Theses /
engineerings sciences
Elizabeth S. Gusentsova, Yana A. Gusentsova,
Alim A. Kovalenko
East Ukrainian National Dall’s University,
Lugansk, Ukraine
The criteria of rational application of
overflush ventilation
Abstract: On the basis of stability analysis of the stratified flows the criterion of the
rational use of overflush ventilation is offered.
Overflush ventilation it is a
tool of requisite high-quality air in the ventilated area. Technology of
overflush ventilation takes advantage
before mixing ventilation in the meeting halls, dinner halls, audiences
and other apartments with the high ceilings.
Since a middle eightieth it finds a wideuse, especially in the
Scandinavian countries. In the systems of ventilation of such type under the
action of raising force stratification
of air is made on the height of apartment, due to what indexes of microclimate
in the attendant area of apartment is high-quality, than in the systems with mixing
ventilation.
Such phenomena, as a temperature gradient, levels of speed in separation
in stream, levels of stratification
and, in the end efficiency of ventilation, can be appraised by the criterion of
Archimedes [1, 2].
The empiric criterion of
typeselection of the ventilation system
is offered in [1]. It application is grounded at the considerable values
of air renewal, heat surplus in the
ventilated area, realization of serve of intensive air flow in small apartments. By the basic lack of
its application, as our researches showed, there is possibility of appearance
of draughts and turbulence of air near
floor.
The use of
overflush ventilation, foremost, is
related to stability of gas flow in relation to small indignations. Our
researches allowed to offer a criterion, that define frames of the rational use
of such type of ventilation.
For the
stratified flow (ignoring diffusive processes, because a flow is laminar),
stability of flow depends on the row of aerodynamic parameters (air density,
speed of its flow, temperature gradient) and geometry of the ventilated area.
Using
Khantli’s addition [3] let enter the units class of the systems 
, in which two independent air density. The system of units of this
class in general case must contain dimension factor [ê] = 
, (i.e. air density and its changes). These parameters are practically
independent for vent system, therefore [ê] will eliminate from a number
determining sizes.
We will
represent the desired dependence as
(1)
All
five arguments of dependence have independent dimensions. Applying π -theorem
(2)
we will get one of
possible values of function of f within a dimensionless multiplier within the
framework of dimensional analysis
(3)
On a
structure the taught function corresponds to the criterion of Richardson, in
accordance with which a flow is steady at
V > 1/4 .
Modifying
it for the terms of overflush ventilation
(4)
where :
, 
, 
- accordingly
perimeter, area and volume of the ventilated area;
- multipleness of
ventilation;
we will get the
criterion of the rational use of overflush
ventilation
(5)
Verification
of this on the existent systems of
overflush ventilation confirmed the
rightness of their use.
Literature:
1.
Alamdari F. Displacement
Ventilation and Cooled Ceilings. Proceedings of Roomvent 98.
Stockholm, 1998.
2.
Ãóñåíöîâà ß.À. Ñèñòåìû âåíòèëÿöèè (Òåõíèêî-ýêîíîìè÷åñêèå õàðàêòåðèñòèêè)
/ ß.À. Ãóñåíöîâà, Ê. Í. Àíäðèé÷óê, Ì.
Å. Øïàðáåð.- Ëóãàíñê.: Èçä – âî ÂÍÓ èì. Â. Äàëÿ, 2005. – 32 ñ.
3.
Ãóñåíöîâà ß.À. Ìàòåìàòè÷åñêîå
ìîäåëèðîâàíèå ñèñòåì âûòåñíÿþùåé âåíòèëÿöèè / Ãóñåíöîâà ß.À. - Õàðê³â.: Ñõ³äíîºâðîïåéñüêèé
æóðíàë ïåðåäîâèõ òåõíîëîã³é, 2008 - ¹ ¼ (31).- Ñ. 9-11.