Browsing by Author "Phipps R"
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- ItemRetrofitting solar air heaters in New Zealand schools – A randomized crossover intervention study(Elsevier B.V, 2024-06-15) Wang Y; Phipps R; Boulic M; Plagmann M; Cunningham C; Guyot GMost New Zealand (NZ) schools rely on natural ventilation and are often inadequately ventilated in winter. NZ school hours typically span from 9 a.m. to 3 p.m. and are well aligned with optimum solar radiation. Existing classrooms could therefore be heated and ventilated using retrofitted solar energy applications. To investigate the suitability of a commercially available solar air heater (SAH) to improve ventilation, a randomized crossover intervention study was conducted in 12 classrooms from six primary schools in Palmerston North, NZ, during the winter of 2014. Typical performance results showed a mean (standard deviation, SD) SAH outlet air temperature of 29.2 (10.4) °C at a mean (SD) velocity of 0.7 (0.3) m·s-1. During most school periods (64–99%) classrooms maintained required thermal comfort. The concurrent use of the extant heaters was reduced, and carbon dioxide levels were improved, lowering exposure for occupants. This study confirmed that retrofitting SAHs contributed to improved classroom ventilation, increased thermal comfort and reduced energy use. Optimising performance would require design improvements to improve airflow in order to comply with NZ ventilation and indoor air quality requirements for schools.
- ItemReview of the thermal efficiency of a tube-type solar air heaters(Elsevier B.V., 2024-05-11) Pardeshi PS; Boulic M; van Heerden AH; Phipps R; Cunningham CWThere is an urgent need to provide evidence that solar air heaters can be effective for heating and ventilating low-rise buildings. Solar air heaters are devices that can convert solar energy into thermal energy for moderate and low-temperature applications such as space heating, preheating, crop drying, and the food industry. However, its efficiency is low due to the low heat transfer coefficient between the absorber and the flowing air, but they are also simple to construct and operate as there is low-risk leakage of heat transfer liquids. The two main types of solar air heaters are flat plate and tube-type. To date, flat plate solar air heaters have received the most attention in the research literature, but evidence of the efficiency gains from using tube-type solar air heaters is growing. The study aims to provide up-to-date information on tube-type solar air heaters, which will help advance the development and uptake of solar air heaters. The research showed that thermal efficiency gains could be achieved by altering the design of the solar air heater including different artificial roughness geometries inside the tubes, integrating solar thermal energy systems, application of coatings or reflectors inside the solar air heaters, or using evacuated tubes and micro heat pipe array systems. This literature study showed that evacuated tubes and micro heat pipe array systems have higher thermal efficiency than other techniques. Based on the detailed discussion of various techniques for improving the thermal efficiency of solar air heaters, a new roughness geometry was proposed.