Dr. AbdelSalam Al-Sarkhi Thermodynamics 1 ME 203 Dr. AbdelSalam Al-Sarkhi

Outline Textbook Catalog Description Grading system Homework Attendance Exams What thermodynamics Topics to be covered during the course Application Areas of Thermal-Fluid Sciences

Text Book 6th Edition THERMODYNAMICS An Engineering Approach By Yunus A. Cengel and Michael A. Boles

Catalog Description: Thermodynamics 1 System and control volume concepts. Properties of a pure substance. Work and heat. The first law of thermodynamics as applied to a system and a control volume, internal energy, enthalpy. The second law of thermodynamics. Carnot cycle, entropy, reversible and irreversible processes. Applications of steady state steady-flow, uniform-flow, and other processes.

Grading System 10% Class Test 10% Homework Assignments 20% First Exam 15% Second Exam 15% Quizzes 30% Final Exam

Homework Homework problems are 5 problems every week. All homework problems assigned during a given week are due in class one week later unless stated otherwise. Late Homework will not be accepted

Attendance Attendance will be checked during each lecture. Excuse should be authorized by the Deanship of Student Affairs and submitted one week later after resumption of class attendance. Any student having more then 9 unexcused absences will receive a grade of DN for the course.

Location: Building 22 Room # 157-1 Phone 860-7725 Office Hours Office Hours: 1:00 – 2:00 SMW 11:00-12:00 ST Location: Building 22 Room # 157-1 Phone 860-7725 email: alsarkhi@kfupm.edu.sa

Air-conditioning systems Refrigeration systems Application Areas of Thermal-Fluid Sciences Power plants The human body Air-conditioning systems Airplanes Car radiators Refrigeration systems

Dimensions and Units Basic Dimensions, Primary or Fundamental such as mass, m, Length, L ,time, t, and Temperature, T Secondary Dimensions or Derived such as velocity V , Energy E and Volume V Two systems of Units English system, which is also known as the United States CustomarySystem (USCS), and The metric SI (from Le Système International d’ Unités), which is also known as the International System. The SI is a simple and logical system based on a decimal relationship between the various units

Dimensions and Units The seven fundamental dimensions and their units in SI (International System).

Decimal Relationship Between Units: SI System

Dimensions and Units

Dimensional Homogeneity E = 25 kJ +7 kJ/kg =? E = 25 kJ +7 km/kg =? E = 25 kJ +7 kJ = 32 kJ So the mistake is kJ/kg must be kJ All sides must have the same units

Unity Conversion Ratios or Conversion Factor If we have 100 lbm ft/s2 how many lbf do we have? Anything multiplied by 1 is the same Answer = 3.108 lbf ……………do it 12 inch = 1 ft ; how many foots in the 23 inch Answer = 1.9166 ft …………do it

Temperature and the Zeroth Law of Thermodynamics Not in Thermal Equilibrium in Thermal Equilibrium The zeroth law of thermodynamics states that: If two bodies are in thermal equilibrium with the third body, they are also in thermal equilibrium with each other or The equality of temperature is the only requirement for thermal equilibrium. two bodies are in thermal equilibrium if both have the same temperature reading even if they are not in contact

Temperature scales Note: it makes no difference to use K or C in formulas involving temperature difference. However, you should use Absolute temperature in formulas involving temperature only like the ideal gas low.

Basic Concepts of Thermodynamics

What is Thermodynamics Thermodynamics (from the Greek words therme (heat) and dynamis (power)), is the science that primarily deals with energy. Thermodynamics is the study of the effects of Work, Heat and energy on a system. So thermodynamics is the science of Energy

What is Thermodynamics Zeroth Law: Thermodynamic Equilibrium and Temperature First Law: Work, Heat, and Energy Second Law: Entropy

Thermodynamics The first law of thermodynamics is simply an expression of the conservation of energy principle, and it asserts that energy is a thermodynamic property. Energy cannot be created or destroyed; it can only change forms (the first law).

Thermodynamics (continued) The second law of thermodynamics asserts that energy has quality as well as quantity, and actual processes occur in the direction of decreasing quality of energy. For example, a cup of hot coffee left on a table eventually cools to room temperature, but a cup of cool coffee in the same room never gets hot by itself. Heat flows in the direction of decreasing temperature.

Heat Transfer Thermodynamics deals with equilibrium states and changes from one equilibrium state to another. Heat transfer, deals with systems lacking thermal equilibrium, and thus it is a non-equilibrium phenomenon. Temperature difference is the driving force for heat transfer. The larger the temperature difference, the higher is the rate of heat transfer.

Closed Systems A closed system (or simply a system), or a control mass, is defined as a quantity of matter or a region in space chosen for study. The mass or region outside the system is called the surroundings. The real or imaginary surface that separates the system from its surroundings is called the boundary.

Closed Systems No mass can cross its boundary But energy can.

Closed Systems with moving boundary Consider the piston-cylinder device shown in the Figure. Let us say that we would like to find out what happens to the enclosed gas when it is heated. Gas is our system. Since no mass is crossing the boundary, therefore, it is still a closed system but with a moving boundary

Closed Systems vs open systems

Open Systems An open system, or a control volume, is a properly selected region in space. Both mass and energy can cross the boundaries of a control volume. It usually encloses a device that involves mass flow such as a compressor, turbine, or nozzle. Flow through these devices is best studied by selecting the region within the device as the control volume.

Open Systems (continued)

Approaches Macroscopic Approach (Classical Thermodynamics) - is concerned with the overall behavior of a system - no model of the structure of matter at the molecular, atomic, and subatomic level is directly use Microscopic Approach (Statistical Thermodynamics) - is concerned directly with the structure of matter - characterize, by statistical means, the average behavior of the particles making up a system of interest and relate this information to the observed macroscopic behavior of the system

Properties of a System Any characteristic of a system is called a property. Some familiar properties are pressure P, temperature T, volume V, and mass m. Properties describe the state of a system only when the system is in an equilibrium state. Not all properties are independent. Density is a dependent property on pressure and temperature.

 = 1/  Density as a property Density is mass per unit volume;  = mass/volume (kg/m3) Specific volume is volume per unit mass.  = Volume/mass, (m3/kg)  = 1/ 