查看更多>>摘要：Film cooling is an essential external cooling technology in turbomachinery. In this paper, firstly, an original hole on the flat model was optimized with the radial basis neural networks surrogate model and cuckoo search optimization algorithm. The optimization variables are the laid-back angle, half of the expend angle and the cylindrical length. Subsequently, the optimized holes are arranged in a linear cascade for experimental verification. To verify the optimization method, the cooling performance of original and optimized holes on the linear cascade was investigated under different blowing ratios and positions. Compared with the original hole, the optimized one has various expand angle, laid-back angle and proportion of the expanded section. The experimental tests were conducted in a linear cascade which has three turbine blades. The mainstream flow parameters were set with Reynolds number (inlet) values of 4.3 x 105 and Mach number (outlet) values of 0.4. The adiabatic temperature near the profile was measured by an infrared camera. As the results of the SS3 row presented, on the surface of the film hole downstream where x/d is within 5, the film cooling effectiveness of the optimized hole is more significant than original hole. In the downstream of hole rows where x/d is between 5 and 40, the eta of optimized hole is lower than original hole, since the optimized hole has a larger expand angle than the original hole. At the PS4 row, the eta of optimized hole is higher than original hole at any M.
查看更多>>摘要：The liquid cooling (LC) systems for large battery modules commonly involve many LC plates (LCPs) or other cooling components for achieving a high cooling efficiency. This leads to a greatly reduced energy density of the battery modules, and raises the cost of the cooling system. To overcome the contradiction between the cooling performance and structure complexity, a simple yet effective LC structure comprising only two LCPs and lightweight Al-plates, is proposed herein by precisely designing the channel shape of the LCPs and systematically optimizing the cooling structure. Based on the finite element method, a three-dimension coupled with multiphysics model is applied for the battery module during the discharge process. The numerical simulation results show that the well-defined structure of the LCPs, i.e., two inlet channels merging into one outlet channel covering all the batteries, can effectively relieve the "edge-overcooling" phenomenon existing in such simple structures. Combining with optimizing the inlet velocity and Al-plate thickness, the cooling performance can be further enhanced to a comparable level with that of the traditional complex structures. For example, with an Al-plate thickness of 4 mm and an inlet velocity of 0.275 m center dot s- 1, the maximum temperature and maximum temperature difference of the battery module can be controlled below 31.80 and 3.70 degrees C, respectively. As highlighted here, apart from the excellent cooling performance, such a simple cooling structure only accounts for 16.4 wt% of the module weight, much lower than those in previous investigations, and can be expanded more easily to largerscaled battery modules with diversified specifications, particularly those simultaneously targeting lightweight and high cooling performance.
查看更多>>摘要：This paper presents a novel dual-mode search algorithm for refrigerant circuitry optimization, which is implemented in two modules, namely, the knowledge-based computational module (KBCM) and the permutationbased computational module (PBCM). The KBCM determines the appropriate number of tubes for each heat exchanger circuit based on the related non-uniform airflow velocity distribution, whereas the PBCM establishes the optimal or near-optimal sequence in which tubes are linked. The method is designed to maximize the heat exchanger capacity while minimizing the computational costs by excluding infeasible circuits. By combining the KBCM and PBCM techniques, significant gains of 9.64%, 9.87%, 6.96%, and 7.16% in the heat exchanger capacity are observed for the part-load cooling conditions according to the European standard EN14825, particularly for outdoor unit heat exchangers with a non-uniform airflow distribution.
查看更多>>摘要：Previously, a set of optimistic studies have been published to show the efficiency of chemically recuperated gas turbines (CRGT) based on steam methane reforming. The thermodynamic efficiency of such turbines is depending not only on temperature and pressure in a cycle but also on temperature, pressure and steam to-methane ratio in a recuperation system. In this paper, the effect of operational parameters (temperature, pressure, steam-to-methane ratio) on the efficiency of CRGT was determined. Exhaust heat recuperation in CRGT is taking place due to methane reforming, steam-methane mixture heating, and steam generation. A thermodynamic enthalpy of steam methane reforming process was determined via Gibbs free energy minimization method. The thermodynamic analysis of CRGT was performed in Aspen HYSYS. The efficiency of CRGT was determined for a wide range of operational parameters (gas turbine inlet temperature of 800- 1500 degrees C, pressure of 5-25 bar, steam-to-methane ratio of 1...3). Based on the analysis it was confirmed that the efficiency of CRGT and thermochemical exhaust heat recuperation system is increasing with an increase in temperature. An increase in temperature and steam-to-methane ratio leads to an increase in a share of recuperated heat in a reformer. The heat recuperation rate is up to 0.63 for a high-temperature gas turbine and a steam-to-methane ratio of 3. The efficiency of CRGT is up to 49% for gas turbines with inlet gas temperature of 1500 degrees C which is an available level in modern gas turbines from Mitsubishi, Siemens, Alstom, etc.
查看更多>>摘要：Efficiency optimizations of industrial processes will play a key role in future actions reducing the global greenhouse gas emissions. This also applies to the industrial high temperature sector whereby the approach of thermochemical recuperation (TCR) is promising for such applications. The current paper thus presents the first report of experimental investigations into TCR in industrial scale (200 kW power input) and in recuperative mode with combined steam reforming and partial oxidation of methane applied inside the reactor. In contrast to previous investigations in industrial scale reported, which exclusively focused on regenerative concepts, the use of oxygen as part of the reactants plays a key role with respect to the following aspects: (I) Methane conversion: CH4 conversion rates higher than 80% were observed for all adjusted operation points. Efficient conversion of methane to syngas was thus provided by the approach. (II) Temperature control: The addition of oxygen influenced the temperature distribution inside the reactor considerably, causing an increase of the average temperature from 771 ? to 801 ?. Consequently, oxygen addition is an appropriate method for temperature control inside the reactor. (III) Efficiency: The furnace power input was increased by a maximum of 12.1% compared to conventional oxy-fuel combustions without TCR.
查看更多>>摘要：Gas driven sorption heat pumps can be an efficient alternative to conventional gas condensing boilers for heating buildings. Measurement results of a functional prototype of a gas adsorption heat pump with 40 kW nominal capacity and the SAPO-34-water working pair are presented. The innovative adsorption heat exchanger is directly crystallized applying the partial support transformation technique. A transient lumped-parameter model of the gas adsorption heat pump is developed. For the first time, it is possible to perform an annual simulation of the GAHP within the heating system of a multi-family house with full adsorption dynamics based on calibrated and validated component models. This annual performance calculation is carried out for the two different low-temperature heat sources geothermal heat (bore hole heat exchanger) and exhaust air. Using exhaust air as low-temperature heat source for a GAHP is an entirely new approach that is evaluated in this study. Compared to a gas condensing boiler, the annual gas consumption is reduced by 22 % for the case of bore hole heat exchanger and by 27 % for the case of exhaust air as low-temperature heat source for a building with heating circuit design temperatures of 45 degrees C/35 degrees C.
查看更多>>摘要：The efficiency improvement of traditional seawater source heat pump system is limited and pipelines of the open seawater cooling air conditioning system experience scaling and corrosion. To overcome these problems, this paper proposes a deep seawater closed cooling air conditioning system. The system directly uses the closed heat exchange pipeline to exchange heat with the deep seawater and extracts the seawater cooling capacity for cooling. Numerical simulation is used to study the effects of different pipe diameters, flow rates, and inlet water temperatures on the heat transfer performance of vertical inlet sections, submarine heat exchange coils and vertical outlet sections. Since seawater has temperature and flow rate gradients in the vertical direction, the use of a hydraulic calculation table of the vertical pipe section and the calculation diagram of design and selection line of submarine heat exchange coil is proposed. Insulating subsections of the outlet section by dividing the section into 3 ?C based on the seawater temperature is proposed. And the subsection insulation layer thickness corresponding to different pipe diameters are given. This study proposes a calculation method for the selection of key design parameters of deep seawater closed cooling air conditioning systems, providing a new method for making full use of seawater resources.
查看更多>>摘要：An efficient and energy-saving battery thermal management system is important for electric vehicle power batteries. Cold plate cooling systems with channels are widely used for lithium-ion batteries, and the optimisation of cold plate structure, channel shape, and number is the key to research. Inspired by the Tesla valve-type microchannel heat sink used in microelectronics, we propose a cold plate with Tesla valve-type channels for rectangular lithium-ion batteries. Compared with the Z-type channel, the Tesla valve-type channel enhances heat exchange and improves temperature uniformity owing to the fluid disturbance caused by its bifurcated structure, especially under strong heat flux. Moreover, based on an accurate battery thermal model at a discharge of 3C established through thermal characteristic experiments, a numerical simulation is conducted to analyse the influence of some factors, including the angle between adjacent Tesla valves, distance between adjacent Tesla valves, distance between adjacent channels, and coolant inlet velocity. Finally, the agent models of evaluation indicators with fit goodness greater than 97% are obtained through a central composite design. The multiobjective optimisation results show that the reverse Tesla valve-type channel cold plate with an angle of 120 degrees, Tesla valve distance of 23.1 mm, channel distance of 28 mm, and inlet velocity of 0.83 m/s have a good balance between heat exchange performance and energy consumption, which controls the battery maximum temperature below 30.5 degrees C while maintaining a low channel pressure drop.
查看更多>>摘要：With rapid rise of advancement in soft computing models, application of Machine Learning (ML) techniques has increasingly grown to successfully evaluate thermal characterizations of solar systems in the last decade. Compared with related literature, this research aimed to obtain accurate relationships based on the ML techniques for predicting the energy and exergy efficiencies of the parabolic dish concentrator box solar still fitted with thermoelectric condensing duct and antiseptic nanofluid (PDCBSSTCDAN) system. Effective variables that affect energy and exergy efficiencies are listed as the nanoparticle volume fraction, fan power, solar radiation, basin temperature, nanofluid temperature, ambient temperature, wind velocity, and productivity. By adding 0.05% and 0.1% by volume of Fe3O4@Ag nanoparticles to the basin water, the maximum production of distilled water has increased by 410 (ml/m(2)) and 580 (ml/m(2)), respectively, compared to the pure fluid. At the most optimal case, the cost of producing distilled water and the payback period are 0.0072 ($/L/m(2)) and 141 day, respectively. After having completed the development of ML techniques, empirical equations based on nature-inspired properties of ML models were obtained to estimate energy and exergy efficiencies with a reasonable degree of accuracy level. Results of ML models indicated that Evolutionary Polynomial Regression (EPR) technique yielded comparatively performance in the prediction of energy (Root Mean Square Error [RMSE] = 0.827) and exergy (Root Mean Square Error [RMSE] = 0.1078) efficiencies than Multivariate Adaptive Regression Analysis (MARS), Gene-Expression Programming (GEP), and M5Model Tree (MT). ML techniques could outperform the results of the previous investigations in terms of precision level and applicability of proposed empirical equations. Overall, the proposed equations can be conveniently utilized to perceive the physical characterizations of solar still systems.
Al Bardan, MayyadaHamouda, Mohamed A.Shaaban, Mostafa F.Eldean, Mohamed A. Sharaf...
25页
查看更多>>摘要：This paper presents a technoeconomic assessment of a solar-driven co-generation system that suits medium/ large-scale water production and power generation. The system consists of a concentrated solar tower combined with a gas turbine cycle for power generation and combines reverse osmosis (RO) with multi-effect distillation (MED) for the desalination. Two operational scenarios for the gas turbine exhaust waste heat were assessed for energy efficiency, cost, and environmental impact. The first scenario involves maximizing power generation using organic Rankine cycle operation. The second scenario uses the waste heat from the solar gas turbine cycle to operate the multistage flash (MSF) to produce more water. The co-generation system with the two scenarios were modeled using MATLAB Simulink toolbox. The results reveal that the second scenario yields remarkable results in terms of lower hourly costs (2974 $/h), total water price (0.27 $/m3), and CO2 emissions (401 tCO2). MSF has the highest exergy destruction rate (5.632e6 kW), followed by the solar gas turbine cycle (8.843e6 kW). However, RO had the lowest exergy destruction rate (3294 kW), followed by the organic Rankine cycle (1.023e4 kW).
NSTL
Elsevier