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Typical Heat Transfer Coefficients of Common Materials

Typical Heat Transfer Coefficients of Common Materials

Typical Heat Transfer Coefficients of Common Materials

(OP)
I am attempting to perform some heat convection calculations on a process with a granular, rubber-type material but don't have the heat transfer coefficient for the material. I figure I could complete my calculations if I was able to find a list of heat transfer coefficients for common materials. Does anyone know where such a list exists online?

RE: Typical Heat Transfer Coefficients of Common Materials

could try matweb

RE: Typical Heat Transfer Coefficients of Common Materials

(OP)
I thought you were onto something but no heat transfer coefficients on Matweb.com.

RE: Typical Heat Transfer Coefficients of Common Materials

Heat transfer coefficient is not a material property.  Much more information is needed.

RE: Typical Heat Transfer Coefficients of Common Materials

Convection is heat transfer from a solid surface to a fluid in motion (like air or water).  The convection coefficient depends on the motion of the fluid and the material properties of the fluid, not on the solid surface material.

RE: Typical Heat Transfer Coefficients of Common Materials

(OP)
I've got this rubbery material in a tank with air blowing over the exposed area. I am attempting to calculate how much quicker it will cool if I use cooler air instead of ambient air. It seems like a convective application to me.

RE: Typical Heat Transfer Coefficients of Common Materials

Matweb has thermal conductivity, which IS the heat transfer coefficient of a solid.

TTFN



RE: Typical Heat Transfer Coefficients of Common Materials


To cltengr, convection involves movement. Thus, it can not be a property of the static exposed solid. You are right in that cooler air may improve the htc over ambient air.

The htc, h, W/(m2.oC) can be approximated for turbulent air in free convection (Gr/Re2> 1.0) over a horizontal surface by

h = 1.43(Δt)1/3

where Δt is in oC

Since, apparently, the process would be of unsteady state heat transfer, with changing Δt, the value of h is bound to drop with time.

RE: Typical Heat Transfer Coefficients of Common Materials

You have two thermal transfers, one from the bulk of the material to the surface and then from the surface to the air.  Cold and fast moving air only solves the second transfer.  

Your "rubbery" material is like a thermal insulator, therefore, you're ultimately limited by your material's thermal conductivity and heat capacity.

TTFN



RE: Typical Heat Transfer Coefficients of Common Materials

Thermal conductivity and heat transfer coefficient are NOT the same thing.

RE: Typical Heat Transfer Coefficients of Common Materials

...but they are mathematically similar:
conduction: q = -k*A*(dT/dx)
convection: q = h*A*(deltaT)

based on the way the original question was worded, I had assumed that the OP wanted conductivity, not a convective htc.  


RE: Typical Heat Transfer Coefficients of Common Materials

from OP: "granular, rubber-type material but don't have the heat transfer coefficient for the material"

That can only be rationally interpreted as requiring a thermal conductivity, since the convective heat transfer coefficient is a function of fluid, not the immersed material.

TTFN



RE: Typical Heat Transfer Coefficients of Common Materials

...depends on how much credit you're willing to give...

RE: Typical Heat Transfer Coefficients of Common Materials

no doubt, as events have shown.

TTFN



RE: Typical Heat Transfer Coefficients of Common Materials

Convection coefficients are not hard to calculate, but often you just need a quick and dirty range to get a ballpark figure.

These are film coefficients.  All units are W/m^2-K

Free convection
air 5-20
water 100-600

Forced convection
air 10-100
water 500-10,000

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