Multilayer insulations heat transfer mechanism

Multilayer insulations have been used in cryogenics first. These insulations have been embedded in cryogen storage tanks. For better imderstanding, we should know major heat transfer mechanisms in such insulations. Schematic of main heat transfer mechanism in multilayer insulations is shown in Figure 13.1. 

FIGURE 13.1 Schematic of main heat transfer mechanisms in multilayer insulations [1]... 

Effect of Mechanical Load. The influence of mechanical load on thermal conductivity of various evacuated multilayer insulations has been investigated. Figure 9 shows the effect of mechanical load on thermal conductivity for the above multilayer insulation. Assuming that the thermal conductivity of insulation under compression is a function of the heat transferred by solid conduction at the contact points, the thermal conductivity is a function of the size of the contact area. The size of the contact area is proportional to the f power of the contact pressure [ ]. The curve representing the f power of mechanical load has the same shape as the experimentally measured points for loads exceeding about 2 psi. 

Multilayer insulations (MLI) consisted of some layers including heat shields and spacers. Heat transfer in such insulations is governed by conduction and radiation mechanisms, simultaneously. 

---