Search results for " Heating"
showing 10 items of 150 documents
A coronal explosion on the flare star CN Leonis
2008
We present simultaneous high-temporal and high-spectral resolution observations at optical and soft X-ray wavelengths of the nearby flare star CN Leo. During our observing campaign a major flare occurred, raising the star's instantaneous energy output by almost three orders of magnitude. The flare shows the often observed impulsive behavior, with a rapid rise and slow decay in the optical and a broad soft X-ray maximum about 200 seconds after the optical flare peak. However, in addition to this usually encountered flare phenomenology we find an extremely short (~2 sec) soft X-ray peak, which is very likely of thermal, rather than non-thermal nature and temporally coincides with the optical …
Long-term performance and life cycle assessment of energy piles in three different climatic conditions
2020
Abstract The main purpose behind the use of energy piles is to enable the exploitation of geothermal energy for meeting the heating/cooling demands of buildings in an efficient and environment-friendly manner. However, the long-term performance of energy piles in different climatic conditions, along with their actual environmental impacts, has not been fully assessed. In this paper, the results of a finite element model taking into consideration the heating and cooling demands of a reference building, and the intermittent operation of a ground source heat pump, are revealed to examine the long-term performance of energy piles. Furthermore, a life cycle assessment model is implemented to com…
Energy and economic analysis of air-to-air heat pumps as an alternative to domestic gas boiler heating systems in the South of Italy
2019
Abstract According to the electricity tariff recently issued by the Italian government for the domestic heating systems fed with heat pumps (HP), an energy and economic analysis was carried out with the aim of investigating the effectiveness of the air-to-air heat pump systems (HPS) as an alternative to the traditional heating using domestic gas boilers systems (GBS). For the purpose of this study, the apartments of three residential buildings were examined. The hourly heating loads were calculated with the ASHRAE radiant time series and the coefficient of performance (COP) of the HPs was evaluated for each operating condition. The costs for the heating system installation and electricity a…
District heating networks: enhancement of the efficiency
2019
International audience; During the decades the district heating's (DH) advantages (more cost-efficient heat generation and reduced air pollution) overcompensated the additional costs of transmission and distribution of the centrally produced thermal energy to consumers. Rapid increase in the efficiency of low-power heaters, development of separated low heat density areas in cities reduce the competitiveness of the large centralized DH systems in comparison with the distributed cluster-size networks and even local heating. Reduction of transmission costs, enhancement of the network efficiency by optimization of the design of the DH networks become a critical issue. The methodology for determ…
Innovative technologies for food preservation
2018
Abstract Several techniques have been developed during the 20th century in order to preserve foods. These innovative technologies vary considerably and embrace physical technologies (e.g., high hydrostatic pressure and high-pressure homogenization), electromagnetic technologies (e.g., pulsed electric fields, ohmic heating, microwaves, radio-frequency, and UV-light), acoustic technologies (e.g., ultrasound and shockwaves), and others such as membrane filtration and dense phase CO 2 . In this chapter, the theoretical background and definition of the technologies are explained together with a description of the equipment, main technological/processing parameters, and some advantages and limita…
Heating glaciers from below
2013
Climate change is affecting the cryosphere from above. Geothermal heat flux from below is also contributing to conditions at the base of Greenland's ice sheet, which sits atop a lithosphere of variable thickness.
Influence of greenhouse volume/area ratio on soil solarization efficiency
2008
Soil temperature under plastic cover is function of incoming radiation and thermal characteristics of the mulching material and the soil, but it could be also affected by greenhouse characteristics (structure, cover, Volume/Area ratio). The aim of this research was to evaluate the effects of different greenhouse unitary volumes and different plastic mulching on soil temperature and soil solarization efficiency. The experiment was carried out in nonheated greenhouses covered with low density transparent polyethilene (PE), located at the experimental field of AAT Department of Palermo University, Italy (138° 7' N, 13° 22' E). Four Volume/Area (V/A) ratios were tested: 1.5 - 2.0 - 2.5 - 3.0. I…
Ohmic treatment of fresh foods: Effect on textural properties
2013
The aim of this work was to verify the effects of ohmic heating (OH) treatment on texture of fresh solid food (without pre-treatment in brine solutions), subjected to constant electrical field gradient (1100 V/m; 2200 V/m; 3300 V/m). Samples of fresh potatoes, carrots and apples cut into cylinders (d = 30 mm, h = 9.0 mm) underwent OH for 60, 120, 180 and 240 seconds. Texture measurements were performed in a universal testing machine Instron 4301, with a 100 N load cell, using a single-cycle compression test. The raw untreated sample was used as control. Stress–deformation behavior of food samples processed by OH differs appreciably from raw untreated samples for all cooking times. Firmness …
Mathematical Model of Solid Food Pasteurization by Ohmic Heating: Influence of Process Parameters
2013
Pasteurization of a solid food undergoing ohmic heating has been analysed by means of a mathematical model, involving the simultaneous solution of Laplace’s equation, which describes the distribution of electrical potential within a food, the heat transfer equation, using a source term involving the displacement of electrical potential, the kinetics of inactivation of microorganisms likely to be contaminating the product. In the model, thermophysical and electrical properties as function of temperature are used. Previous works have shown the occurrence of heat loss from food products to the external environment during ohmic heating. The current model predicts that, when temperature gradient…
Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating
2017
We describe a new technique for the efficient generation of high-energy ions with electromagnetic ion cyclotron waves in multi-ion plasmas. The discussed ‘three-ion’ scenarios are especially suited for strong wave absorption by a very low number of resonant ions. To observe this effect, the plasma composition has to be properly adjusted, as prescribed by theory. We demonstrate the potential of the method on the world-largest plasma magnetic confinement device, JET (Joint European Torus, Culham, UK), and the high-magnetic-field tokamak Alcator C-Mod (Cambridge, USA). The obtained results demonstrate efficient acceleration of 3He ions to high energies in dedicated hydrogen–deuterium mixtures.…