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Heat Recovery (heat + recovery)
Selected AbstractsEnhancement of Thermoelectric Figure-of-Merit by a Bulk Nanostructuring ApproachADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Yucheng Lan Abstract Recently a significant figure-of-merit (ZT) improvement in the most-studied existing thermoelectric materials has been achieved by creating nanograins and nanostructures in the grains using the combination of high-energy ball milling and a direct-current-induced hot-press process. Thermoelectric transport measurements, coupled with microstructure studies and theoretical modeling, show that the ZT improvement is the result of low lattice thermal conductivity due to the increased phonon scattering by grain boundaries and structural defects. In this article, the synthesis process and the relationship between the microstructures and the thermoelectric properties of the nanostructured thermoelectric bulk materials with an enhanced ZT value are reviewed. It is expected that the nanostructured materials described here will be useful for a variety of applications such as waste heat recovery, solar energy conversion, and environmentally friendly refrigeration. [source] Performance analysis of an industrial waste heat-based trigeneration systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2009A. Khaliq Abstract The thermodynamic performance of an industrial waste heat recovery-based trigeneration system is studied through energy and exergy efficiency parameters. The effects of exhaust gas inlet temperature, process heat pressure, and ambient temperature on both energy and exergy efficiencies, and electrical to thermal energy ratio of the system are investigated. The energy efficiency increases while electrical to thermal energy ratio and exergy efficiency decrease with increasing exhaust gas inlet temperature. On the other hand, with the increase in process heat pressure, energy efficiency decreases but exergy efficiency and electrical to thermal energy ratio increase. The effect of ambient temperature is also observed due to the fact that with an increase in ambient temperature, energy and exergy efficiencies, and electrical to thermal energy ratio decrease slightly. These results clearly show that performance evaluation of trigeneration system based on energy analysis is not adequate and hence more meaningful evaluation must include exergy analysis. The present analysis contributes to further information on the role of exhaust gas inlet temperature, process heat pressure, ambient temperature influence on the performance of waste heat recovery-based trigeneration from a thermodynamic point of view. Copyright © 2009 John Wiley & Sons, Ltd. [source] On the steady-state modelling of a two-stage evaporator systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2001M. N. A. Hawlader Abstract We develop and validate against experimental measurements a steady-state two-stage flooded refrigerant evaporator model for a heat pump drying system. A prototype two-stage heat pump dryer test facility was designed, built and instrumented to provide the required measurements for the validation of the model. Repeatability and data quality tests were conducted to evaluate the accuracy of measurements. Experimental data could be reproduced to within ±6.5 per cent of replicated air and refrigerant side measurements for the same evaporator's air inlet conditions while the discrepancy of energy balance at the air-side and refrigerant-side was observed to be within ±8.9 per cent. The two-stage evaporator model predicted the air-side total heat and latent heat transfer of the two-stage evaporator to within (,6.3 per cent, 7.6 per cent) and (,11.5 per cent, 9.5 per cent), respectively. On the refrigerant-side, the model enabled the calculation of the degree of superheat to within (,10.6 per cent, 1.7 per cent). The model has shown that there is significant improvement in the heat recovered from a two-stage evaporator system compared to a single evaporator system. In addition, the model demonstrated that the improvement in total heat recovery could be as high as 40 per cent over its base-value when the latent to total load at the two-stage evaporator is increased. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis of mechanical driver and power generation configurations, Part 1: Optimization frameworkAICHE JOURNAL, Issue 9 2010Frank L. Del Nogal Abstract This article presents a novel, systematic, and robust procedure for driver and power plant selection based on mathematical programming. The discrete nature of gas turbines is considered as gas turbine drivers and gas turbine-based power plants are selected from a group of candidates. Plant availability with considering parallel compression has also been included, which allows a more comprehensive exploitation of the trade-offs between capital costs, operating costs, and availability. When neglecting process heating and any steam equipment, the formulation can be applied to heavily power dominated processes, such as LNG. However, a more comprehensive formulation, allowing waste heat recovery and the integration with a multilevel steam system, is also proposed to produce more thermally efficient systems. This approach proved to be flexible and robust and is the first in producing solutions ranging from no-steam to all-steam systems, including all-gas turbine, all-motor and hybrid gas turbine/motor/steam systems. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Development of an electrochemical cell for efficient hydrogen production through the IS processAICHE JOURNAL, Issue 8 2004Mikihiro Nomura Abstract The Bunsen reaction (SO2 + I2 + 2H2O = H2SO4 + 2HI) was examined by an electrochemical cell featuring a cation-exchange membrane as the separator, using sulfuric acid dissolving sulfur dioxide as the anolyte and hydriodic acid dissolving iodine as the catholyte. In galvanostatic electrolysis, the molality of H2SO4 in the anolyte and that of HI in the catholyte were increased up to 17.8 and 14.9 mol kgH2O,1, respectively. These concentrations were far higher than those that were obtained by the Bunsen reaction carried out in the presence of a large amount of iodine (such as I2/HI = 4). I2 concentration after the concentration procedure was at I2/HI = 0.95, which is lower than the reported value. I2 is one of the recycling agents in the IS process. HI and H2SO4 were successfully concentrated under low I2 concentration. The concentration of HI agreed with the calculated value, based on the amount of electricity consumed, indicating high current efficiency. Heat/mass balance using this type of electrochemical cell through the IS process is discussed for evaluation of the reactor. The thermal efficiency to produce hydrogen was calculated at 42.1%, without heat recovery for electricity, by optimizing HI and H2SO4 concentrations after application of the electrochemical cell. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1991,1998, 2004 [source] Erkenntnisse über Lüftung und Energieverbrauch sowie Bodenplattendämmung aus Monitoring-Untersuchungen an einem Passivhaus-SchulgebäudeBAUPHYSIK, Issue 1 2008Søren Peper Dipl.-Ing. Über zweieinhalb Jahre Monitoring einer Passivhaus-Schule und Kindertagesstätte (KiTa) in Frankfurt a.M. zeigt behagliche raumklimatische Bedingungen bei guten Luftqualitäten. Die Heizwärmeverbrauchswerte liegen wie erwartet niedrig und zeigen Einsparungen um 90 % gegenüber dem Durchschnitt im Bestand. Auch primärenergetisch bewertet, weist die Schule beste Resultate auf. Die Ergebnisse zu weiteren Untersuchungen der effizienten Lüftungsanlage mit Wärmerückgewinnung, den umlaufenden Dämmschürzen als Alternative zur Bodenplattendämmung und dem Einfluss der Luftwechselrate durch die Eingangstüren werden vorgestellt. Monitoring of a Passive House School Building. More than two and a half years of monitoring of a Passive House school and day-care centre in Frankfurt a. M. show comfortable indoor climate and good air quality. The space heat consumption is low and shows savings of approximately 90 % as compared to average existing schools. Excellent performance was also achieved in terms of primary energy. The results of further analyses of the efficient ventilation system with heat recovery, the perimeter insulation as an alternative to floor slab insulation and the influence of the air change due to the entrance door are presented. [source] | ||||||||||