Effect of Fouling on Performance of Exchangers Cooled by Air. Ramifications for Exchanged Heat and Cooling Effectiveness

Résumé ou Introduction

This work is concerned with the effects of fouling on different fin tubes and exchangers cooled by air.

During operation of heat exchangers layers of deposits or corrosive products may be formed and accumulated on heat exchanger surfaces over time. This leads to additional heat transfer resistance and constriction of fluid flow area. In consequence, the exchanged heat duty is badly affected. The loss of heat duty is extreme if local heat transfer coefficients are high at clean conditions. However, maintaining cooling effectiveness is paramount in most applications. As a remedy, surfaces must be regularly cleaned.

Fin tubes are core elements in air cooled exchangers or condensers to transfer heat. Fin tube exchangers are characterized by a multitude of circular, elliptical or channel type core tubes with air-side finning. Generally, the process medium flows on the tube internal side with air as coolant on the external fin side. The report deals with air cooled heat exchangers and condensers under forced or natural draft in dry cooling applications with the focus on the effect of fin side fouling. Water spray injection into the cooling air flow is excluded.

Consequently, the effect of fin side fouling layers will be assessed as well as the consequence for air flowrate and heat duty at different convection types. Special attention is given to the effect of fouling on the performance of dry air cooled condensers. Also, differences of forced, induced or natural draft dry cooling applications will be covered.