Study on the effects of apex angle of the delta-type radiator on thermo-flow performance of natural draft dry cooling tower

Abstract

A numerical model was established to reveal the effects of apex angle of the vertical arranged delta-type radiators on thermo-flow performance of natural draft dry cooling tower. When radiator number is fixed, a large apex angle along with the corresponding long tower base diameter contribute to tower performance improvement. The wide apex angle slightly mitigates air inflow deviation at radiator’s inlet and draws in more fresh air. The long base diameter alleviates the adverse impacts of internal vortex formed after air inflow convergence on heat transfer of the downstream radiators. The maximum increment of cooling capacity of the tower 15.6% is achieved under the medium wind speed of 8 m/s as apex angel increases from 48° to 60°. As wind speed further increases, sideward and leeward radiators suffer a sharp performance decline, and their performances achieve much smaller enhancement brought by apex angle increase, compared with windward radiators. So downwind deflection of internal rising airflows is more severe under a larger apex angle. When tower base diameter is fixed, larger apex angle results in fewer radiators. Although cooling capacity of the entire tower drops under this strategy, the greater heat dissipation capacity of windward radiators under a larger apex angle would gradually make up the defect of fewer radiators as wind speed increases. However, using larger apex angle but fewer radiators causes an aggravated air inflow rate imbalance among the radiators, which accelerates performance degradations of leeward radiators.