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Basic Heat TransferBasic Heat Transfer

Presented By:Presented By:

Dr.Ehab A. KarakishDr.Ehab A. Karakish

الحراري االنتقال أساسياتمهندس :دكتور

قراقيش السالم عبد إيهابالتشغيل مدير

المصريه البتروكيماويات شركة

Basic Heat Transfer Concepts Basic Heat Transfer Concepts

• Since the accuracy of the temperature measurement is dependent upon getting the sensing element inside the sensor to the same temperature you are trying to measure, an understanding of some fundamental heat transfer concepts is in order.

Concept #1: Concept #1: What is heat? What is heat?

Heat is a relative term used to identify the presence of thermal energy in an object.

Concept #2:Concept #2: Hot and Cold. Hot and Cold.

• Hot and cold are terms that indicate the relative amount of heat that is present in one or more objects.

• For example, a hot object would have a higher amount of heat than a cold object.

Concept #3: Concept #3: What is temperature?What is temperature?

• Over the years methods have been developed for classifying the amount of heat that is present in an object.

• Normally we refer to this as an object's temperature.

• There are three conventions used for quantifying the temperature of an object, these include the Fahrenheit, Celcius and Kelvin temperature scales.

Concept #4: Heat always travels from hot to cold.

• When two items are at different temperatures, heat will always move from the hotter object to the colder object.

• Heat never goes from a colder object to a warmer one.

Concept #5: Objects always try to reach a state of equilibrium.

• When subjected to an environment that is not isothermal, heat will transfer from hot to cold until a steady state condition is reached.

Concept #6:Concept #6: There are three ways There are three ways to transfer heatto transfer heat

• There are three ways to transfer heat: Conduction, Convection and Radiation. Solid objects transfer heat by conduction.

• Conduction is the fastest and most efficient way of transferring heat between two solid objects.

• Fluids (liquids and gases) transfer heat by convection.

• Convection is the second fastest way to transfer heat between objects.

• Radiation is the slowest method of transferring heat. • All objects radiate heat, but the effects of radiation

are most pronounced when dealing with large differences in the amount of heat present.

• Radiation can occur in a vacuum where conduction and convection cannot.