Iefreviewoftheirmaincharacteristic PartI
Iefreviewoftheirmaincharacteristic PartI
Iefreviewoftheirmaincharacteristic PartI
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The air conditioner system. Brief review of its main characteristics. Part I
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ABSTRACT
This research is a compilation of the fundamental aspects of the different systems of air conditioning that are used in
practice. They constitute an approach for the engineers in the design process of these systems for buildings. Information
related to the classification of the same, the advantages and disadvantages, as well as systems recommended for spe-
cific applications, are focused throughout the article. Finally, studies that improve the efficiency of the same from the
design phase are summarized
Keywords:
HVAC, configuration, design, air conditioner systems.
RESUMEN
La presente investigación es una recopilación de los aspectos fundamentales de los distintos sistemas de aire acon-
dicionado que en la práctica se emplean. Los mismos constituyen un acercamiento para los ingenieros en el proceso
de diseño de estos sistemas para las edificaciones. Información relacionada con la clasificación de los mismos, las
ventajas y desventajas, así como sistemas recomendados para aplicaciones específicas, se abordan a lo largo del
artículo. Finalmente se resumen estudios que mejoran la eficiencia de los mismos desde la fase de diseño
Palabras clave:
HVAC, diseño, configuraciones, sistemas de aire acondicionado.
UNIVERSIDAD Y SOCIEDAD | Have Scientific of the University of Cienfuegos | ISSN: 2218-3620 Volume 12 | Number 1 | January-February, 2019
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to provide all-air air conditioning to many zones by adop- used for existing building when space is limited. The de-
ting different schemes: Single Duct, Constant Volume sign operation and maintenance of chilled water plants
System (CVS), Single Duct, and Variable Volume System has a very large impact on building energy use and ener-
(VAV). Dual Duct, CVS and VAV. Single duct normally con- gy operating cost.
sumes less energy than dual duct system. But just can
Table 1. Performance and cooling capacities of various
provide cooling or heating, no both (simultaneously) as
commercial chillers.
the dual duct. The VAV is designed with a volume control
damper, controlled by the zone thermostat, in each zone. Chiller type Cooling capacities COP
This damper acts as a throttle to allow more or less cool Absorption 10 to 20 500 kW 0.5-1.1
air into the zone. The VAV system adjusts for varying coo-
Adsorption 19 to 1 000 kW 0.5-0.65
ling loads in different zones by individually throttling the
supply air volume to each zone. VAV is more efficient than Centrifugal 280 to over 14 MW 6.1
constant volume systems. VAV systems usually reduce the Reciprocating 7 to 1600 kW 2.81
amount of total air delivered to the space during part-load Screw 100 to 4400 kW 2.84
conditions to achieve energy efficiency. However, when Scroll 528 to 1,056 kW 3.02
the space loads change, this can result in loss of indoor Source: Kohlenbach & Jakob (2014).
humidity control, even though indoor space temperatures
remain at acceptable levels. The chillers in the plant can be connected in series or in
parallel. Multiple chiller systems are more common than
The advantages are: effective room air distribution and single chiller systems. Chillers with different capacities
ventilation under widely varying load conditions; Major guarantee high energy efficiency at partial loads. If the sys-
equipment is centrally located in dedicated service spa- tem is properly designed then energy required to operate
ce, which allows maintenance to take place in unoccu- a second chiller can be conserved. A study conducted
pied areas, can be remotely located, well away from con- by Yu & Chan (2007) four design options were analyzed
ditioned space. It helps to reduce noise levels in occupied to decide the optimal number and size of chillers opera-
spaces; present great opportunities for energy conserva- ting with maximum system performance. Result estimated
tion such as heat recovery wheels; heat recovery systems that electricity savings of 10.1% could be achieved with
can also be easily integrated into main air-conditioning six chillers of three different sizes instead of four equally
units the greatest potential for use of outside air for ¨free¨ sized chillers. Conventionally, a centrifugal chiller is more
cooling. Generally, all air systems are used in IT data cen- efficient at full or nearly full load, while rotary screw type
ter, hospitals, clean rooms etc. where precise control of chillers usually have the best efficiency at partial load. In
space humidity is required. The main disadvantage are: contrast, reciprocating chillers performance varies and
Additional requirement add to building envelopment for the exact unit specifications should be verified.
duct space and higher installation and operation costs,
use significant amount of energy to move air (approxi- All-variable speed chillers (VSC) plant can operate mu-
mately 40 % energy use is fan energy); providing ready cho more efficiently at part load that conventional cons-
maintenance accessibility to terminal devices requires tant speed plant. Qureshi & Tassou (1996), established
close coordination between mechanical, architectural, that has been applied successfully to perform capacity
and structural designers modulation for chillers compressor. The use of VSC and/or
variable flow, primary –only pumping was a viable means
In all water systems, or hydronic systems, selecting chi- to eliminate an important drop in systems performance at
llers is a critical step. The chiller plant is usually consisted part load operation while accommodating the low delta T
of chillers, cooling towers, condensing water pumps, chi- syndrome of chilled water circuits.
lled water distribution pumps, chilled water storage tanks,
and distribution pipes. Chillers are available in different Chillers could be condensed by water or air. Spite that wa-
ranges in terms of cooling capacity depending on a speci- ter cooled systems have a great efficiency than air cooled,
fic compressor type and coefficient of performance (COP) air cooled chillers are dominant. The main causes of the
as see in table 1, and it is a key component that decides lack of proliferation of water cooled spite the efficiency
the system configuration of the primary system. Many de- are: the progressive insufficient water supply, air cooled
sign options of chilled water system are implemented to is easy for maintenance, less corrosion, les incrustations
achieve desired chilled water temperature. Each option and there nor risk of freezing issues. Water cooled chillers
depends on flow, required temperature, and system con- need special requirement regarding water treatment regi-
figuration and operation strategy. All water systems are mens, beside the additional cost. Water must be of good
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quality and treated further to avoid scaling, corrosion, fou- to perimeter zones. Initial cost of these systems could be
ling and biological growth. The risk of bacteria must be high compared to all air systems.
prevented by proven chemical or physical controls.
Air-Water combination is suitable for buildings with large
Chillers also allowed the possibility of implement the ther- exposures. Since there is no latent load on cooling coil,
mal energy storage (TES). It could be a key for a better troubles due to condensation do not occur. It prevents
power generation management. Their design allowed the marshy or damp regions in the conditioned space. This
reduction of the installed capacity with a consequent re- configuration needs very less apace as compared to all
duction of fixed costs; reduced peak demand and energy air systems for same capacity, it is more suitable for indi-
consumption in times of increased cost of electricity also vidual room/ zone control, simultaneous cooling and hea-
possible to decrease the electricity bill. Other advanta- ting with 4-pipe. As a disadvantage the initial cost of these
ges associated with TES are: more efficient and elective systems could be high compared to all air systems. Control
system operation, improved indoor air quality and increa- of space humidity is limited, Separate ventilation system
se flexibility of operation. Henze, et al. (2008), reported must be used to supply fresh air, which adds to cost. Also
25% savings of the operation cost, when introducing in a control of ventilation air is not precise. Condensate may
chilled water TES system into a colossal air-conditioning cause problems of dampness in ceiling or walls if conden-
system for a pharmaceutical industry, Gang, et al. (2016), sate drain fails. Require higher maintenance compared to
using the uncertainty-based design optimization method all-air systems. As systems are complicated with greater
investigated the performance of a District cooling sys- extent of controls, normally air-water systems are costlier
tems integrate with ice storage. The results revealed that than all water systems and Constant supply of fresh air
the annual operation cost had a probability of 80 % to be has to be supplied to all zones, no matter whether spaces
lower than a system without TES. are occupied are not. Because control is only for cooling/
heating coil through room thermostat
As an important advantage in the all water systems the
thermal distribution system required significantly less In the Direct expansion (DX) systems or unitary refrige-
space compared to the all-air systems, those systems are rant-based systems usually are best for low cost and very
suitable on existing building with limited space. Individual low load intermittent applications; they are simple and
room control and simultaneous cooling and heating are inexpensive room control and lower initial cost compared
also possible. They are well suited for retrofit applications to central systems. For example: Windows units are pri-
due to their distribution efficiency. But maintenance de- mary found in residential applications, and they not have
mands can be high and maintenance must be performed ducted air distribution.
on terminals within occupied spaces. Condensate drain
The appearance and noise of these units limit their appli-
pans and a drain system are required; in addition, they
cation. Rooftop units are primarily applied in low-rise buil-
must be cleaned periodically. Ventilation is not centrally
dings with flat roofs. For better air distribution in the con-
provided or controlled and is often accomplished by ope-
ditioned space the conditioned air should be ducted from
ning windows or via an outdoor air inlet at each terminal
the rooftop unit to multiple outlets instead of introducing
unit; thus, providing for acceptable indoor air quality can
the total airflow rate at one position. The split system, ser-
be a serious concern. Relative humidity in spaces may
ving such small facilities, usually conveys the conditioned
be high in summer, particularly if modulating chilled-water
air through ducts to the spaces served by the conditioner
valves are used to control room temperature.
is a ductless product were designed as quieter, more effi-
In case of Air –Water system their use the best features cient alternatives to window units. Multi-split was desig-
of all air and all water. Most of the energy is carried in the ned mainly for small to medium commercial applications
water. Often the air quantities distributed are only enough where the installation of ductwork was either too expen-
for ventilation. Therefore, the total shaft and ceiling space sive, or aesthetically unacceptable. The heat pump (HP)
required is small. In addition, the air is usually carried at offer one of the most practicable solutions to the green-
high velocities. Air-water systems are typically categori- house effect offering energy efficient and environmentally
zed in three types, such as induction system with two or friendly heating and cooling in applications ranging from
four pipe systems, fan-coil systems, and radiant panels. In domestic and commercial buildings to process industries.
such systems, it is possible to provide simultaneous coo-
An important improvement of DX systems it can found
ling and control on individual zone in an economic way
multi-and variable-speed drives, novel compressor, fan,
through thermostats. However, the overall operation and
motor, and heat exchanger designs, electronic expansion
control are complicated due to handling both primary air
valves, and advanced controls. Other attractive improve
and secondary water. In general, such systems are limited
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is the Variable refrigerant flow (VRF) air conditioning sys- more expensive, and the multi-split VRF was 111% more
tems due to better energy performance than traditional expensive.
systems. VFR provides a better occupant’s thermal com-
Santamouris (2016), reported that Split systems present
port, energy savings, flexible operation, ease of installa-
the highest share of the market with a total sale close to
tion, low noise, zone control, and comfort using all-electric
74.5 billon US$. VFR systems present a significant growth
technology.
as well, reaching a total market value close to 9.7 billon
The main energy saving of VRF systems was due to: the US$. A less share was observed for the PTAC, Indoor pac-
used of variable speed air cooled compressor, the reduc- kaged and windows air conditioning systems. Unitary sys-
tion of fan energy and the ductwork for space cooling or tems are less flexible in terms of air flow rate, condenser
heating zones, the capability of heating and cooling at the and evaporator sizes. Power consumption per kW could
same time for different zones without required for reheat, be higher compared to central systems, see table 2. The
the ability of providing heat recovery between zones at the efficiency parameters in the case of this systems is de-
same time, the used of refrigerant instead of water lead to fined as energy efficiency ratio (EER), in British thermal
required less energy to transfer the fluids heat and for last unit per Watt-hours (Btu/(Wh)), and defined by equation
using outside air systems with energy recovery. EER = 3.412 COP. Cooling SEER to EER estimated using
de-rating estimates from Table 2 of the authors Cutler, et
VRF systems achieved ranging from 10% to 60% of ener-
al. (2013).
gy savings depending on climate and the type of system
displaced, among other factors. Studies relate to the sa- Table 2. Current performance of residential cooling
ving potential it found in Amarnath & Blatt (2008). The technologies.
multi-split VRF system has high energy efficiency under
part load condition, due to the modulation of the com- Air conditioning type Measured Unit
pressor speed to adapt the load changing. In addition, Residential air conditioning 10.8 EER
duct losses in the multi-split VRF systems can be almost Residential Air Source Heat 14
eliminated due to the in-space location of the indoor units SEER
Pumps
estimated to be 10% up to 20% of total airflow in a ducted Residential Ground Source Heat 14.2
system. Compared to conventional air conditionings are EER
Pumps
its high respond to fluctuations in space load conditions. Residential Gas Heat Pumps 0.6 COP
These systems are suitable for cases when have different
zones with different space conditioning requirements. Commercial Roof Top Air condi- 11.2 EER
tioner
The main disadvantages of VRF system is its high initial Split 14.9 SEER
cost and the ventilation issue which they cannot provide Source: Cutler, et al. (2013).
any fresh air to the indoors during the conditioning proces-
ses. To overcome this drawback, an additional ventilation The drawbacks of unitary systems are that there are relati-
system is required which incremental the total cost. The vely few options with respect to sizing the evaporator, con-
design of VRF systems is more complicated and requires denser, fans, compressor, and controls. Since each unit
additional work compared to designing a conventional DX must be capable of meeting the peak load of the space
system. Long refrigerant runs and large numbers of con- it serves, the installed capacity and connected electrical
nections could result in refrigerant leakage that could be load are usually larger than with a central system. Other
significant, causing safety issues and repair difficulties. problem probe by different authors is the quality of indoor
environment. Ai, et al. (2016), referred that a deficiency of
Total costs of VRF systems are likely to be about 5% to room air conditioner was the lack or very little outdoor air.
20% higher than chilled water systems of similar capa- In studies conducted in residential building, Park, Jee &
city. About 30% to 50% more than equivalent capacity Jeong (2014), showed that the ventilation rates were less
single package ducted system and more than twice as than the minimum requirement recommended by ventila-
much as packaged terminal units. Study conducted by tion standards, ASHRAE Standard 62.1, 2013 of 7.5 l/s/p.
Cassidy & Sweet (2000), compared the whole-life costs of Those associated with low ventilation rates and excessive
four common air-conditioning systems used in a modern CO2 concentrations (>1000 ppm) reported by Beko, et al.
new-build. The result showed that, a system with four-pipe (2010). Other studies (Sundell, et al., 2011) showed the
fan-coil units was 53% more expensive than the chilled strong correlations between insufficient ventilation and the
ceilings option, the variable air volume system was 74% prevalence of illnesses and sick building syndrome, besi-
de insufficient ventilations in bedrooms was responsible
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for a poor sleep quality and reduction of physical and phy- strong solution concentration and generator temperature
siological performance of persons. have the greatest impact on total annual cost can run at
a lower temperature. Absence of moving/rotating parts
Technologies based renewable energy resources are also
makes them more reliable, low maintenance cost. They
penetrating in the HVAC sector. The main reasons are
do not suffer problem of crystallization and corrosion. It is
environmental issues due to CO2 emissions, and ozone
not so sensitive to the fluctuation in heat source tempera-
depleting mediums in conventional systems i.e. CFCs,
ture. A small amount of intrinsic electricity consumption is
and HCFCs, due the probability of working fluids escaped
due to the absence of a pump. An adsorption system is
through leakages from cooling equipment during normal
simpler to design than an absorption system. Because of
operation (filling or empting) or after accidents (dama-
fewer individual parts, the cost of production is comparati-
ges) gather in significant quantities at high levels of the
vely lower. Their disadvantages are: The COP and cooling
stratosphere.
capacities of adsorption systems are still low compared
Even the production of CFCs and HCFCs as R-11, R-12, to absorption. This is due to porous adsorbent materials
R-113, R114 and R-115 was stopped since 1995 but are are bad conductors of heat, and the fixed bed operation
still being used widely in existing residential and small also leads to poor heat and mass transfer. Leakages and
commercial air conditioning units and heat pumps. Other adsorbent deterioration require high vacuum tightness of
refrigerant as R-22 is the most common chiller refrige- the container and careful design of external hydraulic cir-
rants. Dominates in small systems using positive displa- cuits due to cyclic temperature variation in the hydraulic
cement (scroll, reciprocating piston, and screw) compres- circuits. Few suppliers in the market with high cost of com-
sors, actually R410A is the primary replacement selected mercially available machines are bulky and expensive.
for R-22. This substitute offers practically zero ODP. But
The sensible and latent loads can be controlled separa-
it increased the GWP by 16 % and lowers the attainable
tely. Better humidity control, more efficient latent load re-
efficiency by 6 %. According (Calm, 2008) R-123 is the
moval and provide better indoor air quality by controlling
most efficient refrigerant for water chillers. However, the
the growth of harmful fungi and bacteria. Operate at near
need for low GWP option with improved system efficiency
atmospheric pressure; the maintenance and construction
still impulse to several investigations.
are simplified and does not utilize condensation to achie-
Other reason was the high energy demand in building ve dehumidification and No Chlorofluorocarbons based
sector and increasing energy prices. In this case the sorp- refrigerant. The electrical energy requirement can be less
tion technology coupled with renewable sources as solar than 25% that of conventional refrigeration systems but
energy is proving relatively efficient alternatives in terms few suppliers in the marked and specially the liquid desic-
of energy saving. Sorption technology can be classified cant systems. The AHU are bulky, the initial investment is
either as closed sorption systems or open sorption sys- higher and is difficult the mounting on existing building.
tems. In closed sorption technology, here are two basic Require pre-cooling and/or post cooling equipment. In hot
methods: absorption refrigeration and adsorption refri- and humid regions, the effectiveness of desiccant dehu-
geration. For open sorption cycles, the basic method is midification would be limited, in this case require higher
desiccant technology. Sorption-based cooling devices regenerating temperature in the order of 90oC or a heavier
are particularly attractive if the power supply is insufficient desiccant dehumidifier, to realize an efficient dehumidi-
or costly, or if thermal energy is easily available, e.g. from fication and cooling. Compared the desiccant systems
solar heat collectors. A summary of the advantages and drive by solar energy with a conventional AHU the energy
disadvantages of each technology are present below: consumption is normally higher due the increment of com-
ponents necessary for the process (dehumidifying wheel,
Its ability to operate with low temperature and use any type
air collectors, and evaporative cooling devices)
of heat source; Low operating and conservations costs
than the rest of thermally-driven air-conditioning systems; The intrinsic qualities of solar energy make it a beneficial
Low noise and vibrations. Simple construction, reliability, utility, especially for countries located in regions with op-
long lifetime, with fewer replacement parts are generally timal access to the sun’s rays as tropical zones and as
bulky, complex and expensive in terms of initial inves- refers before the combine of solar energy whit HVAC tech-
tment. Also some cycles required wet heat-rejection coo- nology it’s called solar cooling technology. It can be clas-
ling due heat rejection from absorption systems are about sified into three categories: solar electrical cooling, solar
1.75- 2.5 times the cooling capacity. In general this system thermal cooling, and solar combined power and coo-
requires advanced knowledge for maintenance high cut ling, as illustrated in Figure 1. Solar cooling technology it
off input temperature for aqua-ammonia absorption chiller, been reviewed by several authors Nkweta & Sandercock
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(2016); Eicker, et al. (2015), and their works are focused on the technologies performance including its technical,
environmental and economic aspects.
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favorable conditions the panels can remove 101 W/m2 As an ICTHS practical applications it can found the
and the free hanging design can remove 196 W/m2. Dedicate Outdoor Air Systems (DOAS), is a better cooling
concept and it is applied in order to achieve a better per-
formance. The reason why DOAS is called ‘‘new concept’’
AC system is that the techniques used in DOAS have
widely been applied but are subtly combined to show its
broad prospect.
Is quite impossible that all-air can attain its functions espe-
cially air ventilation in an energy efficient manner. DOAS
is an air-conditioning systems that consist of two parallel
systems: a dedicated outdoor air ventilation systems for
delivering outdoor air ventilation that handles both the la-
tent and sensible loads of conditioning the ventilation air
and a parallel air terminal unit to handle the (mostly sensi-
ble heat) loads generated by indoor/process sources and
those that pass through the building enclosure. Typical
DOAS, shown in figure 3:
Today’s, the practice to the increment of humidity due the DOAS consist of the following parts: Cold source: could
weather, is to reduce the set-point temperature and then be PTACs, small packaged or split DX units, radiant
re-condition the air after passing the cooling coil to the chilled ceilings, passive chilled beams, or VRF equipment;
proper temperature, which results in a plenty of energy Outdoor air processor: To ensure that indoor terminal de-
wastefulness. Regarding Huang & Niu (2016), the ICTHS vices run in dry condition, outdoor air heat load, total la-
is the best development in the indoor environmental con- tent heat load and partial sensible heat load are removed
trol area for the last 25 years, also refers that it high prob- by outdoor air processor; Sensible heat removing terminal
ability in become in the best HVAC configurations in the devices: could be include cooling ceiling, fan coil units
future. Besides, the energy potential of for HVAC config- and unitary air conditioner. In the Li & Zhan (2007), study
urations: a constant volume all air systems, an all-air whit confirm that its can save until 18 % of primary energy if
total heat recovery ventilator, a chilled-ceiling with a con- use cooling ceiling in the DOAS configurations. Total heat
ventional AHU and finally a chilled ceiling with solid des- exchanger: its can use an AHU compose by desiccant
iccant cooling. The result shows that the benefits of the wheel and heat recovery wheel for dehumidified outdoor
individuals’ techniques chilled ceiling and dehumidifica- air. Finally, an automatic control system: is necessary for
tion by desiccant lead to among all configurations; it can DOAS. The controlled parameters mainly include the out-
save 44 % of primary energy, in comparison with constant let water temperature and the cold water flux of outdoor air
volume all air, achieve much thermal comfort and finally processor, cold water flux and inlet water temperature of
be driven by low-grade thermal energy suitable for the sensible heat removing terminal devices, indoor dry-bulb
use of renewable source. temperature and dew-point temperature.
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DOAS is an all air system without return air, and it elimina- the strategy was a CO2-sensor based demand controlled
tes inter crossing infection existing in all air system with re- displacement ventilation (DCDV-CO2). During daytime
turn air. The advantages of DOAS among to a conventional operation, DCDV-CO2 allows the reduction of the requi-
all-air are: less noise, lower draft, better thermal comfort red ventilation air volume by 65–75% when compared
and good potential for reductions of the first and operating to Constant air volume. During the daytime the reduc-
cost. More benefits likes enhanced indoor environmental tion of the total heating energy demand was up to 21%.
quality, increased degree of freedom in the selection of Concurrently, the amount of unrecovered heat in the ex-
local units. The energy saving exhibits by DOAS it can haust ventilation air was reduced by 54% followed by
found in several investigations. When the effectiveness the lower average airflow rate by 50%. Other innovative
of total heat exchanger is 65%, DOAS using cooling coil techniques developed are combined CC/DV with cooling
as sensible heat removing terminal devices can save the jackets that are either passively cooled by phase change
electric energy by 42%, compared with conventional VAV materials, actively cooled by connecting the cooled jacket
systems. During part-load conditions, with local unit(s) to external cooling system, personalized ventilators and
running under reduced capacity mode to fulfill the redu- personalized evaporative cooler.
ced sensible loads, the DOAS unit continues to supply air
Selection of a HVAC system configuration is typically de-
at a low enough dew point to maintain acceptable indoor
cided in the early stage of the design process when the
humidity levels. This humidity control benefit is potentially
maximum opportunities for energy efficiency occur. All the
available for almost all DOAS system configurations.
technologies have certain technical and economic bene-
Other important evolution of these advanced configura- fits. Few are better than other for specific application and
tions of HVAC systems that provide an efficient configu- many alternatives can be used for cooling proposes.
ration is the chilled ceiling displacement ventilation (CC/
An important point of view is to considering installing an
DV). It is a room air distribution strategy; provide high in-
air-conditioning system centralized or individual, but it’s
door air quality by introducing 100 % fresh supply close to
necessary to considerer that centralized systems include
the floor level displacing warm air into exhaust and crea-
a distribution system in the building such as pipes, ducts,
ting a clean environment zone. Coupling the displacement
tanks, pumps, fans, or exchangers. The efficiency of the
ventilation and chilled ceiling allows larger load handling
overall system depends on the efficiency of all its com-
capacity and a higher thermal comfort level by reducing
ponents, for example an efficient chiller can become an
vertical temperature difference and draft. Other advanta-
inefficient air conditioner system if parts are poorly con-
ge are the operate temperature of chilled ceiling around
nected and badly calibrated. In individual systems, the
17◦C–19◦C compared with conventional air-conditioning
efficiency often depends alone on the efficiency in the
system, which show a great potential on energy and in-
cooling source only.
vestment saving. Besides, the stratified could achieve a
higher indoor thermal comfort level as well as air quality Operating cost has also an influence in selection proce-
with relatively low energy consumption. dure, for example the energy consumption for a typical
air handling units can achieve up to 20 000 W and a typi-
Kanaan, Ghaddar & Ghali (2010), reported that CC/DV
cal desiccant cooling systems can consume up to 55 000
systems consumed 53 % less cooling energy than con-
W of electrical. Electrical and economic comparison of
ventional systems but it did not offer energy savings with
four different cooling systems its show in figure 4. Perez-
mixed conventional systems. In order to improve this re-
Lombard, et al. (2011), established a set of low-level re-
cords Chakroun, Ghaddar & Ghali (2011), developed a
quirements in the selection of efficient components: equi-
model to predict the indoor quality in a typical office in
pment minimum efficiencies, fluid distribution systems,
Kuwait conditioned by CC/DV and compared with 100 %
HVAC control ventilation, heat recovery and free-cooling.
fresh air system and with mixed conventional system. The
energy consumption was founded to be substantially less
when mixing was present. A mixing fraction of 60% fresh
air resulted in 37% less measured energy consumption
of the system when compared with 100%. The energy
consumption analyzed of mixed air system was less by
15–20% from the conventional system.
It can reach better energy efficient if combine DV with de-
mand control. A real study case in two Norwegian schools
was published in, Wachenfeldt, Mysen & Schild (2007);
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Beko, G., Lund, T., Nors, F., Toftum, J., & Clausen, G.
(2010). Ventilation rates in the bedrooms of 500 Danish
children, Build. Environ, 45(10), 2289–2295.
Calm, M. J. (2008) The next generation of refrigerants-
Historical review, considerations, and outlook.
International Journal of refrigeration, 31(7), 1123-1133.
Chakroun, W., Ghaddar, N., & Ghali, K. (2011). Chilled
ceiling and displacement ventilation aided with
personalized evaporative cooler. Energy and Bulding,
43(11), 3250-3257.
Figure 4. Comparison of cost and power of building heating, Cutler, D., Winkler, J., Kruis, N., Christensen, C., &
ventilation and air-conditioning (HVAC) systems on the log scale. Brendemuehl, M. (2013). Improved Modeling of
Source: Perez-Lombard, et al. (2011). Residential Air Conditioners and Heat Pumps for
Energy Calculations. National Renewable Energy
An overall solution that determines the most convenient
Laboratory.
system does not exist and the techno-economic viability
of a HVAC system depended on many factors such as: Eicker, U., Pietruschka, D., Schmitt, A., & Haag, M. (2015).
Building design, location issues, and utilities: availability Comparison of photovoltaic and solar thermal cooling
and cost, indoor requirements and loads, client issues. systems for office buildings in different climates. Sol
Generally, once all objectives were analyzed and identi- Energy, 118, 243–255.
fied one or two HVAC systems, a detail qualitative eva- Gang, W., Augenbroe, G., Wang, S., Fan, C., & Xiao, F.
luation must have made. A brief report that addresses the (2016). An uncertainty-based design optimization
following was proposed: the goal; criteria for selection; method for district cooling systems. Energy, 102, 516-
important factors, including advantages and disadvanta- 527.
ges; other goals; security concerns; basic design; HVAC
system analysis and selection matrix; system narratives; Henze, G. P., Biffar, B., Kohn, D., & Becker, M. (2008).
budget cost and recommendations. Different methods Optimal design and operation of a thermal storage
could be used to complete analytical analysis. Simplest system for a chilled water plant serving pharmaceutical
as rate each items in qualitative form or more complex buildings, Energy Build, 40(6), 1004–1019.
as numerical rating. Finally, the highest numerical value Huang, Y., & Niu, J. (2016). A review of advanced of HVAC
obtain will becomes the recommended HVAC systems to technologies as witnesses’ publications in the period
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45.
CONCLUSIONS
Kanaan, M., Ghaddar, N., & Ghali, K. (2010). Simplified
In this work the main characteristic of the air conditio-
model of contaminant dispersion in rooms conditioned
ning systems was given. It can be concluded from the
by chilled ceiling displacement ventilation system,
numerous existing HVAC system configurations that the
HVAC and R Journal, 16(6), 765–783.
selection of a suitable system configurations is really com-
plicated at the initial design stage. The evaluation of all Kohlenbach, P., & Jakob, U. (2014). Solar cooling: The
available options requires considerable amount of time earths can expert guide to solar cooling systems.
and efforts. But it’s important considers that savings can Taylor & Francis
achieve if a proper HVAC systems were selected. Hence, Li, Y.X., & Zhang, X. (2007). Energy efficiency comparison
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