It refers to a box that is loaded from the front and is capable of maintaining high temperatures (95degreeC-1600degreeC) within. Both ovens and kilns (thermally insulated chamber) qualify as Muffle Furnaces by this definition. In historical usage it is a furnace in which the subject material is isolated from the fuel and all of the products of combustion including gases and flying ash. After the development of high-temperature electric heating elements and widespread electrification in developed countries, new Muffle Furnaces quickly moved to electric designs.
These Muffle Furnaces use open coil heating elements on both sides of the heating chamber to allow fast heating with minimal temperature gradient. This energy efficiency is enhanced through the use of high thermal-efficient ceramic insulation surrounding the chamber. The free-floating, ceramic fiber door includes a chamber plug that prevents heat loss around the door by totally sealing when the spring-loaded door is closed. These ovens have a door safety switch which cuts power to the elements if the door is opened during use.
Operating principle
The furnace chamber is heated by Electric Resistance Elements and is insulated with Ceramic Fiber Insulation. The controller is located under the Furnace Chamber and is well insulated from the heat generated in the Furnace Chamber. A door safety switch removes power to the heating elements whenever the Furnace door is opened. The temperature is controlled by one of three types of controllers.
A Muffle Furnace most frequently uses the heating method known as Conduction, which involves heating a surface and allowing the heat to radiate into nearby areas such as holding cavity. However, some Muffle Furnaces use Convection heating instead, which involves the circulation of hot air and sometimes Black Body Radiation method too.
Applications
Muffle Furnaces are used in a variety of applications
i) Craft Applications
- Hardening enamel coating onto clay
- Firing ceramics
- Melting and fusing glass
- Soldering items together
- Brazing
ii) In sciences; A common procedure in chemistry is to burn a sample of particular material to determine Chemical Composition, including water content and the proportion of combustible and non-combustible materials. The presence of ash after a complete burning indicates certain chemical property and can be used to determine the level of volatile versus non-volatile products in the sample.
iii) Used in Nutritional Analysis, making it possible to determine the relative proportions of proteins, fat, carbohydrate, and water in food under study.