How To Calculate Cycles of Concentration for Cooling Tower

Introduction

In cooling tower operation, cycles of concentration (COC) is a key performance and water-efficiency metric. It describes how many times the dissolved solids in the circulating water concentrate before blowdown (controlled bleed) is required. Understanding and calculating COC helps optimize water usage, reduce chemical costs, and prevent scale, corrosion, and biological growth.

In this article, we explain what cycles of concentration are, why they matter, and how to calculate them step-by-step with real examples. We also discuss how manufacturers like Mach Cooling Tower (https://www.machcooling.com/) support efficient and reliable cooling tower systems.

 What Are Cycles of Concentration?

 Basic Definition

The cycles of concentration is defined as the ratio of dissolved solids (usually measured as TDS — total dissolved solids) in circulating water to those in the makeup water.

If makeup water has 200 mg/L TDS and circulating water has 1000 mg/L TDS:

This means dissolved solids have concentrated 5 times before blowdown.

 Why Cycles of Concentration Matter

COC influences:

• Water usage: Higher COC = less makeup water required

• Blowdown volume: Lower blowdown needed with higher COC

• Chemical dosing: Scale and corrosion control depend on concentration

• System efficiency: Balanced COC reduces operational cost

Efficient cooling tower systems designed by Mach Cooling Tower often integrate monitoring and blowdown control to maintain target COC.

 How COC Works in Cooling Towers

The Role of Evaporation

In a cooling tower:

• Warm water enters the tower

• Heat is rejected by evaporation

• Evaporation removes pure water without dissolved solids

As evaporation continues, the concentration of dissolved solids increases — this is the basis for cycles of concentration.

 Makeup and Blowdown

There are two key streams:

• Makeup water: Fresh water added to replace evaporation and drift losses

• Blowdown: Water removed to control dissolved solid concentration

The balance of these flows determines the COC.

 Step-by-Step Calculation

H3: Basic Formula

 Example Calculation

Given:

• Makeup water TDS = 300 mg/L

• Circulating water TDS = 1200 mg/L

• Desired COC = ?

    COC=1200/400=3

So the cooling tower is operating at 4 cycles of concentration.

 Expansion with Water Balance

If we also know water flows:

• Makeup = 10,000 L/day

• Blowdown = 2,500 L/day

Then:

This confirms a COC of 5 based on flow balance.

 Target Cycles of Concentration

 Typical Ranges

Higher COC is desirable for water savings, but also increases scaling risk. Modern systems from Mach Cooling Tower often incorporate controls to safely push COC higher without compromising equipment.

 Tools and Techniques for Managing COC

 Online Monitoring

Continuous monitoring of:

• Conductivity

• pH

• Temperature

• TDS

ensures real-time calculation of COC and alarm generation when limits are exceeded.

Blowdown Control

Automated blowdown valves and conductivity controllers keep COC within the target range while minimizing water waste.

Practical Tips for Cooling Tower Operators

 Keep Makeup Water Quality High

Better makeup quality allows higher COC, reducing water usage and blowdown.

Maintain Blowdown Devices

Ensure valves and sensors operate correctly to maintain accurate COC and stable chemistry.

 Use Proper Water Treatment

Scale and corrosion inhibitors help systems operate safely at desired COC.

Why Controlling COC Saves Money

 Reduced Water Consumption

Higher COC = less makeup water = lower water bill.

Lower Chemical Costs

With optimized COC, you use only necessary inhibitors.

Prolonged Equipment Life

Balanced cycles prevent excessive corrosion and scaling.

 How Mach Cooling Tower Supports Optimal COC

Mach Cooling Tower (https://www.machcooling.com/) designs cooling systems with:

• Efficient blowdown and makeup control

• Conductivity-based COC management

• Robust mechanical components for long-term stability

Their engineered systems integrate best practices in water management, enabling operators to achieve target COC easily and sustainably.

COC and Sustainability

Managing COC effectively contributes to:

• Water conservation

• Energy efficiency

• Reduced environmental impact

Many facilities set COC targets explicitly as part of sustainability objectives.

Conclusion

Calculating cycles of concentration for cooling towers is essential for efficient water usage, chemical control, and long-term equipment reliability. By using the formulas shown and combining monitoring with automatic control, operators can maintain optimal COC in any cooling tower system.

When specifying or upgrading cooling towers, working with an experienced manufacturer like Mach Cooling Tower ensures that your system is designed for accurate COC control, longer life, and lower operating cost.