Experimental investigation of PCM cold storage

This article presents an experimental analysis of cooling buildings using nighttime cold accumulation in a phase change material (PCM), otherwise known as the “free-cooling principle”. Studies of the ceiling and floor free-cooling principle, as well as passive cooling, are presented. The free-cooling principle is explained and some of the types of PCMs suitable for summer cooling are listed. An experiment was conducted using paraffin with a melting point of 22 °C as the PCM to store cold during the nighttime and to cool hot air during the daytime in summer. Air temperatures and heat fluxes as a function of time are presented for different air velocities and inlet temperatures.     

Detecting Power Imbalance in Multi-Cylinder Inline Diesel Engine Genset

A model of fuel injection adjustment for balancing the 4-stroke six cylinder diesel engine coupling geneset is developed by detecting imbalance in operating engine by the frequency analysis of the crankshaft＇s speed variation. In this work, the crankshaft is considered to be a rigid body, so that the variation of its angular speed could be directly correlated to the total gas-pressure torque. By analyzing only the lower harmonic orders, the speed variation spectrum can filter out the distortions produced by the dynamic response of the crankshaft. The information carried by these harmonic orders permits to establish correlations between measurements and the average gas pressure torque of the engine, and to detect imbalance and identify faulty cylinders. Detailed experimental reading are taken on diesel engine coupling genset on the test bed of Greaves Cotton Ltd Pane, India.     

Creation of stable nanoconstrictions in metallic thin films via progressive narrowing by focused-ion-beam technique and in situ control of resistance

This work describes the use of focused-ion-beam for the fabrication of metallic nanoconstrictions on a Fe thin film with in situ monitoring of the structure’s resistance. With this approach the sequential FIB steps that are used for the gradual narrowing of the nanoconstriction are observed as changes in the measured resistance, thus providing very good control of the milling process. The FIB patterning enables precise termination of the process just before the crossover between the metallic and tunneling regimes near the conductance quantum value G₀ (G₀ = 2e²/h). Compared to previous approaches to create nanoconstrictions with focused-ion-beam, this new technique determines precisely the current direction and minimizes Ga damage at the nanoconstriction.     

Assessing operational complexity of manufacturing systems based on statistical complexity

The aim of this paper is to contribute to complex systems thinking in manufacturing organisations through the development of a metric for operational complexity. Operational complexity is concerned with the temporal aspects of coordination and control in manufacturing systems. Statistical complexity from computational mechanics theory is proposed as the metric. The metric can potentially be used to support decision making by objective assessment of complexity. The properties of the metric are explored through simulation studies. The simulation results confirm that the proposed metric captures the intuitive notion of complexity. It is shown that operational complexity is influenced by internal factors such as system structure, as well as external ones such as demand, and that complexity can be managed through the application of appropriate control methods. A case study is presented that applies the metric to real production data. The case study shows that the global recession had resulted in a decreased operational complexity of outputs.     

Energy saving in building with PCM cold storage

This article presents an experimental and numerical analysis of cooling buildings using night‐time cold accumulation in phase change material (PCM), otherwise known as the ‘free‐cooling principle’. Experimental and numerical studies of the ceiling and floor free‐cooling principle, as well as passive cooling, are presented. The free‐cooling principle is explained and some of the types of PCMs suitable for summer cooling are listed. An experiment was conducted using paraffin with a melting point of 22°C as the PCM to store cold during the night‐time and to cool hot air during the daytime in summer. Air temperatures and heat fluxes as a function of time and dimensionless cold discharging values are presented for different air velocities. Experimental analysis of one week of measuring under real conditions is presented in order to show how cold storage functions. Copyright © 2007 John Wiley & Sons, Ltd.     

X-ray absorption in atomic potassium

A new high-temperature absorption cell for potassium vapor is described. X-ray absorption coefficient of atomic potassium is determined in the energy interval of 600 eV above the K edge where thresholds for simultaneous excitations of 1s and outer electrons, down to [1s2p] excitation, appear. The result represents also the atomic absorption background for XAFS (X-ray absorption fine structure) structure analysis. The K ionization energy in the potassium vapor is determined and compared with theoretical data and with the value for the metal.     

Optimization of a thermal storage unit combined with a biomass boiler for heating buildings

The performance of a boiler with a built-in thermal storage unit is presented. The thermal storage unit is an insulated water tank that absorbs surplus heat from the boiler. The stored heat in the thermal storage unit makes it possible to heat even when the boiler is not operating, thus increasing the heating efficiency. A system with three components is described. The model of the system and the mathematical model were made using the TRNSYS program package and a test reference year (TRY). The degree of efficiency, which optimizes the thermal storage volume and the heating power of the boiler, was determined. The thermal storage must also ensure that the heat is stored at the highest possible exergy level, and complete mixing of the water is a condition for optimizing the thermal storage. The matching of the boiler’s heating capacity with the thermal storage unit ensures a supply of heat even when the boiler is not operating.     

Review of green electricity production in Slovenia

The article presents a short review of electricity production from renewable energy sources in Slovenia. In Introduction the term of “green electricity” is defined. Comparison of structures of electricity production is presented for the years 1990 and 2003. The main part of the article presents an approximate data for technical and theoretical potentials of renewable energy sources in Slovenia. State-of-the-art regarding individual technologies of electricity production from renewable energy sources and political targets according to Directive 2001/77/EC for green electricity are also presented. At the end of the article different stimulation models are described and uniform prices and premiums for the purchase of green electrical energy are presented.     

A multi-agent approach to process planning and fabrication in distributed manufacturing

In the paper a multi-agent approach to the development of a distributed manufacturing architecture is presented. An essential building block introduced here is the virtual work system (VWS) which represents a manufacturing work system in the information space. The VWS is structured as an autonomous agent and is a constituent entity of an agent network. In the network dynamic clusters of cooperating agents are solving manufacturing tasks. A machining work system and its VWS is demonstrated in a case study. Its role in the agent communication network is discussed in a process planning and fabrication domain.     

The influence of deuterium exposures on subsequent outgassing rate of an UHV system

The accuracy of results in experiments where a well-processed UHV system is exposed to hydrogen depends on the hydrogen absorption rate and kinetics of subsequent spontaneous release from the system itself. In experiments to date, the sensitivity required to detect very low rates has been achieved only when tritium has been used as a tracer gas. Unfortunately, tritiated water from the surface prevails among released gas species which is not expected for well-outgassed surfaces. In the present studies, UHV system behaviour at 303 K during three deuterium exposures of duration 92 and 72 h at an initial pressure of 1 mbar was explored. The rate of decrease of pressure was constant during the whole of these periods as monitored by non-ionizing vacuum gauges. It corresponded to an effective sticking probability of the order of 1×10^-12 and resulted in absorption of 5×10¹⁴ D atoms/cm². The release kinetics were observed for several days starting immediately after deuterium had been pumped from the system. Initially, the deuterium release rate exceeded the background hydrogen outgassing by more than three orders of magnitude. These results demonstrate that extremely high sensitivity for deuterium absorption and release can be achieved with a precise pressure measuring technique otherwise attributed exclusively to tritium scintillation methods.