Mechanical vapor compression Economics

A general discussion of the economic efficiency of mechanical vapor compression is found in [2.13]. The use of vapor compressors is already of economic benefit if... 

Perhaps the highest thermal vapor compression technology in any field can be found in the water desalination industry. Technology in that industry has advanced to designs with more than eight successive effects with steam economies over 12. Thermal compression evaporators beyond seven effects In process industries does not appear to be economical because mechanical vapor compression systems offer a better alternative. 

Many of these disadvantages may also be present for any evaporator system. Mechanical vapor compression systems can ba operated under vacuum, and many times ara the bast economical choice. 

When the black box is a compressor, it is mechanical energy that makes the vapor more valuable, and the technique is referred to as mechanical vapor recompression (MVR). The steam temperature in the heating element of the evaporator must give a reasonable AT for heat transfer. This sets the condensing pressure, and the vapor from the evaporator must be compressed at least to that pressure. There is an economic balance to be struck between energy cost and evaporator surface area. Low compression ratios reduce compressor energy consumption but provide smaller temperature differentials and therefore require more heat-transfer surface. 

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