2. • Heat is a form of energy,
–Any Physical or chemical heat flows into or
out of system
–Sources --- Steam or electric power
• Application –
Evaporation
Distillation
Drying
Crystallization
Sterilization
3. Mechanisms of Heat flow
• Conduction- is achieved by the transfer of the
momentum of individual atoms or molecules without
mixing.(Rod)
• Convection – is achieved by actual mixing of warmer
portion with cooler portion of same material.(Water)
• Radiation – by means of electromagnetic
waves.(steam)
4. Conduction
• Basic law
Rate = Driving Force
Resistance
Fourier’s law-the rate of heat flow through a uniform
material is proportional to the area and the
temperature drop and inversely proportional to the
length of the path of flow.
q = KmAt/L
Thermal Conductivity- quantity of heat that flows
across a unit surface area in unit time when temp. drop
constant
5. Convection
• Types
A) Forced Convection
B) Natural Convection
Film Coefficients- is the quantity of the heat flowing
through unit area of the film for unit drop in temp.
• Principle of heat flow in fluids
6. Radiation
• Black body- as a body that radiates maximum
possible amount of energy at a given temp.
Total amount of radiation emitted by black body
q = bAT4
Stefan-Boltzmann law
Grey Body- as the body whose absorbing capacity is
constant at all wavelengths of radiation at given temp.
Total amount of heat transferred by Grey body
q = b A(T1
4 –T2
4 )
Stefan Law
