Insulation Most Relevant for a Fridge

[sasuke07]

Homework Statement

So you have a fridge, the walls of the fridge are made of aluminum, plastic and insulation. Which is the most relevant and why for the fridge.

Homework Equations

Thermal conductivity of aluminum=250
Plastic=.03
insulation=0.035 - 0.16

The Attempt at a Solution

I thought by just common sense to be insluation because insulation is mainly used to keep heat either in or out. But i don't know how to describe it in a scientific way? help.

 

[NascentOxygen]

I thought by just common sense to be insluation because insulation is mainly used to keep heat either in or out. But i don't know how to describe it in a scientific way? help.

Hi sasuke07! Google is a great resource for finding science information.
Search on: "thermal conductivity" equation[/color]

Here's a good start:
http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Physical_Chemical/ThermalConductivity.htm

Enjoy!

 

[sasuke07]

Thanks, but i had already found the thermal conductivity of all 3 of the materials. I am just having trouble articluating why insulation is more important than say plastic, if they have a similar thermal conductivity.

 

[NascentOxygen]

Insulation foam is generally not a very robust surface, and a fridge made of nothing but insulation foam will not please fastidious housewives!

 

[sasuke07]

lol, that's funny, But in terms of thermal conductiviy alone, would insulation be the most important, would plastic be just as good if its thermal conductiviy were similar?

 

[LawrenceC]

When you build any large product, weight is a concern. The density of plastic is roughly the same as water. The density of a foam insulating material is significantly less. Refrigerators are quite heavy objects. If plastic were used instead of a low density foam, the weight would be significantly more.

 

[NascentOxygen]

Foam is cheaper to manufacture than plastic.