1. TEKNIK MESIN FAKULTAS TEKNOLOGI INDUSTRI UNIVERSITAS MERCU BUANA
MODUL PERTAMA
THERMODINAMIKA DASAR
NANANG RUHYAT
THERMODINAMIK
Thermodinamika = thermo ( temperatur ) ; dinamika ( dinamis, berubah-ubah ).
Thermodinamika dapat dikatakan ilmu yng mempelajari tentang perubahan temperature,
sebab-akibat, sifat , dll
Thermodynamics (from the Greek thermos meaning heat and dynamics meaning power) is
a branch of physics that studies the effects of changes in temperature, pressure, and volume
on physical systems at the macroscopic scale by analyzing the collective motion of their
particles using statistics. Roughly, heat means "energy in transit" and dynamics relates to
"movement"; thus, in essence thermodynamics studies the movement of energy and how
energy instills movement. Historically, thermodynamics developed out of the need to
increase the efficiency of early steam engines.
Typical thermodynamic system - heat moves from hot (boiler) to cold (condenser) and
work is extracted.
The starting point for most thermodynamic considerations are the laws of thermodynamics,
which postulate that energy can be exchanged between physical systems as heat or work.
They also postulate the existence of a quantity named entropy, which can be defined for any
system. In thermodynamics, interactions between large ensembles of objects are studied
and categorized. Central to this are the concepts of system and surroundings. A system is
PUSAT PENGEMBANGAN BAHAN AJAR-UMB
Ir. Nanang Ruhyat
THERMODINAMIKA DASAR 1
MT.

2. 3 http://www.mercubuana.ac.id
classical thermodynamics derives from physicist Robert Boyle’s 1662 postulate that the
pressure P of a given quantity of gas varies inversely as its volume V at constant
temperature; i.e. in equation form: PV = k, a constant. From here, a semblance of a thermo-
science began to develop with the construction of the first successful atmospheric steam
engines in England by Thomas Savery in 1697 and Thomas Newcomen in The first
and second laws of thermodynamics emerged simultaneously in the 1850s, primarily out of
the works of William Rankine, Rudolf Clausius, and William Thomson (Lord Kelvin).
Statistical thermodynamics
With the development of atomic and molecular theories in the late 19th century,
thermodynamics was given a molecular interpretation. This field is called statistical
thermodynamics, which can be thought of as a bridge between macroscopic and
microscopic properties of systems. Essentially, statistical thermodynamics is an approach to
thermodynamics situated upon statistical mechanics, which focuses on the derivation of
macroscopic results from first principles. It can be opposed to its historical predecessor
phenomenological thermodynamics, which gives scientific descriptions of phenomena with
avoidance of microscopic details
Chemical Thermodynamics
Chemical thermodynamics is the study of the interrelation of heat with chemical reactions
or with a physical change of state within the confines of the laws of thermodynamics. During
the years the American mathematical physicist Willard Gibbs published a series of
three papers, the most famous being On the Equilibrium of Heterogeneous Substances, in
which he showed how thermodynamic processes could be graphically analyzed, by studying
the energy, entropy, volume, temperature and pressure of the thermodynamic system, in
such a manner to determine if a process would occur spontaneously. During the early 20th
century, chemists such as Gilbert Lewis, Merle Randall, and E. A. Guggenheim began to
apply the mathematical methods of Gibbs to the analysis of chemical processes.
Thermodynamics System
An important concept in thermodynamics is the “system”. A system is the region of the
universe under study. A system is separated from the remainder of the universe by a
boundary which may be imaginary or not, but which by convention delimits a finite volume.
The possible exchanges of work, heat, or matter between the system and the surroundings
take place across this boundary. There are five dominant classes of systems:
Isolated Systems – matter and energy may not cross the boundary.
Adiabatic Systems – heat may not cross the boundary.
Diathermic Systems - heat may cross boundary.
PUSAT PENGEMBANGAN BAHAN AJAR-UMB
Ir. Nanang Ruhyat
THERMODINAMIKA DASAR 3
MT.

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instantaneous quantitative description of a system with a set number of variables held
constant
Thermodynamic processes
A thermodynamic process may be defined as the energetic evolution of a thermodynamic
system proceeding from an initial state to a final state. Typically, each thermodynamic
process is distinguished from other processes, in energetic character, according to what
parameters, as temperature, pressure, or volume, etc., are held fixed. Furthermore, it is
useful to group these processes into pairs, in which each variable held constant is one
member of a conjugate pair. The six most common thermodynamic processes are shown
below:
An isobaric process occurs at constant pressure.
An isochoric process, or isometric/isovolumetric process, occurs at constant volume.
An isothermal process occurs at a constant temperature.
An isentropic process occurs at a constant entropy.
An isenthalpic process occurs at a constant enthalpy.
An adiabatic process occurs without loss or gain of heat.
The laws of thermodynamics
In thermodynamics, there are four laws of very general validity, and as such they do not
depend on the details of the interactions or the systems being studied. Hence, they can be
applied to systems about which one knows nothing other than the balance of energy and
matter transfer. Examples of this include Einstein's prediction of spontaneous emission
around the turn of the 20th century and current research into the thermodynamics of black
holes.
The four laws are:
Zeroth law of thermodynamics, stating that thermodynamic equilibrium is an equivalence
relation. If two thermodynamic systems are separately in thermal equilibrium with a third,
they are also in thermal equilibrium with each other.
First law of thermodynamics, about the conservation of energy
The change in the internal energy of a closed thermodynamic system is equal to the
sum of the amount of heat energy supplied to the system and the work done on the
system.
PUSAT PENGEMBANGAN BAHAN AJAR-UMB
Ir. Nanang Ruhyat
THERMODINAMIKA DASAR 5
MT.