Plate heat disadvantages

The advantages and disadvantages of plate heat exchangers, compared with conventional shell and tube exchangers are listed below ... 

The choice of abradant should be made primarily to give the best correlation with service, and the usual abrasive wheels and papers really only relate to situations where cutting abrasion predominates. Materials such as textiles and smooth metal plates may be more appropriate for other applications. In practice, the abradant is often chosen largely for reasons of convenience and surfaces such as plain steel have the disadvantage of abrading slowly and, if the conditions are accelerated, give rise to excessive heat build-up. Consequently, abrasive wheels and papers are used in situations where they are inappropriate for assessment of service performance. 

In this method preconcentration is achieved by evaporating the sample to low volume under a heat lamp or on a hot plate. An obvious disadvantage of this technique is that in addition to the analyte being concentrated, other species which might interfere in later analysis will be concentrated with it. The method is also subject to contamination throughout the evaporation period and furthermore, losses of volatile elements may occur. Notwithstanding, the technique has an application in water analysis where waters are relatively clean with a low total dissolved solids content. 

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