Termodinamika Teknik II
Ideal Gas Mixtures
Kontrak Perkuliahan
• Penilaian:
• UTS: 35%
• UAS : 35%
• Tugas : 25%
• Absensi : 5%
• Do’s
• Hadir tepat waktu
• Mengabarkan dosen jika berhalangan hadir
• Don’ts
• Terlambat atau tidak hadir tanpa pemberitahuan
• Mengganggu kegiatan pembelajaran
• Bermain dengan gadget
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Silabus
3 Pertemu
an Pokok Bahasan Mata Kuliah Team Teaching
1 Pemodelan Sistem Daya Uap, Siklus Rankine Aditia Aulia, S.T., M.Sc.
2 Superheat dan Reheat, Siklus Daya Uap Regeneratif Aditia Aulia, S.T., M.Sc.
3 Siklus Otto, Siklus Diesel, Siklus Dual Aditia Aulia, S.T., M.Sc.
4 Pemodelan Pembangkit Listrik Turbin Gas, Siklus Brayton, Turbin Gas Regeneratif Aditia Aulia, S.T., M.Sc.
5 Turbin Gas Pada Pesawat, Siklus Kombinasi Uap-Gas Aditia Aulia, S.T., M.Sc.
6 Sistem Refijerasi Uap, Sistem Refrijerasi Kompresi Uap, Sifat-Sifat Refrijeran Aditia Aulia, S.T., M.Sc.
7 Sistem Kompresi Uap Multi Tahap, Refrijerasi Absorpsi, Sistem Pompa Termal, Sistem
Refrijerasi Gas Aditia Aulia, S.T., M.Sc.
8 Ujian Tengah Semester (UTS) Aditia Aulia, S.T., M.Sc.
9 Komposisi Campuran, Hubungan P, V, dan T Untuk Campuran Gas Ideal, Evaluasi U, H, S,
dan Panas Spesifik, Analisa Sistem Campuran Aditia Aulia, S.T., M.Sc.
10 Prinsip Psikrometrik, Pengukuran Bola Basah, Temperatur Bola Kering Aditia Aulia, S.T., M.Sc.
11 Analisa Proses Pengkondisian Udara, Cooling Towers Aditia Aulia, S.T., M.Sc.
12 Diagram Psikrometrik Aditia Aulia, S.T., M.Sc.
13 Dasar-Dasar Pembakaran, Konservasi Energi Untuk Sistem Bereaksi Aditia Aulia, S.T., M.Sc.
14 Temperatur Nyala Adiabatik Aditia Aulia, S.T., M.Sc.
15 Fuel cell, Entropi absolut, Hukum III Termo Aditia Aulia, S.T., M.Sc.
16 Ujian Akhir Semester (UAS) Aditia Aulia, S.T., M.Sc.
Introduction
Many systems of engineering involve gas mixtures of two or more components. To apply the principles of thermodynamics introduced thus far to these systems requires that we evaluate properties of the mixtures. Means are available for determining the properties of mixtures from the mixture composition and the properties of the individual pure components from which the mixtures are formed.
The objective of the present chapter is to study mixtures where the overall mixture and each of its components can be modeled as ideal gases.
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Describing Mixture Composition
Consider a closed system consisting of a gaseous mixture of two or more components. The composition of the mixture can be described by giving the mass or the number of moles of each component present. With Equation below, the mass, the number of moles, and the molecular weight of a component i are related by
where mi is the mass, ni is the number of moles, and Mi is the molecular weight of component i, respectively. When mi is expressed in terms of the kilogram, ni is in kmol.
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Describing Mixture Composition
The total Mixture, m, is the sum of the masses of its components
The relative amounts of the components present in the mixture can be
specified in terms of mass fractions. The mass fraction mfi of component i is defined as
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Describing Mixture Composition
The relative amounts of the components present in the mixture also can be described in terms of mole fractions. The mole fraction y of component i is defined as
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Describing Mixture Composition
The average molecular weight of the mixture, M, is defined as the ratio of the total mass of the mixture, m, to the total number of moles of mixture, n
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Example
The molar analysis of the gaseous products of combustion of a certain hydrocarbon fuel is CO2, 0.08; H2O, 0.11; O2, 0.07; N2, 0.74. (a) Determine the apparent molecular weight of the mixture. (b) Determine the composition in terms of mass fractions (gravimetric analysis).
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Example
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Relating p, V, and T for Ideal Gas Mixtures
Consider a system consisting of a number of gases contained within a closed vessel of volume V as shown in Fig. 12.1. The temperature of the gas mixture is T and the pressure is p. The overall mixture is considered an ideal gas, so p, V, T, and the total number of moles of mixture n are related by the ideal gas equation of state
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Partial Pressure
The partial pressure of component i, pi, is the pressure that ni moles of component i would exert if the component were alone in the volume V at the mixture temperature T. The partial pressure can be evaluated using the ideal gas equation of state
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Evaluating U, H, S, and Specific Heats
To apply the conservation of energy principle to a system involving an ideal gas mixture requires evaluation of the internal energy, enthalpy, or specific heats of the mixture at various states. Similarly, to conduct an analysis using the second law normally requires the entropy of the mixture.
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Evaluating U, H, S, and Specific Heats
Under the ideal-gas approximation, the properties of a gas are not influenced by the presence of other gases, and each gas component in the mixture behaves as if it exists alone at the mixture temperature and mixture volume.
This principle is known as the Gibbs–Dalton law, which is an extension of Dalton’s law of additive pressures. Also, the h, u, cv , and cp of an ideal gas depend on temperature only and are independent of the pressure or the volume of the ideal-gas mixture.
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Evaluating U, H, S, and Specific Heats
where Ui and Hi are the internal energy and enthalpy, respectively, of component i evaluated at the mixture temperature.
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Evaluating U, H, S, and Specific Heats
Equations 12.17 and 12.18 can be rewritten on a molar basis as
where and are the specific internal energy and enthalpy of the mixture per mole of mixture, and and are the specific internal energy and enthalpy of component i per mole of i.
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Evaluating U, H, S, and Specific Heats
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Evaluating U, H, S, and Specific Heats
where Si is the entropy of component i evaluated at the mixture temperature T and partial pressure pi (or at temperature T and total volume V).
where is the entropy of the mixture per mole of mixture and where is the entropy of component i per mole of i.
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Evaluating Δs
in evaluating the Δs of the components since the entropy of an ideal gas depends on the pressure or volume of the component as well as on its temperature. The entropy change of individual gases in an ideal-gas mixture during a process can be
determined from
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Example
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Example
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Example
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