Principles of Thermodynamics and Thermal Fluids (CHPE 203) Lecturer: Dr Sagheer Onaizi Room : 5D-40, College of Engineering Email:sagheer.onaizi@unizwa.edu.om

Class Policy Do not: Come late Miss the class Ask for extension for assignment due Ask changing the exam time Argue for the marks Use handphone in the class or my office

Late Submission of Assignments All assignments must be submitted on due date before lecture. Any assignment submitted after due date WILL NOT be accepted and student will get zero in that assignment.

Quizzes There will be Quizzes taken in class Any student misses a Quiz WILL get zero in that Quiz. Quiz date may not be revealed to students (Surprise Quiz).

Exams There will be two Midterm Exams and Final Exam. University regulations will be applied in case of absence from Exams.

Assessment Details

Plagiarism Policy As per the University Policy UoN-STC-CR-1-2009, the following actions (not limited to), without proper attribution (quoting and/or referencing), will attract stringent penalties: copy the work of another student; directly copy any part of another person’s work; summaries another person’s work; use or develop an idea or thesis derived from another person’s work; or use experimental results or data obtained or gathered by another person. cheating during exam

Attendance Policy As per the University Absentee Regulations Uon-RR-AP-1-2009, Absentee warning notice will be issued to the student according to: “Absentee Warning 1” has to be issued to student who has missed 5% of course contact hours. “Absentee Warning 2” has to be issued to student who has missed 10% of course contact hours. “Drop one Grade” has to be issued to student who has missed 15% of course contact hours. “Barred from Examination” has to be issued to student who has missed 25% of course contact hours.

What is thermal fluid science? Thermal fluid science involves: 1. Transfer of energy 2. Transport of energy 3. Conversion of energy, Thermal fluid science is usually studied under the sub-categories of: 1. Thermodynamics, 2. Heat transfer, and 3. Fluid mechanics. 9

Example of Thermal Fluids in Human Body The heart is constantly pumping blood to all parts of the human body, various energy conversions occur in trillions of body cells, and the body heat generated is constantly rejected to the environment. 10

Example of Thermal Fluid Applications Designing the radiator of a car involves: the determination of the amount of energy transfer from a knowledge of the properties of the coolant using thermodynamics, the determination of the size and shape of the inner tubes and the outer fins using heat transfer, and the determination of the size and type of the water pump using fluid mechanics. 11

Heat Transfer Heat Transfer deals with the determination of the rates and mechanism of energy being transferred. Energy that can be transferred from one system to another as a result of temperature difference.

What is Thermodynamics? Thermodynamics can be defined as the science of energy. words therme (heat) and dynamis (power), the ability to cause changes. The change in the energy content of a system is equal to the difference between the energy input and the energy output, and the energy balance is expressed as: ΔE = Ein - Eout 13

Difference between Heat Transfer and Thermodynamics deals with systems that lack thermal equilibrium (non-equilibrium phenomenon), and provides the rate and mechanism of heat being transferred. Thermodynamics: deals with equilibrium states and changes from one equilibrium state to another.

Thermodynamic Laws Zeroth Law of Thermodynamics First Law of Thermodynamics Second Law of Thermodynamics Third Law of Thermodynamics

Zeroth law of Thermodynamics: The zeroth law states that “Two objects are in thermal equilibrium if both have the same temperature reading even if they are not in contact”.

First law of thermodynamics First law of thermodynamics is simply an expression of the conservation of energy principle, and it states that “Energy cannot be created or destroyed BUT it can be changed from one form to another”.

Second law of thermodynamics Second law of thermodynamics states 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.

Third Law of Thermodynamics Entropy is the measure of molecular disorder or randomness. As a system becomes more disordered, the position of the molecules becomes less predictable and the entropy increases. Entropy is the lowest in a solid because molecules are held in place and simply vibrate and highest in a gas where the molecules are free to move in any direction. Third Law of Thermodynamics States that: “Entropy of a pure crystalline substance at absolute zero temperature (zero Kelvin) is zero since the state of each molecule is known”.

Fluid mechanics Is defined as the science that deals with the behaviour of fluids at rest (fluid statics) or in motion (fluid dynamics). fluid refers to a substance in the liquid or gas phase Hydro-dynamics deals with liquid flows in pipes and open channels. Gas dynamics deals with flow of fluids that undergo significant density changes, such as the flow of gases through nozzles at high speeds. Aerodynamics deals with the flow of gases (especially air) over bodies such as aircraft, rockets. 20

Unit Systems Any physical quantity characterized by dimensions called units: Primary dimensions: such as mass m, length L, time t, and temperature T. Secondary dimensions: such as velocity u, energy E, and volume V are expressed in terms of the primary dimensions (derived from primary).

Systems of Units 1- English system: which is also known as the United States Customary System (USCS). (ft, lb, gal, etc). 2- Metric SI: which is known as the International System. (m, kg, m3). 1 lbm (pound mass) = 0.45359 kg ft = 0.3048 m

Force In SI system, N (Newton) force required to accelerate a mass of 1 kg at a rate of 1 m/s2. In the English system, the force unit is the pound-force (lbf ) and is defined as the force required to accelerate a mass of 32.174 lbm at a rate of 1 ft/s2. That is, 1 N = 1 kg · m/s2 1 lbf = 32.174 lbm · ft/s2   Unlike mass, weight (W) is a force. It is the gravitational force applied to a body, and its magnitude is determined from: W = mg = (N) OR Force=mass x acceleration where m is the mass of the body, and g is the local gravitational acceleration (g is 9.81 m/s2 or 32.174 ft/s2 at sea level). The specific weight (γ) and is determined from γ =ρg, where ρ is density.

Energy In the English system, energy unit is the Btu (British thermal unit) = energy required to raise the temperature of 1 lbm of water at 68 oF by 1 oF. In the SI system, the amount of energy needed to raise the temperature of 1 g of water at 15 oC by 1 oC is defined as 1 calorie (cal), and 1 cal= 4.1868 J. The magnitudes of the kilo-joule and Btu are almost identical (1 Btu=1.055 kJ). Work : a form of energy, defined as force times distance; therefore, it has the unit “Newton. meter (N ·m),” called a Joule (J), 1 J = 1 N · m and, the kilo-joule (1 kJ=103J).

Dimensional Homogeneity In engineering, all equations must be dimensionally homogeneous. That is, every term in an equation must have the same unit. E= 25 kJ + 7 kJ/kg Invalid E= 25 kJ + 7 kJ = 32 KJ Valid Example: A tank is filled with oil whose density is ρ= 850 kg/m3. If the volume of the tank is V=2 m3, determine the amount of mass m in the tank. It is clear that: m = ρ . V = (850 kg/m3) (2 m3) =1700 kg

Operations with Units Only add and subtract numbers with the same associated units 2 kg + 3 m Invalid If the dimensions are the same but the units differ, first convert to a common set of units 1 lb + 400 g Invalid 1 lb + 400 g 1 lb + 0.88 lb = 1.88 lb Valid You can multiply and/or divide unlike units, but you cannot cancel units unless they are the same Valid 26

Tutorial

Question: Answer:

PROBLEM-SOLVING TECHNIQUE Step 1: Problem Statement Step 2: Schematic Step 3: Assumptions and Approximations Step4: Physical Laws Step 5: Properties Step 6: Calculations Step 7: Reasoning, Verification, and Discussion

End of Chapter One