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It's a conversion factor let's look at the units we're working with: Cp is in kJ/(kg·°C) Temperature difference is in °C We need the final answer in m/s When we multiply these: Cp × ΔT = (kJ/(kg·°C)) × °C = kJ/kg The issue is that kJ/kg needs to be converted to (m/s)² to be compatible with V₁² Let's convert kJ to base SI units: 1 kJ = 1000 J 1 J = 1 kg·m²/s² Therefore: 1 kJ/kg = 1000 J/kg = 1000 (kg·m²/s²)/kg = 1000 m²/s²

شكرا للمشاهدة.

Your understanding is correct in recognizing that work is done on the system, but the enthalpy change already includes this work, making the calculation straightforward using the enthalpy values. Here's why This is a constant pressure process (isobaric), where the refrigerant is simply being cooled While the volume changes during cooling (as shown in the T-v diagram), any work done by pressure forces during this process is already accounted for in the enthalpy values (h = u + Pv) For an isobaric process: Work = P(v₂ - v₁) This work term is automatically included in the enthalpy difference That's why we can use the simple equation Q = m(h₂ - h₁) The work you're thinking of (compression work) would occur if we were actively compressing the refrigerant to a higher pressure. But in this case, we're just cooling it while maintaining the same pressure of 800 kPa.

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Thanks for watching. Good luck in your exam and all the best in your studies

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Yunus and Cengal 9th, 10th and 11th edition

Upon reviewing it appears to be incomplete. I'll add to the pinned comment. Heat supply rate = P_input - P_out Heat supply rate = 310.83 W - 186.5 W = 124.33 W To clarify The 186.5 W (0.25 hp) is the OUTPUT shaft power of the motor (sometimes called P2) . Shaft Output Power (P_output): This is the mechanical power delivered by the motor to the load (in this case, the fan). It is given as 0.25 horsepower, which is approximately 186.5 watts. This is the mechanical power delivered to the fan Given the efficiency is 60%, we work backwards to find input power (P1): Efficiency (η): This is the ratio of the mechanical output power to the electrical input power. It is given as 60%, or 0.60 Efficiency = Output power / Input power . 0.60 = 186.5 W / Input power Input power (P1) = 186.5 W / 0.60 = 310.83 W Electrical Input Power (P_input): This is the electrical power supplied to the motor. Due to the motor's efficiency, not all of this power is converted to mechanical output; some is lost as heat.

I can see your concern and conceptually you are correct. I have put a correction in the pinned comment. You left out the load factor 2.5 hp (1,865 W) motor with 77% efficiency would draw about 2,967.5 W of electrical power, and heat loss should be: Heat loss = Electrical input - Shaft output = 2,967.5 - 1,865 = 1,102.5 W Full shaft output = 2.5 hp = 1,865 W At 70% load (load factor 0.7): Actual shaft output = 1,865 × 0.7 = 1,305.5 W Input power = (Actual shaft output)/(Efficiency) = 1,305.5/0.77 = 1,696.1 W Heat loss = Input power - Actual shaft output = 1,696.1 - 1,305.5 = 391.6 W

Yes you are correct, mistakes happen from time to time. I'll add it to the pinned comment.

@@SuemonKwok Thank you for yor good work !!

It's a case by case biases. It depends how accurate you want your answer to be and depends on the problem and the context. If it's not critical a general approximation using the tables to next highest values works but if it is critical where system failure or human lives are at risk then finding exact value is needed. If it is dynamic and there is moving parts or values change then use the average value.

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The thermodynamic uses a standard of 300K as an approximation for ideal gas at room temperature. C_v applies to low temperatures only. At high temperatures C_p and C_v change due to the movement in the molecules so we use different tables at high temperatures

@@SuemonKwok so any temperature close to 300k , we can use those Cv, Cp values from A-2(a) table right? and the other way i thought is that finding average of the temperatures and getting the values from A-2(b) at that Tavg, or interpolate if we dont have the exact temperature at the table. Would it be correct?

@@kayaiine Yes for low temperatures use the table

Yunus and Cengal 9th, 10th, 11th

#&$#5#66$3(❤️

Yunus and Cengal 9th, 10th and 11th edition and beyond. Introduction to thermodynamics. Depending on the university they may use different editions or newer editions

Greetings, I can see why you might think it's Q_exhaust however see explanation below Q_total = Q_water + Q_loss. The naming convention encompasses all heat transfer where as Q_exhaust is only a portion of the equation. In this heat transfer problem, we need to account for the total heat transfer from the exhaust gases, which includes: 1. Heat transferred to the water 2. Heat lost to the surroundings Step 8 Formula Explanation: ∆Texhaust = Qtotal / (mexhaust × Cp) Where: - ∆Texhaust is the temperature drop of exhaust gases - Qtotal is the total heat transferred (including heat to water and heat loss) - mexhaust is the mass flow rate of exhaust gases - Cp is the specific heat capacity of the exhaust gases Step 9 Total Heat Transfer Calculation: Qtotal = Qwater / (1 - f_heat_loss) The key points to understand are: - Not all heat from exhaust gases goes to the water - 10% of heat is lost to surroundings - So, the total heat transfer must be larger than heat to water - We divide Qwater by (1 - 0.1) = 0.9 to account for heat loss Mathematical Derivation: 1. Heat to water = 97.26 kW 2. Heat loss = 10% of total heat 3. Total heat = Heat to water ÷ (1 - Heat loss fraction) 4. Qtotal = 97.26 kW ÷ 0.9 = 108.07 kW

EES uses different values. The manual way is linear interpolation. Yes you get a vastly different answer. Values taken from text book 1. Pressure Interpolation (at 15°C): For v_f (saturated liquid specific volume): - x1 = 90 kPa, y1 = 0.0007222 - x2 = 100 kPa, y2 = 0.0007258 - x = 90.4 kPa v_f = 0.0007222 + (90.4 - 90) * (0.0007258 - 0.0007222) / (100 - 90) = 0.0007222 + 0.4 * (0.0000036) / 10 = 0.0007222 + 0.0000001440 = 0.0007223 m³/kg For v_g (saturated vapor specific volume): - x1 = 90 kPa, y1 = 0.21261 - x2 = 100 kPa, y2 = 0.19255 - x = 90.4 kPa v_g = 0.21261 + (90.4 - 90) * (0.19255 - 0.21261) / (100 - 90) = 0.21261 + 0.4 * (-0.02006) / 10 = 0.21261 - 0.0080240 = 0.20459 m³/kg 2. Temperature Interpolation (at 90.4 kPa): For v_f (saturated liquid specific volume): - x1 = 14°C, y1 = 0.0008018 - x2 = 16°C, y2 = 0.0008064 - x = 15°C v_f = 0.0008018 + (15 - 14) * (0.0008064 - 0.0008018) / (16 - 14) = 0.0008018 + 1 * (0.0000046) / 2 = 0.0008018 + 0.0000023 = 0.0008041 m³/kg For v_g (saturated vapor specific volume): - x1 = 14°C, y1 = 0.043471 - x2 = 16°C, y2 = 0.040798 - x = 15°C v_g = 0.043471 + (15 - 14) * (0.040798 - 0.043471) / (16 - 14) = 0.043471 + 1 * (-0.002673) / 2 = 0.043471 - 0.0013365 = 0.0421345 m³/kg 3. Volume Change Calculation: Assuming the refrigerant is initially saturated vapor at -10°C and 90.4 kPa, and you need to find the final volume at 15°C and 90.4 kPa: Initial volume: V1 = m * v1 Final volume: V2 = m * v2 Given mass = 0.85 kg V2 - V1 = 0.85 * (v2 - v1) Initial conditions (-10°C): Specific volume of saturated vapor (v_g) = 0.099600 m³/kg Mass = 0.85 kg Final conditions (15°C): Specific volume at 90.4 kPa = 0.0421345 m³/kg (interpolated) Volume change calculation: ΔV = m * (v2 - v1) = 0.85 kg * (0.0421345 - 0.099600) = 0.85 * (-0.0574655) = -0.04884 m³ ≈ -0.049 m³

Thanks for watching. Yunnus and Cengal 9th, 10th and 11th edition.

In step 2 the conservation of energy equation is ṁ(h₁ + V₁²/2) = ṁ(h₂ + V₂²/2) Step-by-Step Derivation: 1. Start with the given equation: Equation: ṁ(h₁ + V₁²/2) = ṁ(h₂ + V₂²/2) 2. Divide both sides by ṁ: h₁ + V₁²/2 = h₂ + V₂²/2 3. Rearrange the equation to isolate h₂: h₁ + V₁²/2 - V₂²/2 = h₂ 4. Combine the terms involving V₁ and V₂: h₁ - V₂²/2 + V₁²/2 = h₂ 5. Factor out the common term 1/2 from the velocity terms: h₁ - 1/2(V₂² - V₁²) = h₂ 6. Final equation: h₂ = h₁ - (V₂² - V₁²)/2 Hope this clarifies step 4 Basically this 1/2(V₁² - V₂²) = -1/2(V₂² - V₁²)

Thanks for watching The first 500 videos are designed for 2nd and 3rd year university students with the expectation of having mastered foundations and attempted the question. It's designed as a review material and check if the process is correct. This is supplementary material to student's learning not a direct copy and paste although it could used as such, the grade will be lower. From 5-31 onward the teaching style shifts towards high school and 1st year university students. If you have a question regarding this tutorial feel free to post in the comments.

Thanks for watching The first 500 videos are designed for 2nd and 3rd year university students with the expectation of having mastered foundations and attempted the question. From 5-31 onward the teaching style shifts towards high school and 1st year university students. If you have a question regarding this tutorial feel free to post in the comments. Good luck in your exam and all the best in your studies

In steady-state flow problems like this diffuser analysis, we use the ideal gas law in a slightly modified way: 1. The mass flow rate does not directly enter into the fundamental equation of state (Pv=RT). 2. Instead, the mass flow rate is used in the energy and continuity equations to determine other properties like velocity, temperature, and pressure. 3. When calculating specific volume (v), we use the local temperature and pressure conditions at the point of interest. If you were to modify the equation to Pv=(mass flow rate)RT, it would not be physically meaningful because: - Mass flow rate has units of kg/s - This would introduce an incorrect dimensionality to the state equation - The ideal gas law describes the relationship between P, v, R, and T for a given mass of gas

Greetings the question states "A compressed spring above the piston exerts a force of 150 N on the piston. " This means the spring force is pushing DOWN on the piston, not upward. Let's break down why. Springs are reactionary compressed spring means there is stored energy that needs be released. Compressed spring above the piston. So when the spring extends to release the energy it will push the piston down.

Textbook: Yunus and Cengal 9th, 10th and 11th for thermodynamics Different universities use different textbooks. Editions don't really matter too much they jumble the questions, the questions are the same. They fix maybe some spelling mistakes. ___________________________________________________________________________________ Here is the approach I used to solve these tutorials and put it up on youtube. I use multiple free Ai chat bots such as Microosoft Copilot, Chat gpt, Claude and Le Chat. I copy and paste the question into the chat bots and ask it to solve it step by step. I check each response if 1 chat bot hallucinates and the other chat bots give the same steps then I follow the ones that are the same. I also ignore the chat bot numerical answer because I know they just make it up. However I know the steps are scrapped off from lecturer notes pdfs, posted on legacy university websites or on forums. So I follow the steps and manually work it out. When you combine the steps of the Ai chat bot with your own engineering knowledge you can tell if it makes sense or not. Example prompt _________________________________________________________________ "Paste question here" Please solve the question above step by step and explain each step _________________________________________________________________ I recommend mastering the foundations and get well versed in calculus. Good luck in your exam and all the best in your studies

Firstly h1 should be kept as kJ/kmol same the table. the reason ΔH = Cp * ΔT approach didn't work is that for real gases, especially at these conditions: Specific heat is not constant. While the pressure is constant, the temperature change is significant enough that the specific heat (Cp) cannot be treated as constant for CO2 Enthalpy changes are not linearly proportional to temperature. This is because vibrational modes (the way CO2 molecules moves) become increasingly active at higher temperatures, causing non-linear enthalpy changes The easiest way to find final temperature in this case is to look up the table where people have already found the experimental value. In our case it is in between so we approximate it using linear interpolation.

@@SuemonKwok i see so you cannot assume Co2 is an ideal gas in this case? I just assumed so since table A-20 where we go to find h its listed as ideal gas properties of Co2

@@marcushooshmand2301 Well you could use it as approximate but the more accurate way is using the ideal gas table to approximate real gas temperature via finding enthalpy through the nozzle equation . However we have an adiabatic nozzle process, so we should use the energy equation: h1 + V1²/2 = h2 + V2²/2 (for steady, adiabatic flow) If used h=C_p*Delta T h2 = 26,423 kJ/kmol C_p = 0.846 kJ/kg·K h2 (specific) = 26,423 kJ/kmol ÷ 44 kg/kmol = 600.52 kJ/kg T2 = h2 / C_p T2 = 600.52 kJ/kg ÷ (0.846 kJ/kg·K) T2 = 710.2 K 710.2K is close to 685.8 K but not negligible. Difference: 24.4 K (or about 3.6%) In engineering thermodynamics, a difference of 3.6% is typically considered: Not negligible for precise calculations Significant enough to warrant explanation For most engineering applications, this difference would be considered meaningful. In critical design scenarios (like aerospace or power generation), you'd want to: Use more precise interpolation methods Consult real gas tables Apply compressibility correction

We assume quasi-equilibrium process. In quasi-equilibrium the system goes through a series of infinitesimally close to equilibrium states. This simplification assumes the process is linear. From that idea we can find the boundary work under the "curve" which is the linear line in the PV diagram which forms the trapezoid shape when you draw dotted lines vertically down. Don't get confused with the saturation curve. P1 + P2 / 2 is used to approximate the average pressure of the trapezoid shape. We do this to make the calculation simple and avoid integration.

Greetings thanks for watching. While I am solving 1 question at per day due to work right now. If you can't wait. Here is the approach I used to solve these tutorials and put it up on youtube. I use multiple free Ai chat bots such as Microosoft Copilot, Chat gpt, Claude and Le Chat. I copy and paste the question into the chat bots and ask it to solve it step by step. I check each response if 1 chat bot hallucinates and the other chat bots give the same steps then I follow the ones that are the same. I also ignore the chat bot numerical answer because I know they just make it up. However I know the steps are scrapped off from lecturer notes pdfs, posted on legacy university websites or on forums. So I follow the steps and manually work it out. When you combine the steps of the Ai chat bot with your own engineering knowledge you can tell if it makes sense or not. Example prompt _________________________________________________________________ "Paste question here" Please solve the question above step by step and explain each step _________________________________________________________________ Good luck in your exam and all the best in your studies

@ thanks for the guidance 🌹

The question states "determine the temperature at the final state in part b." Because it explicitly states that the final pressure in part (b) is 500 kPa not part (a) which 1 MPa (a) 1.0 MPa and 250°C and (b) 500 kPa. (c) Also determine the temperature at the final state in part b.

All assumptions for constant pressure. The hair dryer is essentially a constant-pressure system. Open device: The hair dryer operates in atmospheric pressure, meaning both the inlet (P1P1​) and outlet (P2P2​) are exposed to the same ambient atmospheric pressure (Inlet 100 kPa and outlet100kPa). There are no significant pressure-changing components The fan provides just enough energy to overcome minor friction losses. Low-speed flow: The hair dryer operates at low speeds, and the changes in velocity are small. For such flows, the pressure losses due to friction and heat addition are negligible. The cross-sectional area changes are minimal. Negligible height difference: There is no significant change in elevation (zz) in a hair dryer. Thus, potential energy effects can be ignored. The flow is treated as steady and incompressible

@@SuemonKwok Thanks 🙏. Is the basis for judgment the picture in the question?

@@David-xg2jq The figure helps visually for the cross sectional area not changing. however they always say it's not to scale. Figure doesn't show piston or pressure changing devices. The rest is something you just to have to assume as they are assumptions.

@@SuemonKwok Okay, thanks 👍 Your videos help me a lot 🫡

Thanks for watching, glad it helped. It is unit conversion converting the velocity squared term from m²/s² to kJ/kg divide by 1000

Thanks for watching and thank you for the support. Even being a member once at lowest tier helps me pay the bills. These are my older videos, my teaching style has improved in newer videos. Videos from 5-31 onward I solve as if I was solving it for the first time. The first 500 videos were designed for 2nd and 3rd year university students who have mastered the foundations and have attempted the questions. If you have any questions about these tutorials, please post in the comments of the respective video and I will reply within 24 hours.

To clarify are you getting a different answer from the this tutorial? See working below if that is the case. If you got a different answer from a different question, please post your working and the new question and can we have a look what's going on. ______________________________________________________________________ Manual working for this question for final velocity V_2=[V_1^2+2C_p (T_1-T_2 )]^0.5 V_1^2 = 350^2 = 122,500 2 * C_p * (T_1 - T_2) * (1000 / 1) = 2 * 1.007 * (30 - 90) * 1000 = -120,840 Then taking the square root of (122,500 - 120,840) gives 40.7 m/s. V_2=40.7 m/s _______________________________________________________________________ Here is python code to check final velocity also in pinned comment. ______________________________________________________________ import math # Given values V1 = 350 # initial velocity in m/s Cp = 1.007 # specific heat capacity in kJ/(kg.°C) T1 = 30 # initial temperature in °C T2 = 90 # final temperature in °C # Convert Cp to m^2/s^2 Cp_converted = Cp * 1000 # (1000 m^2/s^2) / (1 kJ/kg) # Calculate final velocity V2 = math.sqrt(V1**2 + 2 * Cp_converted * (T1 - T2)) print(f"The final velocity V2 is {V2:.2f} m/s")

Thanks for watching. If it's the meme lol. If you're referring to the Malay legend I am honored. The name "Tuah" in Malay has a beautiful meaning. It translates to "luck" or "fortune" in English. So Hang Tuah's name essentially means someone who brings or embodies good luck. Hang Tuah is a highly significant figure in Malay folklore and history. He is often depicted as an incredibly loyal warrior and a national hero who served the Sultan of Malacca with unwavering devotion. His legendary status is similar to that of heroic figures in other cultures' national narratives. In traditional Malay stories, Hang Tuah is known for his exceptional skills in silat, his intelligence, and his famous quote: "Takkan Melayu hilang di dunia" which means "The Malays will never vanish from the face of the earth" - a powerful statement of cultural pride and resilience.

@@SuemonKwokKwok Tuah!!

@@reece2574 Thanks for watching

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Here is generic approach. However these video tutorials are thermodynamics. Heat transfer is what you need but I'll be making those videos in the far future maybe 5 years from now when I finish thermodynamics chapters. Step 1: Determine the Heat Transfer Rate First, calculate the heat transferred from the refrigerant (R-134a) to the air. 1. **Refrigerant Side:** - Determine the enthalpy of R-134a at the inlet (1 MPa, 90°C) and outlet (1 MPa, 30°C) conditions. You can use thermodynamic tables or software like REFPROP or EES for this. - Calculate the heat released by the refrigerant: Equation: Q_refrigerant = ṁ_refrigerant × (h_in - h_out) where ṁ_refrigerant is the mass flow rate of the refrigerant, h_in is the enthalpy at the inlet, and h_out is the enthalpy at the outlet. 2. **Air Side:** - Determine the enthalpy of air at the inlet (100 kPa, 27°C) and outlet (95 kPa, 60°C) conditions. - Calculate the heat absorbed by the air: Equation: Q_air = ṁ_air × (h_out - h_in) where ṁ_air is the mass flow rate of the air, h_in is the enthalpy at the inlet, and h_out is the enthalpy at the outlet. Since the heat transferred from the refrigerant to the air should be equal: Equation: Q_refrigerant = Q_air Step 2: Calculate the Mass Flow Rate of the Refrigerant Using the heat transfer rate and the enthalpy change of the refrigerant, you can solve for the mass flow rate of the refrigerant: Equation: ṁ_refrigerant = Q_air ÷ (h_in - h_out) ### Step 3: Determine the Heat Transfer Area The heat transfer area A can be calculated using the overall heat transfer coefficient U and the log mean temperature difference (LMTD): Equation: Q = U × A × LMTD 1. **Log Mean Temperature Difference (LMTD):** Equation: LMTD = [(T_hot,out - T_cold,in) - (T_hot,in - T_cold,out)] ÷ ln[(T_hot,out - T_cold,in) ÷ (T_hot,in - T_cold,out)] where T_hot,out is the outlet temperature of the refrigerant, T_cold,in is the inlet temperature of the air, T_hot,in is the inlet temperature of the refrigerant, and T_cold,out is the outlet temperature of the air. 2. **Overall Heat Transfer Coefficient U:** This can be determined from empirical correlations or experimental data. 3. **Heat Transfer Area A:** Equation: A = Q ÷ (U × LMTD) Step 4: Determine the Length of the Condenser The length L of the condenser can be determined if you know the geometry of the condenser (e.g., the diameter of the tubes and the number of tubes). 1. **Surface Area per Unit Length:** If the condenser consists of tubes, the surface area per unit length can be calculated as: Equation: A_surface = N × π × D × L where N is the number of tubes, D is the diameter of the tubes, and L is the length of the tubes. 2. **Length of the Condenser:** Equation: L = A ÷ (N × π × D) Summary 1. Calculate the heat transfer rate Q. 2. Determine the mass flow rate of the refrigerant ṁ_refrigerant. 3. Calculate the heat transfer area A using the overall heat transfer coefficient U and LMTD. 4. Determine the length L of the condenser based on its geometry. This approach will give you the length and area of the cooling condenser. If you have specific values for the overall heat transfer coefficient and the geometry of the condenser, you can plug those in to get the exact dimensions.

​@@SuemonKwok❤ Thank you very much ❤❤❤❤❤

Yunus and Cengal 9th, 10th and 11th and lecture notes

@@SuemonKwok thanks our teacher put this question in test now I know from where

Yunus and Cengal 9th, 10th and 11th and lecture notes

Here is a general guide but every scenario may vary 1) First Law of Thermodynamics: The first law states that ΔU = Q - W Where: - ΔU = Change in internal energy - Q = Heat added to the system - W = Work done by the system 2) Isobaric Process Characteristics: - Constant pressure (P = constant) - The pressure remains unchanged throughout the process 3) Insulated Piston-Cylinder: - No heat transfer occurs (Q = 0) - The system is thermally insulated 4) Analysis: - Since Q = 0 (no heat transfer due to insulation) - Work is done at constant pressure: W = P ΔV - Substituting into the First Law: ΔU = -W = -P ΔV 5) Implications: - The entire change in internal energy comes from the work done by the system - The change in internal energy is entirely due to the volume change - ΔU = -P ΔV Example Let's say you have a piston-cylinder system with a constant pressure of 100 kPa and the volume changes from 1 m³ to 2 m³. The work done by the system would be: W = P ΔV = 100 kPa × (2 m³ - 1 m³) = 100 kPa × 1 m³ = 100 kJ The change in internal energy would be: ΔU = -W = -100 kJ Key points: - No heat is added or removed - Work is done by expanding or compressing the system - The change in internal energy is directly related to the work and volume change

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It depends on on the information given. The question will give you pressure and temperature but limited to those two. From there you check the tables.

This is a steam turbine question. It doesn't use ideal gas so you can't use ideal gas for this question. Steam is water (superheated water above saturated vapor) Steam is not an ideal gas

@ Now I understand,Thank you Sir ❤️