Kunelbayev M, Nurahmetova G
Calculation of efficiency tubular solar collector
The Kazakh State Women’s Training Pedagogical University
Republic of Kazakhstan, Almaty murat7508rambler.ru
Abstract
The this work of the basic characteristics of a solar power plant, as well as any
power installation, is efficiency which can be calculated by known techniques
or it is defined experimentally, on a parity it is useful for made thermal
energy and total intensity of sunlight. However the formula of calculation
of efficiency demands check since the
developed collector contains new constructive elements. Settlement and experimental
daily efficiency have satisfactory convergence within 7 % that testifies to
reliability of settlement formulas.
One of the
basic characteristics of a solar power plant, as well as any power
installation, is efficiency which can be calculated by known techniques or it
is defined experimentally, on a parity it is useful for made thermal energy and
total intensity of sunlight. However the formula of calculation of efficiency demands check since the
developed collector contains new constructive elements.
Average
for each business hour of efficiency of a collector can be defined from
expression:
(1.1)
Where:
Å - density of a stream of solar radiation on a collector surface;
Q - hour value of useful energy;
Sc - the collector
area;
The size of daily is not equal to average value of
efficiency and is defined in a kind:
(1.2)
Where
Qï - the full useful energy received in a collector for days;
Qï
- the daily sum of density of a stream of solar radiation.
According
to the equation of thermal balance for stationary conditions, the quantity of
useful energy received in solar collector is defined, how a difference between
size of falling solar energy and quantity ýíåðãèé lost in
environment:
(1.3)
Where
Sê - the absorber area (an absorbing surface);
Å - density of a stream
of total solar radiation in a plane
The
lecturer;
T1 - Ambient temperature;
T 2 - average temperature of the
absorbing panel of a collector.
In practice for calculation Qï the equation of Waller is used
Where FR - the factor
of heat removal equal
The
initial data for calculation of factor of thermal losses through ëàâñàíîâîå a covering for a concrete collector are following parameters:
|
d1,ì
|
d2,ì |
d3,ì |
d4,
ì |
T1,°Ñ |
T4,°Ñ |
|
|
|
|
|
|
0,036 |
0,05 |
0,080 |
0,080 |
28 |
53 |
0,22 |
0,260 |
0,185 |
297 |
25,7 |
Calculation
of factor of thermal losses for a tubular collector we will make óïðîùåííî, as for a pipe multilayered èçîëÿöèîííûì
the screen under the formula:
Having
substituted corresponding values of parameters of a collector in the given
formula we make calculations and we define that UL=4,9 Vat/m2.ch.
The
initial data for efficiency calculation is:
|
UL
Âò/ì2×ãðàä |
W,ì |
d2,
ì |
|
( |
Sê
ì2 |
Gêã/ñ |
|
4,9 |
0,1 |
0,04 |
300 |
0,89 |
1,68 |
0,018 |
)å
F¢
=1/[1+(UL/h)]=0,98. (1.7)
=0,806.
(1.8)
Hour
change of power consumption of a water tank in experiment it is defined under
the formula:
Qá=c (mâDÒâ
+mñDÒñ+míDÒí),
(1.9)
Where
with - the specific thermal capacity of water
equal 4,2 êZhou / (kg ×C °);
mâ, mñ, mí - weight of water according to the top, average and bottom zone
the tank, equal 51 kg;
DÒâ, DÒñ,
difference of water temperatures in corresponding zones
At
expense G=v × 
= 0,00128 kg/with results of
calculation thermal
productivity solar power plants and capacities solar collector are presented
according to drawing 1.
Drawing
1 - Dependence of calculation in hour efficiency solar collector from heating
time
Theoretical calculation
of average daily efficiency shows that:
=
(1.10)
Daily
average EFFICIENCY ÒÊ according to experiment according to drawing 2 it is equal:
(1.11)
Settlement
and experimental daily efficiency have satisfactory convergence within 7 % that
testifies to reliability of settlement formulas. It speaks the successful
constructive decision, application of mirror reflectors and cellular structure
of a transparent covering that confirms an initial hypothesis.
Literature
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Òåïëîìàññîîîáìåí. Ìîñêâà.- Ýíåðãèÿ, 1978
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USA. New York. 1982.
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Panel
Report, 1972, Available from National Technical Information Service,
Springfield,
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