Keyword: thermal

9 results found.

Research Article
Thermal Performance Assessment of External Wall Construction for Energy-Efficient Buildings
European Journal of Sustainable Development Research, 2022, 6(3), em0189,
ABSTRACT: Building envelope such as external walls are still constructed from poor materials which results in higher heating and cooling loads thereby raising energy bills. Improving building energy efficiency with advanced technologies is being sought. In this context, a numerical study was conducted to solve the coupled heat transfers through a standard wall structure used in Libyan residential buildings. Different techniques were compared to reduce the thermal transmittance of the traditional wall structure for saving energy including the application of radiant shield, low-e coating, insulating filling and external insulation. The numerical results revealed that the thermal radiation inside the cavities of hollow block is important and accounts for 21% of total heat transfer, while conductive and convective heat transfer contributes by 65% and 14% from the total, respectively. The obtained thermal transmittance value of the common wall structure was considered as high as 2.33 W/m2·K due to lower resistance of wall elements. The adoption of 50 mm layer of expanded polystyrene insulation (EPS) to the exterior wall showed the best thermal performance with a reduction of thermal transmittance by 45%. On the other hand, filling the interior of cavities with EPS resulted in a 37% reduction of thermal transmittance compared to 20% of using 3 mm aluminum foil as a radiant barrier in the middle of the cavities. The last case was less effective with a reduction of almost 10% when a commercial coating of 0.4 surface emissivity was applied to the interior of cavities.
Review Article
Selected Thermo-Chemical Biorefining: Evaluation of the Current Trends and Progressions
European Journal of Sustainable Development Research, 2021, 5(2), em0154,
ABSTRACT: The review paper embodies the current trends and advancements involved in the transformation of biomass to enhanced products, bioenergy, and chemicals. Some selected chemical process like the slow-fast pyrolysis, catalytic fast pyrolysis, hydrothermal liquefaction, transesterification and lignin valorization by depolymerization are aptly suited for biorefinery processing, and were discussed in this review. The (catalytic) fast pyrolysis and hydrothermal liquefaction are quite similar, but differ in their feedstock preparations, reactor configuration and thermal or energy optimization. The review covers the biomass selection, chemical conversion techniques and most importantly the required heterogeneous catalysts (where applicable). The work further suggests the superiority of dedicated chemicals over drop-in and smart drop-in chemicals, due the complete usage of biomass. Relative to the oil refinery process, biorefining is quite novel and accompanied by its drawbacks. These challenges range from catalyst poisoning and deactivation to energy intensiveness and eventually as being cost-ineffective. The challenge encountered in biorefinery is in the economic feasibility, as it is inferred from this review that the pre-treatment process takes up to about 20% of the conversion cost. Although the biorefinery plant employ lignocellulosic biomass, but study shows that the use of biomass is largely under-utilized. The solid products/ wastes from pyrolysis for example, can be utilized as source of energy for the process. In the pursuit for sustainability, it is essential to ensure a balance-energy-mix, where every other type of energy will have a role to play to avoid dependence on only one solution for the future. Therefore, in contrast to the dwindling fossil fuels, it can be generally speculated that the future for biorefining is bright. It was concluded that with vast knowledge on the suitable heterogeneous catalysts and proper optimization of process parameters (temperatures, pressure, and reactant species); some of the biorefining processes will result into a significant increase in industrial fuels and bio-based drop-in chemicals leading towards commercialization.
Research Article
Performance Study of an Advanced Micro-gasifier Stove with Coconut Shell
European Journal of Sustainable Development Research, 2019, 3(4), em0101,
ABSTRACT: In this paper, an attempt has been made to study ACS IES-15 micro-gasifier stove tested with Coconut shell. The testing procedure followed to evaluate the performance of the stove is as per the standard protocol WBT 4.2.3, and the results are analysed in terms of thermal efficiency, firepower, specific fuel consumption, turndown ratio and specific energy consumption. It was found that the thermal efficiency of fixed bed advanced micro-gasifier cook stove ACS IES-15 is 36.7±0.4%. Experiments have also been accomplished to provide data to investigate the performance parameters of the new stove. Prominently the turndown ratio was found to be 3.3 shows better control on the combustion of new stove. Economic analysis of the stove reveals better pay back period for coconut shell.
Research Article
Performance Evaluation and parametric optimization of a Heat Sink for Cooling of Electronic Devices with Entropy Generation Minimization
European Journal of Sustainable Development Research, 2019, 3(4), em0100,
ABSTRACT: Thermal management is essential for electronics products. Experimental and CFD analysis of a heat sink for thermal management are represented. After analysis, compared with the experimental and computation analysis. Also, Entropy generation model, fluid flow model and heat transfer model are described. Total entropy generation calculated Sgen and entropy generation minimization are done for best utilization of heat sink for cost, size and better power management. Optimized heat sink by two method one Parametric Optimization and other Multi-variable optimization for minimizing entropy generation. From the results behaviour of mass flow rates with temperature, velocity, pressure drops and other parameters are analysed. The maximum temperature is located at heated base surface of heat sink, below the channel outlet, due to the low velocity of the fluid flow and resulting high concentration of heat flux. The combined conduction–convection heat transfer in the heat sink produces very complex three-dimensional heat flow pattern with large, longitudinal, upstream directed heat recirculation zones in the highly conducting aluminium materials, where the fluid and solid are in direct contact. A detailed description of the average heat transfer coefficient, temperature, heat flux and Nusselt number was obtained. The goal of this research is to find the cooling of heat sink at minimum entropy generation for saving energy and sustainable development.
Research Article
Heat Transfer Performance Analysis of Screen Mesh Wick Heat Pipe Using CuO Nano Fluid
European Journal of Sustainable Development Research, 2019, 3(2), em0080,
ABSTRACT: In this paper, the effect of multilayer screen mesh wicks and CuO nano-fluid as working fluid is investigated on the performance of heat pipe. Three heat pipes were fabricated with different layers of screen mesh wicks to improve capillary action of working fluid. Heat pipes of 350 mm length and 19.5 mm diameter were used. The different mesh configurations used in this work were 100+150 mesh, 100+2X150 mesh and 4X150 meshes. The concentration of CuO nano-fluids in the experiments was maintained at 1% by weight of water. The heat pipes are tested with water and CuO as working fluid for different heat inputs of 35W, 50W 75W, 100W and 120W. The thermal resistance and heat transfer rate were determined. It is found that the thermal resistance decreases with increase in heat input. There is increase in heat transfer rate in case of CuO nanofluid loading in ordinary water compared to distilled water as working fluid. For all orientation the maximum heat transfer through the heat pipe increased as the number of mesh layer of the wick is increased. The heat transfer rate is found to be maximum at 100 l/h mass flow rate compared to that of 150 l/h.
Research Article
On Differential Temperature Controller Setpoint Selection for Active Photovoltaic-Thermal (PV-T) Systems
European Journal of Sustainable Development Research, 2019, 3(1), em0066,
ABSTRACT: Active photovoltaic-thermal (PV-T) systems for solar heating and electricity generation are likely to employ the same differential temperature pump controllers as equivalent non-hybrid solar thermal (ST) systems. However, the typical controller setpoint selection methods for cost-effective and stable pump operation fail to consider the effect on photovoltaic (PV) electricity generation taking place in PV-T systems. Analytical relations for the same goals were derived to anticipate this influence using the steady-state Florschuetz PV-T collector model and compared with equivalent numerical methods relying on an extension of the Perers model designed to encompass PV-T collectors, namely by modelling electricity generation and the associated thermal performance reduction. Both methods indicate the minimum turn-on and turn-off setpoints for cost-effective and stable operation increase and decrease, respectively, relative to those for non-hybrid operation of PV-T systems or equivalent non-hybrid systems, and more so at higher irradiance levels, though the variations are shown not to be significant for a range of PV-T systems represented and can be reasoned to be inflated or of limited practical relevance. In conclusion, the effect of pump operation on electricity generation is not predicted to be a determining factor for differential temperature controller setpoint selection in PV-T systems.
Research Article
Optimization of Economic Load Dispatch for 2.5 MW Solar Power System
European Journal of Sustainable Development Research, 2018, 2(3), 27,
ABSTRACT: Economic load dispatch (ELD) is a complicated issue, when renewable energy sources are also considered with thermal power generation systems. It becomes challenging and difficult to find the optimum solution at lower fuel costs, in order for generated power to meet the active power load demand. This paper primarily focuses on the modeling of ELD for solar power plants synchronized with Thermal power plants. In this paper, the purposed optimization method used is Genetic algorithm (GA). According to which, all thermal generators in the system will supply output power at lowest fuel rate however satisfying the system limitations. Minimum fuel cost of a generator will be calculated by using generator characteristic curve for all generators present in the system. With the help of GA, achievable range for best solution is attained while restricting the output power of thermal generators. Proposed system priority to achieve is solar at first and generators on second such that generator or combination of generators resulting in lowest cost will be on second priority. Simulations on various test systems were performed including one with six thermal generators and the other with six thermal generators and solar power system. By using MATLAB the proposed problem is simulated.
Research Article
Balancing Comfort and Energy Use for Sustainable Buildings: Thermal Comfort Modeling using a Space-variant Manikin
European Journal of Sustainable Development Research, 2018, 2(1), 07,
ABSTRACT: To help balance comfort and energy use in residential, institutional and commercial buildings in order to make them more sustainable, a thermal comfort model is coupled with a computational fluid dynamic approach. The developed tool provides an effective tool for demand side management of energy use in buildings. The asymmetrical thermal environment in a university cafeteria building is modeled, and a two dimensional numerical simulation is prepared separately of the thermal sensation in the cafeteria. A finite volume formulation is used to provide the temperature distribution around a space-variant manikin, which is in turn utilized to determine the convective heat transfer coefficients for the simulation of thermal sensation around the manikin.
Research Article
Economic and Environmental Considerations for Zero-emission Transport and Thermal Energy Generation on an Energy Autonomous Island
European Journal of Sustainable Development Research, 2018, 2(1), 05,
ABSTRACT: The high cost and environmental impact of fossil-fuel energy generation in remote regions can make renewable energy applications more competitive than business-as-usual scenarios. Furthermore, energy and transport are two of the main sectors that significantly contribute to global greenhouse gas emissions. This paper focuses on the generation of thermal energy and the transport sector of a fossil fuel-based energy independent island in Greece. We evaluate (1) technologies for fully renewable thermal energy generation using building-specific solar thermal systems and (2) the replacement of the vehicle fleet of the island with electric and hydrogen-fueled vehicles. The analysis, based on economic and environmental criteria, shows that although solar thermal decreases greenhouse gases by 83%, when compared to the current diesel-based situation, it only becomes economically attractive with subsidy scenarios equal to or higher than 50%. However, in the transport sector, the sum of fuel and maintenance costs of fuel-cell and electric vehicles is found to be 45% lower than that of the current fleet, due to their approximately seven times lower fuel cost. Lastly, it will take approximately six years of use of the new vehicles to balance out the emissions of their manufacturing phase.