What is Cycle: Definition and 673 Discussions

The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea (NH2)2CO from ammonia (NH3). This cycle occurs in ureotelic organisms. The urea cycle converts highly toxic ammonia to urea for excretion. This cycle was the first metabolic cycle to be discovered (Hans Krebs and Kurt Henseleit, 1932), five years before the discovery of the TCA cycle. This cycle was described in more detail later on by Ratner and Cohen. The urea cycle takes place primarily in the liver and, to a lesser extent, in the kidneys.

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  1. R

    Carnot Cycle: Doubt in Reversible Isothermal Heat Addition

    In Carnot cycle during the process - "Reversible isothermal heat addition" Q (supplied) = ∫pdV This means that the supplied heat is utilized for pdV work. My doubt is if the Q supplied is converted to work in this process then how Carnot cycle can reject heat during the upcoming isothermal...
  2. F

    I Question about Schwave's cycle

    Hello everybody. After reading about solar variability in the past I have found that the eleven year cycle of solar activity doen't affect the magnetic field of the sun so it is impossible to know the distribution of sunspots previous to 1610, when the observation started. But on the other...
  3. V

    Thermodynamics cycle work question

    Homework Statement A mass of gas occupying volume V1 = 2 m3 at the pressure P1 = 4*10^5 Pa performs the cycle represented in the Figure that i have uploaded.What is the work of gas in this cycle, knowing that the pressure P2 = 10^5 Pa Homework Equations Work=1/2 * (P1 - P2) * (V1 - V3) The...
  4. P

    Carnot Cycle: Analysis of Energy Exchange

    A refrigerator operates on a Carnot cycle. In this cycles, it absorbs 120 J of energy at a temperature Tc while 300 J of work is done on the gas undergoing the cycle. How much energy is exhausted as heat during this process? The answer is 420 J. I am unsure of where to start for this...
  5. T

    Is the PV diagram in this quasi-static cycle correct?

    Homework Statement Hi guys can someone tell me if I am wrong, or missing reading this question. For part a I need to draw a PV diagram now it states that is is being expand isothermally yet when I look at the pressure it dose not change, which is confusing me beacuse it dose in a isothermal...
  6. B

    Maximum work done in a Carnot Cycle

    Given that in a Carnot Cycle the two adiabatic processes are essentially equal and opposite in magnitude the total work done by the cycle is in the two isotherms. The total work of the system is generally given as -NR(Th-Tc)ln(Vb/Va). Does this mean that the work done by a monatomic ideal gas is...
  7. knc

    What is the Work Done by a Gas in a Cycle?

    Homework Statement Homework Equations PV = nRT \\ W = - \int_{V_i}^{V_f} P dV \Delta E_{int} = Q + W The Attempt at a Solution a)[/B] Since this is a cyclic process, the change in internal energy of the system is 0. \Delta E_{int} = 0 The process causes some ice to melt, meaning heat...
  8. grandpa2390

    Find the work of this cycle

    Homework Statement Homework Equations PV = nRT T= constant The Attempt at a Solution I did the adiabatic process already. I got that P= 103862 Pa, T = 363.862 K V = .035 m^3 n = 1.203 moles at the end. So the Temperature through the isothermal process should be 362.862 in order to...
  9. Pull and Twist

    Calculating work of Otto cycle stages - Thermodynamics.

    One big coincidence of thermodynamics is that automobiles are usually powered by an Otto cycle This cycle consists of an adiabatic compression (the cylinder compresses), isochoric compression (the fuel ignites, increasing the temperature in too short a time for the piston to move), adiabatic...
  10. W

    Thermodynamic cycle of a solar cell

    Mechanical Engineering Undergrad here: So this didn't seem explicitly like a homework question, but I was wondering how to describe a solar cell in terms of thermodynamics. If I had to model it with the first law of thermodynamics, I would consider it a simple loop of heat/work exchange...
  11. Lei

    How to control turbine in Organic Rankine Cycle system

    I am currently working on turbine design for small scale ORC system to produce power from low-enthalpy heat source. In ORC, turbine inlet pressure and flow rate are controlled by pump, and turbine inlet temperature is determined by evaporator when the flow rate of refrigerant and enthalpy of...
  12. T

    A Every graph GG containing a cycle satisfies g(G)≤2d+1

    Proof: Let C be a shortest cycle in G. If g(G)>= 2diam(G) + 2, then C has two vertices whose distance in C is at least diam(G)+1. Question: why is it at least diam(G)+1? cont. of proof: In G, these vertices have a lesser distance; any shortest path P between them is therefore not a subgraph of...
  13. G

    Error in this depiction of a Stirling engine?

    Hi. In my (German) physics lecture notes, I found this depiction of a Stirling engine: According to the text, it should be A: isothermal expansion B: isochoric cooling C: isothermal compression D: isochoric heating This seems correct for the PV diagram, but strange in the illustration on the...
  14. G

    Heat injection and work during Rankine cycle

    I have been researching the Rankine cycle. I know that it consists of two adiabatic and two isobaric processes. However, I'm not entirely sure why we ignore the work done during the isobaric processes (this seems to be the case in the analysis I'm looking at). Is that because the work done there...
  15. G

    Stirling cycle: Why neglect isochoric heat transfers?

    Hi. To prove that the Stirling cycle has Carnot efficiency, one needs to neglect the isochoric heat transfers. Sure they have the same absolute value (but different signs), but it's still heat energy lost to the cold reservoir during the isothermic compression.
  16. G

    Definition of efficiency of a thermodynamic cycle

    Hi. Sorting the exchanges of heat and mechanical work in a thermodynamic cycle by the signs and summarizing, I get ##Q_{in}>0##: heat transferred into the system ##Q_{out}<0##: heat transferred to the cold reservoir ##W_{out}<0##: work done by the system ##W_{in}>0##: work done on the system...
  17. S

    Carnot Engine cycle on PV Diagram

    I posted this in the engineer / comp science thread, but I've had no one reply or help. I really could use some guidance and I don't know where else to post. Homework Statement I am tasked to create a PV Diagram of a Carnot Engine Cycle. I must find pressure, volume, Q, W, ΔU, and ΔS on all...
  18. S

    SN diagram vs. Cycle Frequency

    Hi, What is the effect of the load cycle frequency on the SN curve (Wöhler curve)? Especially when the frequency matches the natural frequency of the component/material? Instinctively, I would think that at the natural frequency the number of load cycles until fracture is lower than at any...
  19. S

    Plotting Carnot Engine Cycle on PV Diagram

    Homework Statement I am tasked to create a PV Diagram of a Carnot Engine Cycle. I must find pressure, volume, Q, W, ΔU, and ΔS on all four points. This is what has been given to me by my teacher: a to b : Isothermal b to c: Adiabatic c to d: Isothermal d to a: Adiabatic TC = 300 K TH = 1700 K...
  20. Villager27

    What is the impact of childhood experiences on academic success?

    On Monday, I was given back my last biology test. Upon looking at one of the questions that I got wrong, I was unable to understand what I did wrong. I attempted to argue my case to my teacher, but she did not think about my arguments before denying them. The question is as follows: One week...
  21. G

    In 3rd step of Carnot cycle, work done on the piston is pdV?

    Hello. First, look at the figure describing Carnot's cycle. In 1st step (A → B) and 2nd step (B → C), I fully understand that the work done on the pistol (surrounding) by the gas (system) is dW = pdV where dV = Adl since F = pA is the only force on the pistol from the gas (I assumed there...
  22. T

    What is the volume of gas at state C?

    Homework Statement 2.00 moles of gas is held in a cylinder with a piston and is initially held at 0.300atm and has an initial volume of 0.200 m^3. The molar heat capacity of the gas at constant volume is 24.94 J mol^−1 K^−1 . The gas is then brought from this initial state (State A) through the...
  23. C

    Different states of a Carnot Cycle

    Homework Statement A Carnot engine with water as the working fluid operates with a water recirculation rate of 1 kg/s. For TH = 475 K and TC = 300 K, determine: a. The pressure of each state b. The quality of each state c. The rate of heat addition d. The rate of heat...
  24. W

    Thermodynamics p-v cycle problem

    Homework Statement a system uses monoatomic ideal gas describing the following cycle (quasi static) and basically the p-v graph is a circle,and it starts on the left side of the circle with states A, B, C, D (so that B and D are top an bottom) and so P on A (PA) is equal to PC and VB= VD given...
  25. physicist007

    How would menstrual cycle be affected if one ovary fails?

    How would the menstrual cycle of a woman be affected if one of the ovaries fails( or removed surgically)?
  26. Mike9119

    How can I put deep cycle batteries in a semi tractor-trailer?

    Hello I drive for a truck company and am getting tired of being charged for idling my truck to keep my batteries from depleting. I have a 2000w inverter now that's hooked to the truck. I had the idea of putting a few deep cycle batteries and charging them somehow with truck inverter or outlets...
  27. Saharka

    Otto cycle combustion heat question

    I have been trying to determine the efficiency of an ideal Otto cycle based on the compression ratio of my car and the heat of combustion of gasoline and I think I'm not entierly wrong but there is something quite off. When trying to calculate the temperature of the combustion stage my result...
  28. FQVBSina

    Finding mass of working fluid needed in a thermo cycle

    This question is related to a project. I have the mass flow rate, RPM, and all other related information regarding a refrigeration cycle, does anyone have an idea on how can I estimate the total amount of working fluid I need to put into the device? In case this comes up: the device is going...
  29. Nirmal Jayanth

    Can Rankine cycle achieve Carnot efficiency?

    Will a rankine cycle have efficiency equal to the carnot cycle, if the mean temperature of heat addition in rankine cycle is equal to the source temperature of Carnot cycle, and the mean temperature of heat rejection is equal to the sink temperature of carnot cycle. My understanding is that in...
  30. C

    MHB Permutation question concerning cycle shapes

    Consider the subset of $S_4$ defined by $$K_4=\{(1)(2)(3)(4),(12)(34),(13)(24),(14)(23)\}$$ Show that for all $f \in K_4$ and all $h \in S_4$, we have $h^{-1}fh \in K_4$ I showed all the possible cycle shapes of h and am trying to show that $h^{-1}fh$ must always have cycle shape $(2,2)$...
  31. Isomorphism

    Heat absorbed by an ideal gas in a cycle

    Homework Statement Homework Equations and the attempt at a solution:[/B] AC is adiabatic and AB is isothermal. Heat absorbed during process AC = 0 (adiabatic). Heat absorbed during process CB = C_p \triangle T=-\frac{\gamma}{\gamma -1} (P_2V_3 - P_2V_2) Heat absorbed during process BA =...
  32. R

    Thermodynamics: Brayton Refrigeration Cycle with Regenerator

    I have a brayton refrigeration cycle with a regeneator same as the picture below only with irreversible regenrator, compressor and turbine (And different values). The given in my problem are: Ti=0 C, T3= 35 C, T5= -80 C, mass flow rate m= 0.4 kg/s Turbine efficiency Et=0.85, Compressor...
  33. TheBigDig

    Finding the work done by a Stirling Cycle

    1. Given the following p-V diagram of an ideal Stirling Cycle, determine the theoretical values of W12, Q12, W34 and Q34 in terms of T1, T2, V1, V2, n (the number of moles) and R (the universal gas constant). Determine the total theoretical p-V work W12341 for the full cycle.2. dU = dQ-Pdv3...
  34. TheBigDig

    Finding the energy dissipated per cycle in a Stirling Engine

    1.Recently, we performed an experiment to measure the efficiency of the Stirling Engine. The experimental method can be seen in the image provided. We have been asked to calculate the power dissipation PR and the energy dissipation per cycle WR as part of our lab report. The other variables...
  35. F

    Carnot's Cycle Diagram: Exploring Its Components

    Consider a Carnot's cycle diagram for an ideal gas. It will resemble a square. How do we know which side represents isothermal expansion/compression, which side shows work done by the gas or on the gas, adiabatic expansion/compression and which side represents the heat was added/exhausted?
  36. I

    Name for the neurotransmitter cycle?

    I was wondering if there is an official term for the cycle that neurotransmitters make as they go from presynaptic to postsynaptic neurons and back? Perhaps "action potential" or "nerve spike" could work? I am guessing every spike would involve the crossing of the neurotransmitters and then...
  37. dexterdev

    A Can a molecular dynamics simulation enter a limit cycle?

    In my rough understanding Molecular Dynamics using Classical Newtonian mechanics is a 6N dimensional non linear system. 6N dimension because you have 3 position vectors and 3 momentum vectors for each N particles. Nonlinearity because of the terms in force fields. In principle this system can...
  38. R

    Heat Engine problem in Thermophysics

    Homework Statement Im working on the following problem and could need some help in answering them: Work is being produced from a cycle. In order to produce this work, energy is being taking from a high temperature sources at a ratio of 1000 kJ/kg and the extra energy is being deliver to a...
  39. F

    12V Marine Deep Cycle Battery Post is Moving -- Is the Battery Damaged?

    The battery post is moving up and down. It doesn't seem to want to come all the way out. Will the battery still perform properly or is it damaged? Can it be repaired? Pictures attached.Thanks in advance.
  40. A

    Why is Qir < than Qr? Carnot cycle and change in G

    I am learning physics on khan academy and they do a proof to show that delta G for a reversible reaction is negative and how for a irreversible reaction it is positive. However in the proof, they assume that the heat put in by the isotherm is less for an irreversible reaction compared with a...
  41. Elvis 123456789

    Change in entropy of an ideal gas during thermodynamic cycle

    Homework Statement An ideal gas with adiabatic index γ is taken around a complete thermodynamic cycle consisting of three steps. Starting at point A, the pressure is increased at constant volume V1 from P1 to P2 at point B. From point B to point C, the gas is allowed to expand adiabatically...
  42. M

    Which Organic Fluid should I used in organic rankine cycle ?

    I'm trying to make a low temp heat exchanger but feeling difficulty in selecting a type of organic fluid some are very toxic, some are not environment friendly. Is there anyone who could suggest me the working organic fluid but it should not be water.
  43. wronski11

    Role of the control rods during the core cycle

    Dear all, I would like to learn more about what happens to CRs during the reactor cycle. At the beginning of the cycle large excess reactivity is present in the core and has to be compensated with burnable absorbers (lumped in rods and WABA coating), chemical shim and CRs. There are several...
  44. P

    Solve Otto Cycle Problem: Heat Rejection (300 kW)

    hey my fellow ME please help me with this problem I am stuck at. 1. Homework Statement An Otto engine has a clearance volume of 7%. It produces 300 kW of power. What is the amount of heat rejected in kW? Homework Equations Wnet=Qadded-Qrejected (v2=Vc)Clearance Volume = (c)Clearance% x...
  45. P

    What is the maximum temperature of a dual cycle with given parameters?

    Homework Statement Find the maximum temperature in deg C of the dual cycle with initial temperature of 30 deg c, compression ratio of 6, cut off ratio of 2.5 and the heat addition at constant volume process of 600 kj/kg. y= 1.4 cp= 1.005 kj/kgk cv=0.718 kj/kgk rv=6 rc=2.5 Qadded @ Cv = 600kj/kg...
  46. T

    Carnot Cycle with negative temperatures

    Homework Statement Heat engines at negative temperatures. Consider using two heat reservoirs to run an engine (analogous to the Carnot cycle of chapter 3), but specify that both temperatures, T_hot and T_cold, are negative temperatures. The engine is to run reversibly. (a) If the engine is to...
  47. P

    Water's Crucial Role in the Efficiency of Kalina Cycle Power Generation

    I hope may of us here have idea about Kalina Cycle. In this process, a mixture of water and ammonia is used and ammonia is the main working fluid to rotate the turbine (or other machinery) to produce power. In this process, water is first used to absorb ammonia at the Condenser and the this...
  48. R

    Thermodynamics rankine cycle problem

    1. Steam is the working in an ideal rankine cycle with super heating . Super heated vapor (state 1) enters the turbine at a temperature of 440 °C. Saturated vapor(state 2) exits the turbine at a pressure of 3.0 bar.2. a) Sketch T-S diagram. b)Determine the thermal efficiency of the ideal...
  49. S

    Can the work of a counterclockwise cycle be positive?

    Consider an ideal gas following a thermodynamics cycle, represented on a ##P-V## plane. I read that if the cycle is "travelled" clockwise then ##W_{gas, cycle}>0## so the gas does positive work, while if the cycle is "travelled" counterclockwise then ##W_{gas, cycle}<0## but it seems to me that...
  50. Nemo's

    Determine the coefficient of performance of this cycle

    Homework Statement In an ideal refrigeration cycle, the temperature of the condensing vapour is 40oC and the temperature during evaporation is -20oC. Determine the coefficient of performance of this cycle for the working fluids; R12 and ammonia. Homework Equations C.O.Pc = TL/(TH-TL) The...
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