Transcript
HEAT TRANSFER
the study of heat flow within an object and from one object to another due to different temperature.
THREE FORMS :
1.RADIATIONHeat energy travels as electromagnetic waves
in the same manner and speed as light.
2. CONDUCTION
Heat energy travels when two objects at different temperature are in direct contract with each
other. During heat conduction, vibrating
atoms / molecules excite the atoms or molecules next to them.
3. CONVECTION
the heat fluids is transferred to cooler regions by current.
SPECIFIC HEAT
the amount of energy required to raise the
temperature of 1kg. of a substance by 1k.
J / KG. K = UNIT OF
MEASURE FOR SPECIFIC HEAT
HEAT / THERMAL CAPACITY
the amount of heat required to raise
temperature by 1 degree.
FORMULA :
Where:Q = amount of heat
transferredm = mass C = specific heatT = change in temperature
How much heat is needed to raise the temperature of 5kg of water 10 k?
Given:
m = 5kgC = 4180 J/kg.KT = 10 KQ = ?
Solution:Q = mC T = (5kg)(4180J/kg.k)(10 K)
= 209 000 J
• How much energy is lost by 10 kg of brass if it is cooled from 35 to 25 C?
38 500 J or about 9200 cal
• It takes 487.5 J to heat 25 grams of copper from 25 °C to 75 °C. What is the specific heat in Joules/g·°C?
c = 0.39 J/g·°C
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