A methodology to compare the economic feasibility of fuel cell‐, gas turbine‐ and microturbine‐based combined heat and power systems

Combined heat and power (CHP) systems are a proven technology to reduce emissions. A methodology was presented to compare the economic feasibility of fuel cell‐based CHP systems with more alternative prime movers (microturbine and gas turbine). For demonstration purposes, the methodology was applied to three distinct case studies of varying size. The developed methodology allowed for the analysis of the system from various economic points of view. Because of the scarcity of complete equation sets modeling the off‐design performance of fuel cells, several novel equations were proposed. All systems utilizing alternative prime movers were unprofitable. The fuel cell‐based systems exhibited some economic potential; however, the results showed it would take close to the entire system lifetime to recover the capital costs. This is consistent with the reviewed literature and hence validates the new methodology and partial load equations proposed. Based on this analysis the fuel cell‐based system for the medium sized case study showed the most economic potential. Because of the susceptibility of emerging technologies (fuel cells) to changes in capital costs, an in‐depth sensitivity analysis was performed. The analysis showed that a 5% decrease in capital costs could reduce the payback period by as much as six months. This indicates that only a small decrease in price is necessary to potentially lead to the adoption of these systems in the near future. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermal Performance of an Air-Cooled Data Center With Raised-Floor and Non-Raised-Floor Configurations

In this paper, the thermal performances of an air-cooled data center with raised-floor and non-raised-floor configurations are compared with respect to the room and ceiling return strategies. The thermal performance of the data center is evaluated in terms of supply heat index, rack cooling index, total irreversible loss, and the number of racks with at least one server exceeding the maximum recommended and allowable inlet air temperature according to American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) thermal guidelines. The numerical simulations are conducted providing an insight into the flow and temperature distributions, and thus giving a better understanding of the cooling issues. It is found that using a ceiling return strategy for the return of hot exhaust air to the computer room air conditioning units gives a better thermal performance of the data center, for both raised- and non-raised-floor strategy, as compared to the room return. The findings are then extended to a geometrically complex operational data center to improve its cooling effectiveness. The paper also highlights the drawback of using supply heat index alone as a performance metric.     

应用红外热像技术测量电子元件正常工作条件下的表面温度

由于电子元件的功率密度不断增加,电子产品的热控制日显重要.红外热像仪有众多优点且可用于电子元件表面温度的测量.探讨了如何在电子元件正常工作条件下,应用红外热像仪获得其真实表面温度,涉及背景温度、目标温度的正确估计,透明材料的选取、透射率的估算,误差及可能的修正方法.     

Infrared Thermography for True Temperature Measurement of the Main Board in Personal Computer

This paper presents a way to measure the true temperature of the electronic devices without disturbing their normal operating conditions, which involved with estimating target emissivity, background temperature correctly and choosing infrared transparent material and its transmission estimation. The temperature distributions of the main board in personal computer were measured by the method presented here with infrared thermography in several different running conditions. The measurement errors and their possible remedies are also discussed.     

Commensurability effects in the magnetoresistance of (TMTSF)2PF6

We present a study of the angular dependence of the magnetoresistance of the quasi-one-dimensiona1 organic conductor (TMTSF)₂PF₆. For some special orientations of magnetic field in the least-conducting plane, a commensurability effect in the electronic open-orbit motion is expected. At these special "magic angles", dips in the resistance along the least-conducting axis in both metallic and field-induced-spin-density-wave (FISDW) states are detected. In the latter states, the dips gradually fade away with the increasing field. Moreover, the commenusurability effect intereferes directly with FISDW transitions: For magic angles, the threshold field goes through a weak minimum and the amplitude of the FISDW magnetoresistance oscillations is diminished.     

如何管理形形色色的云

管理技术通常是构成“云”的根本要素,这种管理能力也有助于保持IT控制,使“云”成为现实。 许多CIO认识到云计算的能力,并期望在自己的IT环境中实施这一技术。尽管云计算的呼声喧嚣于市,但企业应如何确定其起步方向？通过了解与服务相关的根本要求,企业将有机会尽享云计算所带来的好处,并改善业务所需的服务。     

Remote predictive mapping of bedrock geology using image classification of Landsat and SPOT data,western Minto Inlier,Victoria Island,Northwest Territories,Canada

Supervised classification (robust classification method) of Landsat-7 and SPOT-5 data was used to analyse the bedrock geology of a part of the western Minto Inlier on Victoria Island, Canada. The robust classification method was used as it provides a series of uncertainty measures for evaluating the classification results. Six bedrock classes including gabbro, basalt, carbonate of the Wynniatt Formation, quartz-arenite of the Kuujjua Formation, evaporite of the Minto Inlet and Killian Formations and Paleozoic carbonate together with six surficial classes including vegetation were defined as the training data set. The resulting classified images derived from the Landsat and SPOT data were very similar in terms of the regional distribution of lithological classes, as reflected by fairly high classification accuracies for both image types. Gabbro and basalt, despite having a similar mineralogical composition, are spectrally distinct throughout most of the study area. Complicating spectral signatures of overlying glacial sediments and/or other overburden materials and spectral similarities between some of the lithologies caused poorer classification in some areas. Generally, the Landsat imagery provided better spectral separability between most of the lithological units than the SPOT imagery. However, in certain areas where the spectral separation between different lithologies is not dependant on the shortwave infrared-2 (SWIR-2; band 7 on Landsat) and/or blue bands (band 1 on Landsat), the SPOT imagery provided a better classification because of higher spatial resolution.     

Thermal optimization of a natural draft wet cooling tower

This study attempts to quantify the potential improvement in a natural draft wet cooling tower (NDWCT) performance that can be attained by optimizing the fill and water distribution profiles across the tower and to provide designers with the modelling tools for such an investigation. A simple two‐dimensional (2D) model is described, which allows rapid evaluation of NDWCT performance for use with an optimization procedure. This model has been coupled with an evolutionary optimization algorithm to determine the optimal fill shape and water distribution profile to maximize the cooling range of a typical NDWCT. The results are compared against a 2D axisymmetric numerical model. The extended 1D model is found to significantly reduce computational time compared with the numerical model, allowing a wide range of parameters to be tested rapidly with reasonable accuracy. The results show that the optimal layout differs significantly from a uniform profile, with both the water flow rate and the fill depth decreasing towards the centre of the tower where the air is warmer with reduced cooling potential. The overall improvement in the tower cooling range is very low under the design conditions tested, due largely to the highly coupled nature of the airflow and heat transfer in the tower. It is concluded that any design modifications of the type considered would need to be carefully optimized to have any possibility of improving performance. Copyright © 2008 John Wiley & Sons, Ltd.     

Fermi surface and physical properties of (TMTSF)2NO3

We studied the Fermi surface of the organic conductor (TMTSF)₂NO₃ through the measurements of magnetic quantum oscillations. Well defined Shuvnikov-de Haas(SdH) oscillations with frequency of ca. 60T can be observed below 8K and above 6T at the ambient pressure. Under a pressure of 8kbar, different oscillations with frequency of ca. 180T is observed above 10T at 450mK. Electron structure at low temperature seems strongly modified upon application of pressure which may explain the absence of superconductivity and the field-induced spin-density waves. The angular magnetoresistance could not be fit neither by Yamaji's model nor by Lebed's.     

Features of heat transport in organic and cuprate superconductors

Thermal conductivity measurements in the cuprates have established two unusual and distinct features of quasi-particle transport in the superconducting state. Both these features (i.e. the abrupt increase in the relaxation time at the onset of superconductivity and a finite zero-energy transport due to presence of nodes in the superconducting gap) may also be present in – (ET) ₂ Cu(NCS) ₂ according to the first study of heat transport in this two-dimensional organic superconductor. In the case of optimally-doped Bi-2212, the modification of low-temperature thermal conductivity by the introduction of point defects was investigated. Results provide new information on the structure of low-energy electronic excitations of the superconducting state.