Efficiency, Performance, Longevity and Design Flexibility: Why Cooking Appliance Manufacturers are Moving in Favour of AES Fibre Thermal Insulation

30/11/2016

In cooking appliances such as ovens and range cookers, thermal insulation is used predominantly to prevent heat loss through conduction in gas, electric and dual fuel models. It is also used in some electric and dual fuel cooking tops to prevent heat transferring to the surrounding work surfaces.

Like many industries, the cooking appliance market is following new scientific and computer based technology advances. Fueled by a food-loving society which demands convenience and speed, ovens are not only getting hotter, but they are offering more highly technical cooking features than ever before. Commercial oven manufacturers in particular are under pressure to deliver products that boast a larger cooking chamber without increasing the size of the external footprint, as well as multiple cooking techniques, smart controls and the all-important pyrolytic (self-cleaning) cycle.

Meeting these design, performance and safety demands requires the specification of materials which can perform under higher temperatures, in smaller or more complex cavities, which is where traditional fibreglass thermal insulation falls short.

Fibreglass, an outdated choice for modern appliances

Fibreglass performs well in less demanding cooking environments, offering acceptable levels of energy efficiency and safety at temperatures below 1000°F (538°C), which is more than adequate for conventional cooking temperatures of between 300°F to 500°F (149°C to 260°C). However, for manufacturers of mid-to-high end cooking appliances, including highly technical commercial ovens, fibreglass is no longer up to the task.

For ovens with electronic, touch-sensitive controls, integrated cooking sensors and other highly sensitive electrical parts, fibreglass simply cannot offer the protection required to prevent these modern additions from becoming damaged from heat.

On the other hand AES fibres, such as Superwool® PlusTM, can withstand temperatures of around 1800°F (982°C) and offer between 5-20% lower thermal conductivity. This means that fibre can be used in reduced thicknesses, making it ideal for bending around small electrical parts to offer complete protection.

When it comes to the sought-after integrated self-cleaning function, the 1000°F (538°C) temperature limit of fibreglass rules it out as an efficient, effective or safe insulation solution. To remove organic matter from inside the oven chamber without the need for detergents or chemicals, pyrolytic ovens use temperatures of between 900°F and 950°F (482°C and 510°C) to burn away unwanted combustibles.           Some parts of the oven can even reach temperatures in excess of this, for periods of many hours, creating a highly challenging environment for any insulation material. Sustained heat of this nature goes beyond the thermal performance limits of fibreglass and other e-glass needle mats, causing irreversible damage, shrinkage and distortion, which over time can change the oven profile.

In addition to increased functionality, aesthetic style is also a key driver in the evolution of commercial and domestic cooking appliances. Touch-screen operation, smaller footprints, slimmer profiles and bigger oven capacity are all important design factors which both homeowners and commercial kitchens desire, without compromising on safety, performance or energy efficiency. Fibreglass is a stiff material and poses real restrictions when it comes to thermally insulating intricate or compact appliance designs. In contrast, AES fibres are flexible and versatile when wrapping or bending around electronic parts.

For slim profile and small footprint ovens or cooking tops, designers and engineers can use smaller quantities of AES fibre to deliver the same thermal conductivity and ensure correct insulation. With a thickness range of 0.25”-2” (0.6-5cm), compared to the 1”-3” (2.5-7.6cm) thickness of standard fibreglass, AES is also crucial in the creation of larger cooking spaces, within a small oven footprint.

AES – advanced performance for a global market

Like its fibreglass counterpart, AES is a man-made, vitreous (amorphous) fibre (MMVF) and between them, AES and fibreglass occupy around 95% of the market for fibre insulation. For many years fibreglass has been the biggest player, offering a highly cost-effective solution for conventional cooking requirements. Now, with an increased demand for mid-to-high end domestic appliances, as well as highly technical commercial models, the scales are starting to tip in favour of AES materials. Consumers now have a greater appreciation for better quality products - and a willingness to invest in return for improved safety, energy efficiencies and product longevity.

For manufacturers at the forefront of technologically-advanced cooking appliance design, this means implementing crucial specification changes in favour of materials which offer optimised performance credentials. For thermal insulation, this means AES fibre, which delivers significant advantages in high temperature insulation applications, including thermal conductivity and low linear shrinkage.

With a maximum performance temperature of around 1800°F (982°C), AES offers superior insulation in the most demanding cooking environments as the temperature shifts from the convective to radiant heat transfer range. This in-turn offers increased safety, consistent cooking performance and far better energy efficiency.

Manufacturers looking to maximise the selling potential of their new or future product ranges also need to consider the global movement of their goods and any regulations which may restrict the sale or component parts. AES fibres (or AES wool) are advantageous for any appliance manufacturer looking to globalise sales, thanks to their low bio-persistence they are suitable for unrestricted global use.

Significantly lower thermal conductivity at higher temperatures

The lower the thermal conductivity of a material, the better it is at restricting the flow of energy from hot to cold. When selecting materials for an application where a set thickness of insulation is required, the material with a lower conductivity will give a greater temperature difference between the hot and cold faces, and therefore deliver the lowest energy loss.

Some market-leading AES materials, like Superwool Plus insulating fibre, contain a higher concentration of fibre per unit making it a more efficient thermal insulating solution without having to increase the density or thickness. Using advances in manufacturing technology, molten glass for Superwool Plus can be made to fiberise more completely. As a result, the ratio of shot to fibre is improved and the size of the pieces of shot are minimised. This carefully managed process enhances the thermal conductivity up to 20% and provides about 30% more fibres, making it more effective in restricting thermal energy transfer.

For design engineers, this means the flexibility to use less material density while maintaining the same thermal profile, or less thickness and the same density to achieve a larger cooking chamber within the same external footprint.

The future of cooking appliance design and manufacture

As the market continues to be driven by technological and design advancements, as well as improved customer awareness around product performance, lifespan and energy efficiency, more appliance manufacturers will move in favor of AES fibres over traditional fibreglass insulation.

Being able to optimise cooking performance, reduce carbon consumption and improve product lifespan, as well as effectively insulate aesthetically pleasing, compact, slim-line and electronically operated modern appliances, are all attractions which will further fuel a market shift that shows no signs of slowing.

Morgan Advanced Materials,
Morgan Thermal Ceramics,