On the Subsurface Cold Air Circulation Observed at Onneyu-Tsutsujiyama, Rubeshibe-cho, Hokkaido

In hot summer, the sun rays strike the roof surface and heat up the enclosed attic. Passive vents (Soffit or Gable) allow some circulation of fresh air. Presently, in India, passive Whirlybird is predominantly used for ventilation purposes, which spins and sucks up the warm air and forces it out upwards through the vent on the roof. Since it depends mainly on the natural wind velocity, it’s efficiency to cost ratio is very low. Also, the accumulation of dust particles has a deleterious effect on the performance and life of the unit. Hence, in this work, a roof top solar ventilator has been designed and developed at low cost to address the above-mentioned problems. This unit has a high-performance brushless DC motor, an adjustable solar panel to achieve optimal solar exposure and it blends seamlessly into roof. The solar panel powers the fan through the motor, thereby increasing the air circulation through the vent. This increased air circulation provides the required pressure to force the hot air out from the attic. During hot summer, the difference in temperature between the floor and the ceiling can reach 10–15 °C, leading to a constant heat pile up in the attic and this system can limit the temperature of the attic to 40°C. In winter season, moist air present inside the house warms up, rises and collides with the cold air entering through the roof. This provides a mixed circulation that prevents the cold air from entering the roof and also reduces freezing of snow on the roof surface. Further, it keeps the inside space cooler and drier. Since this ventilator operates on renewable energy source, it is a simple and feasible solution that is environmentally friendly at low-cost. This provides healthy, energy efficient homes and work spaces as it reduces the usage of air conditions and heaters. A comparative study on the performance, life and cost of both the existing and the newly developed ventilators has been made and the same is reported.

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Jambu drying with cold air circulation

Journal of bioenergy and Food Science ◽

10.18067/jbfs.v2i2.28 ◽

2015 ◽

Vol 2 (2) ◽

pp. 46-54

Author(s):

Alan Franco Barbosa ◽

◽

Tatiana Valesca Rodriguez Aliceo ◽

Fernando Morais Rodrigues ◽

Liliane Garcia da Silva Morais Rodrigues ◽

...

Keyword(s):

Cold Air ◽

Air Circulation

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Ice in caves and its effect on thermal inversion and permafrost in the case of the Velika ledena jama v Paradani, Smrekova draga and neighbouring dolines

Acta Carsologica ◽

10.3986/ac.v50i2-3.10495 ◽

2021 ◽

Vol 50 (2-3) ◽

Author(s):

Andrej Mihevc

Keyword(s):

Sea Level ◽

Surrounding Area ◽

Cold Air ◽

Thermal Inversion ◽

Average Temperature ◽

Cave Entrance ◽

Air Temperatures ◽

Winter Cold ◽

Air Circulation ◽

Similar Development

In the Velika ledena jama v Paradani, in the karstic blowholes on the slopes of Smrekova draga and in the nearby dolines I measured and interpreted air temperatures and the effect of the summer outflow of cold air from them into the surrounding area. In winter, cold air enters the cave, radically cooling the entrance part of the cave, where for this reason there is permanent cave ice. The summertime circulation is reversed: emerging from the inner part of cave, which has an average temperature of around 4° C, is air which only when it transits through the sub-cooled entrance part is then cooled to around 1° C. This air comes to the surface and in the hollow at the cave entrance maintains a distinct thermal inversion during the warm part of the year. There is a similar air circulation and similar development of annual temperatures observed at the vents, where cave air emerges through rubble spread over cave entrances on slopes or at the bottom of dolines. The stable summer air temperatures of around 1° C in the vents where I conducted measurements indicate that underneath them there is also permafrost or sub-cooled rock and permanent ice. This is created and preserved, just like in the caves, due to the advection of cold air in winter. In Trnovski gozd, such karstic permafrost is found at an altitude of 1,100 m above sea level. The outflow of cold air from the vents in the summer, just like inside the cave, causes a distinct thermal inversion in dolines on the surface.

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