What is a low-temperature chiller?

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A low-temperature chiller typically operates below -10°C. They are usually used in the pharmaceutical, chemical, new energy, semiconductor, aerospace and other industries. Some high-performance units can go below -150°C. Once you’re past -80°C, you’re in ultra-low territory — that’s where specialized chillers step in.

Key technologies of low-temperature chillers

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Have you ever wondered why the output temperature of some chillers can be as low as -150℃, while some can only reach -10℃? The key differences between them are in the following aspects:

Multi-stage compression technology

At very low temperatures, evaporation pressure drops sharply. If you use a single-stage system, the compressor has to work way harder — sometimes facing a compression ratio of 15:1 or more. That means more wear, more energy, and poor cooling efficiency, making it difficult to reach temperatures of -40℃, -80℃ or even -100℃. Chiller manufacturers usually use multi-stage compression technology.
 
 It’s still the same refrigerant running through the system — but instead of one big push, the compression is split into two, three, or even more steps. After each stage of compression, intercooling is performed to reduce the temperature and volume of the refrigerant gas. Think of it like climbing stairs. Single-stage compression is like climbing 10 floors at a time, and multi-stage compression is equivalent to taking a break after climbing a few floors and then climbing a few more floors. Obviously, the latter is easier.
 
Taking the two-stage compression system as an example, the refrigerant needs to undergo two compressions. The first-stage compressor compresses the low-temperature and low-pressure refrigerant gas coming back from the evaporator to the intermediate pressure. Then the medium-pressure refrigerant gas enters the intercooler and is cooled. The second-stage compressor can compress the medium-pressure gas to high pressure, allowing the refrigerant gas that meets the pressure conditions to enter the condenser.
 
Multi-stage systems simply push the limits. They help chillers go colder than single-stage setups ever could. It has relatively high performance requirements for the compressor and requires the use of a compressor brand with strong low-temperature starting capability.

Cascade refrigeration technology

Cascade refrigeration also referred to as cascade cooling. It combines multiple independent refrigeration circuits into a refrigeration system. The compressor, oil separator, electronic expansion valve and PID control system of each refrigeration circuit are independent of each other.
 
Take the two-stage cascade refrigeration system as an example. It includes a high-temperature system and a low-temperature system. The two systems use refrigerants with different boiling points. The high-temperature system uses a refrigerant with a higher boiling point than the one used in the low-temperature stage. There is a cascade heat exchanger between them to transfer heat, so that the high-temperature system can provide condensation conditions for the condenser of the low-temperature system, and the low-temperature system is responsible for the final cooling.
 
Common cascade refrigeration system combinations are as follows:

High-Temperature Stage Refrigerant	Low-Temperature Stage Refrigerant	Achievable Temperature Range (°C)
R404A	R23	-40°C ~ -70°C
R507	R508B	-60°C ~ -90°C
R134a	R170 / R14	-70°C ~ -120°C

Cascade refrigeration technology can achieve lower cooling temperatures than multi-stage compression technology, but it is difficult to control and more expensive.

Coolant

Coolants carry the cold from your chiller to where it’s needed. In order to reduce cooling loss and improve cooling efficiency, a coolant that matches the operating temperature of the cooling system must be used.

Temperature Range (°C)	Common Coolants
+5 ~ +30	Acqua
0 ~ -10	10–20% Ethylene Glycol Solution
-10 ~ -25	25–35% Propylene Glycol-water mixture
-25 ~ -40	40–50% Ethylene/Propylene Glycol-water mixture, Calcium Chloride Brine
-40 ~ -60	Alcohols , Dynalene HC-20/30
-60 ~ -90	Dimethyl Silicone Oil (-80°C grade), Dynalene HC-40
< -90	Specialty Organic Coolants, Liquid Nitrogen (for secondary loop)

Refrigerants

A refrigerant’s boiling point and pressure limits decide how cold your system can really go. The following are different types of refrigerants and their corresponding operating temperature ranges and suitable refrigeration systems:

Temperature Range (°C)	Recommended Refrigerants	System Type
+30 ~ -10	R134a, R410A, R407C	Single-stage compression
-10 ~ -40	R404A, R507, R407F, R448A	Single-stage or enhanced systems
-40 ~ -60	R23, R508B, R170 (Ethane), R1150 (Ethylene)	Two-stage or cascade systems
-60 ~ -100	R469A/B, Ethanol, Silicone Oil, Dynalene HC-20/40	Cascade + secondary loop
Below -100	Liquid nitrogen (LN₂), Liquid helium (He), organic blends	Ultra-low temp / indirect cooling