The effects of varying dietary protein level (200, 250, 300 and 350 g protein kg )1 diet) and plant : animal protein ratio (1 : 2, 1 : 1, 1 : 1.5 and 2 : 1) on growth of juvenile Macrobrachium rosenbergii (de Man) with approximately 0.27 g initial body weight were evaluated in two separate 30-days study using practical diets. Significantly lower survival rate was recorded in prawns fed a diet containing 200 g kg )1 dietary protein (66.67%) whilst 300 and 350 g kg )1 protein gave the highest survival (96.67%). Significant differences (P < 0.05) in feed conversion ratio and protein efficiency ratio were recorded among different dietary protein levels. The results of the study showed that highest growth rate and maximum utilization of protein were recorded in prawns fed 300 g kg )1 dietary protein and further increase in the dietary protein does not have any added advantage. There existed no statistically significant difference (P > 0.05) in the specific growth rate, protein efficiency ratio, weight gain and survival rate among the juveniles of M. rosenbergii fed varying plant-animal protein ratios at 300 g kg )1 protein. Better-feed conversion ratio was recorded in diets having a plant to animal protein ratio of 1 : 1 (2.62) followed by 1 : 1.5 (2.66), however there was no significant difference between them (P > 0.05). Based on the present study, it would be possible to replace animal protein by low-cost plant protein in prawn feed. Better growth performance in juveniles of M. rosenbergii can be achieved by the incorporation of equal proportions of plant and animal protein (A : P ¼ 1) in the diet. KEY WORDS KEY WORDS: dietary protein requirement, Macrobrachium rosenbergii, plant-animal protein ratio
Computational fluid dynamics (CFD) and finite element analysis (FEA) are important modelling and simulation techniques to design and develop fuel cell stacks and their balance of plant (BoP) systems. The aim of this work is to design a microtubular solid oxide fuel cell (SOFC) stack by coupling CFD and FEA models to capture the multiphysics nature of the system. The focus is to study the distribution of fluids inside the fuel cell stack, the dissipation of heat from the fuel cell bundle, and any deformation of the fuel cells and the stack canister due to thermal stresses, which is important to address during the design process. The stack is part of an innovative all-in-one SOFC generator with an integrated BoP system to power a fixed wing mini unmanned aerial vehicle. Including the computational optimisation at an early stage of the development process is hence a prerequisite in developing a reliable and robust all-in-one SOFC generator system. The presented computational model considers the bundle of fuel cells as the heat source. This could be improved in the future by replacing the heat source with electrochemical reactions to accurately predict the influence of heat on the stack design.
This work presents a three-dimensional thermo fluid and thermo mechanical computational analysis of a microtubular solid oxide fuel cell (SOFC) stack as part of a microtubular SOFC generator. The latter powers a lithium-ion battery as a microtubular SOFC hybrid power system to extend the flight endurance of a mini unmanned aerial vehicle.The microtubular SOFC stack and balance of plant components, comprising microtubular SOFC generator, were designed based on computational fluid dynamics (CFD) assumptions. The stack design process has been further upgraded with thermo mechanical finite element analysis (FEA) simulation to capture deformations and stresses in the stack due to thermal expansion of microtubular SOFCs and manifolds. The developed microtubular SOFC stack will be built based on CFD and FEA predictions and tested to determine the suitability of the microtubular SOFC hybrid power system for this application.
A microtubular design for a solid oxide fuel cell (MT-SOFC) is studied for use in stacks for high strength and portability. Adapting readily available butane as the fuel source and intermediate temperature operation, MT-SOFC can replace batteries for various portable applications. This work studies the fabrication and preliminary performance results of a 5W MT-SOFC stack using butane as the fuel. The tubes were produced using a standard die extruder into a Ni-ceria-10mol% scandia stabilized zirconia (ScSZ) anode support. A ScSZ electrolyte and a La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathode were added on top of the tube, respectively, via a dip-coating method. The outer and inner diameters of the unit cell were 3mm and 2mm, respectively. The fabrication process was optimized and the electrochemical properties of a unit cell operated at intermediate (600~700oC) temperature are described. Unit cells were then stacked for an output of 5 watts.
Fig. 1. (a) Pre-sintered anode support MT-SOFC; (b) Fabricated anode support MT-SOFCs; (b) Schematic of 5W MT-SOFC stack.
Acknowledgement
This work was sponsored by KETEP No. 4.0010459.01.
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