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Abstract Waste heat recovery has attracted a significant attention because of the world growth in energy demand. In this paper, we report the study on an energy recovery system utilizing low-grade waste heat below 100 °C. This system called a thermal-driven electrochemical generator is composed of reverse electrodialysis (RED) power generation and thermal separation using waste heat. We especially focus on the experimental characterization of the RED process with ammonium bicarbonate (NH4HCO3) solution, which is known to be easily decomposed at the temperature around 60 °C. We characterized this NH4HCO3-RED system with various parameters including the concentration difference, the membrane type, the inlet flow rate, and the compartment thickness. We found the best power density at the concentrated solution of 1.5 mol L−1 and the diluted solution of 0.01 mol L−1. The maximum power density increases as the inlet flow rate increases or the compartment thickness decreases owing to the decrease in the internal resistance. We obtained the excellent power density of 0.77 W m−2, compared with the previous studies.

Abstract In this study, performance of R430A is examined numerically and experimentally in an effort to replace HFC134a used in refrigeration system of domestic water purifiers. Even though HFC134a is used predominantly in such a system these days, it needs to be phased out in near future in most of the developed countries due to its high global warming potential. To solve this problem, cycle simulation and experiments are carried out with a new refrigerant mixture of 76%R152a/24%R600a using actual water purifiers. This mixture is numbered and listed as R430A by ASHRAE recently. Test results show that the system performance is greatly influenced by the amount of charge due to the small internal volume of the refrigeration system in water purifiers. With the optimum amount of charge of 21–22 g, about 50% of HFC134a, the energy consumption of R430A is 13.4% lower than that of HFC134a. The compressor dome and discharge temperatures and condenser center temperature of R430A are very similar to those of HFC134a for the optimum charge. Overall, R430A, a new long term environmentally safe refrigerant, is a good alternative for HFC134a in domestic water purifiers requiring no major change in the system.

Abstract How to send CO2 into deep ocean is one of the key technologies for the ocean storage of CO2. In this paper, techcical aspects on sending liquid CO2 into deep ocean with a long vertical pipe hung from a floating platform are investigated. Among lots of technical subjects to be solved, the prediction method of CO2 condition in temperature and pressure along the pipe is studied, and also the dynamic behavior of the pipe under the storm condition is discussed. The feasibility is fundamentally confirmed in the case study.

Abstract Afforestation on a large scale has a possibility to be a countermeasure against the global carbon dioxide problem. There are, however, many problems that should be solved. In the present paper, the importance of systems approach of greening is emphasized and discussed. The systems adopted here are the system of land utilization, social and industrial, and energy supply as well as the estimation method of energy balance. And also several technological problems are discussed in terms of construction of ecological model and simulation of artificial rainfall for water.

This study is concerned with dynamic simulation of a CaO/Ca(OH)2 chemical heat pump system. The system consists of a hydration/dehydration reactor connected to a condenser/evaporator with a control valve between. During the dehydration process, heat is supplied at 673 K for dehydration of Ca(OH)2, and steam is condensed at 293 K. During the hydration process, heat is supplied at 290 K for evaporation of water, and the heat of hydration is supplied to a load at 353 K. A mathematical model has been developed using time dependent mass and energy conservation equations and kinetic equations. Thermodynamic functions are used to calculate the thermodynamic parameters, and heat transfer in both reactors is considered. Using the dynamic model, simulation of an experimental prototype system has been performed. Various time dependent parameters, such as CaO/Ca(OH)2 temperature, dehydration energy, condensation energy, evaporation energy, hydration energy etc. have been compared with experimental data. The results showed that the model and the computer code was satisfactory and could be used for dynamic simulation of CaO/Ca(OH)2 heat pump systems in various applications.

Abstract This study used moving line source technique as a practical approach to simultaneously determine effective thermal conductivity, groundwater velocity and borehole resistance. It mainly focused on the applicability of this approach for observing the effect of groundwater extraction, in particular for ungrouted ground heat exchangers. The thermal response tests were carried out for different ground heat exchangers at two sites on the Akita University campus, northern Japan. The test conditions varied, based on different borehole filling condition (grouted/ungrouted), heat loads and presence of an extra pump for groundwater extraction. The hydro-thermal parameters of the ground were determined by a MATLAB code, especially for consideration of the effect of artificial groundwater velocity under a special test, where a water pump extracts the groundwater from the casing of the borehole during the test. This method can estimate the groundwater velocity and the effective thermal conductivity of the soil by reproducing the temperature distribution in the well and minimizing the root mean squared error between the calculated results and the measured data. As a result, the groundwater velocity and thermal conductivity calculated by this method improved to 205.3 cm/day and 7.48 W/m K, respectively, due to presence of the external pump, whereas the undisturbed groundwater velocity in the other cases without pumping was estimated in the range of 15 to 16 cm/day. Furthermore, the minimum groundwater velocity and thermal conductivity were reported for the grouted well as being equal to 10.79 cm/day and 1.16 W/m K, respectively.

Abstract In this study, two pure hydrocarbon refrigerants, R1270 (propylene) and R290 (propane), and three binary mixtures composed of R1270, R290 and R152a were tested in a refrigerating bench tester with a scroll compressor in an attempt to substitute R502, which is used in most low temperature and transport refrigeration applications. The test bench provided 3–3.5 kW capacity, and water and water/glycol mixture were employed as the secondary heat transfer fluids. All tests were conducted under the same external conditions, resulting in the average saturation temperatures of −28 and 45 °C in the evaporator and condenser, respectively. The test results showed that all refrigerants tested had 9.6–18.7% higher capacity and 17.1–27.3% higher COP than R502. The compressor discharge temperature of R1270 was similar to that of R502, while those of all the other refrigerants were 23.7–27.9 °C lower than that of R502. For all alternative refrigerants, the charge was reduced up to 60% as compared to R502. There, of course, was no problem with mineral oil, since the mixtures were mainly composed of hydrocarbons. Since some of them are mixtures, one can change their compositions a little to suit various needs in many applications without significant deterioration of the performance. Overall, these alternative refrigerants offer better system performance and reliability than R502 and can be used as long term substitutes for R502 due to their excellent environmental properties.

Abstract One of major complications, expected in the scale-up of operation of a MEA process, in which 2-aminoethanol is used as a chemical absorbent, is an increase in gallons of waste amine solution disposed from reclaimer bottoms by degradation. This study was designed to evaluate the use of biodegradation by pure cultures of Escherichia coli K12 for that treatment. The results obtained indicate that this microorganism effectively cleaves waste 2-aminoethanol to ammonium ion and acetaldehyde, assimilates ammonium ion as a nitrogen source and transforms acetaldehyde to acetic acid. The biodegradation activity was positively affected by the presence of impurities in waste 2-aminoethanol solution. An experiment with chemostat resulted a degradation rate of 1.64g/(dm3·h), which is suggestive of a good possibility of an integration of this ecotechnology to the MEA process.

Abstract The wastewater of the textile industry has approximately 60 °C of temperature and a sufficient quantity of organic compounds for biofuel yielding. The low-grade heat recovery and biofuel extractability of the effluent are considered to be two potentials for the generation of the various energy demands such as cooling, heat, and power (CCHP). In this study, a novel cascade trigeneration system driven by a biofuel production source (BPS) from the textile wastewater is introduced and modeled energetically and economically. The BPS system consists of two separate thermophilic and mesophilic stirred tanks, which operate based on the anaerobic digestion process. The CCHP system comprises a Brayton top power cycle (BC) and three bottoming sub-systems, including the Rankine power cycle (RC), modified Kalina/vapor-compression refrigeration system (KVC34), and water heating unit (WHU). The feasibility demonstration and parametrical optimization of the proposed system were conducted from thermal, technical, and economic points of view. The results demonstrated that that textile wastewater has a transcendent potential for biofuel production. Moreover, the methane content of biofuel was enhanced by roughly 28% by dividing the AD process into two separate thermophilic and mesophilic reactors. additionally, the synchronic cooling, heating, and power efficiency of the trigeneration system was around 62%, with approximately five years of the discounted payback period.