State Polytechnic of Malang Malang 217 Heat Effect Thermodynamics Course Agung Ari Wibowo S.T., M.Sc
Learning Objective Sensible Heat Heat Capacity & Integral Evaluation of Sensible Heat Laten Heat of Pure Subtance Standard Heat of Reaction and Formation Standard Heat of Combustion Standard Enthalpy as function of Temperature Heat Effect in Industrial Process Literature Used J M Smith, H C Van Ness, M M Abbott, Introduction to Chemical Engineering Thermodynamics 7 th
Sensible Heat What happen when you add heat to the water? Temperature 1 Temperature rise Boil Water 2 Water Start to boil 3 Continous Evaporation (phase change to vapor)
Sensible Heat What is Sensible Heat?? At constan Pressure Process dh = H T P dt + T2 Q = H = න C p dt T1 H P T dp Heat which causing the rise in temperature to the certain degree with no change in phase and composition
Heat Capacity T2 H = න C p dt T1 C P R = A + BT + CT2 + DT 2 Each substance have their own A, B, C and D constant. These constant are listed in Appendiks C Heat capacity of ideal gas can be written as C v ig and C p ig ig ig C v R = C p R 1 C p ig R = A + BT + CT2 + DT 2
Heat Capacity Mixture of gases A B C What is the heat capacity of mixture? ig C p camp ig ig ig = y A C pa + yb C pb + yc C pc Where y is mol fraction of the gas in mixture Mixed ABC Do you get it??
Integral Evaluation of Sensible Heat What we know?? T2 H = න C p dt T1 T C T p න T R dt = න A + BT + CT 2 + DT 2 dt T = A + B 2 T τ + 1 + C 3 T 2 τ 2 + τ + 1 + D τt 2 T T How we get the exact number?? T C T p න T R dt = න A + BT + CT 2 + DT 2 dt T It is still in Integral Equation C p H R OK,ok.. Here much simpler form for you τ 1 = T T T = A + B 2 T τ + 1 + C 3 T 2 τ 2 + τ + 1 + D τt 2 H = C P H x (T T ሻ Can we get simpler equation??
Latent Heat of Pure Subtance Lest back to our first case Can you see the bubles??
Latent Heat of Pure Subtance Lest back to our first case Amount of energi needed to change the phase
Latent Heat of Pure Subtance How can we know the number?? Here are the equations 4. Watson Eq: 1. Clayperon Eq: H = T V Psat H = Latent Heat; H V = Volume change occupied 2 = 1 phase T.38 r2 change; P sat = saturated vapor H pressure 1 1 (evaluated T r1 by Antoine Eq) 2. Troutons Eq : H RT n ~ 1 dt 5. Using Steam tables (only for water) Tn is absolut boiling point. H evap = H v H l 3. Riedel Eq : H 1,92 (ln Pc 1,13ሻ = RT n,93 Tr n Pc is critical pressure and Tr n is reduced temperature.(tr = T/Tc)
Heat of Reaction Consider this reaction 1 2 N 2 + 3 2 H 2 NH 3 H = 46,11 J H = ΔH product ΔH reactant T2 H reactant or H product = න C p dt T1 Actual T of materials T reference, usually 25 C
Standard Heat of Reaction Consider this reaction 1 Exothermic reaction N 2 2 + 3 H 2 2 NH 3 H 298 = 46,11 J What And is What the meaning is standard of this condition? symbol? Standard heat of reaction is written as H 298, 298 means this heat were calculated at 298,15 K Standard Condition : - Gas : Pure subtance in ideal gas condition at Pressure 1 bar - Liquid dan solid : Pure subtance in real condition at Pressure 1 bar.
Standard Heat of Formation Consider this reaction C + 1 2 O 2 + 2H 2 CH 3 OH Which one is formation reaction? Generally formation reaction is written in form of : C s + O 2 g CO 2 g H f298 = 339,59 J H 2 O + SO 3 H 2 SO 4 Definition : Formation reaction was defined as reaction to produce 1 compound from its molecular element, in which the product is 1 mole in amount as basis f stand for formation The chosen condition is T 298.15 K or 25
Standard Heat of Formation Calculate the heat of reaction from reaction below CO 2 g + H 2 g CO g + H 2 O g Break down the reaction to get heat of formation of each compound CO 2 g C s + O 2 g H f298 = 339,59 J Wait, waittt Where is H 2?? C s + 1 2 O 2 g CO g H 2 s + 1 2 O 2 g H 2 O l H f298 H f298 = 11,525 J = 285,83 J H 2 O l H 2 O g H f298 = 44,12J CO 2 g + H 2 g CO g + H 2 O g H 298 = 41,66 J Answer : H 2 is only constructed from 1 kind of element, so its H f298 =
Standard Heat of Combustion Definiton : Heat of Combustion (enthalpy of combustion) of a substance is the heat liberated when 1 mole of the substance undergoes complete combustion with oxygen at constant pressure. Have you ever heard methanol gel? Wedding party food heater
Standard Heat of Combustion The use of heat of combustion 4C s + 5H 2 g C 4 H 1 g 4C s + 4O 2 g 4CO 2 g H f298 = 4 x( 339,59ሻJ Wait sir, C and H just only consist of 1 element How can I know its? H f298 5H 2 g + 2,5 O 2 g 5H 2 O l H f298 = 5 x( 285,83ሻ J 4CO 2 g + 5H 2 O l C 4 H 1 g + 6,5 O 2 g H 298 = 2877,396 J 4C s + 5H 2 g C 4 H 1 g H f298 = 125,79 J
Temperature Dependent of H H What about standard reaction at different temperature or not at R 298,15 K? Heat Chemical of reaction Reaction at certain : temperature can be calculated if the heats of reaction at standard v 1 Acondition 1 + v 2 2 + were determined v 3 A 3 + vfirst 4 A 4 + H = i v i H fi H = H 298 = 2,66 11,525 CO g + 2H = 9,135 2 CHJ 3 OH g H = H + R T T = 8 T C P R dt Calculating Cp C P = A + B 2 T τ + 1 + C 3 T 2 τ 2 + τ + 1 + D H = H + C P H(T T ൯ i vi A 1 3 B 1 6 C 1-5 D CH 3 OH 1 2,211 12,216-3,45 CO -1 3,376,557 -,31 H 2-2 3,249,249,83 Reference : T = 298,15 K A=(1)(2,211)+(-1)(3,376)+(-2)(3,249) = -7,663 B=1,815 x 1-3 ; C=-3,45x1-6 ; D=-,135x1 5 H = H + R T T C P What about at T = 8 R dt = -9,135 + 8,314 (-1615,5) = -13,556 J τt 2
Heat Effect of Industrial Reactions Process Flow Diagram of Cumene Production Hmmm,,, I smell problem here Reactor Temperature 377 K
Heat Effect of Industrial Reactions 1 2 4HCl g + O 2 g 2H 2 O g + 2Cl 2 g H = σ l i n i C pi (T 298,15) H C pi = R x C P H R H R H p Total enthalpy change : H 298 H = H R + H 298 + H p Material entering reactor ( R ) : HCl, O 2 Material Out ( P ) : HCl, O 2 Cl 2, H 2 O T reference = 298,15 K H R = perubahan entalpi reaktan pada suhu T 1 ke suhu referens 298,15 K H 298 = entalpi reaksi standar pada suhu 298,15 K H p = perubahan entalpi produk dari suhu referens 298,15 K ke suhu T