Incorporating the Use of a Fouling Model in the Design and Operation of Cooling Networks

The importance of knowing how fouling develops and deteriorates the thermal-hydraulic performance of heat transfer processes becomes evident when the problem is already there and is difficult to eliminate. Fouling prediction is importantin grassroot design and even more, in retrofit applications. The aim of the present work is to show the use of a fouling model to predict scaling in cooling systems in order to derive design guidelines. Fluid temperature and velocity are the two more important variables that determine the rate at which scaling takes places. This work focuses on retrofit of existing cooling systems for situations where new heat exchangers need to be incorporated into the network. It is shown how the pressure drop, fluid velocity and flow distribution are affected depending on the decision of where to place the new exchangers. All these factors are intimately related to the development of fouling. The model presented in this work includes the prediction with timeof the increase of pressure drop and flow redistribution as fouling builds up. The use of the model is illustrated through a case study that shows that in the retrofit ofcooling systems,the incorporation of new heat exchangers in parallel is recommended

Designing Spiral Plate Heat Exchangers to Extend Its Service and Enhance the Thermal and Hydraulic Performance

Spiral plate heat exchangers are well suitable for handling fluids with features linked to fouling, high viscosities, fluids with suspended fragments of solids and process streams with tough heat transfer targets. Correlations to describe the thermal and hydraulic performance are a function of the geometrical configuration of the equipment. The present work shows procedures to design spiral plate heat exchangers as a function of the fluid arrangements, government flow, as well whether the thermal equipment is for condensing, cooling or heating duty. An additional study looking for determining the geometrical variables that allow to enhance and improve the thermal and hydraulic performance is presented. Moreover, computational fluid dynamics to validate the thermal and hydraulic method is performed

Light absorption properties of mesoporous barium hexaferrite, BaFe12O19

Light absorption properties are one of the most important characteristics of semiconductor materials, since it is related to particle size, electric resistance, powder density, and dielectric constant. Barium hexaferrite (BaFe12O19) particles were synthesized by ceramic and chemical co-precipitation method. Light absorption properties were studied in relation to the particle size, morphology, and surface porosity. The band gap was calculated by the Kubelka-Munk method from the obtained experimental absorption spectrum. Band gap energies of 1.82 and 1.86 eV were estimated for the particles synthesized by the ceramic method and for the co-precipitation method respectively. The results show that both synthesized BaFe12O19 samples can be effectively excited with visible light irradiation. In addition to this, due to its other good characteristics such as its magnetic properties, high resistance to corrosion, and chemical stability, make the barium hexaferrite an excellent material for diverse technological applications

Comprehensive analysis of the thermohydraulic performance of cooling networks subject to fouling and undergoing retrofit projects

The aim of this paper is to develop guidelines for the placing of new coolers in cooling systems subject to retrofit. The effects of the accumulation of scale on the flow system are considered. A methodology to assess the interconnected effect of local fluid velocity and fouling deposition is developed. The local average fluid velocity depends on the water flow rate distribution across the piping network. The methodology has four main calculation components: a) the determination of the flow rate distribution across the piping network, b) the prediction of fouling deposition, c) determination of the hydraulic changes and the effect on fouling brought about by the placing of new exchangers into an existing structure, and d) the calculation of the total cooling load and pressure drop of the system. The set of disturbances introduced to the system through fouling and the incorporation of new coolers, create network responses that eventually influence the cooling capacity and the pressure drop. In this work, these interactions are analysed using two case studies. The results indicate that, from the thermal point of view, the incorporation of new heat exchangers is recommended in series. The limit is the point where the increase of the total pressure drop causes a reduction in the overall volumetric flow rate. New coolers added in parallel create a reduction of pressure drop and an increase in the overall water flow rate; however, this increase is not enough to counteract the reduction of fluid velocity and heat capacity removal