The insulation material used in MAJUS products is a microporous insulation called Izoflex®. Its thermal performance improves by a factor of 3 to 4 under reduced pressure (medium to low vacuum). This is called the microporous effect.
What is the microporous effect?
“The microporous effect is the restriction of collisions between air molecules which leads to heat transfer, by ensuring that the voids in the material are smaller than the mean free path of the air molecules (approximately 100 nm at atmospheric pressure). Under these circumstances most of the collisions an air molecule experiences are with the walls of the pores, a process which transfers little energy. The thermal conductivity of Izoflex® microporous insulation is actually lower than the thermal conductivity of still air.”
“Izoflex® designed to provide maximum resistance to all modes of heat transfer. Solid conduction, gaseous conduction and radiation are all kept to an absolute minimum.
Convection cannot occur in a microporous material due to the absence of sufficiently large air volumes.
Solid conduction is very effectively minimised in three ways.
- Approximately 90% of the volume is void space where only less efficient gaseous conduction can take place.
- The nano-sized particles making up Izoflex® have very restricted contact with one another, limiting thermal pathways (amount of heat conducted is directly proportional to the cross section of the conduction path).
- The heat paths through the solid matrix are very tortuous, and therefore long. This decreases the rate at which heat can flow by solid conduction (amount of heat conducted is inversely proportional to the length of the conduction path).
Gaseous conduction is restricted by the microporous effect. This is unique to Izoflex® and other microporous insulations and is the property which gives these materials their step-change decrease in thermal conductivity over conventional insulations.
The microporous effect is the restriction of collisions between air molecules which leads to heat transfer, by ensuring that the voids in the material are smaller than the mean free path of the air molecules (approximately 100 nm at atmospheric pressure). Under these circumstances most of the collisions an air molecule experiences are with the walls of the pores, a process which transfers little energy. The thermal conductivity of Izoflex® is actually lower than the thermal conductivity of still air.
Radiation is the major mode of heat transfer at higher temperatures. Izoflex® is formulated to be almost entirely opaque to infra-red radiation. This means that the thermal conductivity rises only slightly with increasing temperature and the performance advantage over conventional insulations becomes more pronounced as the operating temperature increases towards 1000 °C (1832 °F) and higher.”
Source: Microtherm Group website
At reduced pressure, low to medium vacuum, the mean free path of air molecules increases and the microporous effect is stronger: the thermal conductivity of the material is divided by a factor of three giving one of the best as-installed thermal conductivity on the market.
Apart from its high thermal performance, the proprietary Izoflex® insulation provides the following benefits:
- Mineral structure (silica based material) ⇒ no ageing
- Safe and clean material: MSDS available upon request
- Low to medium vacuum only requested to boost the thermal performance ⇒ no need for getters
- Wide temperature application range: -195°C to 900°C (-320°F to 1600°F)
- Load bearing insulation ⇒ no need for centralizers, the Izoflex® acts as a continuous centralizer due to its excellent compressive strength
- Base material proven in industries such as aeronautics, automotive & nuclear since the 1960's
- In operation since 1998 in subsea oil & gas flowline