Pre-cooling water applied to porous plates of evaporative cooling systems

Efeito do pré-resfriamento da água aplicada em placas porosas de sistemas de resfriamento evaporativo

ABSTRACT:

This study assessed the ways the thermal environment is influenced by pre-cooling the water employed in wetting the porous plates present in the evaporative cooling systems (ECS). The experiment was performed using two physical models constructed on a distorted and reduced scale, which simulated closed agricultural facilities equipped with ECS made up of porous cellulose panels. In one physical model, the plates were made wet using chilled water (ECS_cw), while in the other they were moistened using natural water, at environment temperature (ECS_nw). Both inside the physical models and outside, in the external environment, the air dry-bulb temperature (t_db), black globe temperature (t_bg) and air relative humidity (RH) were measured, at 10 sec intervals. Later, the environmental indices, ECS_nw cooling effectiveness and ECS_cw performance factor were assessed. When the porous ECS plates were thoroughly wet using pre-cooled water, lowering of the thermal variables and comfort indices was seen to be greater than when wetting the plates was done using water at room temperature. An empirical equation was proposed to determine the cooling performance factor applied to the ECS_cw related to water temperature, t_db and air wet-bulb temperature.

Key words:
thermal environment; air cooling; air conditioning; chilled water