Dropshafts with an internal divider for air circulation are proposed to reduce air entrainment in plunging type dropshafts. Dropshafts typically operate under a pressurized downstream condition and with limited air supply from the top. In this study, experiments were conducted to investigate the performance of the dropshaft with an internal divider under different downstream conditions and air inlet conditions. From the experiments, a pressurized downstream condition would increase the air pressure in the dropshaft, reduce the outside air entrainment while increase the internal air circulation. Reducing the size of the air inlet would decrease the air pressure, meanwhile cause an increase in internal air circulation and a reduction in outside air entrainment. A dimensionless parameter of ‘effectiveness factor’ was also proposed to measure the effectiveness of the internal air circulation on reducing the outside air entrainment. This study considers the performance of the dropshaft with a divider under the conditions close to real situations, which is important to its design and application.

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