# Heat flux with oscillating heat sink

1. Apr 14, 2014

### tempneff

I am curious about the effects of oscillation in a heat transfer system. For example consider a simple system consisting of a heat source, a heat sink, and some generic material through which we will flow heat.

http://tempneff.com/Hflux.png [Broken]

If we stack them all together, without thermal grease or other treatments, then they should transfer heat by $\frac{Q}{t}=\frac{\kappa A(T_{hot}-T_{cold})}{d}$

where Q= heat transferred, t=time, $\kappa$ = thermal conductivity of barrier, A = area, T= temp, and d=thickness of barrier. Right?

What would be the effect if I were to vibrate the cold side? Instinctively I thought it would interrupt heat flow decreasing Q/t, but I am reading (unless I misunderstand) that sometimes heat transfer is improved by oscillation.

Any thought?

Last edited by a moderator: May 6, 2017
2. Apr 14, 2014

### Seth.T

If i understand you correctly, I think the logic is similar to having a fan blowing to the heatsink on the other end, decreases Q/t because it increases heat dispersion thus improves natural convection on the outer surface, therefore improve Heat flux to surrounding.

3. Apr 14, 2014

### tempneff

I'll buy that. I still wonder about the magnitude of effect from other dynamics. At high frequency would the friction created have a noticeable effect on the net flux? What about the change in surface area when part of the cold block is shifted off of the 'material'?

4. Apr 14, 2014

### Seth.T

Higher frequency means more oscillation, so its similar to a higher RPM fan which gives better cooling measure..