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THERMAL EFFICIENCY OF THE SOLAR HEATING SYSTEM BASED ON FLAT REFLECTORS INSTALLED..,
Imomov Sh. B., Kodirov I. N., Mamatova M. Sh., Panjiev J. E.,
Karshi Engineering and Economic Institute
Uzbekistan
E-mail: [email protected]
THERMAL EFFICIENCY OF THE SOLAR HEATING SYSTEM BASED ON FLAT REFLECTORS INSTALLED FROM THE NORTHERN SIDE OF THE BUILDING
Abstract: The Considered system three flat reflectors, set up with north sides of the building, in passive system of the solar heating. They Are Determined радиационный mode and heat efficiency flat reflector, providing arrival to solar radiation in heated premises through lightopenings with north sides of the building.
Keywords: solar radiation, the heating season, the northern light aperture, heat balance, flat reflector.
Traditionally, heat collectors (solar collectors, air heaters) in solar heating systems have a strictly directed southern orientation. Since heat receivers are integral architectural and constructive parts of the building, in many cases urban planning, architectural, relief, and other reasons, the southern orientation of the building or the actual heat receiver is not always possible.
The application of a system of flat reflectors, installed on the north side of the building, allows to expand the possibilities and options for using solar energy, to increase the density of solar radiation in the plane of the heat receiver [1].
To determine the thermal balance and temperature of the system, the building + reflectors were previously installed:
1) the radiation and shadow modes of a system of plane reflectors [2];
2) thermal and exergetic efficiency of the system of flat reflectors [1, 3];
3) the model of the heat balance of the building + reflectors system is compiled.
When preparing the heat balance, the following conditions are accepted:
- interacting elements: internal and external air environment, enclosing structures, a system of flat reflectors;
- the influence of interior items on the heat balance of the premises is not taken into account;
- walls, ceiling ceiling, floor spaces are considered as multi-layer, windows and doors - as single-layer fences;
- the walls, combined with the control and tambour rooms, are considered as multi-layered fences with air interlayer;
- with respect to the environment, the building is treated as a stand-alone facility.
In general, the heat balance of a room is determined by the equation:
O-ab ^^rnn; ( 1)
where Qab - is the total absorbed heat of the solar radiation, in the room, W;
Qhl - total heat loss in the room, W.
Section 4. Technical science
The total solar radiation that has passed into the is the absorption coefficient solar radiation heat re-room: ceiver.
Op = Op, + Qp,. (2)
The total solar radiation entering through the Qpi window and the light-hole Qp3, is determined by the formulas:
Qps = (Sp, + Dpi) F; % = (Sp3 + Dp3) F3;(3)
Where S . and D are the density of the trans-
pi p '
mitted direct and scattered solar radiation, W/ m2; F5 and F3 are the area of the glazed window surface and light, m2.
Direct solar radiation in the lightguard comes from the reflectors:
SP3 = Spo + 2 Spi sinr; (4)
Where S , S is the direct solar radiation com-
p0 pi
ing from the mean and right + left reflectors, W/ m2; Y - angle of incidence of rays on the plane of the heat receiver, deg.
Solar radiation entering the room is absorbed, internal surfaces and heat sink:
Total heat loss in the room:
Qhi = Qhj+ Qa>
(6)
QbS - Ac Ops' Qab4 - Am Qs'
(5)
Where Ac - is the reduced absorption coefficient of solar radiation internal surfaces of the room; A -
Where Q^ - heat loss through fences, W; Q -heat loss infiltration of air, W.
The use of a system of reflectors installed on the north side of the building provides an increase in the density of solar radiation intake in the plane of the heat receiver by a factor of 1.7-2.
The temperature regime of the room is considered in the period of the least arrival of solar radiation (the average values for 19-22 December 2006) and the period of the lowest outdoor temperatures (January 20-23, 2007) in the city ofKarshi. In the period from 10-11 hours and up to 15 hours the temperature of the air in the room exceeds the normative value t =
a
20 °C. During this period, it becomes necessary to accumulate excess heat from solar radiation. The study of the room temperature in the building + reflectors system allows us to predict the effectiveness of the system of reflectors installed on the north side of the building during the heating season.
References:
1. Imomov Sh. B., Kim V. D., Khayriddinov B. E. Thermal efficiency of flat reflectors installed on the north side of the building, in passive solar heating systems // Heliotechnics. - T.: Fan. - 2003. - No. 4. -P. 39-44.
2. Imomov Sh. B., Kim V. D., Khayriddinov B. E. Shading of flat reflectors in passive solar heating systems. // Heliotechnics. - 2003. - No. 2. - from. P. 50-53.
3. Imomov Sh. B. The exergic efficiency of the system of flat reflectors, installed from the north side of the building, // Fan, ta-karket va shoshar. Ilmiy-amaliy conference materialary. Karshi - 2008. Nasaf, from. - P. 245-247.
