Reverse engineering

Examples of Reverse engineering in the following topics:

• Carnot Cycles

  • What is crucial to the Carnot cycle is that only reversible processes are used.
  • Obviously, then, reversible processes are superior.
  • Furthermore, all engines employing only reversible processes have this same maximum efficiency when operating between the same given temperatures.
  • Recall that both isothermal and adiabatic processes are, in principle, reversible .
  • PV diagram for a Carnot cycle, employing only reversible isothermal and adiabatic processes.

• What is Entropy?

  • We can see how entropy is defined by recalling our discussion of the Carnot engine.
  • The definition of ΔS is strictly valid only for reversible processes, such as used in a Carnot engine.
  • Now let us take a look at the change in entropy of a Carnot engine and its heat reservoirs for one full cycle .
  • Also shown is a schematic of a Carnot engine operating between hot and cold reservoirs at temperatures Th and Tc.
  • Calculate the total change in entropy for a system in a reversible process

• Improving pump efficiency

  • By redesigning the layout of the entire system, however, the main engineer, a man named Jan Schilham, was able to cut costs, improve efficiency and reduce the overall pumping power needed by 92%.
  • Traditionally, engineering students are taught that the extra cost of fatter pipes does not justify the cost of the pumping energy saved.
  • Schilham's second money-saving idea was to lay out the pipes first and install the pumps afterward – which is exactly the reverse of how most people construct a pumping system.
  • Most engineers install pumps and motors in a convenient or arbitrary spot and then attach pipes to them.

• Heat and Work

  • Work can be completely converted into heat, but the reverse is not true: heat energy cannot be wholly transformed into work energy.
  • Scientists and engineers have been able to exploit the principles of thermochemistry to develop technologies ranging from hot/cold packs to gasoline powered combustion engines.

• Genetic Engineering

  • In genetic engineering, an organism's genotype is altered using recombinant DNA, created by molecular cloning, to modify an organism's DNA.
  • Genetic engineering is the alteration of an organism's genotype using recombinant DNA technology to modify an organism's DNA to achieve desirable traits.
  • The addition of foreign DNA in the form of recombinant DNA vectors generated by molecular cloning is the most common method of genetic engineering.
  • " This technique, called reverse genetics, has resulted in reversing the classic genetic methodology.
  • Borer-resistant corn is an example of a genetically- modified organism made possible through genetic engineering methods that allow scientists to alter an organism's DNA to achieve specific traits, such as herbicide resistance.

• Free Energy and Work

  • Gibbs energy is the maximum useful work that a system can do on its surroundings when the process occurring within the system is reversible at constant temperature and pressure.
  • The appellation "free energy" for G has led to so much confusion that many scientists now refer to it simply as the "Gibbs energy. " The "free" part of the older name reflects the steam-engine origins of thermodynamics, with its interest in converting heat into work.
  • The reversible condition implies wmax and qmin.

• The Second Law

  • If the process can go in only one direction, then the reverse path differs fundamentally and the process cannot be reversible.
  • Furthermore, mechanical energy, such as kinetic energy, can be completely converted to thermal energy by friction, but the reverse is impossible.
  • The Second Law of Thermodynamics(first expression): Heat transfer occurs spontaneously from higher- to lower-temperature bodies but never spontaneously in the reverse direction.
  • The reverse process is impossible.
  • A brief introduction to heat engines and thermodynamic concepts such as the Carnot Engine for students.

• Reversing Entries

  • Reversing entries are journal entries made at the beginning of each accounting period.
  • Most often, the entries reverse accrued revenues or expenses for the previous period.
  • Some examples of reversing entries are salary or wages payable and interest payable.
  • Reversing entries are most often used with accrual-type adjusting entries.
  • At the beginning of the month B that expense is reversed via a reversing entry.

• Heat Pumps and Refrigerators

  • (In a cooling cycle, the evaporator and condenser coils exchange roles and the flow direction of the fluid is reversed. )
  • Since the efficiency of a heat engine is Eff=W/Qh, we see that COPhp=1/Eff.
  • Since the efficiency of any heat engine is less than 1, it means that COPhp is always greater than 1—that is, a heat pump always has more heat transfer Qh than work put into it.
  • The efficiency of a perfect engine (or Carnot engine) is

• Charging a Battery: EMFs in Series and Parallel

  • You would therefore end up with the same 12v emf, though the internal resistance would then be doubled, causing issues for you when you want to start your engine.
  • When it is reversed, it produces an emf that opposes the other, and results in a difference between the two voltage sources .
  • The charger must have a larger emf than the battery to reverse current through it.