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Energy Flow in Air Conditioner or Fridge Simulation:

This is Energy Flow in an Air Conditioner or Fridge Simulation.

This simulation shows the energy flow for an air conditioner or fridge.

It takes some amount of work (W) to remove 100 J (QL) from a colder temperature location, with the total of the W and QL being the net heat (QH) that is dumped into the higher temperature region.

The minimum amount of work needed to remove a certain amount of heat from the colder location depends on the two temperatures the device is operating between.

For a given pair of temperatures, the ideal coefficient of performance (COP) of the device is given by:

ideal COP = TL/(TH - TL) = QL/Wmin

Real devices are less efficient than the ideal case.

The slider at the bottom allows you to adjust the coefficient of performance to be more realistic than the ideal case.

Meaning of the Variables:

e (Efficiency):

  • Meaning: The ratio of the useful work you get out of the engine to the total heat energy you put in. It's a measure of how good the engine is at converting heat into work.
  • Formula: e = W / QH.
  • Example: If you put in 100 J of heat and get 25 J of work, the efficiency is 25 J / 100 J = 0.25 or 25%.

TH (High Temperature):

  • Meaning: The absolute temperature (measured in Kelvin, K) of the heat source. This is the temperature of the burning fuel-air mixture in the engine's cylinders.
  • Important: The formulas require temperature in Kelvin (K), not Celsius or Fahrenheit. (To convert Celsius to Kelvin: K = °C + 273).

TL (Low Temperature):

  • Meaning: The absolute temperature (in Kelvin, K) of the heat sink. This is the temperature of the environment where the waste heat is dumped, usually the outside air.
  • Example: If the outside air is 27°C, then TL = 27 + 273 = 300 K.

QH (Heat Input):

  • Meaning: The amount of heat energy (in Joules, J) absorbed by the engine from the high-temperature reservoir (the hot burned fuel).

QL (Heat Rejected/Waste Heat):

  • Meaning: The amount of heat energy (in Joules, J) that is wasted and expelled into the low-temperature reservoir (the environment).

W (Work Output):

  • Meaning: The amount of useful energy (in Joules, J) the engine produces. This is the energy that actually does the job, like propelling the car.
  • Connection: According to the law of conservation of energy (the First Law of Thermodynamics), the energy in must equal the energy out: QH = W + QL.
How to Use:
  • Adjust the temperature sliders to set high and low temperatures
  • Use the COP percentage slider to adjust efficiency
  • Observe how energy flows change based on your adjustments
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