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

What is linear sweep, Linear Sweep In linear sweep, the path is a linea...

Linear Sweep In linear sweep, the path is a linear or circular vector described by a linear, most often parametric. Linear sweep can be divided into translational and rotationa

FEA, Consider the rocket on a test stand as described in Chapter 3 of the l...

Consider the rocket on a test stand as described in Chapter 3 of the lecture notes. The nose of the rocket is fixed. The rocket is of length L, constant EA and constant m, mass per

Evaluate the dynamically equivalent two mass system, A Small connecting rod...

A Small connecting rod 220mm long between the centres has a mass of 2kg and mass moment of inertia of 0.02 kg- m² about its centre of gravity. The centre of gravity is located at a

Heat - thermodynamics, He a t: Sol: Heat can be energy transferred...

He a t: Sol: Heat can be energy transferred across the boundary of a system because of temperature difference between system and surrounding. The heat is transferred by th

Explain about ducts and flues in steam generators, Q. Explain about Ducts a...

Q. Explain about Ducts and Flues in steam generators? All air ducts and gas flues connecting the forced draft fan, fan intake silencer, preheater, and transition piece at the g

Head loss, calculate the head required

calculate the head required

Mechatronics, what is plc and how does it works

what is plc and how does it works

Cylinder head-basic components of engine , Cylinder Head: It is fitted at...

Cylinder Head: It is fitted at top of the cylinder block. It provides space for the arrangement of spark plug, combustion chamber, camshaft, cam chain, valves and intake and exha

Components vs. Parts, What is the difference between a mechanical component...

What is the difference between a mechanical component and a mechanical part?

Explain working of plate heat exchangers, Q. Explain working of plate heat ...

Q. Explain working of plate heat exchangers? For gasket plate heat exchangers handling flammable materials, the same spacing requirements for air coolers should be applied. If

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