How Does an Ultra-Low Temperature Freezer Work in Your Lab?

Alongside the prevalence of administering COVID19 vaccines worldwide, demand for ultra-low temperature freezers(ULT) has escalated remarkably.

To spot the upsurge in demand, you need to know the freezer’s usage and working mechanism.

But, before that, let us make ourselves familiar with the what-abouts of such cold storage units.

What is a ULT Freezer?

ULT freezers are the most critical equipment for research laboratories and medical facilities to store delicate and temperature-sensitive items effectively.

Like biological samples, vaccines, some medication, etc., many items require shallow temperature environments to stay potent. And when it comes to storing extremely temperature-sensitive items, like the COVID19 vaccines, no healthcare facility can back-off from investing in an ultra-low temperature freezer

In simple terms, you can regard a ULT freezer as a piece of specialized cold-storage equipment that safeguards temperature-sensitive items by keeping them at freezing temperatures. 

Typically, a ULT freezer can provide an operating temperature within -45 to -89 degrees C. The remarkable temperature range is the main distinguishing feature of such cold storage units.


ULT freezers come in two variants–upright and chest. The upright variant is the most common as laboratories look to save space.


The internal storage capacity of a ULT freezer can vary within 200 to 800 liters. Some manufacturers can provide you with customized volumes.


Typically, such freezers have shelves in the interior to keep items. And each shelf has an internal door to maintain a uniform temperature.


ULT freezers bear polyurethane-based insulation, which is free of polluting substances. You can find the insulation between the external and internal walls. The internal temperature remains stable inside the unit due to the high insulation coefficient of the material.


The gasket seal extends all along the freezer cabinet’s perimeter and seals the freezer cabinet tightly.

Silicone quadruple-step seals are the most efficient seals to maintain more excellent temperature stability.

Access Door

The main door also bears polyurethane insulation guarantees maintaining stable temperatures inside the unit.


With swivel castors at the bottom, ULT freezers can move around in the laboratory.


The best ULT freezer brands bear an electronic PLC controller and a display to indicate freezing parameters. A back-up battery is also a part of such freezers to ensure that the display works even during power outages.

How Does a ULT Freezer Work?

Usually, ULT freezers are based on the cascade refrigeration method. It involves two or more vapor compressors containing different refrigerants and an inter-stage heat exchanger to lower the freezer temperature to the necessary range. 

Gaseous compounds like propane and ethane are the typical refrigerants for such freezers. These refrigerants can liquefy quickly and bear characteristic properties, like evaporation temperature.

Imagine two compressors, A and B, in a cascade refrigeration system to understand the working methodology.

A is the compressor with the lower temperature system. And with the evaporation of a refrigerant, A removes heat and subsequently transfers it to a heat exchanger.

Evaporation takes place utilizing steel plate heat exchangers or through a coil. While the copper or copper-aluminum coil evaporator runs along the walls and bottom in ULT freezers’ chest variants, it runs along the walls and at the top in upright freezers. 

Subsequently, the higher temperature system B transfers heat to a conventional condenser, where fan or water-cool mechanisms can cool the ULT freezer’s entire heat output. Usually, ULT freezers used in labs are air-cooled, which is also the reason behind the continual loud noise. 

How to Choose a ULT Freezer?

You cannot measure your prospective ULT freezer’s capability with one attribute alone because its performance is the cumulative measure of many factors.

So, assess the following factors before you eventually put money in a ULT freezer:


Reliability is the foremost concern as you need to store your delicate and temperature-sensitive items in the right temperature environment. 

Ensure that your prospective freezer has digital temperature control mechanisms to allow the temperature to stay within the prescribed range.

In every freezer, you will find locations within the cabinet that are colder or warmer than the average. Choose a unit that has the minimal temperature spread, also called peak variation. 

Freezers with the minimum peak variation within the cabinet and temperature stability are the best. The factors must ensure that the stored items do not repeatedly thaw and freeze when the door opens and closes.

The most critical component in a ULT freezer is the compressor, so you need to make the proper selection. 

It is best to choose a compressor that is powered by adaptive V-drive technology. The compressor accelerates and decelerates in response to usage and the environment, creating the necessary temperature environments. 

The gradual speeding up and slowing down reduces the compressor’s stress and prolongs the compressor’s life.


Choose a ULT freezer variant that has easy-to-use features. For example, an easy to open door that you can open and close with one hand can be beneficial for your laboratory for the long term.

Remote monitoring and control features are the things you should not overlook. They can lower the risk of any malfunctions affecting your samples during off-hours or natural calamities.

It will help if you choose a unit that bears numerical indicators to display the internal temperature to keep track of the temperature status.


During your freezer selection, do not undermine the sustainability element. When it comes to a ULT freezer, sustainability becomes a top concern as they are among the energy-intensive lab solutions due to low operating temperatures. Choose a freezer that works in sustainable ways without damaging the stored items. 


As thieves can steal your valuable items inside the freezer, it has to bear robust security features. 

Choose a unit that comes with an electronic lock and built-in temperature monitoring systems, which can ensure that your stored items are safe from any unauthorized access.

With thick insulation, the freezer’s warm-up time will increase to provide a more extended response window in an emergency.


Procuring a ULT entails a significant investment. Therefore, make efforts to choose the suitable unit of a reputed and reliable brand.

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