Why cool the water (part 4)

Range of process plants that can be cooled with evaporative systems. Importance of volumes of energy to be disposed of. Cost-effectiveness of the cooling system.
For high volumes of heat to be disposed, evaporative systems are much used for cooling water, relatively to the amount of water used to transport the same heat. That is, water with a big difference in temperature between hot water and cold water (more than 5 ° C) .
What data is needed for sizing water cooling system. 
Water and air are the two main elements for an evaporative water cooling system.
The data for doing calculations are: 
  • water inlet temperature, outlet temperature, amount to cool within a unit of time,
  • air room temperature (from dry thermometer) and relative humidity or temperature from wet thermometer,
  • the amount of air, and the speed set by the designer, are the result of sizing the plant.
Nature of the system. 
  • Period of operation: “batch” or continuous.
  • Production: quantity.
  • Energy (power) used.
Energy (heat) brought outside the process plant by means of the finished product in the form of material quantity and temperature difference of the material between the beginning and the end of the process.
In the case of exothermic production processes: heat development during the process (for example, in chemical plants – Pharmaceutical) and determination of the amount of heat produced during the process.
How to measure the efficiency of an evaporative cooling system. 
Normally, with time, the efficiency of the cooling system decreases due to: 
  • Deterioration of the plant’s construction material.
  • Wear and tear of the system’s moving parts, for example: fans electric motors, water recycle pumps.
  • Loss of efficiency of the system filling material due to limescale deposits or mucilage, dramatically changing the predesignated air flow rate set as design data.
What are the consequences the decreased efficiency of a cooling system.
The lesser efficiency of the cooling system is directly proportional to the lesser efficiency of the driven system. The consequences in terms of economic and energy are easily evaluated because the use of energy for operating the system is inversely proportional to its own efficiency.
If the cooling system is not efficient, or better yet is not in the operating conditions as designed, there is a waste of energy, not so much from the cooling system, but in the main cooled system.
This is the way, for example, the efficiency of a power plant decreases, for the drop of yield in turbine efficiency due to water not adequately cooled. Also, the yields of the refrigeration units drop for the same reason.
It’s very important to note that the whole plant process or production estimates yields less, as we said, easily verifiable in terms of wasted energy and operating costs. 
Materials with which parts of a cooling system are built.

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