Reflection | 'AINUN SAILAH SIHAR's Profile

REFLECTION JOURNAL ON SKKK 2123 COURSE

(semester 1 session 2012/2013)

Lecturer        : Prof. Kamarul ‘Asri Ibrahim

Section          : 06

Course Code : SKKK 2123

This course introduces students to the chemical engineering profession and the fundamental operations of chemical process equipment. It also provides students with the basic principles of chemical engineering energy balances as well as calculation technique to solve material and energy balance problems for chemical process system and equipment.

Stated below are the time tables for the semester 1 session 2012/2013 for SKKK 2123 course.

WEEK 1 - 4

1.0    Balance on Non-reactive processes

1.1    State Properties

1.2    Hypothetical Process Paths

1.3    Procedures for energy balance calculations

1.4    Changes in P at Constant T (no phase change or reactions)

1.5    Changes in T at Constant V (no phase change or reactions)

1.6    Changes in T at Constant P (no phase change or reactions)

1.7    Heat capacities and estimation

1.8    Energy balances on single-phase systems

1.9    Energy balances on Processes Involving Phase Change Operations

1.10Psychometric Charts

1.11Adiabatic Humidification

 WEEK 5 – 8

2.0    Energy Balance For Reactive Processes

2.1    Heat of Reaction

2.2    Hess’s Law

2.3    Heat of Formation

2.4    Heat of Combustion

2.5    Energy Balance Techniques for Reactive Processes

2.6    Fuels and Combustion

WEEK 9 – 12

3.0    The Second Law of Thermodynamics

3.1    Statements of the Second Law of Thermodynamics

3.2    The Carnot Cycle and Heat Engine

3.3    The definition of Entropy

3.4    Entropy of Pure Substance

3.5    Entropy Generation

3.6    Efficiency

WEEK 13 – 15       

4.0    Power and Refrigeration Systems

4.1    Power Systems

4.2    The Rankine Cycle

4.3    Effect of pressure and temperature on the Rankine Cycle

4.4    Deviation of the actual cycle from ideal cycle

4.5    The Vapor-Compression Refrigeration Cycle

4.6    Deviation   of the actual Vapor-Compression Refrigeration Cycle from the ideal  cycle 

The students that taking this course will be evaluates on :-

By the end of this course, students should be able to :

1. Write basis, reference conditions and carry out unit conversion and equipment identification for various chemical processes, process variable and unit operations in chemical industry.
2. Perform and solve energy balances with respect to changes in temperature, pressure and phase for non-reactive process.
3. Calculate the standard heat of reaction using Hess’s Law, heat of formation and heat of combustions and then solve problems for reactive processes.
4. Define entropy and then calculate the entropy changes in a given process.
5. Analyze and calculate the performances of power and refrigeration cycles.
6. Conduct problem solving solution of mass and energy problem using principle of conservation.
7. Commit in the preparation of learning experience process using E-Portfolio.

Reflection Journal on Quizzes

Through out the semester, about 12 quizzes were conducted by our lecturer, Prof. Kamarul 'Asri Ibrahim. Same as the last semester, the quiz session was conducted before the lecture class is begin. This session took about ±15 minutes. In my opinion, all those quizzes help me to understand more based on the mistakes that I had done. Those mistakes opened my eyes to take note which part of the question should I improve on and as a reminder to me to not do the same mistake again.

Quiz 1 till Quiz 8 covers Energy Balance topics while Quiz 9 till Quiz 12 covers Thermodynamics topics. The quizzes on Energy Balance topics assessed us how to perform and solve energy balances with respect to changes in temperature, pressure and phase for non-reactive process. As for Quiz 3, we have to perform and solve the energy balances using psychometric chart provided. For me it was quite tough since we should have a strong understanding in Mass Balance in order to solve the Energy Balance. On the other hand, Quiz 4 till Quiz 8 assessed us on the ability to calculate the standard heat of reactions using Hess’s Law, heat of formation and also heat of combustion and then solve problems for the reactive processes.

Quiz 9 till Quiz 12 assessed us on the ability to define the entropy and calculate the entropy changes in a given process. Others are the ability to analyze and calculate the performance of power cycles and refrigeration cycles. These topics need a lot of understanding in order to solve the problems given.

REFLECTION JOURNAL ON TEST 2

Test 2 for the Principles of Chemical Processes II subject was held on 8 Nov 2012. This time, Test 2 covers CO1 and CO3 (course outcome) which are :-

• CO1 : ability to write basis, references conditions and carry out unit conversion and equipment identification for various chemical processes, process variables and unit operations in chemical industry.
• CO3 : ability to calculate the standard heat of reactions using Hess’s Law, heat of formation and heat of combustions and then solve problems for reactive process.

 Firstly, Question 1 was asked to calculate the standard heat of reaction for the combustion of liquid n-pentane at 25^oC with water product in liquid form. So, the chemical equation for the production water liquid as follows :

 C₂H₁₂ (l) + 8 O₂ (g) ----------> 5 CO₂ (g) + 6 H₂O (l)

 I just take an easy way to solve without noticed that I should do hypothetical path first to solve this question. So, the correct solution for the standard heat of reaction for the combustion of liquid n-pentane to form liquid water is equal to the summation of heat of vaporization of C₂H₁₂ (l), heat of combustion of C₂H₁₂ (g) and of heat of vaporization of H₂O (g).

 Secondly, Question 2 was asked to determine the standard enthalpy change for this reaction, 2 C (s) + 2 H₂O (g) ----------> CH₄ (g) + CO₂ (g), from the given standard enthalpies of reaction. In the lecture class, we were taught to calculate the standard heat of reaction using 3 methods which are using Hess’s Law, heat of formation and also heat of reaction (combustion) as stated on above explanation (CO3). For this question Hess’s Law method is the most suitable method to use.

 Thirdly, Question 3 was required us to perform mass balance to solve the problem which carry about 5 marks from the total marks of this question which is 30 marks. It is look simple to answer it since it only 5/30 marks, but if the students failed to perform mass balance the next sub-questions will be affected when we have to calculate the standard heat of reaction then. This situation happened to me on Question 4 and I lost a lot of marks there.

 Question 3 and 4 are look alike. The difference is Question 3 asked to calculate the amount of heat produced using the heat formation method while Question 4 asked to calculate the heat transfer using heat of reaction method. The other difference is the fractional conversion for the reaction in Question 3 is 100%. Instead, Question 4’s fractional conversion for the reaction is 65%. The term “100% excess air” made me confused at that time. As a result, my mass balance was wrong except for the SO₃ and SO₂ balance.

 In conclusion, the whole Test 2 is quite okay compared to the last test. But, still below the par . The next test will covers CO1 and CO4.                        

REFLECTION JOURNAL ON TEST 1

"Worst PCP's test ever." 

That sentence really opened my eyes to work hard for this subject. If the last semester we learned about MASS BALANCE in PCP I, this semester we are learning ENERGY BALANCE in PCP II. Truthfully, in my opinion mass balance is more interesting than energy balance but somehow these two topics are quite tough.

Back to the test that i undergo last 2 weeks, for the question 1 I made a mistake in drawing a hypothetical path which I did it reversely. The question was asked to find specific enthalpy of Toluene (s) relative to Toleune (v). The value of heat capacity for both compund were given but I did not used it instead I used heat capacity value from Table B2.

Suppose to be like this :

 toluene (v) --------> toluene (s)

but I did :

toluene (s) --------> toluene (v)

For the question 2, I did not have any idea to solve it. Suddenly, my mind got blank when heat exchanger question came out. To solve the energy balance, I have to do mass balance first on the heat exchanger. But, the problem was I can not solve the mass balance, so how can I solve the energy balance?

For the next question which is question number 3, the cooling tower figure made me frightened enough to solve it. For me the figure was so complicated, but the lecturer said it was a normal figure for a cooling tower. I try to solve the volumetric flow rate using psychrometric chart by finding humid volume and also moist content/mass dry air (DA). I thought that my answer was correct but then, when I received it back, I got wrong. I realized that I had misconception when doing mass balance in this question.

For the last question, I got the highest mark compared to the rest questions. My solution steps are correct but the final anwer was wrong.

The failure I faced this time will drive me to do more exercises to improve my mark and I will do the best for the second test in the future.