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[en] For three sites located in Burundi, Madagascar and Rwanda which have been selected after a previous study, this document reports a feasibility study and the definition of the characteristics of micro geothermal plants which could be installed there. These plants convert thermodynamic energy into mechanical and electric energy, with a recoverable power of 15 kWe. After a description of the operation of such micro-plants (principle, hot water and cold water circuits, exchangers, engine, freon circuit, electric power production, regulation and automatism), and a description of the selected sites (location, physical and chemical characteristics), a pre-sizing is reported (fluid selection, needed water flow rates, components). The report discusses the use of the produced electric power, and reports an assessment of construction costs (site development, plant construction and installation), discusses the exploitation and installation of the plant. Results are globally discussed in terms of thermal and cold water flow rates, of possible electric power, and of chemistry of underground waters. If the operation appears to be technically feasible, the cost appears to be high due to the characteristics of the thermal water temperature
[en] Thermal energy recovery of pyrometallurgy slags is a worldwide problem that is widely concerned for decades. As chemical recovery method, molten slag cascade recovery method (MS-WHCR) is proposed in this work. As typical endothermic chemical reactions, pyrolysis, gasification, calcination and reforming reactions are applied in this method. Gasification–pyrolysis system, calcination–pyrolysis system, enhanced pyrolysis system (R-SEP) and fixed carbon gasification and sorption-enhanced pyrolysis system (CG–SEP) systems of MS-WHCR method are designed. Based on the first law of thermodynamics and second law of thermodynamics, enthalpy–exergy compass analysis method is applied to analyze the exergy efficiency, consumption of reactants and products of designed MS-WHCR method, compared with traditional water quenched (WQ) method and gravity bed waste heat recovery (GWHR) method. As calculation example, 1000kg copper slag is used in this paper. The results showed that the exergy efficiency and exergy loss of WQ method are 20.7% and −947 MJ respectively. By WQ method, energy quality of molten copper slag is discounted. Copper slag particles should be fast cooled during granulation process. Thus, lots of air is blown in to make enough heat transfer with copper slag particles, which generate some exergy loss. And exergy efficiency of GWHR method is 76.9%. Using chemical endothermic reactions, MS-WHCR method improves the exergy efficiency of molten slag waste heat recovery. There is a slight fluctuation of exergy efficiency by MS-WHCR method for four kinds of systems from 66.6 to 70.1%. Fixed carbon and combustible syngas are acquired by MS-WHCR. And enhanced pyrolysis process in proposed R-SEP and CG–SEP systems improves hydrogen contents in syngas.
[en] Highlights: • An innovative exhaust air energy recovery system consisting of a BIPV/T and a TW. • Pre-heating/pre-cooling ambient air in winter/summer and producing electricity. • Genetic algorithm-based multi-objective optimization approach for BIPV/T-TW system. • Optimization leads to a 118.3% enhancement in the first-law efficiency of system. • Optimization leads to a 59.7% enhancement in the TW effectiveness. - Abstract: This paper presents a feasibility investigation of integrating an air-based photovoltaic/thermal (PV/T) system with a thermal wheel (TW) system for residential applications. The innovative system is capable of pre-heating/pre-cooling the ambient fresh air in winter/summer as well as producing electricity. The performance of the system is numerically evaluated and compared with the conventional building integrated PV/T (BIPV/T) and TW systems. Then, a multi-objective optimization approach is utilized to find the optimum values of geometric and operating parameters in order to maximize the annual average effectiveness of the TW and the first-law efficiency of the BIPV/T collector. The performances of the optimized and un-optimized BIPV/T-TW systems are compared for a complete year. The results demonstrated that the BIPV/T-TW system has a better thermal performance compared with the BIPV/T and TW systems, while it has a slightly lower electrical performance compared with the BIPV/T system. Furthermore, it was found that the annual average first-law efficiency and TW effectiveness of the optimized BIPV/T-TW system is 118.3% and 59.7% higher than that of the un-optimized system.
[en] Highlights: • Triplex loop heat pump system for ventilation heat recover is proposed. • Mass flow rate in heat pump system can be improved by triplex loop system. • COP of triplex loop is increase with the decrease of outdoor temperature. • The performance of triplex system is higher than traditional system in most cases. - Abstract: Ventilation heat recovery is an important means of effectively reducing the energy consumption of buildings. To improve the performance of a heat pump heat recovery system under large temperature difference conditions in winter, a triplex loop heat pump system, which contains three independent heat pump cycles, is proposed in place of its single loop counterpart. Operating characteristics and system performance were analyzed while indoor temperature was constant at 20 °C and as outdoor temperature dropped from 15 °C to −20 °C. Results showed that with the decrease of the outdoor temperature, the mass flow rate and temperature effectiveness of the triplex loop heat recovery system decreased whereas the heating capacity and the coefficient of performance (COP) increased. Under the experimental conditions, the COP of the triplex loop system had an advantage over the traditional heat pump system when the outdoor temperature was below 2.5 °C. When the outdoor temperature was −20 °C, the COP of the triplex system could reach 9.33, which was 23.1% higher than that of the traditional system.
[en] In the solid Breeder Blanket (BB) concepts both tritium release and heat recovery depend on the thermal performances of the breeding zone. Within the R&D activities of the Helium Cooled Pebble Bed (HCPB) breeding blanket, the knowledge of the thermal diffusivity of the breeder beds is of fundamental importance to model the transient heat transfer during the power pulses of the fusion machine. The aim of the present study is to investigate the thermal diffusivity of the breeder beds at BB relevant conditions; to this end the line heat source probe method was employed together with differential scanning calorimetry. An experimental facility, based on the line heat source probe method, was devised for the investigation of the thermal diffusivity of granular beds at breeder blanket relevant temperatures, mechanical state, purge gas type and pressure. Besides the experimental approach, literature values were used to estimate the specific heat capacity of the breeder materials starting from the specific heat capacity of the constituent compounds based on the mole fraction. In addition to the thermal diffusivity and heat capacity, a preliminary insight on the phase transitions of the reference and advanced ceramic breeder beds is given.
[en] Highlights: • A novel system for the hydrogen production utilizing steel furnace waste heat. • Heat source is integrated with the thermochemical copper-chlorine (Cu-Cl) cycle. • Energetic and exergetic performance assessment of the integrated system. • The overall energy and exergy efficiencies are 38.2% and 39.8% respectively. - Abstract: A novel integrated system for the production of hydrogen at a high pressure utilizing steel furnace waste heat is presented and analyzed in this paper. The system utilizes a hybrid thermochemical copper-chlorine (Cu-Cl) cycle. This study integrates the industrial waste heat source with the thermochemical Cu-Cl cycle combined with a hydrogen compression system. The electrical energy required by the system is provided by a supporting Rankine cycle. The hydrogen compression system compresses hydrogen to a pressure of 750 bars. The integrated system is simulated with Aspen Plus software. Energy and exergy analyses are performed for the integrated system. Results from the simulations are presented and discussed. The overall energy efficiency is 38.2% and overall exergy efficiency is found to be 39.8%.
[en] The aim of the work was to study the catalytic role of copper flash smelter deposit in the SO2-to-SO3 conversion. In addition, the effect of process gas temperature at 548 K to 1173 K (275 °C to 900 °C) on the amount of SO3 formed was addressed both in the absence and presence of genuine copper flash smelter deposit. The SO3 conversion rate changed as a function of process gas temperature, peaking at 1023 K (750 °C). A dramatic increase in the SO2-to-SO3 conversion was observed when process dust was present, clearly indicating that process dust catalyzes the SO2-to-SO3 conversion. Based on these results, the catalytic ability of the deposit may lead to sulfuric acid dew point corrosion.
[en] Highlights: • Presentation of a novel off-design method to predict radial turbine performance. • Effect of employed working fluids on radial inflow turbine performance. • The proposed meanline model presents low computational cost and high accuracy. • Accurate prediction of expander off-design performance for various fluids. • Model-based radial expander design for automotive waste heat recovery. - Abstract: This paper outlines a novel meanline off-design model to predict the performance characteristics of a radial inflow turbine that operates with ideal and real working fluids. Experimental data available in open literature were used for validation, including radial turbines that operate with both ideal gas (air) and real working fluids (R123). Initially the differences in the expansion process on a thermodynamic base between ideal and real fluids are highlighted. Then, the proposed meanline off-design model is calibrated for a few selected points and validated against experimental data for both air and R123. The comparison between the predicted and measured results presented errors less than 10% for both ideal and real gas fluids. Finally, the predicted air turbine was simulated with a real gas fluid. Relative to air, operation with R123 revealed that the peak efficiency is 12% lower and occurs at 70% lower rotational speed. The proposed methodology gives insights for accurate model-based design of organic Rankine cycle systems, as the radial turbo expander is the most crucial and expensive component of such heat recovery systems.
[en] Wastewater, collected and transported in sewers to treatment plants, is a potential source of low-carbon energy through heat recovery. This solution is particularly interesting where consistent flows of wastewater and waste heat circulate close to potential users such as swimming pools and buildings. But before looking for potential users, it is necessary to identify the sections of the sewer network with the highest waste heat recovery potential. The Department of Seine-Saint-Denis decided, as part of its energy and environment policy, to map the waste heat potential of its 550 km combined and separate sewers. Several criteria were studied to select potentially promising sections, including minimum and average dry weather flow rates. Flow rate data are abundant but disseminated in numerous documents resulting from temporary measurement campaigns carried out by municipalities and by the Department to investigate dry weather flows, or need to be calculated from continuous measurements performed for sewers operation. In both cases, the available information is very local and describes flow-rate only over a relatively small area, without directly providing information on a larger scale. This work consists therefore in collecting all the available flow-rate data (about 300 measurement points) and, through extrapolation, to provide the most comprehensive estimate of heat recovery potential possible. The result of this work comes out as a cartographic tool that allows the Seine-Saint-Denis to respond quickly to planners' requests with various information, both on the flow rates and estimated recoverable waste heat and on the reliability of the available data. (authors)
[en] Highlights: • A new model with performance reassessment is developed for HEN retrofit problem. • Temperature and duty distributions are affected by areas of reused heat exchangers. • The deviation between supply and demand of area is considered. • Network retrofitting has considerable retrofit profit with a short payback period. • 7–59% energy saving and 59–79% heat recovery rate are obtained in case studies. - Abstract: Reusing as many existing heat exchangers as possible is one of the most important strategies in retrofitting of heat exchanger networks, which can reduce investment costs and increase heat recovery in the process industry. However, the performance degradation of the existing heat exchangers due to the rough increase or decrease of the heat exchange area during the reuse of the heat exchanger seriously affects the effective implementation of the heat exchanger network retrofit scheme. To fully evaluate the performance of a heat exchanger network, a new methodology for heat exchanger network retrofit is proposed in this work. The performance simulation is introduced into heat exchanger network retrofit model to reassess the performance of reused heat exchange units. The temperature distribution and heat load distribution in the network are corrected. So the performance indicators of the retrofitted network can be accurately evaluated and then the optimal decision can be made. Genetic algorithm is adopted for the optimization of the proposed retrofit problem. Case studies show that the proposed retrofit method can achieve energy saving of 7–59% with a relatively short payback period of investment, and energy recovery of the retrofitted network can reach 59–79%.