Showing papers by "Leibniz University of Hanover published in 1974"

Changes in catechins and hydroxycinnamic acid derivatives during development of apples and pears

Abstract: We used quantitative methods to show that there are changes in the concentrations of catechins and hydroxycinnamic acids during the development of apples and pears. First, the concentrations of the phenolic compounds rise sharply until an age of about 2 to 3 months and then the catechin content is reduced (mg/whole fruit). Second, large quantities of catechins and hydroxycinnamic acid derivatives are formed in the early fruit (mg/1000 g). After a few weeks these concentrations decline very sharply, especially during the progressive growth of the fruits, to reach a more steady level at maturity.

Stability criteria for tidal basins

Abstract: The contribution deals with the morphologic examinations and calculations for a deep-water harbour which is to be constructed in the tidal flats of the Elbe estuary near the North Sea islands of Scharhorn and Neuwerk. An attempt is made to examine the stability of tidal channels (gullies)and tidal flats which may be disturbed to a greater or lesser extent by the various proposals for the connecting dike between the industrial area near the harbour and the coastline. The underlying logic for the determination of the equilibrium of the flats and the quantitative solution for the sand-balance is as follows: It has been shown in several empirical investigations that the increase of the relative volume of the tidal basin (V/VM ), referenced to the gully volume for MLW, can be determined as a simple function to the base (a)logarithm of the geodetic elevation (z*) between MLW and any higher contour level up to MHW. Furthermore it can be shown that (VMT ) is also a function of the tidal drainage area (E). The base(a)has been related to the size of the tidal drainage area (E), because this area is subject to considerable modification by offshore structures such as dikes and causeways.

Wave transmission through vertical slotted walls

Abstract: This paper deals with the wave transmission through a vertical slotted wall. In an experimental study the transmission coefficient has been investigated as a function of the shape of the wall elements (rectangular shape and H-beam shape), of the ratio of solid wall to total wall length (wall-element ratio) and of the wave approach direction. The test results for a wave direction perpendicular to the wall are compared with previous investigations and theoretical derivations. For an oblique wave approach the test results are described by a semi-empirical formula. This formula, combined with a theoretical solution for perpendicular wave approach is used to describe the transmission coefficient for any angle of wave approach.

Layout and Present Status of the Closed-Cycle Helium Turbine Plant Oberhausen

Abstract: The Oberhausen gas turbine plant now under construction is designed as a fossil-fired heating power station to produce a net electrical output at terminals of 50 MW. Helium as a working medium is employed for the first time in a closed-cycle industrial power plant system. A report is given on the layout of the circuit parameters, on the physical size of the turbomachines and heat exchangers as well as on the design of the gas-fired helium heater. Moreover, the arrangement of circuit components is discussed. The Oberhausen plant was projected under the aspect of a commercial thermal power station. Besides, the plant is of considerable importance concerning the German program for developing high-temperature reactors with helium turbines (HHT). Its significance is, on the one hand, based on the fact that the turbomachines and heat exchangers are constructed in many details to meet the requirements which occur in nuclear helium turbines of high output. Some of these components closely resemble dimensions and stresses as in a HHT-power plant. On the other hand the operational behavior of component parts will be tested under real conditions of a commercial power plant.Copyright © 1974 by ASME

Operation and Control of the 50-Mw Closed-Cycle Helium Turbine Oberhausen

Abstract: The Oberhausen helium turbine plant will have a multi-compartment storage system for varying the pressure level and two separate bypasses, one for speed control during isolated operation and the other for emergency shutdown. A newly developed safety system with a multiple-protection effect is provided. The report contains the results of the extensive calculation work relating to the operating behavior of the plant, as well as important layout criteria resulting therefrom.Copyright © 1974 by ASME

The Influence of He-Ne, He-N2, and He-CO2 Gas Mixtures on Closed-Cycle Gas Turbines

Abstract: With reference to a proposal made by Prof. Ackeret studies have been made on the composition of an optimal working medium for closed-cycle gas turbines. These studies are based on the assumption that this aim could be achieved by mixing helium with a gas of higher molecular weight, using neon, nitrogen, and carbon dioxide here. The influence of these gas mixtures on the circuit parameters and on the layout of the turbomachines and heat exchanging apparatus is shown. The calculations have been carried out giving consideration to the real gas behavior of the mentioned gas mixtures. In addition to this, the relationship of the costs of the turbomachinery and apparatus are shown in relation to a reference plant with pure helium as working agent. The basis for these studies is a process with the thermal efficiency, the upper and lower process temperatures and the turbine inlet pressure being the same for all gas mixtures. The results of the calculations are that, for certain gas compositions, cost advantages can be gained relative to the layout with pure helium. These advantages and the mixture compositions, for which they appear, are dependent on the admixed gases. For these calculations the cost relationship of turbomachines and heat exchangers to the total cost have been considered.Copyright © 1974 by ASME

On the Energy Transfer in Centrifugal Compressors

Abstract: In the layout and calculation of centrifugal compressors there are still considerable uncertainties when it comes to the theoretical determination of energy transfer from the impeller to the flowing medium and to the subsequent energy conversion in the diffuser. These problems arise particularly where compressor stage design with high pressure ratios and mass flow rates are concerned. A solution to these questions can presumably be found only through a physically balanced interpretation of the extremely complex flow mechanisms in the impeller. Since purely theoretical methods have hardly led to any reliable conclusions concerning the criteria of flow separation in the impeller or the secondary character of the impeller flow, there is still little knowledge about the creation of the jet-and-wake zones in the impeller and their decay (associated with large losses) in the connected diffuser. In studying the energy conversion process in the stage as a whole, great attention has to be devoted to the effects of the momentum exchange directly downstream the impeller. Hence the only possible way of solving these problems seems to be specific experimentation. For high flow velocities, this necessitates a special nonsteady measuring technique which also gives information about the relative flow in the rotating impeller.Copyright © 1974 by ASME

Prediction of the height of tidal dunes in estuaries

Abstract: In this paper prototype data of echo soundings of tidal dunes are analysed. A good relation between the fresh water discharge and the sand wave migration velocity in the upper part of a tidal river could be determined. The limitation of the dune heights as a function of the mean current velocities over the crests and the bed material characteristics is presented. States of equilibrium are described by dimensionless parameters and the latter compared with model tests.

Similarity conditions for thermal-hydraulic model tests of tidal estuaries

Abstract: In connection with the design of proposed nuclear power plants on the Lower Weser River and on the Lower Elbe River in Germany, tidal models were constructed and tests carried out at the Franzius-Institute of the Technical University of Hannover for the purpose of studying the mixing and spreading of the hot water discharge. Thermal-hydraulic models are today still the most reliable method for the prediction of temperature distributions in the total area of temperature increase, especially in tidal regions. Hydraulic models with free surface flow are in general based on the FROUDE scaling lav;. The flow fields in both the hydraulic model and in the prototype show a dynamic similitude when the FROUDE numbers of the flow in the model and in the nature are equal at corresponding points.