Find out more information about the evaporation technology.

The concept of heat exchanger technology has been improved to enhance wastewater treatment potentiality for the three different production lines of EVALED™ evaporators. Each one of them offers opportunities to reduce energy consumption according to the Client’s needs.

WHAT IS HEAT TRANSFER?
Heat (energy) is exchanged between two systems at different temperatures. Should any heat be produced (presence of chemical reactions), the quantity of heat produced during this process will be equal to the quantity transferred from the first system to the second system (principle of energy conservation). Heat exchange can take place under the following conditions:

  • Conduction: when there is a temperature gradient in a liquid or solid stationary medium
  • Convection: when heat exchange takes place from the contact of a surface and a fluid both at different temperatures
  • Radiation: it occurs between two surfaces at different temperatures, through energy emission from electromagnetic waves and without any interposed mean (radiation of the sun on the earth).

WHAT DOES THE HEAT EXCHANGE BY CONDUCTION DEPEND ON?
Heat exchange is connected to the width of the thermal gradient (delta T) and to the exchange surface, according to a constant depending on material, on surface composition, on the fouling factor of the surface, on the basis of the following formula:

Q = K x S x ∆T / s

Heat exchange by conduction occurs between objects with different temperature levels, with no exchange of matter. An object with a surface (S) and a thickness (s) with a certain internal Temperature (T1) and another lower external temperature (T2), will generate a proportional heat exchange according to the difference between temperatures (∆T = T1-T2) of the two surfaces, depending on the characteristics of the latter, according to a (K) heat transmission constant.

The higher the flow (Q) is:

  • the greater the wall surface is
  • the smaller its thickness is
  • the greater constant K is

This means that the greater the difference of temperature is, the more relevant the heat quantity is, the greater the heat exchange surface is, the smaller the thickness of this surface is, the higher the coefficient of transmission or thermal conductivity is. The coefficient of thermal conductivity K depends on the type of the materials, on their shape and fouling.

ARE THERE ANY TECHNOLOGY THAT REDUCES ENERGY CONSUMPTION TO EVAPORATE WATER?
To take water (1 kg) from room temperature to boiling temperature and change its status from liquid to vapor, under normal atmospheric pressure conditions (100 kPa), the system needs about 2500 kJ (corresponding to approximately 700 Wh). This energy would be lost in the atmosphere if latent heat from condensation is not recovered. Some technologies recover this energy to reuse it within the production cycle, with a lower energy consumption for water evaporation:

  • Heat pump vacuum evaporation
  • Multiple effect evaporation
  • Mechanical vapor recompression evaporation
  • Thermal vapor compression evaporation

Energy consumption might decrease by about 25 times if one of the technologies above is employed.