Closed Circuit vs open circuit cooling tower
Core Difference
- Open Circuit Cooling Tower: Process water is exposed directly to the atmosphere for cooling.
- Closed Circuit Cooling Tower: Process fluid is contained within a coil; only the external spray water is exposed.
Comparison Table
| Feature | Open Circuit Cooling Tower | Closed Circuit Cooling Tower |
| Process Fluid | Open to the atmosphere. | Contained within a sealed coil. |
| Contamination Risk | High. Fluid is exposed to air, dust, and debris. | Very Low. The loop is closed and protected. |
| Water Quality | Uses the process water for evaporation. | Uses clean spray water for evaporation; process fluid stays separate. |
| Maintenance | Focused on the entire water system (pipes, pumps, etc.), which gets dirty. | Focused only on the external spray system; the process loop stays clean. |
| Freeze Protection | Difficult. Adding glycol to the entire system is costly and messy. | Easy. Glycol can be used in the sealed process loop. |
| Initial Cost (CAPEX) | Lower. Simpler design and construction. | Higher. More complex due to the coil. |
| Operational Cost (OPEX) | Higher water and chemical consumption for the entire process volume. | Lower chemical use (only for spray water) and no process water loss. |
| Energy Efficiency | Slightly more efficient in ideal conditions (direct evaporation). | Slightly less efficient due to heat transfer through the coil wall. |
| Space | Often has a smaller footprint for a given capacity. | Typically requires more space due to the coil and spray system. |
When to Choose Which?
- Choose an OPEN Circuit Tower when:
- Cooling standard water (e.g., chiller condenser loops).
- Lowest upfront cost is the main priority.
- The system is in a location with good water quality and air cleanliness.
- Choose a CLOSED-Circuit Tower when:
- Cooling expensive or sensitive equipment (lasers, medical devices).
- The process fluid must be kept clean and contaminant-free (pharmaceuticals, food production).
- Freeze protection with glycol is required.
You want to minimize long-term chemical treatment costs.