Insulators-ceramics-refractory and abrasive material, Mechanical Engineering

Assignment Help:

Insulators

Thermal insulators are essential in industrial practices, domestic and equipment appliances. That type of materials is basically those that do not have free electrons in their structure and heat conduction in only because of lattice vibration in form of elastic waves. Those elastic vibrations are affected via impurity atoms and defects like grain boundaries, dislocations and vacancies. The interference among elastic waves and defects causes also anisotropy of heat conductivity. This is easy to know that in crystalline materials the interference will reduce along with decreasing temperature along with consequent increase in thermal conductivity as in figure of Schematic Variation of Thermal Conductivity. Such interferences do not exist in amorphous materials like plastics and glasses and their thermal conductivity therefore, increases with increasing temperature. Following figure of Thermal Conductivity as Functions of Temperature shows variation of thermal conductivity of some solids utilized at high temperatures. The normal insulating materials are mixtures of cellular, granular of fibrous bodies along with voids filled through air. Airs being a bad thermal conductor, such porous materials are good insulator.

                                                              1673_insulator.png

                                                  Figure: Schematic Variation of Thermal Conductivity

The insulating materials are separated in four groups. Low temperature insulators are for employ up to 10oC. Porous polymeric materials might carry gases that freeze in pores to create vacuum. Vacuum is greatly better insulator because it terminates elastic wave. Such insulators are utilized for cryogenic applications. Building insulators are utilized in the range of 10oC to 150oC. Such are generally wood and plastics. Industrial insulators form the group that is utilized between 150oC to 315oC. Bricks, concrete are primarily utilized in this range but are often more insulated by minerals, slag wools, glasses and various inorganic powders filled between sheets. High temperature insulators are such group which is utilized above 315oC. Porous ceramic bricks for refractory and ceramic powders are utilized as insulators at such temperatures. Insulating bricks can't sustain flames directly but firebricks can withstand flame.

                                                                791_Insulators.png

                                                      Figure: Thermal Conductivity as Functions of Temperature


Related Discussions:- Insulators-ceramics-refractory and abrasive material

Otto cycle - thermodynamics, Ott o Cycle (1876): This cycle consists...

Ott o Cycle (1876): This cycle consists of the two reversible adiabatic processes and the two constant volume processes as shown in the figure given below on P - V and T -

Shock absorbers, how bike''s hydraulic shock absorbers work?

how bike''s hydraulic shock absorbers work?

Vibration, what is vibration in terms of mechanical term

what is vibration in terms of mechanical term

Explain the newer machining processes, Explain the Newer Machining Processe...

Explain the Newer Machining Processes In recent years a number of new material have been developed which are being commonly used in space research missiles and nuclear indu

MECHANICS, CLOSED CIOL HELICAL ,WIRE DAI 10MM AND COMLITE10 TURNS WITH MEAN...

CLOSED CIOL HELICAL ,WIRE DAI 10MM AND COMLITE10 TURNS WITH MEAN RADIOUS AND AXIAL LOAD 200N ,C=80KN/MM2.FIND DIFLECTION OF SPRING?

Overall deformation of a component, Q. Overall deformation of a component? ...

Q. Overall deformation of a component? The overall deformation of a component is a function of the applied load, the materials' creep rate, the maximum in-service temperature,

Refractory materials, Refractory Materials These materials are made up...

Refractory Materials These materials are made up of engineering ceramics that are quite expensive in their pure forms. Such materials are also complicated to form. Most indust

Deliberately placing column from centre in footing, Describe method of deli...

Describe method of deliberately placing column from centre in footing. The method of deliberately placing a column away from the centre of the footing so that resulting soil pr

Evaluate resultant force on the bucket, A single jet pelton wheel runs at 3...

A single jet pelton wheel runs at 300 rpm under a head of 510 m. the jet diameter is 200m, its deflection inside the bucket is 165 o and its relative velocity is reduced by 15% be

Determine elongation of bar, Determine elongation of bar: A conical b...

Determine elongation of bar: A conical bar tapers uniformly from diameter of 4 cm to 1.5 cm in length of 40 cm. If axial force of 80 kN is applied at each end, determine elon

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd