Performance of heat pumps charged with R170/R290 mixture

In this study, thermodynamic performance of R170/R290 mixture is measured on a heat pump bench tester in an attempt to substitute R22. The bench tester is equipped with a commercial hermetic rotary compressor providing a nominal capacity of 3.5 kW. All tests are conducted under the summer cooling and winter heating conditions of 7/45 °C and −7/41 °C in the evaporator and condenser, respectively. During the tests, the composition in R170/R290 mixture is varied from 0% to 10% with an interval of 2%. Test results show that the coefficient of performance (COP) and capacity of R290 are up to 15.4% higher and 7.5% lower, respectively than those of R22 for two conditions. For R170/R290 mixture, the COP decreases and the capacity increases with an increase in the composition of R170. The mixture of R170/R290 mixture at 4%/96% composition shows the similar capacity and COP as those of R22. For the mixture, the compressor discharge temperature is 17–28 °C lower than that of R22. For R170/R290 mixture, there is no problem with mineral oil since the mixture is composed of hydrocarbons. The amount of charge is reduced up to 58% as compared to R22. Overall, R170/R290 mixture is a good long term ‘drop-in’ candidate from the view point of energy efficiency and greenhouse warming to replace R22 in residential air-conditioners and heat pumps.     

Seismic behavior of a buried gas pipeline under earthquake excitations

Earthquake time-history analyses have been performed for a buried gas pipeline of API 5L Grade X65, which is popularly used in Korea. For this purpose, various parameters such as the type of buried gas pipeline, end-restraint conditions, soil characteristics, single and multiple earthquake input ground motions, and burial depths are selected. A comparative study has been performed to obtain the response characteristics of strains in a buried pipeline section, axial relative displacement, and transverse relative displacement. The capacity evaluation of the pipeline with respect to the response characteristics has been performed in comparison with the allowable strain and displacement capacity in axial and transverse directions, as suggested by the Guidelines for the Seismic Design of Buried Gas Pipelines, KOGAS. The present study is expected to provide useful information for an effective seismic evaluation of a buried gas pipeline.     

Aircore mechanism during draining based on influence of pressure difference and drain port diameter

An understanding of the mechanism of aircore phenomenon during draining is very important. In this study, numerical simulations were conducted for different pressurized and suction pressure water tanks, as well as for different drain port diameters, to explain and validate the proposed aircore mechanism. It was found that increasing the pressure at the top surface of the tank results in suppression of the aircore, whereas an increase in the suction pressure at the drain port outlet enhances the development of the aircore. For different drain port diameters, it was observed that the duration of the aircore during draining decreases with a decrease in the drain port diameter, and that the aircore is suppressed for a very small drain port diameter.     

Modelling and analysis of energy footprint of manufacturing systems

Increasing the energy efficiency of manufacturing plants will reduce the production costs and environmental impact. In order to analyse and improve the energy efficiency of manufacturing plants, however, we need models to evaluate the energy footprints of the plants. A key challenge of estimating plant-level footprints is that systemic methods of connecting information on the product, machine and plant levels are not available. Thus, we propose methods to parameterise product-level elements and to model machine-level factors based on those elements. From the machine-level models, the proposed approach performs simulation experiments and provides the energy footprints in closed-form equations for the plant level. We also suggest that the resulting model can be combined with probabilistic techniques to benchmark the energy efficiency of plants at the industry level. In a case study, we demonstrate how to apply the proposed methods to estimate the energy footprint of a hypothetical plant. The procedures introduced here enable manufacturers to evaluate the energy consumption of their facilities at early stages of manufacturing, and provide tools to assess the energy efficiency of their plant by comparison with peers.     

Bacteriocins as food preservatives: Challenges and emerging horizons

ABSTRACT

The increasing demand for fresh-like food products and the potential health hazards of chemically preserved and processed food products have led to the advent of alternative technologies for the preservation and maintenance of the freshness of the food products. One such preservation strategy is the usage of bacteriocins or bacteriocins producing starter cultures for the preservation of the intended food matrixes. Bacteriocins are ribosomally synthesized smaller polypeptide molecules that exert antagonistic activity against closely related and unrelated group of bacteria. This review is aimed at bringing to lime light the various class of bacteriocins mainly from gram positive bacteria. The desirable characteristics of the bacteriocins which earn them a place in food preservation technology, the success story of the same in various food systems, the various challenges and the strategies employed to put them to work efficiently in various food systems has been discussed in this review. From the industrial point of view various aspects like the improvement of the producer strains, downstream processing and purification of the bacteriocins and recent trends in engineered bacteriocins has also been briefly discussed in this review.     

Thermodynamic optimization of the K2O-Al2O3-SiO2 system

A critical evaluation and thermodynamic optimization of experimental phase diagrams and thermodynamic properties of the K₂O-Al₂O₃-SiO₂ system was performed at 1?bar total pressure. A set of self-consistent thermodynamic functions of all phases in the K₂O-Al₂O₃-SiO₂ system was obtained. The liquid phase was described using the Modified Quasichemical Model with the KAlO₂ associate component. The set of optimized model parameters obtained for all phases reproduces available and reliable thermodynamic properties and phase diagram data as well as the melt structure of the K₂O-Al₂O₃-SiO₂ system within the experimental error limits.     

Structural and thermoelectric properties of hydrothermal-processed Ag-doped Fe2O3

Fe_2-xAg_xO₃ (0?≤?x?≤?0.04) nanopowders with various Ag contents were synthesized at different hydrothermal reaction temperatures (150?°C and 180?°C). Their structural properties were fully investigated through an X-ray diffraction, a Fourier transform infrared spectroscopy, and an X-ray photoelectron spectroscopy. The hydrothermal reaction temperature, time, and Ag content remarkably affected the morphological characteristics and crystal structure of the synthesized powders. The Fe_2-xAg_xO₃ (0?≤?x?≤?0.04) powders synthesized at 150?°C for 6?h and the Fe_2-xAg_xO₃ (0.02?≤?x?≤?0.04) powders synthesized at 180?°C for 12?h formed the orthorhombic α-FeOOH phase with a rod-like morphology, whereas the Fe_2-xAg_xO₃ (0?≤?x?≤?0.01) powders synthesized at 180?°C for 12?h formed the rhombohedral α-Fe₂O₃ phase with a spherical-like morphology. The Fe_1.98Ag_0.02O₃ fabricated by utilizing Fe_1.98Ag_0.02O₃ powders synthesized at 180?°C showed the largest power factor (0.64?×10^?5 Wm^?1 K^?2) and dimensionless figure-of-merit (0.0036) at 800?°C.     

Optimal schedule and effort considering the penalty cost of schedule delay in software development

This study presents an optimization model that considers the penalty cost due to the contract-schedule delay, when trading off between scheduling and effort in software development project. The optimal combination between the schedule and the effort is shown to depend on the penalty cost. This study also addresses analysis for the effects of software size misestimation and penalty cost change. A simple example is given to illustrate the results of our study.