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Thermodynamics Forum
What is a model?
Ans: A model is a mathematical representation that idealizes a "complicated" physical situation (or system) to a greater or lesser degree, depending on the interest and knowledge"
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Sep 13
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Thermodynamics Forum
Sign convention for heat and work
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Sep 12
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Thermodynamics Forum
What are some examples of thermal-fluid engineering systems?
Answer: 1. jet engines 2. refrigerator 3. water pump 4. air compressor 5. solar over 6. radiator 7. petrol and diesel engines 8. air conditioners 9. thermal power plants 10. nuclear power plants 11. rockets 12. water heaters 13. electronic cooling systems, etc
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Sep 10
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Thermodynamics Forum
What is the difference between solid and Newtonian fluid?
Answer: A solid material will first deform under shear stress and then stop deforming and achieve a new equilibrium state on the other hand a Newtonian fluid will deform and continue to deform no matter how small the shear stress is applied to it.
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Sep 10
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Thermodynamics Forum
What is fluid?
Answer: Material that flows under the action of a shear stress no matter how small the shear stress is. Note: This definition of fluids is mainly applicable to only Newtonian fluids such as water, air, motor oil, etc
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Sep 10
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Thermodynamics Forum
How to learn anything new in 2023?
1. Decide on the topic 2. Find the expert in that topic from Google (Expert is someone who has either won some prestigious award in that field or is a pioneer of the field or has several years of experience) 3. Search him on YouTube 4. Find 10 videos which are more than 20 minutes in length and crea
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Aug 13
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Bboy88
Why Cp
Why can we use specific heat capacity at constant pressure to calculate work into the compressor? Eg Brayton cycle: W_1-2 = mCp(T2 - T1) This always confuses me as it is not a constant pressure process! Help :(
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Jul 26
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George Glenn
thermodynamic problem
A balloon is connected to a helium cylinder at 5 bar through a regulating valve. Ambient pressure is 1 bar. The valve is opened, 0.1 m3 of helium goes inside the balloon, then the valve is closed. Finally, the pressure of helium inside the balloon in Pa is
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Jul 24
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jamesbenstead6
Heat transfer equation
I'm a little rusty as i've not done this since Uni about 20 years ago, so sorry if it seems a dumb question. I have a solar thermal panel heating a hot water cylinder and i've always wondered how much energy it actually puts out in kW. The fluid (water) being pumped from the solar panel header to th
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Jul 16
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Oliver Meyer
Vapor-Mixtures (real-gas calculation for high pressures) and Enthalpie Calculations
I would like to calculate the entropy or enthalpies (steam, specific and inner energy) using the SRK [suave-redlich-kwong] equation, the Wilson approximation and (if necessary) the Antoine equation. and the Clausius-Clapeyron equation for a mixture of 0.199 mol/l nitrogen and 0.811 mol/l carbon diox
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Apr 20
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Thermodynamics Forum
What is a thermodynamic process?
Ans: A process occurs when a system undergoes a change of state with or without interactions with the environment.
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Sep 12
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Thermodynamics Forum
What is the property of the system?
Ans: Observables (measurable macroscopic quantities) that are definable at a particular instant and are not dependant on the system's history. The property of the system is also called "state variable" examples: mass temperature energy enthalpy velocity position volume, etc
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Sep 11
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Thermodynamics Forum
What is efficiency in layman's terms?
Answer: Efficiency is the ratio of what you "want" to what you "pay".
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Sep 10
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Thermodynamics Forum
What is non-Newtonian fluid?
Answer: A non-Newtonian fluid first needs a finite amount of shear stress before it starts to flow. Examples: Toothpaste, Yogurt, Silly putty, etc
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Sep 10
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Thermodynamics Forum
What is continuum mechanics?
The word 'continuum' is a contraction of two words continuous and medium In continuum mechanics, we neglect the molecular nature of the material under consideration. The material is treated as single piece of matter. We can describe quantities such as the velocity as a function of position and time
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Sep 10
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Bboy88
Final temperature & Heat added to superheated steam
A rigid tank contains 2.0 kg of superheated steam initially at temperature of 250 °C and pressure 0.5 MPa (state 1). Heat is added to the steam leading to a rise in temperature and pressure. The final pressure at state 2 is 1.0 MPa. Consider that the specific volume remains constant throughout the p
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Aug 01
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Bboy88
Brayton cycle
I have used the two efficiency formulae to solve the following problem, but I get a different answer from each: If I use the 1 - (1/PR^1.4-1/1) I get approx. 40% If I use Work_nett/Heat_in I get approx. 27% I can't figure why there is a discrepancy, is it do with the isentropic efficiencies
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Jul 25
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hippieholgy
Radiation of two surfaces
It is a thought experiment: Imagine two bodies (A and B) of different surface area, made of the same material. Imagine all heat radiation of body A could be directed to body B and all radiation of Body B could be directed to body A. After some time this would lead to a balance of radiation. Radiatio
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Jul 16
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Bernardo Tostes
Cutoff ratio in diesel engines
Hello, Does anyone know typical values of cutoff ratio in diesel engines? And how have they evolved through time? Thank you!
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May 27
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L Schuh
Gibbs Free Energy Ammonia Synthesis
When I solve an exercise to calculate Gibbs Free Energs delta G I look in Tables and collect for Data for enthalpy and entropy and fill them in the formula deltaG = deltaH - T*deltaS. I am confused about the system and surrounding. Is this treated a open or closed System? Is it isothern .. I think y
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Mar 29
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Thermodynamics Forum
What is heat transfer?
Ans: "Heat transfer is the energy transfer that is driven by temperature difference (gradient) between the system and the environment."
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Sep 12
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Thermodynamics Forum
What is the state of the system?
Answer: Condition of a system at any given instant. It is characterized by a series of observable (macroscopic quantities) called properties.
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Sep 11
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Thermodynamics Forum
Give some examples of Newtonian and non-Newtonian fluids.
Newtonian fluids: water, air, motor oil, alcohol, glycerol, etc Non-Newtonian fluids: toothpaste, yogurt, silly putty, corn starch, blood, paint, shampoo, etc
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Sep 10
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Thermodynamics Forum
What is Newtonian fluid?
Answer: A Newtonian fluid will deform and continue to deform no matter how small the shear stress is applied.
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Sep 10
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Thermodynamics Forum
What is fluid mechanics?
Answer: Branch of continuum mechanics that describes the motion of fluids (such as for example air, water, blood, yogurt, lava, etc)
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Sep 10
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Govind Prajapat
Gibbs free energy of activation and Activation energy
Let's consider a reaction A (reactant) -> B(product) and activated complex is denoted by C. This graph ( potential energy vs reaction coordinate ) tells us that reactant need some amount of activation energy (Ea) to convert in product, which has low potential energy which is shown here in terms
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Jul 31
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Federico Marzocchi
Hi I have a problem with and advanced thermodinamic exercise, can someone help me?
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Jul 25
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Bboy88
polytropic
How do I start this problem please? A closed cylinder contains 40 ml of gas at 800 kPa. The gas expands to a volume of 400 ml according to the relationship pV1.1 = constant. If the heat transfer from the gas to the surroundings is 300 J, calculate the change in internal energy of the gas during the
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Jul 16
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Bboy88
Heat transfer from gas flow through pipe
Here's a question: A gas flows in a pipe at a rate of 1 kg/s. The pressure and temperature at one section of the pipe are 0.6 MPa and 527K. At the second section of the pipe, the pressure is 0.5MPa and temperature is 320K. The specific volume of the inlet gas is 0.249 m3/kg and at the second section
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Apr 24
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Bboy88
Work & Entropy
Hi all, Any idea about how to solve this problem? Consider a cylinder fitted with a piston which contains saturated Steam at 30°C with 80% quality. Let this vapor be compresses in a reversible adiabatic process until the pressure is 10 bars in superheated conditions .Determine the work per kilogra
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Mar 28
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