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 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. 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. 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? 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. The piston driving frequency is approximately 80Hz. The piston motion creates a pressure differential that drives the displacer.
That differential goes through the refrigerant because it needs to keep a certain phase angle of the displacer to the piston. In essence, the refrigerant is expanded and compressed by the linear motor that drives the piston.
Thanks to that, you have an expansion cool space and compression warm space. That is the basic explanation of a Stirling cycle. What makes a free piston Stirling cooler unique?
The fact that Rigid added a feature that piston does not have to be physically connected with the displacer. Applications with Stirling cryogenerators are used in a wide range of applications, including the production of liquid gases, cooling gases and liquids, and cooling during industrial processes. Download the Stirling Cycle brochure. The central element in all equipment made by Stirling Cryogenics is the Stirling cryogenerator, operating according to the principles of the Stirling cycle.
This cycle is remarkable because it enables the cryogenerator to produce extremely low temperatures less than 20 K , and allows virtually all gases and liquids to be cooled. The Stirling cycle is a closed cycle, which means that the cryogenerator working gas which is Helium gas never comes into contact with the substance gas or liquid being cooled.
This also eliminates contamination of the working gas, which results in greater operational safety. The closed Stirling cycle also brings more advantages:.
The Stirling cryogenerator is extremely environmentally friendly: it does not cause ozone layer depletion in any way, does not contribute to the greenhouse effect, and does not discharge any harmful or toxic gases.
The Stirling cryogenerator is extremely efficient, especially when compared to other cryogenic processes. Stirling is the only company in the world that success -fully produces Stirling cycle- based cryogenerators with cooling power of 1,, watt at 77 K. The Stirling cycle involves alternately compressing and expanding a fixed quantity of a nearly perfect gas also known as ideal gas in a closed cycle. Helium is being used for this.
The compression takes place at room temperature to facilitate the discharge of heat caused by compression, whereas the expansion is performed at the required low temperature. The Stirling cycle alternately compresses and expands a fixed quantity of a nearly perfect gas also know as an ideal gas in a closed cycle Helium. The compression takes place at room temperature to facilitate the discharge of heat, caused by compression, whereas the expansion is performed at the required low temperature.
The annular channel F connects spaces D and E, and contains three heat exchangers: the regenerator G, the cooler H and the freezer J. In position 1 most of the gas is in space D and at room temperature. Phase 1: The gas is compressed by piston B. Phase 2: The gas is displaced by means of the displacer from space D to space E, which is already at a lowtemperature.
During this displacement the gas passes through the heat exchangers. Louis, Missouri, October. Martini, W. Design Manual for Stirling Engines. Collie , Noyes Data Corp. Prast, G. Qvale, E. Power 91 , —, April. Rios, P. Schmidt, G. Schock, A. Stoddart, D. Urieli, I. C, Boston, Massachusetts. Vogelhuber, W. First Int. Walker, G. Congress, Detroit, Michigan, January. Stirling Cycle Machines. Oxford University Press, Oxford, England. Stirling Engines. West, C.
Zimmerman, J. Printing Office. Graham Walker 1 1. The University of Calgary Calgary Canada. Personalised recommendations.
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