Abstract
The integration of chemisorption cycle with turbine/expander opens up enormous opportunities of recovering low grade heat to meet different energy demands including heating, cooling and power generation. In the present study, a novel advanced resorption power generation (RPG) cycle with reheating process has been proposed for the first time to significantly improve the thermal efficiency and exergy efficiency of the basic RPG cycle. Such a reheating concept is built on the premise of chemisorption monovariant characteristic and identification of the optimal desorption temperature aiming at producing the maximum work output under the given working conditions. The identified optimal desorption temperature might be lower than the available heat source temperature, and the desorbed ammonia vapour is subsequently reheated to the heat source temperature before it undergoes vapour expansion for power generation. This study explored the potential of the proposed advanced RPG cycle and investigated the system performance using three representative resorption sorbent pairs, including manganese chloride – sodium bromide, manganese chloride – strontium chloride, and strontium chloride – sodium bromide, all with ammonia as the refrigerant. The application of reheating concept can improve the total work output of RPG cycle by 10–600%, depending on different sorbent pairs and different heat source temperatures studied in this work, e.g., when the heat source temperature is at 200°C, the thermal efficiency is increased by 1.4–4.5 times and the exergy efficiency is boosted by 2.0–8.3 times. Another valuable merit of the proposed RPG cycle is that there is a great potential of considerable amount of additional cooling output without compromising the maximum work output, leading to further improvement of system efficiency. Compared to other bottoming cycles for power generations, the proposed advanced RPG cycle exhibits the highest thermal efficiency when the heat source temperature is between 120°C and 200°C.
Highlights
There have been massive researches and developing efforts on sorption technology, including absorption and adsorption cycles for air conditioning and refrigeration [1], heat pump and heat transformation [2,3], dehumidification and desalination [4], energy⇑ Corresponding author.storage [5], etc
The work output using different sorbent pairs in the first half resorption power generation (RPG) cycle are shown in Fig. 5(a), (c) and (e) under different heat source temperature and different desorption temperature; the work output in the second half-cycles are shown in Fig. 5(b), (d) and (f)
Compared to the basic RPG cycles, the thermal efficiency of the advanced RPG cycle is increased by 1.4, 2.0 and 4.6 times and the exergy efficiency is boosted by 2.9, 2.0 and 8.3 times, respectively for MnCl2– SrCl2, MnCl2–NaBr, and SrCl2–NaBr pair when the heat source temperature is at 200 °C
Summary
There have been massive researches and developing efforts on sorption technology, including absorption and adsorption cycles for air conditioning and refrigeration [1], heat pump and heat transformation [2,3], dehumidification and desalination [4], energy⇑ Corresponding author.storage [5], etc. There have been massive researches and developing efforts on sorption technology, including absorption and adsorption cycles for air conditioning and refrigeration [1], heat pump and heat transformation [2,3], dehumidification and desalination [4], energy. The current sorption technology encounters challenges not just from technical aspect and in relation to economical issue as it is trudging towards the fiercely competitive and crucial commercial market, above all different specific reasons, the prevailing argument in favour of sorption systems is the potential of using environmentally friendly refrigerants and harnessing low grade heat, leading to energy efficiency improvement and CO2 emission reduction [1,2].
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