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The Development of Passive Downdraught Evaporative Cooling Systems Using Porous Ceramic Evaporators and their application in residential buildings

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This paper seeks to demonstrate that passive evaporative cooling using porous ceramic components can achieve comfort conditions inside residential buildings in hot-dry climates, and that the components can be integrated simply and effectively within existing 60s and 70s housing buildings now due for refurbishment. A case study building in South of Spain (Seville) was investigated in order to performance test different constructional and engineering solutions for the design of the system prototypes to meet different spatial and energy requirements. A performance analysis of the case study building assessed the viability of the proposed system in housing buildings and the related energy and CO 2 savings.
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Plea2004 - The 21th Conference on Passive and Low Energy Architecture. Eindhoven, The Netherlands, 19 - 22
September 2004 Page 1 of 6
The Development of Passive Downdraught
Evaporative Cooling Systems Using Porous Ceramic
Evaporators and their application in residential
buildings
Rosa Schiano-Phan1
1 School of Architecture, Environment and Energy Programme, Architectural Association, London, UK
ABSTRACT: This paper seeks to demonstrate that passive evaporative cooling using porous
ceramic components can achieve comfort conditions inside residential buildings in hot-dry climates,
and that the components can be integrated simply and effectively within existing 60s and 70s
housing buildings now due for refurbishment. A case study building in South of Spain (Seville) was
investigated in order to performance test different constructional and engineering solutions for the
design of the system prototypes to meet different spatial and energy requirements. A performance
analysis of the case study building assessed the viability of the proposed system in housing buildings
and the related energy and CO2 savings.
Conference Topic: 2 Design strategies and tools
Keywords: energy, passive evaporative cooling, porous ceramic
INTRODUCTION
The Energy Consumption in residential and
commercial European buildings represents 41% of
Europe’s energy budget. A proportion of this is used
for cooling; this varies by country and building type
[1]. The environmental impact of conventional air-
conditioning is represented by CO2 emissions from
fossil fuel and, to a lesser degree, by
chlofluorocarbons (CFCs) leaking from compressors.
This contributes to the depletion of the ozone layer
and consequently increases the greenhouse effect
and climate change.
Passive Evaporative Cooling is a cooling method
that uses the evaporation of water to cool the air. Its
application is based on the availability of water
resources and use of draughts into the building. The
use of clay and porous ceramic in passive
downdraught evaporative cooling has a track record
in the vernacular architecture of many hot and dry
regions of the world. Wind towers, opening systems,
fountains, pools and vegetation were the compositive
elements of such cooling systems, used and
combined according to different needs and local
tradition (Fig. 1).
Nowadays the development of an ‘innovative’
passive evaporative cooling system is required to
provide hot-dry countries with a low-tech and passive
alternative to conventional air-conditioning; a system
which could make full use of the local climatic
potential and be easily integrated into modern
construction. Desert Coolers are and have been for
decades a popular low-cost and compact cooling
solution in many hot-dry countries. However, they are
not building integrated and their main disadvantages
are noise and energy consumption from the fan. Also,
the use of wet cellulose pads as porous media can
easily promote the growth of harmful bacteria. The
use of porous ceramic components in evaporative
cooling systems can be potentially combined with
more functions, providing comfort conditions and
improving the performance of the building envelope at
the same time. The advantages of using porous
ceramic evaporators as opposed to other spray based
direct evaporative systems are: no use of high
pressure systems, no water treatment required, and
no risk of microbiological contamination (Legionella
disease).
Figure 1: Muscatese evaporative cooling system
(source: A. Cain et al.)
An EC funded research (Evapcool) [2] developed
porous ceramic components for passive evaporative
cooling systems in non-domestic buildings (Fig. 2). It
concluded that it is possible to effectively integrate
Hot air escaping from high
claustre work opening
Shutters control ai
r
movement
Sun Shade
Porous water pot
Evaporative cooling as
breeze passes over surface
of porous water po
t
Plea2004 - The 21th Conference on Passive and Low Energy Architecture. Eindhoven, The Netherlands, 19 - 22
September 2004 Page 2 of 6
modular porous ceramic evaporators in different
building components, generating comfort conditions
into the indoor space. The research showed that the
cooling capacity of the systems is dependent on the
ceramic surface area and on the dry to wet bulb
temperature depression [3]. A case study project in
Iran was performance tested and it was predicted that
comfort conditions could be achieved for
approximately 90% of the time during the summer [4].
The current doctoral research builds on the EC
research project and aims to investigate the
application of the Evapcool system in the residential
sector with particular reference to a case study
building in Seville, South of Spain. This paper focuses
on the building integration of the proposed system in
apartment blocks and its performance analysis.
Figure 2: Physical model of types of integration of
the Evapcool system
2. BUILDING INTEGRATION IN HOUSING
2.1 Housing in Spain
The increasing demand for low cost residential
buildings and the scarce availability of land call for a
sustainable approach to be adopted in the
development and design of high density housing
schemes as well as the retrofit of the existing housing
stock. Statistical data on the housing stock in Spain
show that the majority of buildings are residential [5].
Data on age of the housing stock for Spain [6] shows
that in the town of Seville nearly half was built
between 1960 and 1980 with 23% built in 1961-70
and 16% in 1971-80. These buildings are often
characterised by a very poor quality of the building
envelope and a poor performance of the indoor
environmental control systems.
It is reported [7] that, although in Spain less than
10% of homes have air-conditioning systems, 71% of
the installed capacity is in the residential sector. The
EERAC (Energy Efficiency of Room Air-Conditioner)
study [8] assessed that the average number of hours
of operation of residential air-conditioning in South of
Spain (Murcia) was equivalent to 1049 hours/year
compared to offices with 1402 hours/year and shops
with 2157 hours /year.
2.2 Principles of Integration
The Evapcool system can be integrated in
different elements of the building envelope [9]. The
most effective option is the wall integrated system
where a column of modular porous ceramic
evaporators is integrated into a perimeter cavity wall.
This is intercepted by a draught of hot-dry air coming
from outside via a high level controllable opening. The
air in contact with the wet surface of the ceramic
evaporators becomes heavier and cooler. It then gets
delivered by negative buoyancy into the indoor space
via a low level opening (fig. 3a). The use of a room
integrated fan might be necessary in still conditions to
assure a constant air flow. Another option for
integration is the roof system, where banks of ceramic
evaporators are integrated in a wind-catcher
termination (fig. 3b). The system can be sized, and
the number of ceramic modules increased, according
to the cooling requirement of the space.
Figure 3: Principles of integration of the system
The Evapcool System can be integrated in any
situation where there is a perimeter wall or a roof and
it mainly operates at room level. This makes it very
versatile and suitable for a wide range of building
typologies. However, there are limitations to be taken
into account when trying to integrate the Evapcool
System (ES) in the building. By looking at the
characteristics of existing housing buildings and
specifically at the typology of apartment blocks, these
limitations can be grouped in the categories of
planning, configuration and construction.
In deep plan buildings only the perimeter rooms
can adopt the Evapcool wall system. For the core
areas, which are usually constituted by corridors,
lobbies or general circulation spaces, mitigation
techniques and alternative cooling solutions can be
found. In apartment blocks the floor level where the
perimeter room is located is an important factor in the
sizing of the system. The ground floors, usually
affected by problems of noise, pollution and often
security (Fig. 4) can benefit from the installation of the
ES as the ingress of ‘fresh’ air through a wet cavity
wall system induces particles and dust to be filtered
and noise to be attenuated. In the intermediate floors,
as well as in the ground floors, the reduced
availability of perimeter space is compensated by
reduced envelope gains (solar and conductive) and
hence reduced cooling requirements. These are
instead higher in the top floor apartments where the
roof can be used as an additional surface for the
integration of the evaporative system (wind-catcher).
Plea2004 - The 21th Conference on Passive and Low Energy Architecture. Eindhoven, The Netherlands, 19 - 22
September 2004 Page 3 of 6
Mitigation techniques, like night time ventilation, solar
control and improvement of the building envelope
results in a considerable reduction of the cooling
loads which can often be absorbed exclusively by the
wall integrated ES.
Figure 4: Strategy of Integration for existing
apartment blocks
The type of construction can influence the design
and integration of the system. Some adjustments in
the specification of the system components and their
configuration can be made according to the
construction of the building envelope. These relate to
the amount of space that the system occupies and its
relationship with the perimeter structure. The ceramic
modules have been designed mainly to be integrated
in a concrete frame construction. This assumes the
partial reconstruction of the infill wall masonry and the
creation of a new cavity wall where the system can be
located (Fig. 5).
Figure 5: Wall Integration - partial removal
When this is not possible a diaphragm wall can be
created on top of the existing perimeter wall (Fig. 6).
This will of course reduce the indoor floor area but it
does not create any major disruption on the outer
façade.
Figure 6: Wall Integration - addition
Where a balcony or terrace is available, the cavity
wall could be built on the outside with no loss of
indoor floor space (Fig. 7). In structural terms, the
Evapcool system constitutes approximately 10% of
the dead load of a concrete frame structure per linear
meter. This implies that for existing buildings a
structural check should be undertaken to verify that
the structure can absorb the additional load.
Figure 7: Wall Integration - external
3. PERFORMANCE ANALYSIS OF A CASE
STUDY BUILDING IN SEVILLE
3.1 Assumptions and methodology
A case study building in the urban context of
Seville was identified in order to investigate the
building performance of the proposed system. The
building is a block of apartments in the housing
development of “Barriada Los Diez Mandamientos”
designed by the Architect Luis Recasens Mendez-
Quipo de Llano in 1958-64 (Fig. 8). The analysis
aimed at assessing the performance of the building in
winter and summer and the cooling loads in the
different rooms. The modelling exercise looked at the
original status of the building as designed in 1958 and
introduced a series of measures for the improvement
of the building envelope and the reduction of the
cooling requirements. Amongst those measures, the
use of porous ceramic evaporators was tested in
order to meet the remaining cooling loads in summer.
The performance of the building envelope was also
tested to evaluate if the integration of the ceramic
Plea2004 - The 21th Conference on Passive and Low Energy Architecture. Eindhoven, The Netherlands, 19 - 22
September 2004 Page 4 of 6
panels could improve the quality of the building fabric
and reduce the heating loads in winter.
Figure 8: Case study building, Seville (source:
Mosquera Adell, E. et al.)
The performance analysis was undertaken using
dynamic thermal simulation [10]. A parametric
analysis simulated gradual improvements of the
building envelope and the introduction of ventilation
and solar control strategies to improve comfort
conditions both in summer and winter.
The model specifically looked at the performance
of a typical top floor apartment (Flat A) and an
intermediate apartment (Flat D). This enabled to
appreciate the different cooling requirements due to
configuration and orientation.
3.2 Thermal modelling analysis
The simulations were run for a typical hot summer
day (day 215 – August 3rd) and a typical winter
season (October to April). The results were
expressed as temperatures profiles, cooling loads
and annual heating demand. The parametric study
showed the presence of residual cooling loads not
met by the selected mitigation strategies. This
constituted a case for the adoption of the proposed
passive evaporative cooling system (Evapcool).
The nominal cooling power of the proposed
system was first simulated as a cooling system with a
set point of 26degC. This simulation modelled the
equivalent cooling energy to be met by the Evapcool
System in summer to keep a temperature of 26degC.
This is an obvious oversimplification but necessary for
a preliminary sizing of the system. This assumption
was based on the analysis of the weather data [11] of
Seville (fig. 9) where the potential delivery
temperature of the evaporative system is below
26degC for 95% of the time in summer. The delivery
temperature was calculated as 2degC above the wet
bulb temperature [12].
0
5
10
15
20
25
30
35
40
123456789101112
Months
Temperature (C)
DBT WBT Depression
Figure 9: Annual weather data for Seville
The results showed that the cooling demand of
the top floor was higher than the intermediate floor.
However, the effect of high internal gains and large
glazing areas induced higher cooling loads in the
intermediate floor living room than in the top floor one
(Fig. 10). Conversely, the top floor South bedroom
had higher cooling demand than the intermediate
floor bedroom and this was mainly due to higher
conductive gains through the roof.
Peak Cooling Loa ds for top (Flat A) and intermdiate (Flat D) floor apartments
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
A Bed
NW
A Livi ng A
Kitchen
A Bed
SW
A Bed
W
D Living D
Kitchen
D Bed
SW
D Bed
N1
D Bed
N2
D Bed
N3
D Bed S
W/m2
Figure 10: Predicted cooling loads
The cooling demand of each room was translated
into the area of Evapcool system necessary to keep
the indoor temperature below 26degC by using the
Performance Chart below (Fig. 11).
Specific Cooling Power per Meter Width and per Meter Hight in
Function of the Temperature Difference
0
10
20
30
40
50
60
70
80
012345678910111213141
temperature difference (Tdb - Twb) [K]
spec. cooling power per meter width
and per meter hight [W/Km2]
h = 1.0 m
h = 0.6 m
h = 0.4 m
h = 0.2 m
Figure 11: Specific cooling power of the ES
The chart [13] gives the specific cooling power of
different heights of Evapcool Systems expressed as a
function of the ambient dry to wet bulb temperature
difference. By entering the temperature differential at
the peak hour of the analysed typical summer day it is
possible to identify the specific cooling power for each
height of the system. For example given a target
cooling power of 610W for the top floor living room
and chosen a system height of 1m the required
system’s width is 1.4m. This is derived from the
formula:
Qt [W] = Qs x T x h x w [W/K.m2 x K x m x m];
Where ‘Qt’ is the total cooling requirement; ‘Qs’ is
the specific cooling power (derived from the chart);
T’ is the dry to wet bulb temperature differential
(derived from weather data and entered on the x axis
of the chart); ‘h’ is the height of the Evapcool System
and ‘w’ is the width of the ES (Fig. 12). Therefore:
FLAT D
FLAT A
Plea2004 - The 21th Conference on Passive and Low Energy Architecture. Eindhoven, The Netherlands, 19 - 22
September 2004 Page 5 of 6
w [m] = Qt/(Qs x T x h) [W/( W/K.m2 x K x m)]
Figure 12: Evapcool Columns
To different heights correspond different widths
and they are chosen according to the availability of
space and possible types of integration. Figure 13
shows possible ways of integrating the ES in the
different rooms.
Figure 13: Top floor plan showing integration of
the Evapcool system
A more detailed analysis of the system was
performed by modelling the temperature output profile
of the system into the indoor spaces. This was done
by specifying an hourly ventilation and temperature
profile into the modelled room. The temperature
profile was based on the hourly variation of the wet
bulb temperature. It was created by adding 2degC to
the wet bulb temperature. The basic ventilation rate
was set to an assumed value corresponding to the
ventilation provided by a room integrated low wattage
fan. However, the volume flow rate was increased to
test the sensitivity on the system performance (fig.
14). The simulation shows that by increasing the
volume flow rate to 0.06m3/s (0.07kg/s) the air
temperature during occupied hours can be kept below
27degC.
0
5
10
15
20
25
30
35
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hr
Temperature (C)
No ES External air temp Inlet T 0.07kg/s 17hrs
Figure 14: Top floor living room’s temperature
profiles with and without ES
The Heating Loads were also calculated to
appreciate the effect of the improved cavity wall in
winter (fig. 15). The cavity wall build-up results in an
improved U-value of 0.3W/m2.K. This has been
applied on the walls of the living rooms where the
requirement for a greater area of ceramic panels
justifies the substitution of the existing external wall
with a new cavity wall. In this instance, the effect of
improving the building envelope of the two flats is
marginal compared to a full re-cladding but it is still
possible to appreciate a drop of the annual heating
demand by 12.8% and 10.4% for the top and
intermediate apartments respectively.
Annual Hea ting Demand f or Top (A) and Int erme diate (B) Flats
0
20
40
60
80
100
120
140
160
Status Quo Int Gains Shading Insulation DG Evapcool
kWh/m2
Flat A Flat D
Figure 15: Annual heating demand for the two flats
3.3 Computational Fluid Dynamics
The performance of the proposed passive
evaporative cooling system integrated in the case
study building was investigated using 2D
computational fluid dynamics [14]. This tested the
effect of the Evapcool System in the top floor South
facing living room and the bedroom. The analysis
took into account different scenarios of integration
and related strategies for the positioning of the
ventilation and cooling inlets and outlets.
In order to simplify the modelling of the Evapcool
System it was assumed that the air delivered at the
inlet is 2degC above the wet bulb temperature (i.e.
23degC) and that the air velocity at the inlet is 0.3m/s.
The CFD analysis investigated the patterns of air
movement, temperatures and comfort in the room
assuming that the conditions within the ES cavity wall
were given. It tested two types of integration: the wall
and the roof system.
Figure 16: Cross section of top floor bedroom
showing CFD temperature profiles
width
d
0.4 m
Height h
width
d
0.4 m
Height h
23.0 ¦23.6 ¦24.3 ¦24.9 ¦25.5 ¦26.2 ¦26.8 ¦27.4
˚C
Plea2004 - The 21th Conference on Passive and Low Energy Architecture. Eindhoven, The Netherlands, 19 - 22
September 2004 Page 6 of 6
The results showed that comfortable conditions
can be achieved in the bedroom (Fig. 16) adopting an
evaporative cooling system which delivers cool air at
a temperature of 23degc and a rate of 0.045m3/s and
by positioning the inlet at low level and the outlet at
high level of the perimeter and rear walls of the room
respectively. This lowers the air and mean-radiant
temperatures of 6degC and 1.5degC respectively with
a PPD of 5% in most of the room. In the living room
the performance of wall and roof systems were
compared (Fig. 17, 18).
Figure 17: Long section of top floor living room
showing temperature stratification for wall system
Figure 18: Long section of top floor living room
showing temperature stratification for roof system
The most efficient strategy resulted to be the
cavity wall solution. There two inlets are placed on the
perimeter wall (high and low level) and one outlet on
the opposite wall. This arrangement coupled with an
air flow rate of 0.06m3/s provides very uniform
temperature distribution with an average temperature
of 26degC and a mean radiant temperature of
27degC. The PPD is also 5%.
CONCLUSION
An ‘innovative’ passive evaporative cooling
system using porous ceramic components can be
integrated in residential buildings. This can meet the
cooling loads of existing housing apartments. The
case study analysis demonstrated that these cooling
loads can be met by a wall integrated system
(Evapcool). The system can vary in height and length
according to the required load. Its integration requires
a minimal intervention in order to create appropriate
cavity wall where to locate the porous ceramic
evaporators. The addition of insulative layers on both
sides of the cavity wall can improve the quality of the
building fabric and it has been estimated that in winter
the heating loads can be reduced by approximately
12%. The total Annual Energy savings (gas and
electricity compared to the use of conventional air
conditioning) from the use of the ES are 1.53MWh
and 1.55MWh for the top and intermediate flats
respectively. This translate in a total CO2 saving of
18.5 Tonnes for the whole building.
ACKNOWLEDGEMENT
I would like to thank my director of study Simos
Yannas and my supervisor Brian Ford for their
continuing help and support during my PhD.
REFERENCES
[1]http://energy.saving.nu/buildingcodes/eucode.shtml
[2] European Commission, ‘Passive Downdraught
Evaporative Cooling using porous ceramic in non-
domestic buildings. Development of key components’
(ENK6-CT-2000-00346, 2001-2003).
[3] L. Shao, E. Ibrahim and Saffa B. Riffat
‘Performance of porous ceramic evaporators for
building cooling application’ Energy and Buildings,
Volume 35, Issue 9, October 2003, Pages 941-949.
[4] ‘The Application of Downdraught Evaporative
Cooling Systems in Non-domestic Buildings. A case
study: the Green Office, Tehran’, with B. Ford, IFCO
Conference, Tehran, Iran.
[5] ‘Construction Stock Data - Census 1990’, Instituto
National Estatistica (INE), 1992.
[6] Ditto
[7] Granados, C. ‘Solar Cooling in Spain – Present
and Future’. Workshop Forshungsverbandund
Sonnergie, Germany, 1997.
[8] Adnot, J. "Energy Efficiency of Room Air-
Conditioners", (EERAC) study for the Directorate
General for Energy (DGXVII) of the Commission of
the European Communities, May 1999.
[9] “Evaporative Cooling Using Porous Ceramic
Evaporators – Product Development and Generic
Building Integration”, with B. Ford, Plea Conference,
Chile, November 2003.
[10] TAS 8.3, EDSL, 2003.
[11] Meteonorm 4.0, 2000
[12] Axima Lab., EC Evapcool Report no. D10
‘Performance Analysis of case study project using
dynamic thermal modelling and CFD’, Winthertur, CH,
2003.
[13] Ditto
[14] Ambiens, EDSL, 2003.
23.0 ¦23.8 ¦24.6 ¦25.4 ¦26.1 ¦26.9 ¦27.7 ¦28.7
23.0 ¦23.8 ¦24.7 ¦25.5 ¦26.3 ¦27.2 ¦28.0 ¦28.8
˚C
˚C
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Mashrabiya is one of the primary features of Arab-Islamic architecture which can be found and still used in different cities around the world. It can be defined as an opening covered with wooden lattice for ventilation, daylight, privacy, and an aesthetic appeal for houses. The motivation for this work stems from the lack of existing field studies on the ventilation and thermal performance of buildings incorporated with Mashrabiya and the potential to enhance its capabilities by combining it with different passive cooling techniques. The present study aims to investigate the influence of Mashrabiya on the indoor environment in a traditional building situated in a hot climate. The case study selected for this work is the Baeshen House which is located in the heart of historic Jeddah and the area with the most traditional Mashrabiyas in Saudi Arabia. The field data of air temperature, relative humidity, globe temperature, and air velocity were collected for two similar rooms (one open Mashrabiya and one close) in the building during typical hot summer conditions when the outdoor temperature ranged between 40-41.6 °C in the afternoon. Different techniques of passive/evaporative cooling strategy were integrated with the Mashrabiya: thermal mass, water pots, water spray, and cloth. The results showed that the closed Mashrabiya contributed to reducing the flow of hot air into rooms during the afternoon, and the indoor temperature was maintained at 35.4-35.8 ° C. Increasing the speed of airflow into the room by opening the Mashrabiya had a minimal effect during the afternoon, but it was observed that the night cooling improved. It was found that the most effective strategy was the use of wetted cloth near the inlet of the Mashrabiya (33.8°C indoor average when the outdoor temperature was at 41.6 °C). The study demonstrated that comfortable conditions could be attained between 1 and 9 a.m. during hot summer conditions. Overall, the Mashrabiya with evaporative cooling was not able to provide comfort during the midday, and other strategies should be considered for hot summer conditions. Future work will focus on investigating different materials and strategies to enhance the performance of Mashrabiyas.
Conference Paper
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Evaporative cooling window system (ECWS) using labu sayong integrated with mechanical ventilation and energy operated using solar electricity is one of the most preferable strategies to increase the indoor thermal comfort inside a building in hot-humid tropic countries like Malaysia. This system will help tackle the issue of increasing costs in keeping the home cool by managing energy consumption and also offers a better indoor environment. Through a preliminary study, the potential of labu sayong as a porous medium in ECWS was shown. Then, a pilot study was conducted in a real building under real hot-humid tropics climate. Despite having a limited time frame, the result still showed that there was a temperature reduction. As continuity from the pilot study, a series of experiments were carried out using the ECWS with labu sayong which was activated using a solar powered extractor fan invented using different parts. The study had identified the effectiveness of ECWS with labu sayong in reducing indoor temperature. An ECWS with five units of labu sayong the most appropriate strategy to be applied in hot-humid tropical buildings because this strategy has succeeded in reducing the temperature as much as-3.70ºC, thus achieving a 53.7% effectiveness of ECWS. This system was evidently effective as the result falls in the acceptable range which is between 50% and 75%. KEY WORDS: Evaporative cooling window system, labu sayong, reducing indoor temperature and hot-humid.
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Direct evaporative cooling has long been demonstrated as an energy efficient ,cost effective and no CFCs emission means for space cooling in hot dry regions .With the aggravating of the global climate warming and energy crisis, using passive cooling technique will be a good solution . In this paper, the theory of passive downdraught evaporative cooling techniques is analyzed. It is an environmental friendly technique in that it can provide more fresh air than the conventional air-conditionings, and also low cost on operation and no CFCs emission compared with conventional air-conditionings. In this paper, some cases will be introduced .The successful PDEC cases in hot dry areas show weather condition is the key factor for the feasibility using PDEC technique. From the analysis on the weather data in Turpan, which presents a typical climatic character in North-west China , predicts a great feasibility of using PDEC technique in public architectures.
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This project determined the performance of a new high efficiency refrigerant, Ikon B, in a residential air conditioner designed to use R-22. ; The refrigerant R-22, used in residential and small commercial air conditioners, is being phased out of production in developed countries beginning this year because of concerns regarding its ozone depletion potential. Although a replacement refrigerant, R-410A, is available, it operates at much higher pressure than R-22 and requires new equipment. R-22 air conditioners will continue to be in use for many years to come. Air conditioning is a large part of expensive summer peak power use in many parts of the U.S. Previous testing and computer simulations of Ikon B indicated that it would have 20 - 25% higher coefficient of performance (COP, the amount of cooling obtained per energy used) than R-22 in an air-cooled air conditioner.; In this project, a typical new R-22 residential air conditioner was obtained, installed in a large environmental chamber, instrumented, and run both with its original charge of R-22 and then with Ikon B. In the environmental chamber, controlled temperature and humidity could be maintained to obtain repeatable and comparable energy use results. Tests with Ikon B included runs with and without a power controller, and an extended run for several months with subsequent analyses to check compatibility of Ikon B with the air conditioner materials and lubricant. ; Baseline energy use of the air conditioner with its original R-22 charge was measured at 90 deg F and 100 deg F. After changeover to Ikon B and a larger expansion orifice, energy use was measured at 90 deg F and 100 deg F. Ikon B proved to have about 19% higher COP at 90 deg F and about 26% higher COP at 100 deg F versus R-22. Ikon B had about 20% lower cooling capacity at 90 deg F and about 17% lower cooling capacity at 100 deg F versus R-22 in this system. All results over multiple runs were within 1% relative standard deviation (RSD). All of these values agree well with previous results and computer simulations of Ikon B performance versus R-22. The lower cooling capacity of Ikon B is not a concern unless a particular air conditioner is near its maximum cooling capacity in application. Typically, oversized A/C systems are installed by contractors to cover contingencies. In the extended run with Ikon B, which lasted about 4.5 months at 100 deg F ambient temperature and 68% compressor on time, the air conditioner performed well with no significant loss of energy efficiency. Post-run analysis of the refrigerant, compressor lubricant oil, compressor, compressor outlet tubing, and the filter/dryer showed minor effects but nothing that was considered significant.; The project was very successful. All objectives were achieved, and the performance of Ikon B indicates that it can easily be retrofitted into R-22 air conditioners to give 15 - 20% energy savings and a 1 - 3 year payback of retrofit costs depending on location and use. Ikon B has the potential to be a successful commercial product.
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An experimental investigation of porous ceramic evaporators for building cooling has been carried out. Prototypes, classified as low, medium and high porosity prototypes in direct evaporative cooling mode were placed in an experimental duct within an environmental chamber. Performance was measured under different conditions of dry bulb temperature (DBT), relative humidity (RH), supply water pressure, and layout within the duct. The high porosity ceramic evaporator consistently performed best, while increased water supply head also improved performance. Dry bulb temperature drops of 6–8 K have been achieved parallel with a 30% rise in relative humidity. Maximum cooling of 224 W/m2 has been measured during test of the high porosity ceramic evaporator placed in a single row stack with water supplied at 1.0 m head. Empirical formulae relating mean cooling performance to [es−e], the ambient to saturated vapour pressure difference have been derived. The direct evaporation of water into supply air using porous ceramic surfaces has demonstrated significant potential for building cooling.
Solar Cooling in Spain – Present and Future'. Workshop Forshungsverbandund Sonnergie
  • C Granados
Granados, C. 'Solar Cooling in Spain – Present and Future'. Workshop Forshungsverbandund Sonnergie, Germany, 1997.
EC Evapcool Report no. D10 'Performance Analysis of case study project using dynamic thermal modelling and CFD
  • Axima Lab
Axima Lab., EC Evapcool Report no. D10 'Performance Analysis of case study project using dynamic thermal modelling and CFD', Winthertur, CH, 2003. [13] Ditto [14] Ambiens, EDSL, 2003.
Solar Cooling in Spain -Present and Future
  • C Granados
Granados, C. 'Solar Cooling in Spain -Present and Future'. Workshop Forshungsverbandund Sonnergie, Germany, 1997.
Energy Efficiency of Room Air-Conditioners", (EERAC) study for the Directorate General for Energy (DGXVII) of the Commission of the European Communities
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Adnot, J. "Energy Efficiency of Room Air-Conditioners", (EERAC) study for the Directorate General for Energy (DGXVII) of the Commission of the European Communities, May 1999.
Report no. D10 'Performance Analysis of case study project using dynamic thermal modelling and CFD
  • Axima Lab
Axima Lab., EC Evapcool Report no. D10 'Performance Analysis of case study project using dynamic thermal modelling and CFD', Winthertur, CH, 2003.