Thermo Sep 18. Dr. Nuri Solak, Asst. Prof.

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Thermo Dr. Nuri Solak, Asst. Prof. http://web.itu.edu.tr/solaknu/ Introduction, Definition of terms, Importance of thermodynamics in 1 20 09 17 metallurgical and materials eng. 2 27 09 17 I.

Law of thermodynamics, enthalpy, heat capacity, Kirchhoff equation 4 11 10 17 Heat of reaction, Hess Law, temperature dependency of heat of reaction 5 18 10 17 Combustion and fuel, adiabatic flame

Law of thermodynamics, 7 01 11 17 variation of entropy as a function of temperature 8 08 11 17 BREAK 9 15 11 17 1. Mid term 10 22 11 17 Standard free energy, equilibrium constant.

06 12 17 of reaction under equilibrium conditions, Phase equilibrium in a onecomponent system Standard free energy, equilibrium constant, calculation of composition 13 13 12 17 of reaction under

1 Thermo Dr. Nuri Solak, Asst. Prof. Introduction, Definition of terms, Importance of thermodynamics in metallurgical and materials eng I. Law of thermodynamics, enthalpy, heat capacity, Kirchhoff equation I. Law of thermodynamics, enthalpy, heat capacity, Kirchhoff equation Heat of reaction, Hess Law, temperature dependency of heat of reaction Combustion and fuel, adiabatic flame temperature Adiabatic flame temperature II. Law of thermodynamics, entropy, III. Law of thermodynamics, variation of entropy as a function of temperature BREAK Mid term Standard free energy, equilibrium constant. Calculation of composition of reaction under equilibrium conditions, Phase equilibrium in a one component system Standard free energy, equilibrium constant, calculation of composition of reaction under equilibrium conditions, Phase equilibrium in a onecomponent system Standard free energy, equilibrium constant, calculation of composition of reaction under equilibrium conditions, Phase equilibrium in a onecomponent system Mid term Ellingham diagrams, Reduction reactions of oxides Recommended Books Gaskel, D.R., Introduction to the Thermodynamics of Materials, Taylor Francis Washington, 2017 Aydın, S., Metalurji ve Malzeme Mühendisleri için Termodinamik, Literatür Kitabevi, 2018 Aytekin, V., Metalurji Termodinamiği, ITU Metalurji Fakültesi Ofset Baskı Atelyesi, Dikeç, F., Aydın, S. Çözümlü Metalurji Termodinamiği Prob, ITU Kim Met Fak Ofset At., DeHoff, R.T.,Thermodynamics in Materials Science, Taylor Francis, 2006 Kubaschewski, O., Alcock, J.B., Spencer, P.J.,Materials Thermochemistry, Pergamon Press, 1993.

(+) What is Thermodynamics Thermodynamics is a science and,

processes that involve changes in temperature, transformation

Thermodynamic is not only related to heat, it gives

Thermodynamics is derived from the Greek words therme, meaning

2 (+) What is Thermodynamics Thermodynamics is a science and, more importantly, an engineering tool used to describe processes that involve changes in temperature, transformation of energy, and the relationships between heat and work. Thermodynamic is not only related to heat, it gives interrelation between different forms of energy. Thermodynamics is derived from the Greek words therme, meaning heat, and dynamis, meaning power. Thermodynamics is concerned only with the equilibrium state of matter.

3 A thermodynamic system (sistem) is a quantity of matter of fixed identity, around which we can draw a boundary. The boundaries may be fixed or moveable. Piston (boundary) and gas (system) Work or heat can be transferred across the system boundary. Everything outside the boundary is the surroundings (çevre). Isolated system (Soyut ): have walls or boundaries that are rigid, do not permit transfer of mechanical energy, perfectly insulating, and impermeable. They have a constant energy and mass content. Adiabatic systems (Adyabatik): Perfectly insulated systems. No energy transfer but matter can be transferred. Closed systems (kapalı): have walls that allow transfer of energy in or out of the system but are impervious to matter. They contain a fixed mass and composition, but variable energy. Open Systems (açık): have walls that allow transfer of both energy and matter to and from the system. Homogenous System: A finite region in the physical system across which the physical and chemical properties are uniformly constant. It is also described as phase. Heterogeneous System: The system when it contains two or more phases, e.g., coexisting of ice and water. Extensive Materials Properties An extensive property is a physical quantity whose value is proportional to the size of the system it describes. ENERGY!!! entropy enthalpy mass momentum volume

4 Instensive Materials Properties It is a physical property of a system that does not depend on the system size or the amount of material in the system temperature density (or specific gravity) viscosity electrical resistivity hardness melting point and boiling point magnetization Macroscopic & Microscopic Energy Potential energy and kinetic energy are macroscopic forms of energy. They can be visualized in terms of the position and the velocity of objects. In addition to these macroscopic forms of energy, a substance possesses several microscopic forms of energy. Microscopic forms of energy include those due to the rotation, vibration, translation, and interactions among the molecules of a substance. It is so called internal energy due to atomic molecular motion. HW 1: How microwave oven works E = U + KE + PE E = total energy U = Internal energy If we calculate change in energy de = q PdV w Change in Energy (other, special conditions) Change in Thermodynamic Properties (Produced work) (Given Energy) de = q PdV d independent of the path taken (yoldan bağımsız) dependent of the path taken (yola bağımlı) If we heat up a system the given energy is not stored in the form of heat energy. It cause increase in internal energy, e.g., increase atomic motions, therefore temperature increases. 1. Law Thermodynamics de = q PdV the change of a body inside an adiabatic system, from a given initial state to a given final state, involves the same amount of work by whatever means the process is carried out Energy cannot be created, nor destroyed energy can change forms

5 E = U + KE + PE E = U de = du = q PdV Thermodynamic properties depend on : Temperature (T), Pressure (P), and Volume (V) T = f(p,v) P = f(t,v) V = f(t,p) E = f(p,v) E = f(t,v) E = f(t,p) In a closed system where E 1 and V 1 q amount of energy is given E 2 and V 2 are reached de = du = q PdV E = E 2 E 1 = q p P (V 2 V 1 ) (E 2 + PV 2 ) (E 1 + PV 1 ) = q p de δp dp δv dv de δt δv dv de δt δp dp Enthalpy H 2 H 1 H = E + PV H 2 H 1 = q p H= q p independent of the path dependent of the path We use SI units! Units Calorie, the quantity of heat required to raise the temperature of 1 gram of water from 14.5 C to 15.5 C. Now, we use Joule as energy unit, 1 cal = 4.18 Joule. Temperature unit is Kelvin (K). Gas constant R = J/mol K Heat Capacity Heat capacity (C) of a system is the ratio of the heat added to or withdrawn from the system to resultant change in the temperature of the system. Heat capacity at constant volume is C v and at constant pressure is C p. C δq C p (δq) p = (dh) p C p δq δq C V δq dh

6 C p Heat Capacity δq dh dh = C p H H 2 H 1 = C p = a + b T + ct 2 C p Kirchhoff s Equation Required energy to increase temperature Heat Capacity If there is a phase transition, e.g., melting of a metal, crystallographic (polymorphic) transition, then transition enthalpy should be included, like you did it at high school for melting latent energy (gizli ısı) for ice. To indicate standart conditions sign is used. It is 1 atm and 25 C. Heat Capacity C p = a + b T + c T 2 C p(a) = T T 2 Heat Capacity H H 2 H 1 = Q = m C T Q = m.l C p Material a b 10 3 c 10 5 Range (K) A Q = mc 1 T + m.l + mc 2 T

Heat Capacity Values of Selected Materials @25 C [C p (J K 1 g 1 or J o C 1 g 1 )] Aluminium C p = 0.90 Water C p = 4.18 Carbon C p = 0.72 Ethanol C p = 2.44 Copper C p = 0.39 H 2 SO 4 C p = 1.

7 Heat Capacity Values of Selected C [C p (J K 1 g 1 or J o C 1 g 1 )] Aluminium C p = 0.90 Water C p = 4.18 Carbon C p = 0.72 Ethanol C p = 2.44 Copper C p = 0.39 H 2 SO 4 C p = 1.42 Lead C p = 0.13 HCl C p = 0.85 Mercury C p = 0.14 KOH C p = 1.18 What happened if the heat capacity of water were 0.4 instead 4 J/mol K Example K 1664K α Fe γ Fe Fe 112 gram of α Fe at 300K and γ Fe at 1200K Calculate required energy to increase temperatere 100K for each case. C p α Fe = T ( K) C pγ Fe = T ( K) HW 2 What are the advantages of high specific heat capacity of water? Fe = 56 gr/mol a) J/112 gr b) 7008 J/112 gr Example 2 at 27 C, take 112 gr Al 2 O 3 In order to increase temperature by 100 C, calculate the required energy. C p Al2O3 = T T 2 ( K) Example 3 Take 1 kg and 1 mol of ZrO 2 and calculate required energy to increase temperature from: a) RT to 1200K 1450K b) RT to 1600 K α H T = 5900 J/mol T transition = 1450 K ZrO 2 = g/mol Answer : J/112 gr Hint: Be careful it is asked from 27 C to 127 C Actually, it means from 300K to 400 K C p α ZrO2 = T T 2 ( K) C p ZrO2 = ( K) a) J/kg b) J/kg

Homework 2 HW 1: How microwave oven works Use Word!!! What are the advantages of high specific heat capacity of water? http://www.tutorvista.

8 Homework 2 HW 1: How microwave oven works Use Word!!! What are the advantages of high specific heat capacity of water? advantages of high specific heat of wateranimation Handwriting!!! Homework 3 Plot Temp vs Cp for Al 2 O 3 for the given temperature: T = 298, 350, 550, 600, 800, 950, 1100, 1500, 1550, 1650, 1800 K C p Al2O3 = T T 2 ( K) Use Excel!!! Hess s Law Hess' law states that the energy change for any chemical or physical process is independent of the pathway or number of steps required to complete the process provided that the final and initial reaction conditions are the same. In other words, an energy change is path independent, only the initial and final states being of importance. (dh) p = (H) p

9 Heat of reaction (H) (Reaksiyon Isısı) As a result of a reaction, the enthalpy difference between initial and final state. Released or absorbed energy of a chemical reaction. H>0 Enthermic reaction, energy required H<0 Exothermic reaction, energy release Enthalpy of Formation (Oluşum, Teşekkül), it is a special form of heat of reaction. H does not have an absolute value (only change in H can be measured). Therefore it is convenient to introduce a convention which allows the comparison of enthalpy difference. The convention assigns the value of zero to the enthalpy of elements in their stable states at 298K. Thus the enthalpy of compound at 298K is simply the heat of formation of compound from its elements. Enthalpy at high temperature dh = C p H H 2 H 1 = H 2 H 1 + C p C p Kirchhoff s Equation Enthalpy Difference T 2 A + B = C T = 298K H 298 H C 298 αh A 298+ H B 298 Hess s law Important: This a chemical reaction, due to the reaction there is an Enthalpy Change! A + B = C T = T H T H C T H A T + H B T Important: This a chemical reaction, due to the reaction there is an Enthalpy Change! H A T2 HA T1 + C p

10 Fuels & Combustion Combustion (Yanma) is used to describe exothermic combustion reaction of fuels. Oxidation reaction such as oxidation of aluminum is an exothermic reaction but it is not considered as combustion. Conventional fuels can be in solid, liquid or gas state. The most commonly used fuels are hydrocarbons. Reaction products are water vapour (H 2 O) and CO 2. Calorific Value (Kalorifik Güç, Isıl Değer) The heating value or energy value of a substance, usually a fuel (or food), is the amount of heat released during the combustion of a specified amount of it. For solid and liquids it is 1 kg. For gases 1 m 3. Reaction at Room Temperature! Reaction is always exothermic but calorific value is taken positive. Adiabatic Flame Temperature (Alev Sıcaklığı) Adiabatic Flame Temperature Fuel Oxidation Agent 298 = Reaction Products TF Q 298 = C Fuel Oxidation Agent 298 = Q + Reaction Products 298 Q + Reaction Products 298 = Reaction Products TF Combustion at room temperature

11 Adiabatic Flame High Temperature Flue gas (baca gazı) Q T = C Q flue = C Always 298K! Reference point! Combustion at high temperature

Thermo. Dr. Nuri Solak, Asst. Prof.

Thermo. Dr. Nuri Solak, Asst. Prof. Thermo Dr. Nuri Solak, Asst. Prof. http://web.itu.edu.tr/solaknu/ www.ninova.itu.edu.tr http://web.itu.edu.tr/solaknu/ 1 11.09.2014 => Introduction, Definition of terms, Importance of thermodynamics