| 1. |
- Bernardo, Ricardo, et al.
(författare)
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Performance Evaluation of a High Solar Fraction CPC-Collector System
- 2011
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Ingår i: Journal of Environment and Engineering. - : Japan Society of Mechanical Engineers. - 1880-988X. ; 6:3, s. 680-692
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Tidskriftsartikel (refereegranskat)abstract
- One of the most important goals on solar collector development is to increase the system’s annual performance without increasing overproduction. The studied collector is formed by a compound parabolic reflector which decreases the collector optical efficiency during the summer period. Hence, it is possible to increase the collector area and thus, the annual solar fraction, without increasing the overproduction. Collector measurements were fed into a validated TRNSYS collector model which estimates the solar fraction of the concentrating system and also that of a traditional flat plate collector, both for domestic hot water production. The system design approach aims to maximise the collector area until an annual overproduction limit is reached. This is defined by a new deterioration factor that takes into account the hours and the collector temperature during stagnation periods. Then, the highest solar fraction achieved by both systems was determined. The results show that, at 50° tilt in Lund, Sweden, the concentrating system achieves 71% solar fraction using 17 m2 of collector area compared to 66% solar fraction and 7 m2 of a flat plate collector system. Thus, it is possible to install 2.4 times more collector area and achieve a higher solar fraction using the load adapted collector. However, the summer optical efficiency reduction was proven to be too abrupt. If the reflector geometry is properly design, the load adapted collector can be a competitive solution in the market if produced in an economical way.
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| 2. |
- Davidsson, Henrik, et al.
(författare)
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Design and Performance of a Hybrid Ventilation System with Heat Recovery for Low Energy Buildings
- 2011
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Ingår i: Journal of Environment and Engineering. - : Japan Society of Mechanical Engineers. - 1880-988X. ; 6:2, s. 469-477
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Tidskriftsartikel (refereegranskat)abstract
- A new hybrid ventilation system for low energy buildings has been investigated theoretically using TRNSYS. The system is based on natural ventilation but utilizes a fan during hours when the natural driving forces are not sufficient. Heat from the exhaust air is recovered in an air-to-water heat exchanger. The heated water is pumped to the incoming ventilation air where it is heat exchanged to preheat the fresh air. Energy from solar collectors is used in combination with heat recovered from the sewage system to heat the ventilation air and to preheat the cold water for domestic use. Results from the TRNSYS simulations show that the bought annual auxiliary energy need for the new hybrid ventilation system is lower than for a conventional fan driven ventilation systems using air-to-air heat recovery units combined with an identical solar collector and sewage heat recovery unit. Since the new system is based on natural ventilation it is also more silent compared to standard mechanical ventilation systems.
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| 3. |
- Namioka, Tomoaki, et al.
(författare)
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Modeling and Analysis of Batch-Type Thermal Sludge Pretreatment for Optimal Design
- 2008
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Ingår i: Journal of Environment and Engineering. - : Japan Society of Mechanical Engineers. - 1880-988X. ; 3:1, s. 170-181
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Tidskriftsartikel (refereegranskat)abstract
- We present a model to simulate the increase in sludge temperature during batch-type thermal pretreatment of sewage sludge. The semi-theoretical model is based on energy balance as a function of operating conditions, including non-ideal factors determined by fitting. The model was verified by comparison with the results of bench-scale runs. It predicted the relationship between the operating conditions and steam input with sufficient accuracy. The test plant needed more energy input than the ideal during operation owing to the influence of the heat capacity of the apparatus. To optimize the scale of the apparatus, we simulated the treatment of 10 t of sludge. The energy input was minimized with 10 runs of a 1-t apparatus if the heat capacity of the ancillary apparatus exceeds a certain threshold, and 5 runs with a 2-t apparatus if the heat capacity is below the threshold. The influence of the boiler's performance on energy input is small, but its effect on the heat-up rate of the sludge is large. A boiler with sufficient equivalent evaporation and rated pressure will shorten the operating time.
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| 4. |
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