Dépôt numérique

Micrometeorological Observations for the Evaluation of the Selective Inverted Sink against Radiation Frost and the Potential of a New Hybrid System.

Ikani, Vahid; Chokmani, Karem; Turcotte, Caroline; Ferland, Mertin; Rainville, Ève; Granberg, Hardy (2015). Micrometeorological Observations for the Evaluation of the Selective Inverted Sink against Radiation Frost and the Potential of a New Hybrid System. Procedia Earth and Planetary Science , vol. 15 . p. 920-927. DOI: 10.1016/j.proeps.2015.08.147.

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For the radiation frost in agricultural fields, it is difficult to determine a satisfactory solution. To solve this problem, Selective Inverted Sink (SIS) is proposed as a new active frost protection method. However, the interactions of the SIS (also known as tower less wind machine) with some topo climatic effects such as cold air drainage and inversion strength are not well known. Consequently, this study was dedicated to two main objectives: First, different micro- topographic conditions are compared to validate the capability of SIS against the radiation frost. Second, a new hybrid system was proposed to improve the SIS effects. For these two purposes, three meteorological field campaigns were conducted on the fields of a vineyard and an orchard in Quebec, Canada. The air temperature was recorded with a fine spatiotemporal resolution min and spatial resolution in a synchronous mode of operation. In addition, the air temperature and humidity were recorded with mobile measurements and launching balloons to infer the general variations of temperature and specific humidity. Based on the topographic maps and field measurement, the several locations for SIS installation were determined. The high-resolution isotherms maps were used to evaluate the influence of SIS on nocturnal air-cooling. These results did not provide conclusive observational evidence that the SIS has impartial efficiency on nocturnal cooling. Indeed, a minor part of the SIS's exhausted flux was from horizontal direction, essentially due to land surface roughness. In contrast, a major part of the flux was from the upper layer around the SIS, which behaves like a funnel. The wind speed in the funnel's direction was 3 times greater than the wind speed in the horizontal direction. Therefore, the SIS was not able to remove a sufficient amount of cold air pool or stagnant air. To elucidate the second objective, a simple and affordable innovation with reliable testing was performed. A hot water SIS hybrid system (HWSH) was proposed to use the “forced convection” produced by the SIS to disperse a maximum of water vapors into the air in order to decrease the air dryness. In this system, hot water with a temperature of 60° C was deployed under the SIS. The observation during a radiation frost night demonstrated that, although the reference area (35 m away from the HWSH) was affected by frost, hybrid system's location area was not affected. However, there was no significant temperature gradient between two points, but the moist enthalpy calculated at 18 m altitude was higher above the HWSH in comparison to reference point. In conclusion, the main physical notion throughout this study is moist enthalpy, which depicts heat content. Nocturnal cooling rate decreased by increasing the moist enthalpy using HWSH system. This environmentally clean hybrid system has potential to be considered as an alternative to some frost protection methods such as heaters and fires burning. In addition, the importance of fine-scale measurement in agricultural field is highlighted in this study.

Type de document: Article
Mots-clés libres: radiation frost; Selective Invers Sink (SIS); enthalpy; nocturnal cooling; cold air drainage
Centre: Centre Eau Terre Environnement
Date de dépôt: 23 avr. 2018 20:31
Dernière modification: 23 avr. 2018 20:31
URI: http://espace.inrs.ca/id/eprint/3948

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