Thermodynamic Modeling of Screw Expander in a Trilateral Flash Cycle

The present paper focuses on the thermodynamic modeling of screw expanders in a trilateral flash cycle. In this process a liquid is pumped from low to high pressure and then heated up close to saturation point. Instead of a vaporous working fluid as usual, a hot liquid is filled in the working chamber of the screw expander. During the filling process the pressure of the liquid drops below the saturation pressure while the temperature remains almost constant due to a fast process. Hence the liquid is in a metastable state. The liquid aspires a stable state and therefore is vaporized during the filling and expansion process due to its increasing chamber volume. Thus a two-phase mixture, vapor and liquid, exists in the working chamber. The simulation presented includes the calculation of fluid states within each chamber to be in thermodynamic equilibrium, which assumes that a sufficient heat transfer exists between the phases to reach a stable state within a time step. Thermodynamic simulations are carried out using water as the working fluid for an exemplary screw expander geometry. The conclusive assessment of the thermodynamic model is demonstrated by the comparison of the simulation results with available experimental measurement results for a corresponding two-phase screw expander

The relationship between perceived coaching behaviours and team cohesion among Malaysian National Junior Athletes

Based on Carron’s (1982) model of cohesion, this study examined the relationship between perceived coaching behaviours and group cohesion in interacting sports teams among national junior athletes in Malaysia. The subjects, which were comprised of 150 athletes, were asked to respond to survey questions based on the Leadership Scale for Sports (LSS) and the Group Environment Questionnaire (GEQ). The results suggest a significant relationship between coaching behaviours and team cohesion. Coaches who were perceived as engaging in democratic behaviours, higher levels of training and instruction, social support and positive feedback, tend to have athletes with higher levels of task and social cohesion within their teams

Development And Practical Application Of A Natural Gas Expansion Turbine For Power Generation Without Additional Heating Equipment

The efficient transportation of natural gas takes place with high pressure before it is distributed to the consumer with a lower pressure. Generally, pressure reduction in gas grids is realized in pressure control stations with a regulating valve, where the dissipative energy remains as heat in the fluid. Nevertheless, the temperature of natural gas decreases during the pressure reduction due to the Joule-Thomson-Effect, depending on pressure difference of the regulating valve. For higher pressure differences it is necessary to preheat the natural gas to prevent condensate formation and freezing of pipelines. Instead of using a regulating valve, an expansion machine can be used for pressure reduction and power generation apart from pressure control stations. For this purpose, a single stage axial flow turbine is developed for power generation in a natural gas pipeline. The “preheating” of natural gas is realized solely with geothermal energy out of the upper layer of earth and thus without additional heating equipment. The temperature of natural gas at the inlet of the expansion machine is given by geothermal energy as e.g. Tinlet = 278 -283 K, which varies dependent of the temperature in the ground. The outlet temperature downstream of the turbine should not fall below e.g. Toutlet = 273 K. The design criterion for the expansion machine is therefore the temperature difference instead of a pressure difference as it is common for expansion processes. Essential criteria for the whole concept are a simplified integration in a pipeline and an economical solution. Design of the axial flow turbine is carried out with mean diameter calculations followed by an empirical prediction method for the turbine efficiency. Using an empirical method the loss of total pressure in a cascade of blades is obtained. One-dimensional simulations are carried out to determine design parameters and inner power of the turbine. Subsequently the upper and lower partial load are examined. The axial flow turbine is designed in a compact module (generator inside pipeline) for a natural gas pipeline with relevant safety standards. A first prototype of a single stage axial turbine with partial admission is manufactured and tested initially in a test rig with air flow and in a pressure control station for natural gas. Results from field measurements and simulation are compared and analyzed with respect to the operational behavior of this new concept of an axial turbine for natural gas without preheating equipment

Numerical modelling of a two-phase twin-screw expander for Trilateral Flash Cycle applications

This paper presents numerical investigations of a twin-screw expander for low grade (≤100°C) heat to power conversion applications based on the bottoming Trilateral Flash Cycle. After a thorough description of the modeling procedure, a first set of simulations shows the effect of different inlet qualities of the R245fa working fluid and of the revolution speed on the expander performance. In particular, at 3750 RPM and an inlet absolute pressure of 5 bar, the volumetric and adiabatic efficiencies will increase from 24.8% and 37.6% to 61.2% and 83.1% if the inlet quality in the intake duct of the expander increased from 0 to 0.1. To further assess the effects of inlet quality, inlet pressure and revolution speed on the expander performance, parametric analyses were carried out in the ranges 0-1 inlet quality, 5-10 bar pressure and 1500-6000RPM speed respectively. © 2018 The Author(s).European Union’s Horizon 2020 Research and Innovation Programme under grant agreement no. 680599, (ii) Innovate UK (project no. 61995-431253, (iii) Engineering and Physical Sciences Research Council UK (EPSRC), grant no. EP/P510294/1 and (iv) Research Councils UK (RCUK), grant no. EP/K011820/1

The role of sediment chemistry in stability and resuspension characteristics of cohesive sediments

Ph.D.Appiah Amirtharaja

Flume studies on resuspension of contaminated sediments

M.S.Appiah Amirtharaja

Utilizing Microalgae Biomass as a Source of Biofertilizer to Grow Agriculture Plant

The employment of inorganic fertilizers in agriculture inflicts adverse effects on both human health and environment. Researchers have discovered that "bio-fertilizer" produced from microalgae is a great substitute for chemical fertilisers, which can stimulate plant development by the production of growth-promoting compounds. Since microalgae biomass is used as a biofertilizer, growth of microalgae must be optimized as well to produce the highest yield of biomass

ULTRARAPID FREEZING OF MOUSE EMBRYOS

Master'sMASTER OF SCIENC