Search Results (2)

The performance of a building drainage system, “BDS”, is determined by the complexity of internal airflow and pressure dynamics, governed by unsteady wastewater flows from randomly discharging appliances such as WCs, sinks, and baths. Designers attempt to optimise system safety by equalising pressure and incorporating ventilation pipes and active devices such as AAVs and positive pressure reduction devices (PPRDs). However, failures within these systems can lead to foul gases and potentially hazardous microbes entering habitable spaces and posing a risk to public health. This study, for the first time, develops a novel model that simulates the effect of air from the sewer on BDS performance, which describes the correlation between system airflow and air pressure under the influence of air from the sewer. A combination of full-scale laboratory experiments representing a 3-storey building and real-world data from a 32-storey test rig configured as a building demonstrated that sewer air significantly modifies airflow and air pressure within a BDS. These findings are crucial for modern urban environments, where the prevalence of tall buildings amplifies the risks associated with air pressure transients. This work paves the way for updating codes to more effectively address real-world challenges. Full article

To improve the consistency of sectional gas velocities in different rows in the pneumatic conveying line for a paddy side-deep fertilisation system, a new airflow equaliser was designed based on the mechanism of gas flow in ventilation engineering. Subsequently, the effects of key structural parameters and a position parameter of the airflow equaliser on the consistency of sectional gas velocities in different rows were investigated using the method of single-factor tests in Fluent, which provided a reasonable range for the next orthogonal test (notch angle (A): 120–180°, extended length (B): 18–30 mm and distance between adjacent branches (C): 120–160 mm). Thereafter, the parameters were optimised through an orthogonal test, using the coefficient of variation of the consistency of the sectional gas velocities in different rows (CV) as an indicator and using Fluent software. The results revealed that the order of primary and secondary factors was evaluated as B > A × B > C > A, and when A, B and C were selected as 150°, 30 mm and 120 mm, respectively, the consistency of the sectional gas velocities in different rows could get a very effective result (CV = 7.07%). Finally, to validate the feasibility of simulations of the performance of the airflow equalisers and to practically evaluate the contribution of the optimised airflow equalisers to improve the consistency of the sectional gas velocities in different rows, a bench test for the line with the optimised airflow equalisers and a simulation test for the line without the optimised airflow equalisers were carried out and the results showed that the CV values were 9.53%, 20.69%, respectively. It concluded that the optimised airflow equalisers could significantly improve the consistency of the sectional gas velocities in different rows by comparing the CV in the three tests including the simulation test for the line with the optimised airflow equalisers. This research provides a good reference for optimising the pneumatic conveying line for a paddy side-deep fertilisation system. Full article