Tag Archives: radiation

2069-2075 P. Kic
Electric infrared heating panels as an alternative source of heating for greenhouses
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Electric infrared heating panels as an alternative source of heating for greenhouses

P. Kic

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamycka 129, CZ165 21 Praha 6, Czech Republic
Correspondence: kic@tf.czu.cz

Abstract:

The aim of this article is to show the possibilities of supplementary heating of greenhouses. There was used for this research an electric infrared heating panel ITA 700. The average total power was 630.8 W in laboratory measurements, of which 504.3 W has been transferred by the front part of the panel, of which 267.2 W has been transmitted by radiation. The total radiation efficiency of the front part was 42.4%. Similar measurements have been carried out in an experimental greenhouse (length 24 m, width 3.5 m). Approximately 448 W of average total power 603.7 W has been transferred by the front part of the panel, of which 159 W has been transferred by radiation. The total radiation efficiency of the front part was 26.3%. Differences between measured surface temperatures confirmed the influence of panel radiation on the flower bed. The average temperature in the soil (9 °C) shows that the influence of heating is mainly on the surface of the flower bed, where it could protect cultivated plants during the lowest temperature period. The obtained results can be useful for choosing suitable panel parameters for the placement in small horticultural or hobby greenhouse.

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237-244 M. Zajicek, and P. Kic
Heating of large agricultural and industrial buildings
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Heating of large agricultural and industrial buildings

M. Zajicek¹,* and P. Kic²

¹Institute of Information Theory and Automation, The Academy of Science of The Czech Republic, v.v.i.; *Correspondence: zajicek@utia.cas.cz 2Czech University of Life Sciences Prague, Faculty of Engineering, Czech Republic

Abstract:

This paper presents the results of the simulation calculations used in the selection and design of an appropriate method of heating of large buildings for agricultural or industrial purposes. These halls are characterized by a large built-up area, large room height and high consumption of energy for heating. The aim of the simulation calculation was to find a way of heating, which leads to a reduction in energy consumption while maintaining the required thermal comfort of indoor environment. The calculations were performed using the CFD software ANSYS-Fluent. For comparison of variants, a 3D model was used, including a heat source, natural convection and heat transfer through surrounding structures. The results of the thermal comfort of the working environment in the level of people or the growing zone of plants or the storage space for goods were mainly studied. The second area of interior space, especially important in terms of heat losses, is the level of the ceiling. The results of the calculations provide a detailed analysis of the vertical temperature profiles and the effect of the surrounding walls surface temperature on the thermal state of an indoor environment. The created model was verified according to the results of experiments in large buildings equipped with different heating systems. Based on the results of the simulation calculations and according to the results of experimental measurements, radiant heating method seems to be the suitable heating system solution for studied types of buildings.

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255-261 J. Palabinskis, A. Aboltins, A. Lauva and N. Karpova-Sadigova
The comparative material investigations of solar collector
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The comparative material investigations of solar collector

J. Palabinskis, A. Aboltins, A. Lauva and N. Karpova-Sadigova

Latvia University of Agriculture, Liela iela 2, Jelgava, LV – 3001, Latvia;e-mails: Janis.Palabinskis@llu.lv; Aivars.Aboltins@inbox.lv; Aigars.Lauva@inbox.lv;Nadezda.Karpova@llu.lv

Abstract:

The prices of energy resources used for grain drying are increasing year by year. In order to reduce costs, research into methods of saving energy in grain drying is in progress in the Research Laboratory of Grain Drying and Storing of the Faculty of Engineering, the LUA. Equipment for experimental research into the materials of solar collectors was built in the research laboratory for research purposes in 2005. The construction of the equipment allows for simultaneous comparative studies of two materials. The experimental data are metered and recorded in the electronic equipment REG. Cell polycarbonate PC (bronze, henceforth referred to as polycarbonate) with absorbers steel-tinplate and black-coloured wood was researched in comparison to the polyvinylchloride film (henceforth referred to as a film). The researches were made with different air velocities. The air heating degree ∆T in the solar collector is dependent on solar radiation I and air velocity v in the solar collector. In the experimental equipment, which is 1.5 meters in length, the air was heated to ∆T = 6°C at the velocity v = 0.5 m s-1.For theoretical investigation of the air heating power in solar systems the mathematicalmodel is applied; the solution can be used for estimation of different materials /absorbents/ and their heat source.

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263-269 I. Pelēce, U. Iljins, and I. Ziemelis
Theoretical calculation of energy received by semi-spherical solar collector
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Theoretical calculation of energy received by semi-spherical solar collector

I. Pelēce, U. Iljins, and I. Ziemelis

Latvia University of Agriculture, Liela str. 2, Jelgava LV3000; e-mail: ilze.pelece@llu.lv

Abstract:

Solar energy is widely used as an environmentally friendly energy source in many countries, Latvia among them. However, geographical and climatic conditions in Latvia, low maximal height of the sun and maximal irradiance, as well as comparatively great cloudiness, present particular challenges. Long days and the long path of the sun in summertime means traditional constructions of solar collectors are not efficient enough for use in Latvia.A new principle in the construction of the solar collector has been developed: a solarcollector with the absorber in the shape of a semi-sphere. It has advantages in comparison with the traditional fixed flat-plate model: it effectively receives both direct and diffuse solar radiation all day. In addition, it is durable against the destructive impact of the wind.This article reports theoretical calculations of received energy which have been carriedout, based on continual visible position of the sun in the sky. Results of these calculations have shown that on a clear sunny day, a semi-spherical collector with the base of 1 m2 receives 1.3 times more energy than a flat-plate collector positioned at optimal (approx. 40o) inclination, and 1.6 times more than the flat horizontal one. In cloudy conditions, the difference is greater because of greater diffused radiation.Such a semi-spherical solar collector has been constructed. Experimental investigation ofthe received heat energy from the semi-spherical solar collector will be carried out in field conditions this summer.

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