Insulation technique

Tanks with contents at lower than atmospheric temperature may require insulation to minimize heat absorption. The insulation must have a vapor barrier at the outside to prevent condensation of atmospheric moisture from reducing its effectiveness. An insulation not damaged by moisture is preferable. The insulation techniques presently used for refrigerated systems can be apphed (see subsection Fow-Temperature and Cryogenic Storage ). 

While adiabatic operation may be approached by the use of efficient insulation techniques, heat losses from insulated reactors can be appreciable. 

While adiabatic operation may be approached by the use of efficient insulation techniques, heat losses from insulated reactors can be appreciable. Indeed, it may be prohibitively expensive to accomplish large reductions in thermal energy losses beyond a certain point, because of the material and labor costs involved. 

The vacuum-reflective method of insulation with a single, floating radiation shield is retained in preference to multiple layer insulation techniques which are becoming popular in low temperature storage vessels [11]. The steady-state thermal performance of multiple layer insulations is better than that of the standard t5rpes, but the time necessary to reach equilibrium for about one-half inch of multiple layer insulation (the approximate thickness of the vacuum space in the present case) is of the order of 24 hr [12], Since the useful length of an experiment is seldom longer than a fraction of an hour, the steady-state performance of the multiple layer insulation would never be realized. 

It is now feasible with known pumping and insulation techniques to pump cryogenic liquids over long distances. However, an economic balance between the desired use, the losses, and rate of transfer is necessary [19]. 

Lindsay, A. E., O Hare, D. A comparative study of thin film insulation techniques for gold electrodes, Electrochim. Acta 2006, 51, 6572-6579. 

The monograph first looks at the various sources of heat flow into a cryogenic system, and considers how these may be reduced to acceptable low values by appropriate insulation techniques. The monograph then develops an understanding of the surface evaporation process and how it can break down under convective instabilities. 

To minimise heat inflow to the stored liquid, it is important to identify all heat sources and then to use available insulation techniques to reduce all flieir heat inflows to the same order of magnitude, or to zero if practicable. It is important to recognise that variation with scale is different for the various heat sources and therefore the effort and cost of reducing the heat in-flows will also vary with scale. 

Dewar s flask works by cutting out heat transfer, from bofli A and B heat flows, by conduction and convection with the use of a vacuum in a low fliermal conductivity vessel, and reducing radiation by the use of low emissivity reflecting films of silver. It still represents a standard for today, by addressing all flie insulation techniques required to minimise boil-off. 

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