Centrifuge: Principles, Applications, and Experimental Procedures

The report provides a comprehensive overview of centrifuges, starting with their definition as equipment utilizing centrifugal force to separate substances based on density. It traces the historical development of centrifuges, from Benjamin Robins' whirling arm apparatus to Alexander Prandtl's butterfat extraction machine. The report details the working principles, emphasizing the role of centrifugal acceleration in sedimentation. Different types of centrifuges are discussed, highlighting the variations in speed and rotor designs. Key applications, such as the separation of blood components and mechanical experiments like centrifugal governors, are described. The report also covers various mixtures separated by centrifuges and the process of centrifugation, including the factors influencing the process like particle size, shape, density, and rotor speed. The document includes a bibliography of relevant sources.

Centrifuge and centrifugation
Centrifuge is defined as an equipment that places an object in a rotation mode through a fixed
axis that is spinning through a circle then apply a perpendicular force through the axis in an
outward direction1. Centrifuge is derived from centrifugal force, which is a virtual force which
pulls spinning objects in an outward direction. The sedimentation principle is widely used during
centrifuge. Under the centrifuge, the centrifugal acceleration which make the substances which a
dense to try to move in an outward radial direction. The less dense substances during the
circulation move on the central point. The first invention and discovery was brought upfront by
Benjamin Robins between 1707 and 1751. Robins invented a whirling arm apparatus which he
used to determine drag. Antonin Prandtl in 1864 continued with the research on centrifuge where
he proposed the method to help separate cream from milk. Then latter Alexander Prandtl put the
proposal into action and made more improvement on the design by coming up with butterfat
extraction machine in 18752. In addition, centrifuge can therefore be defined a machine that
houses a rapidly rotating container used to separate mixture contents by density.
There are different types of centrifuges but all are based on the same technique. The only
difference is on their applications. The speed of rotation and rotor designs are the major
differences which define the manner of operation of the centrifuges. The speed of rotation
defines the use of the centrifuge. For instance, very high speed and ultra-centrifuges are used to
separate molecules found in different masses. Additionally, most laboratory centrifuges also
rotate and high speed due to their functionality.
1 Enwezor, Okwui, Damian Lentini, and Sarah Sze. Sarah Sze: centrifuge. (Köln : Verlag der Buchhandlung
Walther König, 2018).
2 Madabhushi, Gopal. Centrifuge modelling for civil engineers. [2017] https://0-www-taylorfrancis-
com.pugwash.lib.warwick.ac.uk/books/9781136458590 accessed on 22nd July 2019

There are different experiments which work on centrifuge. One of the common experiment is the
sedimentation. The rate of the sedimentation of particles is based on their sizes when centrifuges
rotate. The spinning exercise is able to separate the particles in terms of their densities. As noted
earlier, the dense particles are able to move to the edges which the lighter one move to the
central part3. The sedimentation experimentation is able to work well as the parts settle at
different locations. In addition, another key experiment where centrifuges work well is the
separation of the blood. In the experiment, the blood which consists of red blood cells and
plasma which is lighter. In this experiment, the blood is placed in test tube and then spinned at a
high speed. The plasma is able to move to the top while the red blood cells settle at the bottom of
the test tube. At the test tube, more centrifugal force is found at the bottom and that is where the
force pushes the heavier red blood cells. Mechanical experiments also are evident in
demonstration of working of centrifuges. Centrifugal governor was widely used to make sure
that machines did not operate at high speed or low speed4. Since there were no sensors to
monitor the speed, the governors which had a pair of weights moving on both arms which is
connected to the spinning shaft. The weights were able to fly out as the shaft spins and as the
speed increases, the valve closes letting in little steam and therefore reducing the speed of the
machine5. Some of the mixtures which are separated by centrifuges includes milk separation, in
science area and medicine fields. Mostly, the centrifuges have been used to separate liquids and
solids particulates from liquids.
3 Lade, PoulV. Physics and Mechanics of Soil Liquefaction [2017]
https://www.taylorfrancis.com/books/9780203743317 accessed on 22nd July 2019
4 Mory, Mathieu. Fluid mechanics for chemical engineering [2011]. London: ISTE.
http://site.ebrary.com/id/10671502 accessed on 22nd July 2019
5 Debnath, Mousumi. Tools and techniques of biotechnology. (Jaipur, India: Pointer Publishers, 2011)

The centrifugation is defined as the method through which different mixtures are separated
through a spinning action. The particles sizes, shape, densities, medium viscosity and rotor speed
help to determine the operation of the centrifugation. The container containing the particles is
placed in a rotor during centrifugation and then spun at a certain speed6. The rotation against the
central axis is able to generate a centrifugal force on the particles where they are suspended as
the speed increases. The number of rpm at different experiments depend on different factors such
as densities and material properties. In addition, some key conditions such as temperature and
independent characteristics to take control and define the amount of rpm which takes place for
centrifugation. Interaction between different particles is able to define the way centrifugation is
able to perform at different experiments. The rotor motor is able to create the centrifugal force
which helps to separate the different particles at different speeds.
6 Taylor, R. N. 2014. Geotechnical Centrifuge Technology [2014]
https://www.taylorfrancis.com/books/9781482269321 accessed on 22nd July 2019

Bibliography
Gopal, M. Centrifuge modelling for civil engineers. [2017] https://0-www-taylorfrancis-
com.pugwash.lib.warwick.ac.uk/books/9781136458590 accessed on 22nd July 2019
Mathieu, M,. Fluid mechanics for chemical engineering [2011]. London: ISTE.
http://site.ebrary.com/id/10671502 accessed on 22nd July 2019
Mousumi, D,. Tools and techniques of biotechnology. (Jaipur, India: Pointer Publishers, 2011)
Okwui, E. Lentini, Da. and Sze S. Sarah Sze: centrifuge. (Köln : Verlag der Buchhandlung
Walther König, 2018).
PoulV, L,. Physics and Mechanics of Soil Liquefaction [2017]
https://www.taylorfrancis.com/books/9780203743317 accessed on 22nd July 2019
Taylor, R. N. 2014. Geotechnical Centrifuge Technology [2014]
https://www.taylorfrancis.com/books/9781482269321 accessed on 22nd July 2019