Textile engineering

1. HEAT TRANSFER
IN TEXTILE

2. CONTENTS
•Introduction
•Heat transfer
•Heat transfer methods
Conduction
Convection
Radiation

3. INTRODUCTION
• The term “heat” is a form of energy that cross the boundary.
• Heat can be defined as “the form of energy traveling from higher to
lower temperature region.”

4. HEAT TRANSFER
• It is the movement of heat energy from one material to another.
• Heat will continue to move until the same temperature exist in
both substances.
• There can only be a heat transfer across the boundary if there is a
temperature difference between the system and its surroundings.
• Conversely, there is no heat transfer across the boundary if the
system and surroundings are at the same temperature.

5. CONDUCTION
• Heat transfer between two solid objects is known as conduction.
• Conduction heat transfer in solid bodies occurs due to vibration due to free
electrons or molecular excitement .
• It depends on the difference in temperature of the hot and cold object.

6. • Heat transfer between thermally contacted bodies due to temperature
difference is known as Conductive Heat Transfer.
• Conduction is the heat transfer between bodies that are in direct contact
with each other.
• The better the conductor, the more rapidly heat will be transferred.
• Metal is a good conduction of heat.

8. Examples:
• When we touch the hot part of textile machine
the heat energy travels from machine part to
our hands and we feel the increase in
temperature.
• Fabric directly contact with drying roller.
• In Singeing fabric also contact with flame.
• Conductive heat transfers between two contact
fabrics or between fabrics and the human skin.

10. CONVECTION
• In convection heat transfer from one place to another due
to the molecular movement of fluids (Air or liquid). When
molecules move from one area to an other they carry heat
with them.
• Air-conditioning, Space Heating, Water Heating,
Convection heating in microwave are various examples of
convective heat transfer.
• Water boiling in a pan is a good example of these
convection. Another good example of convection is in the
atmosphere.
• The earth's surface is warmed by the sun, the warm air rise
and cool air moves in.

12. • Convective Heat transfer can be classified in two types.
1) Natural Convection
• Natural convection heat transfer is the heat transfer due to movement of liquid and air
molecules without external source such as a pump or fan. It occurs due to forces generated by
density differences caused by temperature difference. These forces are known as Buoyancy
Forces.
• For example when cold air comes in contact with hot object. Air temperature increases whereas
hot body temperature decreases. Which results in lower air density near hot objects. After that
gravitational force pulls high density cold air and replace it with hot air.

13. 2) Forced Convection
• Forced convective heat transfer occurs when flow of fluid/air is caused
by an external force such as fan or Pump. For example, Air conditioner
cools the room with forced air.
• Forced convection involves fluid motion as well as conduction. It
increases the convective heat transfer rate. Rate of heat transfer in forced
convection depends on the velocity of air. Higher the air velocity, higher
will be the convection heat transfer.

14. Examples:
• convective drying is a very common method of removing water from textiles.
• In textile, convective transfer of mainly depends on the openness of the fabric and is not
affected by the fabric thickness

15. Thank You