Free Piston Stirling Cooler is a kind of Magnetic Levitation Cooler. It is widely used for precise temperature control for under -100℃.
This is the Stirling Cooler, which we refer to as FPSC (Free Piston Stirling Cooler). The default version of Stirling coolers includes pistons, heat exchangers, and compression spaces. But we are seeing the technology advancements in all industries, and Stirling refrigerators aren’t an exception.
The Stirling Cooler use Helium as a gas, which differs from a compressor, is a cooling system continuously repeats gas compression and adiabatic expansion and uses naturally helium gas as the refrigerant. Helium is a very safe gas. It is entirely harmless to our environment.
The typical use of our Stirling Cooler is deep temperature refrigerators, freezers, but RIGID is also developing a product lineup for use in laboratory equipment, and other equipment used for low temperature distribution of goods.
RIGID, one of the leading Chinese companies in terms of innovation, designed a free piston Stirling cooler – FPSC. The unit takes the entire product to a whole new level where it can save a lot of energy and significantly improve efficiency.
Thanks to that, these units are eco-friendly solutions suitable for all those individuals and corporate clients who want to demonstrate their care for the planet. The new cooler doesn’t contain any CFC, and it is interesting to note that the role of coolant was taken by helium. It is even more impressive that FPSCs use doesn’t need a big amount of helium – it is a small quantity that can do the cooling.
What Is a Stirling Cooler?
The Free Piston Stirling Cooler (FPSC) is an elegant, completely sealed heat transfer system that has only two moving parts (a piston and a displacer), and which can use helium as the working fluid without concern about seal leakage.
The piston is typically driven by an oscillating magnetic field that is the source of the power needed to drive the refrigeration cycle. The magnetic drive allows the piston to be driven without requiring any seals, gaskets, O-rings, or other compromises to the hermetically sealed system.
Claimed advantages for the system include environmental friendliness, cooling capacity, lightweight, compact size, precise controllability, and high efficiency.
Stirling coolers are nothing but cryocoolers that use a Stirling cycle to work. These cooling systems function as standalone units, and you can find them in various sizes.
In most cases, Stirling coolers are tabletop models that can cool down different objects and items to cryogenic temperatures.
Free piston Stirling coolers use a Stirling engine, which has only two parts that move. The unit has a casing made of stainless steel, and all sensitive components are hermetically sealed inside.
- Biotech/Pharmaceutical – you can use low temperatures for maintaining chemicals and other pharmaceutical products, including vaccines.
- Energy/Chemical – you can create a cryogenic environment and analyze and inspect different chemicals and test reactions of chemicals.
- Metrology – if you need to maintain precise temperature, and keep it at the desired low level, these units are the right choice.
- Foods/Logistics – if you are doing food delivery, you can keep the food refrigerated to maintain its freshness and deliciousness. Additionally, Stirling coolers can be used in portable freezers.
- Medicine/Vaccine - you can use Rigid Stirling Cooler for compact and deep freezer. The lowest maximum temperature can reach minus -100℃.
How Does Free Piston Stirling Cooler Work?
Since Free Piston Stirling Coolers (FPSC) are new and revolutionary units, you are probably wondering how they work. Here is a quick explanation.
You have the main body with a fin or cylinder protruding from it. The product uses a heat exchanger to cool the cylinder down. The heat exchange involves repeating compression cycles.
The main body also contains a piston that moves up and down continuously. The material of choice for these pistons is usually stainless steel. The moving of the piston combined with the compression leads to a gas explosion.
The upper compression chamber of the cooling system contains two pistons and balancing floats. The manufacturer uses helium gas to fill the chamber, and a linear motor to drive the piston.
The driving action transfers helium to the 80Hz balancing float. The system can control the difference in temperature at 80C.
You will also find an expansion space on the top of the balancing float. At the same time, compression space is between the piston and the float for balancing. Finally, a helium gas flow channel is the annular space that surrounds the balancing float.
Now, let’s focus on the flow passage. In the expansion space, you will find a cold side cylinder (fin), and the compression space is where the designers put the heat sink. You will also find a regenerator in the space between the heat sink and the cold cylinder fin.
Why would you need a regenerator? The idea is to ensure helium’s heat exchange, as well as capture that heat, store it, and return it to the helium gas.
In case there is something unclear, you can check out the photo above. The picture clearly explains the working principle of a Stirling cooler engine, and you can use it to understand previous paragraphs better.
Here is another photo that can better explain the working principle of a free piston Stirling cooler. It is a 3D image of various components included in the FPSC.
The piston driving frequency is approximately 80Hz. The piston motion creates a pressure differential that drives the displacer.