To maintain the energy quality with high temperature and reduce the energy loss of seasonal heat-storage in solar-assisted ground-source heat pumps (SAGSHPs), a novel SAGSHP system with the heat-cascading of borehole heat-exchangers was designed and its field-test was conducted in this paper. The borehole heat-exchangers were divided into two regions: the core region and the peripheral region. The core region can maintain a high temperature (e.g. 45 ℃), which is much higher than in previous studies, and the heat from this region can be used directly, without the operation of a heat pump. The field-test was conducted in a community in the province Shandong, China. The results indicate that a sufficient soil-temperature gradient (the temperature is high in the core but low at the periphery) can be created and maintained.The monthly averaged borehole-wall-temperature difference between the borehole heatexchangers (BHEs) at the core and the periphery can be as high as 30.1 ℃. This means that both cascaded heat-storage and heat-utilization can be realized. In addition, an average performance of CCOP=5.15 and SCOP=4.66 can be achieved. Compared with previous studies, despite the lower CCOP, a higher SCOP can be attained, thanks to heat cascade storage andutilization. The novel approach described in this paper represents a viable alternative for space heating in North China.
Improving the ventilation of sewers could control the production of hydrogen sulfide (H2S) and methane (CH4), which are associated with anaerobic conditions. In this manuscript, a ventilation method using inhaled air from the drainage of the vertical stack of a building was proposed, and a model based on the dimensional method was established to calculate the airflow rate of the inhaled air. By observing the air pressure and air velocity of the ventilation cowl and the opening hole of the sewers, it was found that the inhaled air flowed down with water and that approximately 94% of the inhaled air would flow into the headspace of the sewer to enhance ventilation. According to the model and the observed service condition of toilets in the building, the daily average quantity of the air that was used to enhance the ventilation of the sewer was approximately 149.978 m3/d. The concentration of H2S and CH4 in the sewers were zero, indicating that the inhaled air in the vertical stack of the building could effectively and persistently enhance the ventilation of sewers.
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