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CH-107

Lecture

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CHEMICAL
ENGINEERING
THERMODYNAMICS-I
Dr
...
M Smith, 7th Edition
...

• “Thermodynamics, an Engineering
Approch” by Yunus A Cengel
...


CHEMICAL ENGINEERING THERMODYNAMICS-I

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Faculty of Chemical Engineering, NEDUET

Lecture Outline
Concept of Internal Energy
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Concept of Enthalpy
...

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Internal Energy

Internal Energy (U)
Internal energy is defined earlier as the sum
of all the microscopic forms of energy of a
system
...

The total energy of a system, can be
contained or stored in a system, and thus
can be viewed as the static forms of energy
...

To this may be added the potential energy of
intermolecular interactions
The internal energy is also associated with
various binding forces between the
molecules of a substance, between the
atoms within a molecule, and between the
particles within an atom and its nucleus
...

U is not a directly measurable property
...


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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Zeroth law

Internal Energy State Function

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Internal Energy

How to Calculate Change in Internal Energy
(U)
Internal energy changes with the states variables
on which it depends
...


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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Internal Energy

Joules Free Expansion Experiment (Const U)

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Internal Energy

Joules Free Expansion Experiment (Const U)

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

1st Law

James Prescott Joule’s experiment

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

1st Law

First Law of Thermodynamics

d(nU) = dQ + dW
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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

1st Law

First Law of Thermodynamics

d(nU)System = dQ + dW
d(nU)Surrounding = -dQ - dW
d(nU)univ = d(nU)system +
d(nU)surrounding

d(nU)univ = 0

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

1st Law

First Law of Thermodynamics

Constant-V and Constant-P
Process
Energy balance for n moles of a homogeneous
fluid contained in a closed system:
d(nU) = dQ + dW
Mechanically reversible, closed system:
dW = -Pd(nV)
Then d(nU) = dQ - Pd(nV)
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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

1st Law

First Law of Thermodynamics

@ Constant-V
If V = cnst dV = 0
for closed system dn = 0 dW = -Pd(nV) = 0
Then
d(nU) = dQ= CvdT
Closed, constant volume system:
Heat transferred = Change in internal energy
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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

1st Law

First Law of Thermodynamics

@ Constant-P

reversible, closed, constant pressure
system:
Heat transferred = Change in enthalpy
CHEMICAL ENGINEERING THERMODYNAMICS-I

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Faculty of Chemical Engineering, NEDUET

Enthalp

Enthalpy (H)

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Enthalp

Enthalpy (H)

Is used to calculate cooling
and heating processes (heat
exchangers, evaporators,
distillation columns, pumps,
turbines, engines, etc)
appears in energy balances to
calculate Q and W
CHEMICAL ENGINEERING THERMODYNAMICS-I

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Faculty of Chemical Engineering, NEDUET

Enthalp

Calculating Enthalpy

H (T,P) =

𝜕𝐻
𝜕𝐻
( ) 𝑃 dT+ ( )𝑇 dP
𝜕𝑇
𝜕𝑃 Joules Thomson Effect (JT Effect)

+

𝜕𝐻
( ) dP
𝜕𝑃 𝑇
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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Energy Balance

General Energy Balance

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Energy Balance

General Energy Balance

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Energy Balance

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Energy Balance

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CHEMICAL ENGINEERING THERMODYNAMICS-I



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