What action should an operator take if the wet-bulb temperature drops by 5 degrees while the dry-bulb temperature remains constant?

When the wet-bulb temperature drops while the dry-bulb temperature remains constant, it indicates a decrease in the moisture content of the air, which means the air is becoming drier. In this situation, lowering the cooling water temperature return can be beneficial.

By reducing the temperature of the cooling water that returns to the cooling system, you allow the system to operate more efficiently, as the lower water temperature will enhance heat transfer and cooling effectiveness. This adjustment helps to maintain optimal performance under the changed atmospheric conditions.

Operating within these parameters allows the cooling system to maximize its efficiency, ensuring that the cooling towers can effectively cool the environment despite the decrease in humidity indicated by the drop in wet-bulb temperature. In contrast, increasing the cooling water temperature or other actions might lead to reduced efficiency and effectiveness of the cooling process.