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| Titel: |
Mechanisms by Which Fouling Can Increase Overall Heat Transfer Coefficients |
| Auteur: |
Crittenden, B. D. Alderman, N. J. |
| Verschenen in: |
Heat transfer engineering |
| Paginering: | Jaargang 13 (1992) nr. 4 pagina's 32-41 |
| Jaar: |
1992 |
| Inhoud: |
Two probable mechanisms exist whereby the overall coefficient of a heat exchanger can be increased when fouling occurs. These are the creation of roughness elements and restrictions to flow, both of which increase film heat transfer coefficients. The change ( increase/decrease) in the overall heat transfer coefficient due to the formation of deposits on a heat transfer surface is dependent on the relative magnitude of many design and operating variables. In this article, the effect of surface roughness changes, based on an earlier scientific study, is briefly described. Whether the formation of rough deposits can effect an increase in thermal performance, which might create the impression that a negative fouling resistance has arisen, depends critically on the flow Reynolds number and the nature of the roughness. The effect of flow restrictions is demonstrated by a simple mathematical analysis. Whether a flow restriction due to fouling can cause an increase in thermal performance is governed by the magnitude of a nondimensional group that takes the form of a Biol number. An increase in thermal performance can occur for small-diameter channels in which the film coefficient is low and the deposit thermal conductivity is relatively high. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 121 van 200 gevonden artikelen
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