Generalization of data on heat transfer and pressure drop in the channels of plate heat exchangers

Abstract

The article presents the generalized dependences in the form of similarity equations for the heat transfer and pressure drop during forced flow of water and steam condensing in the channels of single-pass plate heat exchangers having heat transfer surfaces made of corrugated plates, which are used at the heat-supply stations of water heat supply systems for the household sector and industrial enterprises. The above-mentioned dependencies were obtained by generalizing the results from calculations, using computer programs, of heat exchangers for 35 versions of heat exchangers from the standard series of apparatuses produced by JSC TehnolnzhPromStroy and JSC Ridan. The generalization is performed for wider ranges of coolant velocity, temperature and pressure drop, which as a rule take place in such heat exchangers in practice. The obtained dependences can be used for estimating the heat transfer intensity and hydraulic losses in similar heat exchangers produced by other manufacturers. A comparison of the obtained dependences with similar dependences obtained by other researchers, including foreign ones, made it possible to reveal common features in the methods used to select the determining similarity numbers and differences between them. In addition, the article presents the following information: the results from digitizing the experimental data obtained in the course of studying the heat transfer and hydrodynamics in the channels of heat exchangers fitted with heat transfer intensifiers having the shape of spherical segments; an analysis of the results obtained from generalization of heat transfer and pressure drop data in channels formed by plates with heat transfer intensifiers in the form of recesses and protrusions arranged in a staggered or in-line manner. It is recommended to replace air heaters and air coolers having a low heat transfer coefficient and significant dimensions by heat exchangers fitted with the above-mentioned heat transfer intensifiers. Heat exchangers fitted with such heat transfer intensifiers require a smaller space for accommodating them. Moreover, with the properly selected size and layout of intensifiers over the plate surface, it is possible to obtain the effect in which the heat transfer intensity grows more rapidly than does the pressure drop. Studies have shown that this effect---in case of using plates with recesses in the form of spherical segments (also known as dimples)—manifests itself to a greater extent than in case of using other surface intensifiers in the form of variously shaped protrusions.