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Renin Angiotensin Mechanism.

Evaporators: Evaporating Pan.

Definition:

  • The equipment used for carrying out the process of evaporation are called “Evaporators”.

  • Evaporators are classified according to the form of the heat movement,

    • Natural circulation evaporators. e.g Evaporating Pan.

    • Forced circulation evaporation. e.g. Modified evaporating pan.

    • Film evaporators. e.g Climbing film evaporator.

Evaporating Pan:

Construction:

  • The apparatus consists of a hemispherical, or shallow pan, constructed from a suitable material such as copper or stainless steel and surrounded by a steam jacket.

  • The hemispherical shape gives the best surface/ volume ratio for heating, and the largest area for separation of vapor.

  • The pan may have a mounting , permitting it to be tilted to remove the product, but the shallow form makes this arrangement somewhat unstable, and an outlet at the bottom is common.

Working:

  • The dilute solution is taken in the pan. 

  • Steam is introduced through the steam inlet into the jacket to heat the pan. 

  • In these evaporators the movement of the liquid results from convection currents set up by the heating process. 

  • The concentrated liquid is collected through the outlet placed at the bottom of the pan.

Advantages:

  1. It is simple and cheap to construct.

  2. It is easy to use, clean and maintain.

Disadvantages:

  1. Having only natural circulation, the overall coefficient of heat transfer will be poor and solids are likely to deposit on the surface, leading to decomposition of the product and a further deterioration in heat transfer.

  2. Many products give rise to foaming.

  3. Entire liquor is heated over all the time, which may be unsatisfactory with thermolabile materials. 

  4. The heating surface is limited and decreases proportionally as the size of the pan increases.

  5. The pan is open, so the vapor passes to the atmosphere, which can lead to saturation of the atmosphere.

  6. Only aqueous liquids can be evaporated in these pans.

  7. Pan evaporation cannot be done under reduced pressure.

  8. Can only be used for thermostable products.

Commonly Asked Questions.

  1. Define evaporation and write a short note on “Evaporating Pan”.

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