are a decreasing function of Rayleigh number. Overall, the heat transfer enhancement is better with rippling fins than with the rectangular fins, with a maximal mass reduction of 47%. The proposed models provide a practical alternative to the widely adopted plate fin heat sinks, which very promising for future thermal developments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Three management strategies are proposed for treating agro-industrial wastes though AD.•Techno-economic and ecological feasibility of AD plants in north-Africa was evaluated.•The optimal waste ...management strategies depend on specific country conditions.•Capital cost and biomethane sale have the highest impact on the plants’ profitability.•The conceived plants can greatly reduce the CO2-eq emissions of the studied countries.
The agro-industrial activity, which is regarded as a pillar of the North-African economy, is responsible for generating considerable waste quantities. These byproducts can be treated through anaerobic digestion (AD), which offers various financial and ecological benefits over traditional waste disposal methods. However, the transition to this sustainable process is faced with several challenges due to the heterogeneity and seasonality of agro-industrial wastes. In this study, we proposed and evaluated three waste management strategies for treating agro-industrial wastes in large-scale AD plants conceived in specific North-African countries. These strategies involve co-digesting seasonal agro-industrial wastes, i.e., three-phase olive pomace (3POP), grape pomace, and orange peel, with the organic fraction of municipal solid waste (OFMSW) throughout the year (MS1); co-digesting the dominant agro-industrial waste (3POP) with OFMSW during the olive harvest season and mono-digesting OFMSW during the rest of the year (MS2); and co-digesting 3POP and OFMSW year-round by storing 3POP in cold storage facilities (MS3). The techno-economic findings show that the proposed AD plants would be profitable in Morocco and Algeria under both MS1 and MS2, with internal rate of return (IRR) values respectively reaching 10.8% and 18.4% under MS1 and 12.4% and 20.1% under MS2. In contrast, the conceived Tunisian plants would be financially feasible only if MS2 is adopted (IRR of 10.7%). Furthermore, the sensitivity analysis indicates that the economic performance of the proposed plants would mostly be affected by the biomethane selling price and capital cost. Additionally, the carbon footprint analysis suggests that the AD plants could, during their lifetime, reduce the CO2-eq emissions by 411, 208, and 26 Mt (under respectively MS1, MS2, and MS3) compared to the currently used waste disposal practices in the North African region.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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