Low-pressure chillers are an essential part of industrial cooling systems, particularly in environments where precise temperature control is required. These chillers operate using low-pressure refrigerants, such as R-123, which are highly effective but prone to leaks. The challenge arises when non-condensable gases, like air or moisture, enter the chiller system. This is where a purge unit becomes essential.
What is a Purge Unit?
A purge unit is a component of a low-pressure chiller designed to remove unwanted non-condensable gases from the refrigerant circuit. Non-condensables, such as air or moisture, disrupt the heat exchange process, reducing the efficiency of the chiller and increasing energy consumption. In a chiller, refrigerant absorbs heat and changes from a liquid to a gas and back to a liquid during the cooling cycle. As their name suggests, non-condensables don’t condense with the refrigerant, so they accumulate in the condenser, which should only contain refrigerant vapour.
The purge unit ensures the integrity of the refrigerant by continuously extracting any non-condensables, helping maintain an optimal performance. In simpler terms, it’s a self-regulating safety mechanism that protects both the efficiency and longevity of the chiller.
How Does a Purge Unit Work?
The working principle of a purge unit revolves around pressure differences. Low-pressure chillers operate below atmospheric pressure, which makes them susceptible to the ingress of air and moisture through tiny leaks. This is where a purge unit comes into play to avoid non-condensables accumulating in the condenser when they enter the system.
Here’s a simplified breakdown of the process:
- Detection: The purge unit constantly monitors the refrigerant for signs of non-condensables.
- Separation: When detected, the purge unit draws a small sample of the refrigerant vapour containing the air or moisture.
- Cooling: The vapour is cooled, causing the refrigerant to condense, while the non-condensables remain in the gaseous state.
- Discharge: The purified refrigerant is returned to the system, while the non-condensables are vented to the atmosphere or collected for safe disposal.
Modern purge units are highly efficient and can remove even trace amounts of air or moisture. Advanced models include sensors and controls that provide real-time data, allowing operators to monitor the system’s performance and make adjustments as needed.
Why Do Chillers Using Low-Pressure Refrigerants Require Purge Units?
As previously mentioned, low-pressure refrigerants, while effective, are prone to leaks because they operate below atmospheric pressure. This negative pressure creates a vacuum effect, making it easier for air or moisture to enter the system. Once non-condensables are inside, they severely compromise the efficiency of the chiller unit.
Non-condensables raise the pressure in the condenser, causing the chiller to work harder to achieve the same cooling output. Over time, this leads to increased energy consumption, higher operational costs, and strain on mechanical components. Furthermore, moisture can react with refrigerants and oils in the system, forming acids that corrode the chiller’s internal components.
By installing a purge unit, operators can prevent these issues and maintain the chiller’s performance at optimal levels. The unit effectively removes non-condensables before they can cause damage, ensuring the system remains energy-efficient and cost-effective over time.
How to Know When a Purge Unit Isn’t Working
If your purge unit isn’t working properly, you may notice several warning signs. The most common is a rise in system pressure, especially in the condenser, as non-condensable gases accumulate. You might also notice longer purge cycle times or more frequent purging, indicating excess air or moisture in the system. If there is excessive venting or frequent system alarms, it could also signal a malfunction. Regular maintenance and monitoring can help detect these issues early.
The Importance of Regular Maintenance for Purge Units
While purge units are highly effective at maintaining system integrity, they require regular maintenance to function correctly. Over time, components may wear out or become contaminated, reducing the unit’s efficiency. Regular servicing of both the chiller and the purge unit can prevent costly repairs and downtime.
At Evolution Cooling, we specialise in the installation, maintenance and servicing of low-pressure chillers and their components, including purge units. Our expert team ensures that your cooling systems remain in top condition, providing peace of mind and improved performance.
Purge units play a vital role in the operation of low-pressure chillers. If you’re looking to optimise the performance of your industrial cooling systems, consider the benefits of regular maintenance and servicing. At Evolution Cooling, we offer tailored solutions to meet your specific requirements, ensuring your chiller units operate at peak efficiency year-round. Get in touch to find out more.
