Marcus Reppich

Optimal design of shell-and-tube heat exchangers

Abstract A new method allowing the optimal design of baffled shell-and-tube heat exchangers will be discussed in this paper. The known commercial design tools do not consist optimization strategies. There are presented as simplified expressions describing interaction between heat transfer and pressure drop that can be used for optimal design of heat exchangers from economic viewpoint. The developed program system HEATDESIGN is realizing a general computer-supported design on the basis of estimation of optimal pressure drops determined by consideration of economic conditions and process data. Examples show the influence of changed economic parameters or process data on the design and costs by means of optimization. In addition the program gives the possibility to optimize components of apparatus.

Use of high performance plate heat exchangers in chemical and process industries

Abstract At present, plate heat exchangers constantly open up new application fields in the chemical, process, and allied industries due to their numerous advantages. The channel flow between individual plates is characterized by high turbulence induced at low flow velocities. Heat transfer coefficients are generally higher in plate heat exchangers than in conventional shell-and-tube heat exchangers. According to the nature of the process, physical properties of the media, and allowable pressure drops, plates with a variety of patterns are available to adapt the equipment optimally to the specific process conditions. For handling aggressive media the module welded plate heat exchanger was developed. The laser welded modular design keeps the inherent advantages of plate type heat exchanger. It can be disassembled and mechanically cleaned outside the modules. The capacity can also be subsequently modified by changing the number of plates, or the plate patterns can be altered as it can be with the gasketed units. Typical applications of module welded plate heat exchangers in the chemical industry are acid coolers, thermal oil coolers, or condensers for hydrocarbon mixtures.

A new design method for segmentally baffled heat exchangers

Abstract The optimization of shell-and-tube heat exchangers from an economic viewpoint gains in importance because of the current and future share of the market of this heat exchanger type in various industries. The developed computer-based design concept assuming from the calculation of optimum tubeside and shellside pressure drops allows to determine the optimum dimensions of segmentally baffled shell-and-tube heat exchangers. As the objective function that is minimized are chosen the total annual costs of the heating or cooling system consisting of the heat exchanger and pumps or compressors. The discussed design method can be used for single-phase liquid or gaseous stream applications.

Wasserstoffherstellung und -speicherung

Wasserstoff wird als Grundstoff in zahlreichen chemischen Prozessen eingesetzt. Jahrlich werden in Deutschland ca. 20 Milliarden Normkubikmeter, weltweit 600 Milliarden Normkubikmeter Wasserstoff hergestellt. Dabei fallen rund 40 % des Wasserstoffs als Nebenprodukt bei petrochemischen Prozessen wie der Benzinreformierung und der Ethylen- und Methanol-Herstellung an.

Evaluation of analytical methods for the determination of the physicochemical properties of fermented, granulated, and roasted cassava pulp - gari

Abstract Simple but reliable methods for the determination of the physicochemical properties of gari were evaluated for the parameters, such as grain size, bulk density, swelling index, moisture content, gross calorific value, cyanide content, and acidity content. The grain sizes were between 525 and 928 μm (weighted means), the bulk densities between 0.541 and 0.699 g/cm³, and the swelling indices between 3.21 and 4.33. The moisture contents ranged from 4.30 to 9.19%. The gross calorific values were found between 15.45 and 15.82 kJ/g. The cyanide contents were between 0 and 4.8 ppm. The acidity contents varied among 0.55 and 1.62%. Correlation tests verified the influences of the grain size and the moisture content on the acidity content with a probability of 99.9%. The methods were regarded as suitable and adaptable for the application in small and medium cassava‐processing industries with special regard to the respect of the consumer`s health safety.

Solar panel cooling system with hollow fibres

Photovoltaic (PV) panel overheating drastically reduces their efficiency and lifespan. Overheating also has the potential to form electric arcs which can melt metal fixtures and burn away the module’s insulating materials. Due to these phenomena, the introduction of water-cooling or, more generally, liquid-cooling systems inside the PV panel appears reasonable. Hollow fibre cooling system consisting of plastic tubes of a small diameter (less than 1 mm) was tested as a simple solution. Fibres can be placed in contact with the back surface of a PV panel and coolant flowing through provides efficient and uniform cooling. Heat removed from the panel may be used for domestic or industrial needs or released to the surroundings. Hollow fibres have very thin walls (about 0.1 mm) to transfer heat easily, and the system is light, compact and resistant to corrosion. Experiments confirmed that such system can cool the PV panel, removing up to 1 kW of heat and lowering the module temperature from 90°C to about 50°C. It was observed that cooling improves the electric efficiency of PV cells by about 50%.

Nutzung der Windenergie

Die ungleichmasige Sonneneinstrahlung auf die Erdoberflache verursacht eine unterschiedliche Erwarmung des Festlandes und der Ozeane sowie der daruber befindlichen Luftmassen. Die resultierenden Dichteunterschiede bewirken eine aufsteigende oder abfallende Luftstromung, die sich in Luftdruckunterschieden ausert. In der Folge entwickeln sich Hoch- und Tiefdruckgebiete. Die ausgleichende Luftstromung, der Wind, die mit einem Stoff- und Energietransport verbunden ist, erfolgt in Bodennahe stets in Richtung des Druckgefalles von Gebieten hoheren Luftdrucks zu Gebieten niedrigeren Luftdrucks.

Nutzung der Solarstrahlung

Die Sonne stellt den Zentralkorper unseres Planetensystems dar. Sie besteht zu etwa 75 % aus Wasserstoff, zu 23 % aus Helium und nur zu ca. 2 % aus schwereren Elementen. ihr Alter wird auf etwa 4,57 Milliarden Jahre geschatzt. Tabelle 3.1 enthalt die einige wichtige Daten von Sonne und Erde.

Bestimmung des Foulingfaktors an Wärmeübertragungsflächen mit Hilfe einer Fuzzy-Wissensbasis

ZusammenfassungDie Bestimmung des Foulingfaktors bei Wärmeübertragern ist objektiv nur bedingt möglich. Aus diesem Grund wurden einige aus der Literatur entnommene Empfehlungen zur Bestimmung des Foulingfaktors mit den Methoden der Fuzzy-Heuristik aufgearbeitet. Durch wissensbasierte Methoden wurden diese primären Erfahrungen als Fuzzy-Sets von einfachen bedingten Aussagen formuliert. Wegen der Vielfalt und Komplexität der Foulingproblematik war es nur möglich, Regeln für den Foulingvorgang durch Sedimentation und den Foulingfaktor für Kohlenwasserstoffgemische aufzustellen. Anhand einer möglichen Version des Fuzzy-Verfahrens werden zwei wirklichkeitsnahe Fragestellungen sowie deren Beantwortung detailliert beschrieben.