Paper 7: Volume 4 No.4 March 2006 Edition
Effect of Pre-Cooling on
Natural Ventilation of Buildings
with Multiple Stacks
T
Chenvidyakarn
BP Institute
for Multiphase Flow,
University of Cambridge
,
UK
School of the Built Environment,
University of Nottingham
,
UK
Abstract
Chenvidyakarn
et al (2004a) investigated the natural ventilation of an occupied
open-plan space, which was connected to an exterior through two stacks and
a low-level vent. Occupants
located at an intermediate level between the stacks and the low-level vent
acted as a uniform source of heat, providing buoyancy to drive the
ventilation. Their work showed
that these conditions could produce up to three steady state ventilation
regimes. In the first regime,
the bottom opening and the shorter stack acted as inflow vents, while the
taller stack acted as an outflow vent.
In the second regime, the bottom opening acted as an inflow vent,
while both stacks acted as outflow vents.
In the third regime, the bottom opening and the taller stack acted
as inflow vents, while the shorter stack acted as an outflow vent.
The present work considers the situation in which a passive cooling
system, such as thermal mass, is connected to the low-level vent to
pre-cool supply air, as may be required in low-energy buildings operating
in summer or warm climates. Using
a combination of laboratory experiments and a theoretical model, the paper
explores how the pre-cooling affects the ventilation and steady state
temperature in the space under the three ventilation regimes.
The study shows that sufficiently large pre-cooling can stall the
inflow through the bottom vent in the first and third regimes, or the
outflow through the shorter stack in the second regime.
Depending on the ventilation regime and resultant flow rate, an
increase in the pre-cooling can lead to either a decrease or an increase
in the temperature in the occupied zone.
To achieve desired ranges of temperatures and ventilation rates
while minimising energy use, an appropriate range of pre-cooling is
required. The paper shows how
to determine such an appropriate range of pre-cooling for a given
ventilation regime.
Key
words: passive cooling,
thermal mass, multiple steady states, natural ventilation, multiple
stacks, experimental measurements, theoretical model.
References
Cengel
YA and Turner RH: (2001) “Fundamentals of thermal-fluid sciences”.
McGraw-Hill.
Chenvidyakarn
T and Woods AW: (2004a) “Multiple steady states in stack ventilation”,
Building and Environment.
40, (3), pp399-410.
Chenvidyakarn
T and Woods AW: (2004b) “The control of pre-cooled ventilation”, Building
Services Engineering Research & Technology.
25, (2), pp127-140.
Chenvidyakarn
T and Woods AW: (2004c) “Top-down pre-cooled natural ventilation”, Building
Services Engineering Research & Technology. 26, (3),
pp181-193.
Churchill
SW: (1976) “A comprehensive correlating equation for forced convection
from flat plates”, American
Institute of Chemical Engineers Journal. 22,
p264.
Churchill
SW and Ozoe H: (1973) “Correlations for laminar forced convection in
flow over an isothermal flat plate in developing and fully developed flow
in an isothermal tube”, Journal of
Heat Transfer. 95, p46.
CIBSE:
(1988) CIBSE Guide, Volume B:
Installation and Equipment Data. Staples Printers (
St Albans
).
Gladstone C and Woods AW: (2001) “On buoyancy-driven natural
ventilation of a room with a heated floor”, Journal
of Fluid Mechanics. 441,
pp293-314.
|
IJV Volume 4 No 4
Contents
Paper
1: Interacting Plumes
Paper
2: Outlet C-Values
Paper
3: Wind Driven Flow
Paper
4: CFD & Full-Scale
Paper
5: Tomography
Paper
6: Time Varying
Paper
7: Pre - Cooling
Paper
8: Wind Catcher
|
