다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

https://eva.fing.edu.uy/pluginfile.php/55828/mod_resource/content/1/kalogiru.pdf

Solar thermal collectors and applications

An introduction to heat transfer

Food systems contribute 19%–29% of global anthropogenic greenhouse gas (GHG) emissions, releasing 9,800–16,900 megatonnes of carbon dioxide equivalent (MtCO2e) in 2008. Agricultural production, including indirect emissions associated with land-cover change, contributes 80%–86% of total food system emissions, with significant regional variation. The impacts of global climate change on food systems are expected to be widespread, complex, geographically and temporally variable, and profoundly influenced by socioeconomic conditions. Historical statistical studies and integrated assessment models provide evidence that climate change will affect agricultural yields and earnings, food prices, reliability of delivery, food quality, and, notably, food safety. Low-income producers and consumers of food will be more vulnerable to climate change owing to their comparatively limited ability to invest in adaptive institutions and technologies under increasing climatic risks. Some synergies among food security, adaptati...

https://sustainabledevelopment.un.org/content/documents/881annurev.pdf

Climate Change and Food Systems

Unwrapped food product display shelf life assessment

In this study the dynamic mode performance of an inverter driven and direct mains driven compressor has been evaluated using a laboratory-based test facility. The aim was to investigate the influence of the inverter on the start-up performance of a refrigeration system and quantify and compare start-up losses for the two modes of operation. The results indicate that an inverter driven system incurs approximately 5 per cent higher start-up losses than a direct mains driven system. This is mainly due to the 'soft' starting capabilities of the inverter (gradual acceleration of the motor). An energy analysis of fixed speed and inverter driven refrigeration systems in air-conditioning applications has shown that despite the additional start-up transient losses of inverter driven systems they lead to higher seasonal efficiencies than fixed-speed systems. This arises from improved steady state performance during low-speed operation at loads below the design load of the system. It has been found that the level of energy savings is a function of the type of compressor employed in the variable-speed system.

Dynamic mode performance evaluation and energy analysis of mains and inverter driven refrigeration compressors

https://bura.brunel.ac.uk/bitstream/2438/18124/1/FullText.pdf

Numerical investigation into the influence of air curtain discharge angles in refrigerated trucks

Industrial processes are currently characterized by thermal energy losses through high temperature exhausts or effluents (above 300°C) that, on a global scale, account for nearly 11.4% of their primary energy consumption, namely 12.1 EJ. For these high temperature exhausts, conventional waste heat to power conversion systems based on bottoming thermodynamic cycles are not very suitable since most of the state of the art working fluids are not able to perform safely and efficiently at high temperatures. Supercritical Carbon Dioxide (sCO2) power systems allow to overcome these limitations because of the chemical and thermo-physical properties of the working fluid. In order to provide insights on the behavior of sCO2 systems, this paper presents the development of a one-dimensional numerical model of a low capacity (50 kWe) simple regenerated system for medium to high temperature waste heat recovery applications. The unit is equipped with single-shaft radial turbomachinery and different heat exchanger technologies such as micro-tube, printed circuit, plate, etc. Flue gas and water are used as heat source and sink respectively. At nominal conditions, i.e. for a flue gas mass flow rate of 1.0 kg/s at 650°C, the unit operates at a cycle pressure ratio of 1.7, generating 50 kWe with a thermal efficiency of 20%. The paper first discusses the modelling methodology, including turbomachinery and heat exchanger models implementation, and then assesses the steady-state performance of the unit at design and off-design operating conditions. From the simulations carried out operating maps of the unit have been obtained to form the baseline for the setting up of control strategies for the sCO2 system. The results show that the system can generate up to 75 kWe for a heat source mass flow rate of 1.2 kg/s and heat source temperature of 700°C.

/pdf/modelling-and-performance-analysis-of-a-supercritical-co2-12vni2asd6.pdf

Savvas A. Tassou

Papers

Unwrapped food product display shelf life assessment

Dynamic mode performance evaluation and energy analysis of mains and inverter driven refrigeration compressors

Numerical investigation into the influence of air curtain discharge angles in refrigerated trucks

Modelling and performance analysis of a supercritical CO2 system for high temperature industrial heat to power conversion at off-design conditions

Energy storage in freezer cabinets using phase change materials.