Status of Core Courses: Biothermodynamics Christopher M. Saffron Department of Biosystems and Agricultural Engineering 07/14/14 1 1

Introduction to Engineering Thermodynamics Therme = heat Dynamis = power Science about the conversion and transfer of different forms of energy Energy Viewed as the ability of systems to cause changes A system has energy if it has the capacity to do work To understand energy, you need to understand energy transfer Energy is in the form of heat if an energy transfer is caused by a temperature difference Energy is in the form of work if its transfer is caused by a force acting through a distance 2 2

Thermodynamics in Engineering Curriculum Course Description: …learn to apply the first and second laws of thermodynamics. Analysis of closed and open systems. Study of power cycles and refrigeration cycles. Study of gas-vapor mixtures and psychrometry. Analysis of reaction equilibria and phase equilibria. Prerequisites at MSU: BE 101. Introduction to Biosystems Engineering MTH 235. Differential Equations (first-order linear equations, exact equations, introduction to PDEs) BS 161. Cells and Molecules (energy metabolism, macromolecules, genetics) Prerequisites at other Universities: Differential Equations, Multivariable Calculus, Introduction to Bio-engineering 3 3

Textbooks MSU Other Universities Çengel and Boles, “Thermodynamics: An Engineering Approach.” 8th ed. (required) Haynie, “Biological Thermodynamics.” 2nd ed. (optional) Other Universities 2 used Çengel and Boles 1 created a custom text through McGraw Hill titled “Thermodynamics for Living Systems”; problems from Çengel and Boles 1 used Moran et al., “Fundamentals of Engineering Thermodynamics,” 7th ed. 1 used Borgnakke and Sonntag, “Fundamentals of Thermodynamics,” 7th ed. 1 used course notes 4 4

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Context in BE at MSU BE 351 Thermodynamics for Biological Engineering BS 161 – Cells and Molecules MTH 235 - Differential Equations BE 101 - Intro to Biosystems Engineering BE 477 – Food Engineering: Fluids BE 478 – Food Engineering: Solids BE 468 – Biomass Conversion Engineering BE 485/487 – Senior Capstone Design 6 6

History and Evolution of the Course at MSU Focus on power cycles (including jet engines) Implies coverage of flow-through devices (open systems) Second law 2000 to 2006 Course title: Environmental Thermodynamics Syllabus includes closed systems, open systems, cycles and psychrometry 2007 to present Course title changed to “Thermodynamics for Biological Engineering” Engineering process focused with biological engineering applications 7 7

Other Engineering Thermodynamics Courses ME 201 Thermodynamics (3 credit hours) Basic concepts of thermodynamics. Property evaluation of ideal gases and compressible substances. Theory and application of the first and second laws of thermodynamics. Entropy and Carnot efficiency. CHE 321 Thermodynamics for Chemical Engineering (4 credit hours) First and second laws. Thermodynamics of flow and energy conversion processes. Properties of single and multi-component systems. Phase equilibria. Chemical equilibria in reacting systems. ENE 481 Environmental Chemistry: Equilibrium Concepts (3 credit hours) Chemistry of natural environmental systems and pollutants. Equilibrium concepts and calculations for acid-base, solubility, complexation, redox and phase partitioning reactions and processes. Applications to ecosystem analysis, pollutant fate and transport, and environmental protection. 8 8

Teaching Practices ABET Hybrid lecture and active learning Problem solving identified as weakness Thermo is critical for advancing problem solving skills Hybrid lecture and active learning 31 lectures 36 problems solved in class ~50% of class time involves student problem solving 8 in-class quizzes 11 assigned homework problem sets, due about weekly At least one FE-type problem per homework set 3 in-semester exams and a final exam 9 9

Laws of thermodynamics First law in any process, the total energy of the universe remains constant, i.e. energy cannot be created or destroyed Second law the entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium energy has quality as well as quantity, a process occurs in the direction of decreasing energy quality Third law as temperature approaches absolute zero, the entropy of a system approaches a constant Zeroth law if two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room. 10

Energy Transfer 88% Heat Work The form of energy that is transferred between two systems, or a system and its surroundings, by virtue of a temperature difference An energy interaction is heat only if it takes place because of a temperature difference Heat is energy in transition, it is recognized only as it crosses the boundary of a system Work Energy transfer associated with a force acting through a distance An energy interaction not caused by a temperature difference between a system and its surroundings Work per time is power Whether energy is transferred as heat or work can depend on how the system boundary is selected, e.g.: Electric oven Heating element Electric oven Heating element Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room. 11

Properties of pure substances v sat’d liquid sat’d vapor sat’d liquid-vapor region subcooled liquid superheated vapor critical point Properties of pure substances P, v, T, U, H, S, G, A, Cp, Cv, etc. Internal energy U Enthalpy -- conveniently defined combination property H = U + PV 88% Nuclear energy Chemical energy * T v critical point Latent energy Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room. Atom subcooled liquid superheated vapor Sensible energy sat’d liquid sat’d vapor Molecule Atom sat’d liquid-vapor region Molecule 12 *Adapted from Cengel and Boles 7th ed. Thermodynamics: An Engineering Approach

Closed System Energy Balances Analysis of the human body as a closed system Humans are really open systems Chemical reactions occur in cells Metabolism—sum total of all chemical reactions in cells Result of burning foods carbohydrates, proteins, fats The rate of metabolism in the resting state is called the basal metabolic rate for an average adult the basal metabolic rate is 72 W the body dissipates energy to the environment at a rate of 72 W chemical energy from food is converted to thermal energy at a rate of 72 W function of activity, e.g. exercise can increase metabolic rate more than 10x 100% P A F ds Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room. 13

Open System Energy Balances 88% Open systems involve mass flow across the system boundaries Work is required to push the mass into or out of the control volume— this work is flow work CV V P m F Imaginary piston Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room. 14

Open System Energy Balances for Engineering Devices Nozzles: Turbines: Typically involve no work: Typically no potential energy change: Large changes in velocity: Energy balance for nozzles: Heat transfer is usually negligible: Potential energy is negligible: High velocities, but velocity change is low, therefore ΔKE is small compared to ΔH: Energy balance for turbines: Compressors and pumps: Throttling devices: Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room. No change in potential energy: Outlet velocity is greater than inlet velocity, but kinetic energy change is negligible: The energy balance reduces to: Valves are isenthalpic devices Heat transfer is usually negligible: Potential energy is negligible: Velocities are typically low: Energy balance: 15

Open System Energy Balances—Unsteady State Mass balance: Energy balance: Wsh Wb We Q min mout Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room. 16

Entropy and the Second Law 88% Energy has quality as well as quantity, and actual processes occur in the direction of decreasing quality The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium Heat cannot spontaneously flow from a material at lower temperature to a material at higher temperature It is impossible to convert heat completely into work Clausius Inequality: Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room. Gibbs Equations:

Heat Engines, Carnot Cycles, Reversibility 100% 100% 88% High-temperature source The Carnot heat engine P 1 QH QH Heat engine 2 Wnet,out Wnet,out Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room. 4 QL 3 Low-temperature sink QL v 18

Reciprocating Piston Power Cycles 25% Isentropic compression V=const. Heat addition Isentropic expansion V=const. Heat rejection 1 2 2-3 air qin 3 4 qout 4-1 Isentropic compression P=const. Heat addition Isentropic expansion V=const. Heat rejection 1 2 air qin 3 4 qout 4-1 Otto Cycle: Diesel Cycle: V P qout Isentropic 1 2 3 4 qin P 3 Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room. qin Isentropic 4 qout 2 Isentropic 1 V TDC BDC

Gas and Vapor Power Cycles Brayton Cycle: 38% Rankine Cycle: 38% Compressor Turbine Heat exchanger Wnet, out 1 3 2 4 qin qout qin Turbine Boiler Wturb,out 1 3 2 4 Condenser qout Wpump,in Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room. Working fluid = Water Working fluid = Air Power plant tour at 2/3 semester

Ideal Vapor Compression Refrigeration Cycle Working fluid = Refrigerant Warm environment at TH > TL Cold refrigerated space at TL QH QL Wnet,in Condenser Evaporator Expansion valve 1 2 3 4 38% T s 1 2 3 4’ QH QL 4 Win Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room.

Differential Property Relations 25% Gibbs Equations: Maxwell Relations: Property Relations:

Air-water Psychrometrics Saturation line, Φ = 100% Φ = constant Absolute humidity, ω Twb = constant h = constant v = constant Dry-bulb temperature Human comfort: 75% Human body can be viewed as a heat engine with food as the energy input Heat transfer is proportional to the temperature difference between the body and the environment In cold environments, the body will lose more heat because of a larger T difference In response to cold T, the body reduces blood flow near the surface of the skin In hot environments, improving heat dissipation is necessary During light exercise, about half of the rejected body heat is dissipated through perspiration as latent heat, and half is dissipated through convection or radiation as sensible heat When resting, ~70% of heat is dissipated as sensible heat When vigorously exercising ~60% of heat is dissipated as latent heat Human comfort primarily depends upon the dry-bulb temperature, the relative humidity, and the air motion Most people feel comfortable between 22 and 27°C Relative humidity between 40 and 60% (higher relative humidity impedes heat rejection by evaporation) Air velocities of about 15 m/min (high air velocities displace the moist air immediately surrounding the body, and therefore increase heat rejection) Absolute humidity, ω humidifying De- Dry-bulb temperature Humidifying Heating and humidifying Cooling and dehumidifying Heating Cooling Second law example. A hot cup of coffee cools to ambient temperature, the high temperature energy is transferred to the environment as energy that is not as useful, and of therefore lower quality. Conversely, a cool cup of coffee will not heat itself in the same the same room.

Chemical Reactions 75% Combustion Chamber Fuel CO2 HOH N2 Air hc = Hprod – Hreact Sensible energy 24 24

Chemical and Phase Equilibrium 1 vapor vapor and liquid liquid Criteria for chemical equilibria at a fixed T and P 100% reactants Equilibrium composition Violation of the 2nd law 50% 63% Henry’s Law: Raoult’s Law: 100% products 25 25

Other topics Non-ideal gas behavior 25% Exergy analysis 25% Energy flow in ecosystems 38% Thermodynamics of cell metabolism 25% Atmospheric thermodynamics and climate change Hydrogen, solid oxide and microbial fuel cells Acid-base chemistry, thermochemistry (esp. combustion) Osmosis Chemical kinetics Fluid mechanics Human systems Mass balances 26 26

Survey Slide 27 27

Student Feedback Generally, BE Thermodynamics courses are well received MSU feedback states “…don’t go any faster” More biological applications desired by students More biomedical engineering thermodynamics Metabolic engineering Pharmacodynamics Thermodynamics of cell metabolism 28 28

In summary, the need for Biological Engineering Thermo… Traditional ME and CHE thermodynamics don’t cover biological applications Limited to no refrigeration Limited to no psychrometry Focus on industrial chemicals in CHE thermo Non-ideal aqueous solutions is standard in biology Discipline relevant topics to consider Energy capture by plants Microbial metabolism Humans as heat engines Energy flow in ecosystems 29 29

Thank you! 30 30