Lasers generate vast amounts of heat and if the laser is to operate properly, the heat must be removed to keep the laser and critical components from overheating.  As time has gone on, lasers have become smaller and more powerful.   The more powerful lasers require recirculating chillers that are able to deliver accurate and consistent cooling.  The power of the laser will determine both the type of cooling and the size of the chiller that is required to adequately maintain the laser temperature.

 For example, a high-powered laser will require a accurately sized recirculating chiller for the most efficient cooling where for a smaller chiller, cooled water to the laser head may be sufficient.  

Proper laser cooling will:

• maintain the laser wavelength
• maintain laser beam quality
• reduce thermal stress

Chillers are an effective way to cool the laser, but only if the chiller is sized correctly.  This simple statement leads to the question

How to Size a Laser Chiller?

Laser manufacturers may provide cooling specifications with the chiller which will contribute to the laser performance and prolong the life of the laser.  The information provided may include the following:

1.  What are the cooling requirements for the laser?
2. What coolant does the laser require?
3. What flow rate does the laser require?
4.  Is there a precise coolant temperature required?
5. Is there a required temperature stability?

Is There a Formula?

There is a single and easy to follow formula for determining the size of chiller you require. However, there are a few factors you must know before you begin:

• The incoming water temperature
• The water temperature you require
• The flow rate

General Laser Chiller Sizing Formula:

1. Calculate Temperature Differential (ΔT°F) ΔT°F = Incoming Water Temperature (°F) – Required Chill Water Temperature
2. Calculate BTU/hr. BTU/hr. = Gallons per hr x 8.33 x ΔT°F
3. Calculate tons of cooling capacity Tons = BTU/hr. ÷ 12,000
4. Oversize the chiller by 20% Ideal Size in Tons = Tons x 1.2

You have the ideal size for your needs

For example, what size chiller is required to cool 10 GPM from 72°F to 58°F?

ΔT°F = 72°F – 58°F = 14°F
BTU/hr. = 10gpm x 60 x 8.33 x 14°F = 69,972 BTU/hr.
Ton Capacity = 69,972 BTU/hr. ÷ 12,000 = 5.831 Tons
Oversize the chiller = 5.831 x 1.2 = 6.9972
A 6.9972 or 7-Ton chiller is required

It’s that simple.

Other features to consider when selecting a chiller for your laser may include:

• Communication Interface
• High/Low Temperature Alarms
• Low-Flow Alarms
• Low Coolant-Level Alarms
• Coolant Filters
• Air-Filters
• Hot Gas By-Pass Valve
• Noise Level
• Ease of Use
• Portability