heat transfer , Temperature , Objective , application

Heat Transfer 

- heat transfer is the form of energy that can be transferred from one system to another as a results of temperature difference .

- heat transfer is the science that deals with the determination of the rate of energy transfer due to energy difference .

- heat always transfer from hot to cold .

- the object will exchange thermal energy , until thermal equilibrium is reached .

Heat Vs Temperature 

Heat :

- Substance do not contain heat . substance which are made up of atoms , molecules and ions , contain energy .

- heat is the form of the energy that can be transferred from  one system to another as a result of temperature difference  .

- the usual symbol of heat is Q .

- the unit of heat are joules and calories.

Temperature :

- Temperature is a measure of the amount of energy possessed by the molecule of a substance .

- Temperature manifests itself as a degree of hotness and can be used to predict the direction of heat transfer .

- The usual symbol for temperature is T.

- The units for temperature are kelvin , Celsius , Fahrenheit .

Objective 

1. Insulation : - it is to reduce the heat transfer as much as possible across a system and its surrounding . this objective can be achieved by using a material with vary low thermal conductivity . 

Example : thermos flask .

2. Enhancement :- it is the promotion of heat transfer cross a finite temperature difference .

Example : power plant uses heat exchangers .

3. Temperature Control : the temperature of a region is maintained close to specific value .

Example : thermo-regulation of human body through more or less flow to localised region coupled with mechanism like sweating .

Application :

-  Heating 

- Evaporation 

- Distillation 

- Drying 

- Sterilization

- Crystalization

Mechanisms :

there are three mechanism by which heat is transferred in the atmosphere .

- Conduction 

-  Convection  

- Radiation .