Heat Transfer Lab Manual
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AEROSPACE ENGINEERING
LAB 1
(MEC 2700)
LABORATORY
MANUAL
JULY 2007
Table of Contents Experiment 1: Heat Capacity of Gases Experiment 2: Thermal and Electrical Conductivity of Metals Experiment 3: Heat Pump Experiment 4: Heat Conduction Experiment 5: Free and Forced Convection Experiment 6: Thermal Radiation
Experiment 1: Heat Capacity of Gases
1. BACKGROUND
The first law of thermodynamics can be illustrated particularly well with an ideal gas. This law describes the relationship between the change in internal intrinsic energy ΔUi the heat exchanged with the surroundings ΔQ and the constant-pressure change pdV.
dQ = dUi + pdV (1)
The molar heat capacity C of a substance results from the amount of absorbed heat and the temperature change per mole:
(2)
n = number of moles
One differentiates between the molar heat capacity at constant volume CV and the molar heat capacity at constant pressure Cp.
According to equations (1) and (2) and under isochoric conditions (V const., dV = 0), the following is true:
(3)
and under isobaric conditions (p = const., dp = 0):
(4)
Taking the equation of state for ideal gases into consideration:
pV = n R T (5)
it follows that the difference between Cp and CV for ideal gases is equal to the universal gas constant R.
Cp – CV = R (6)
It is obvious from equation (3) that the molar heat capacity CV is a function of the internal intrinsic energy of the gas. The internal energy can be calculated with the aid of the kinetic gas theory from the number of degrees of freedom f:
(7) where kB = 1.38 · 10-23 J/K (Boltzmann Constant)
NA = 6.02 · 1023 mol-1 (Avogadro's number)
Through substitution of
R = kB NA (8)
it follows that
(9)
and taking equation (6) into
AEROSPACE ENGINEERING
LAB 1
(MEC 2700)
LABORATORY
MANUAL
JULY 2007
Table of Contents Experiment 1: Heat Capacity of Gases Experiment 2: Thermal and Electrical Conductivity of Metals Experiment 3: Heat Pump Experiment 4: Heat Conduction Experiment 5: Free and Forced Convection Experiment 6: Thermal Radiation
Experiment 1: Heat Capacity of Gases
1. BACKGROUND
The first law of thermodynamics can be illustrated particularly well with an ideal gas. This law describes the relationship between the change in internal intrinsic energy ΔUi the heat exchanged with the surroundings ΔQ and the constant-pressure change pdV.
dQ = dUi + pdV (1)
The molar heat capacity C of a substance results from the amount of absorbed heat and the temperature change per mole:
(2)
n = number of moles
One differentiates between the molar heat capacity at constant volume CV and the molar heat capacity at constant pressure Cp.
According to equations (1) and (2) and under isochoric conditions (V const., dV = 0), the following is true:
(3)
and under isobaric conditions (p = const., dp = 0):
(4)
Taking the equation of state for ideal gases into consideration:
pV = n R T (5)
it follows that the difference between Cp and CV for ideal gases is equal to the universal gas constant R.
Cp – CV = R (6)
It is obvious from equation (3) that the molar heat capacity CV is a function of the internal intrinsic energy of the gas. The internal energy can be calculated with the aid of the kinetic gas theory from the number of degrees of freedom f:
(7) where kB = 1.38 · 10-23 J/K (Boltzmann Constant)
NA = 6.02 · 1023 mol-1 (Avogadro's number)
Through substitution of
R = kB NA (8)
it follows that
(9)
and taking equation (6) into