Hello Readers, welcome to your own website to understand each and every topic related to the manufacturing process where we transform complex content into simpler ones. In this article, we are focused to cover the thermal property, specific heat, mechanism of thermal conductivity, thermal properties in manufacturing, advantages, disadvantages, and applications.
WHAT IS THERMAL PROPERTY?
Thermal properties of matter play a important role as the impact of temperature is there on the volumetric properties of materials.
Surely, thermal expansion, melting, and heat of fusion are thermal properties since temperature decides the thermal energy level of the atoms, leading to the adjustment in the materials.
The current section examines number of additional thermal properties after it relates to the storage and flow of heat within a substance.
The usual properties of interest are specific heat and thermal conductivity, values of which are compiled for selected materials.
SPECIFIC HEAT AND THERMAL CONDUCTIVITY:
The specific heat C of a material is characterised as the quantity of heat energy needed to
increase the temperature of a unit mass of the material by one degree.
Some typical values are listed to determine the amount of energy needed to heat a certain weight of a metal in a furnace to a given temperature.
The following equation can be used,
H = CW(T2 – T1)
H = amount of heat energy, J (Btu)
C = specific heat of the material, J/kg C (Btu/lb F)
W = its weight, kg (lb)
(T2 – T1) = change in temperature, C (F).
The volumetric heat stock pilling limit of a material is often of interest.
This is simply density multiplied by specific heat.
Subsquently volumetric specific heat is the heat energy needed to elevate the temperature of a unit volume of material by one degree, J mm3 C (Btu/in3 F).
Conduction is a fundamental heat transfer process.
It involves transfer of thermal energy inside a material from one molecule to another molecule by purely thermal movements; no exchange of mass occurs.
The thermal conductivity of a substance is therefore its capability to transfer heat through itself by physical mechanism.
It is estimated by the coefficient of thermal conductivity k, which has average units of J/s mm C (Btu/in hr F).
The coefficient of thermal conductivity is typically high in metals, low in ceramics and plastics.
The proportion of thermal conductivity to volumetric specific heat is often times experienced in heat transfer observation.
It is known as the thermal diffusivity K and is resolved as,
K = k / pc
It can be utilized to compute the cutting temperatures in machining.
MECHANISM OF THERMAL CONDUCTIVITY:
Heat is transferred in two ways electronic contribution and vibrational (phonon) contribution.
In metals, electronic contribution is very high.
Thus metals have higher thermal conductivities.
It is same as electrical conduction.
Both conductivities are related through Wiedemann-Franz law:
k / σT = L
L = Lorentz constant (5.5×10-9 cal.ohm/ sec.K2)
As various contributions to conduction shift with temperature, the above relation is
valid to a restricted extension for some metals.
With expansion in temperature, both number of transporter electrons and contribution of
lattice vibrations increase.
Then in this manner thermal conductivity of a metal is expected to increase.
So due to the greater lattice vibrations, electron mobility may reduce.
The joined impact of these elements helps in various behavior for various metals.
Eg. Thermal conductivity of iron first time reduces then increases marginally; thermal
conductivity decreases with increase in temperature for aluminium; while it increases for platinum.
THERMAL PROPERTIES IN MANUFACTURING:
Thermal properties of matter assume a significant part in manufacturing since heat generation is common in so many processes.
In certain operations heat is the energy that achieves the process; in others heat is produced as a consequence of the process.
Specific heat is of interest for few reasons.
In whole cycle that needed heating of the material (e.g., casting, heat treating, and hot metal forming), specific heat determines the amount of heat energy needed to raise the temperature to a desired level.
In numerous processes completed at surrounding temperature, the mechanical energy to
play out the operation is changed to heat, which raises the temperature of the work part.
This is very well known in machining and cold forming of metals.
The increase in temperature is a function of the metal’s specific heat.
Coolants are regularly utilized in machining to decrese these temperatures, and here the fluid’s heat capacity is critical.
Water is quite often utilized as the base for these liquid due to its more heat carrying limit.
Thermal conductivity functions to dissipate heat in manufacturing processes, may be sometimes advantageous or sometimes may not also.
In mechanical cycle for eg. as metal forming and machining, most of the power required to handle the process is changed to heat.
The capacity of the work material and tooling to lead heat away from its source is exceptionally desirable in these cycle.
Then again, high thermal conductivity of the work metal bothers in fusion welding cycle like as arc welding.
For example, copper is typically hard to weld due to its high thermal conductivity.
The thickness is too much low, typically below 0.3 mm, and it has strong adhesiveness and can be utilized to fix little radiators.
The thickness should not be too thick.
If the product has a certain gap, it can not be used, it can not be reused, and the thermal conductivity is very low.
Thermal properties of matter are used frequently to decide the thermal conductivity and the thermal diffusivity of biomaterials.
The valvano measured tissue thermal properties as a function of temperature with the help of using the constant thermistor heating method.
We have covered all the important concepts related to thermal properties of matter. Hope you all are crystal clear with understanding all the concepts mentioned here. If you have any questions please use the comments section to get in touch with us. Till then have fun and always keep reading!