ISSN 0003-701X, Applied Solar Energy, 2018, Vol. 54, No. 2, pp. 95–98. © Allerton Press, Inc., 2018.
Original Russian Text © Yu.K. Rashidov, 2018, published in Geliotekhnika, 2018, No. 2, pp. 26–30.
Calculating the Hydrodynamic Characteristics of the Active Section
of the Self-Draining Solar Loop of a Heating System
Yu. K. Rashidov
Tashkent Institute of Architecture and Civil Engineering, 100011 Uzbekistan
Received February 15, 2017
Abstract—The article considers experimental studies of the hydrodynamic characteristics of the active section
of the self-draining solar loop of a heating system. This element is designed as a flow constrictor referred to
as Ventury tube, with a high degree of f low constriction of 2–5 in the region with strong viscous resistance.
The experimental data are processed in a criteria form, the general type of which is obtained by dimen-
sional technique and compared with data from other authors. The obtained criteria dependences can be
used to calculate the hydrodynamic characteristics of the active section of the self-draining solar loop of a
Studies [1–3] consider the description, operational
principle, energy efficiency, and calculation of the
self-draining solar loop of a water heating system with
an active element designed as a flow restrictor, i.e., a
This study is aimed at finding dependences to calcu-
late the hydrodynamic characteristics of the active sec-
tion of the self-draining solar loop of a heating system.
It is a difficult task to calculate the hydraulic resis-
tance of the active element designed as a Ventury tube
for its known geometric dimensions. The mode of
action of the resistance force is so complex that there
is still no accurate technique for finding the resistance
coefficient ζ. The values of the resistance coefficient
required in engineering design are most often given in
references as average figures or in tables with experi-
mental data for different combinations of geometric
dimensions of transition. In this case, the only possi-
ble way to calculate ζ for Ventury tubes is to find the
necessary data experimentally and then generalize the
results to the form of criteria.
Let us now use the dimensional technique to derive
the criteria equation for pressure losses in a Ventury
tube. These losses can be represented as a power func-
tion of the following independent variables:
Now let us express the dimensions of the variables
from (1) in the MLT system of three quantities : M
is mass, L is length, and T is time (Table 1).
We substitute in (1) the symbols of the variables for
Uniformity of Eq. (2) with respect to the dimen-
sions is attained when the following correlations
between the exponents are met:
Now let us simplify correlations (3) and express
them via a, b, d as
In light of (4), dependence (1) is written as
Having integrated terms with equal exponents, we
obtain the dependence of five dimensionless sets:
Dimensionless sets (6) are the commonly known
Euler (Eu) and Reynolds (Re) criteria. In the light of
this, dependence (6) can be written as
=ϕ ρ μ δ
abcd e f K
[( ) ,( ) ,( ) , , , , ].
LT ML ML T L L L L
−= − − + +
:1 3 .
=− − − −
=ϕ ρ μ δ
pW d D
( ) ( ) ( )
SOLAR POWER PLANTS
AND THEIR APPLICATION