Reservoir

Examples of Reservoir in the following topics:

• Torricelli's Law

  • Applying Bernoulli between the top of a reservoir and an exit hole at a height h below the top of the reservoir results in,
  • If we assume both the top of reservoir and the exit are open to the atmosphere, the zero for potential energy is at the exit hole, and the fluid velocity at the top of the reservoir is essentially zero (large reservoir, small hole), we arrive at
  • where again ht is the height difference between the top of the reservoir and the exit hole.
  • As the height in the reservoir decreases, the exit velocity will decrease as well.
  • Potential energy at the top of the reservoir becomes kinetic energy at the exit.

• Sources and Sinks of Essential Elements

  • Locations where elements are stored for long periods of time are called reservoirs.
  • Coal is a reservoir for carbon, and coal deposits can house carbon for thousands of years.
  • The atmosphere is considered a reservoir for nitrogen.
  • However, human activity can change the proportion of nutrients that are in reservoirs and in circulation.
  • Likewise, phosphorous and nitrogen are extracted from geological reservoirs and used in phosphorous, and excesses of these elements have caused the overgrowth of plant matter and the disruption of many ecosystems.

• Disease Reservoirs and Epidemics

  • A natural reservoir refers to the long-term host of the pathogen of an infectious disease.
  • Some examples of natural reservoirs of infectious diseases include:
  • Some diseases have no non-human reservoir: poliomyelitis and smallpox are prominent examples.
  • The natural reservoirs of some diseases still remain unknown.
  • Affected individuals may become independent reservoirs leading to further exposures.

• Heat Engines

  • Heat transfer from the hot object (or hot reservoir) is denoted as Qh, while heat transfer into the cold object (or cold reservoir) is Qc, and the work done by the engine is W.
  • The temperatures of the hot and cold reservoirs are Th and Tc, respectively.
  • Because the hot reservoir is heated externally, which is energy intensive, it is important that the work is done as efficiently as possible.
  • The hot and cold objects are called the hot and cold reservoirs.
  • Qh is the heat transfer out of the hot reservoir, W is the work output, and Qc is the heat transfer into the cold reservoir.

• Application of Bernoulli's Equation: Pressure and Speed

  • Bernoulli's equation can be applied when syphoning fluid between two reservoirs .
  • Another useful application of the Bernoulli equation is in the derivation of Torricelli's law for flow out of a sharp edged hole in a reservoir.
  • A streamline can be drawn from the top of the reservoir, where the total energy is known, to the exit point where the static pressure and potential energy are known but the dynamic pressure (flow velocity out) is not.
  • Syphoning fluid between two reservoirs.

• The Carbon Cycle

  • As stated, the atmosphere, a major reservoir of carbon in the form of carbon dioxide, is essential to the process of photosynthesis.
  • The level of carbon dioxide in the atmosphere is greatly influenced by the reservoir of carbon in the oceans.
  • The exchange of carbon between the atmosphere and water reservoirs influences how much carbon is found in each location; each affects the other reciprocally.
  • Over geologic time, the calcium carbonate forms limestone, which comprises the largest carbon reservoir on earth.
  • This carbon can be leached into the water reservoirs by surface runoff.

• What is Entropy?

  • Now let us take a look at the change in entropy of a Carnot engine and its heat reservoirs for one full cycle .
  • The hot reservoir has a loss of entropy ΔSh=−Qh/Th, because heat transfer occurs out of it (remember that when heat transfers out, then Q has a negative sign).
  • The cold reservoir has a gain of entropy ΔSc=Qc/Tc, because heat transfer occurs into it.
  • (We assume the reservoirs are sufficiently large that their temperatures are constant. ) So the total change in entropy is
  • Also shown is a schematic of a Carnot engine operating between hot and cold reservoirs at temperatures Th and Tc.

• Purification of Drinking Water

  • In order to purify drinking water from a source (such as a lake, river, reservoir or groundwater), the water must go through several steps to remove large particles and different types of pathogens .
  • Storage: Water is stored in reservoirs, tanks, and water towers in preparation for purification.
  • A chemical that causes particle aggregation is added to the water, and clumps of particles form and settle to the bottom of the reservoir.

• Isothermal Processes

  • This typically occurs when a system is in contact with an outside thermal reservoir (heat bath), and the change occurs slowly enough to allow the system to continually adjust to the temperature of the reservoir through heat exchange.

• Heat Pumps and Refrigerators

  • Heat transfer (Qc) occurs from a cold reservoir and into a hot one.
  • Thus the heat transfer to the hot reservoir is Qh=Qc+W.
  • Explain how the the components of a heat pump cause heat to transfer from a cold reservoir to a hot reservoir