12/10/06
Heat Transfer and Possible Materials
Heat transfer occurs between two mediums that can be of the same material, but
there is a difference in temperature. There are three main ways in which heat can be
transferred from one medium to another. First is the most simple to understand
conduction. This is the transfer of heat between two mediums that are in contact with
one another. Convection is the second most recognizable form of heat transfer. This
kind of transfer occurs when either a fluid is flowing past another medium or when
gravity induced flow falls across the surface of another medium (i.e. Cool air falling
down the warm side of building. The third is transfer between two bodies that are not in
contact, but transfer heat through radiation. In our particular situation the toner is fused
to the paper by pressure and heat (or temperature4). Most specifically the heat is
transferred to the toner and paper through conduction the when fuser rollers come into
contact with the former.
Concerning materials, it is necessary that the temperature be even throughout to
be sure that when the results are analyzed the conditions are isometric. In printers the
fusers are wrapped in a polyurethane, but based on polyurethane’s properties it is not a
material well suited for control of temperature and strain (from pressure). This leads to
the basic question of “would any plastic material be suitable?” Looking ahead and
knowing that plastics have a tendency to warp, and behave with less predictability than
metals; plastics do not appear to be a good solution to the fuser test-bed fixture. This
leaves various assortments of possible metals.
Some standard metals that are 6000 series Aluminum, 1000 series Steel, and the
300 and 400 series Stainless Steel. The following is a list to of links to some of the more
common metals of these series.
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MQ304A
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MA6061T6
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=M1018D
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MQ416B
The aluminum provides the best thermal conductivity, while the stainless steels provide
the most resistance. In our application it is desirable that the heat can be controlled and
modified quickly when needed. The gut instinct would be to use the 6061 aluminum with
nickel plating, but upon reading the uses of the materials another possibility arose. In the
uses of 304 stainless steel, cooking pans are mentioned, and the thought of possibly using
aluminum with a Teflon coating seems like it might be a possibility worth further
investigation and discussion. The following link discusses some of Teflon coatings’
properties.
http://www.lubecoat.com/coating.html
Extra Information:
1. Basic Energy equation: E=U+KE+PE+others
a.) U = m*(u2-u1)
2.
Neglecting KE and PE for a closed system
a.) (|Qin|-|Qout|) + (|Win|-|Wout|) =U
b.) Q is heat
c.) W is work (Electrical)
d.) U is internal Energy
3. Basic Heat Transfer qin-qout+qgen=qstored
a.) Conduction-Electron transfer of Heat through matter
b.) Convection- Motion transfer (natural gravity or fluid flow).
c.) Radiation (blackbody) - Does not need matter for transfer of heat.
4. Basic Formulas for Conduction (Convection and Radiation are dominated by
conduction).