There are three main types of heat transfer: conduction, convection, and radiation. Conduction involves the transfer of heat through direct contact between two objects. Convection refers to the transfer of heat by the circulation of fluids like air and water. Radiation transfers heat through electromagnetic waves and does not require direct contact between the heat source and object. Understanding these different heat transfer methods helps chefs control the cooking process.

1. TYPES OF HEAT TRANSFER
To cook food up to desired texture & taste, heat must be
transferred from it’s source (gas flame or electric element) to food.
Understanding the ways & speed which transfer the heat, that
helps the chef to control the cooking process.
Heat is transferred in 3 different ways:
1.CONDUCTION
2.CONVECTION
3.RADIATION
In the next slide, we will discuss, all 3 methods in detail

2. CONDUCTION
When heat moves from its source & heats an item by touching
e.g. electricity flows through a wire the same way.
CONDUCTION OCCURS IN 2 WAYS
1.When heat moves from one item to other item by touching e.g.
gas flame heat a fry pan when placed on top of burner
2.When heat moves from one part of an item to an adjacent part o
the same item e.g. heat moves from pan bottom to handle
DIFFERENT MATERIALS CONDUCT HEAT AT DIFFERENT SPEEDS
Heat moves rapidly through copper & aluminum
Heat moves slowly in glass, stainless steel & porcelain.

3. CONVECTION
When heat moves by the movement of air, liquid or steam, the
movement of heat or convection is classified in 2 types:
1. NATURAL CONVECTION:
It occurs naturally when heat is applied to liquid, air, warmer ones
rise & cooler ones sink, it causes constant natural heat circulation
2. MECHANICAL CONVECTION:
It refers to movement of heat by artificial mechanical action e.g.
using a fan or stirring to circulate the heat

4. RADIATION
Unlike conduction & convection, radiation does not require
physical contact between heat source & food to be cooked.
Instead, heat is transferred by waves of heat.
The waves themselves are not actually heat energy, they are
changed into heat when they strike food.
Light waves, radio waves, X-rays are examples of radiation
not used for cooking.
The two kinds of radiation are used in kitchen, they are
discussed in next slide.

5. INFRARED RADIATION
This method uses an electrical coil, which is heated to very
high temperature, as a result it releases heat, that cook the food
Few examples of equipments which releases radiant heat:
toasters, salamander & glowing charcoal also considered.
MICROWAVE RADIATION
This method uses a special oven, which agitates the natural
water molecules present in the food & creates heat.
The heat is then spread by conduction & convection method
& cook the food

6. MUST REMEMBER WHEN USING MICROWAVE
Microwave cooking affects food containing water only, any
waterless material (e.g. plate) will not get hot.
But heat felt in a plate when cooking food in microwave, that
result from heat being conducted from food to the plate.
Microwave cooking requires certain types of utensils, such
as ceramic, heat resistant glass or microwaveable plastic.
Never use aluminum or stainless steel inside the microwave,
because metal prevent microwaves & also damage the oven.