An Application Test of Centralized Spray Cooling System Modeled on Boiling Movement

A centralized spray cooling system for farm buildings was developed and tested under a practical production condition in summer. The inner air passage of its cooling installation was made as the shape of a funnel, gradually enlarged from the bottom to the top, so that the airflow velocity in the cooling installation decreased from the bottom to the top gradually. Higher air velocity near the air inlet at the bottom could resist most drops falling, lower velocity near the top could make the drops which were moving upward with airflow slow down and fall back to the bottom of the installation, so that the time that spray drops contact with airflow could be prolonged, and a high density of drops in airflow could be kept with a lower water flow. The tests covered the ranges of average airflow velocity from 1.1m/s to 2.8m/s, and spray pressure from 0.06MPa to 0.16MPa, water/air coefficient (the ratio of the mass of sprayed water to airflow) from 0.08 to 0.5. It was showed that the evaporative cooling efficiency of the cooling installation could attain 80 % or more even at lower water/air coefficient from 0.1 to 0.2. In fair weather, the inside air temperature of the greenhouse, in which the centralized spray cooling installation was employed, was 2～5.5 ℃ lower than outside temperature, and 4～7.5 ℃ lower than that by mechanical ventilation only. When the cooling installation was running, the inside air relative humidity was 70 %～95 %. The total ventilation pressure loss was 40.3 Pa. In addition, the distribution of drops with different sizes in the cooling installation was surveyed and analyzed.