Kein Folientitel

1
ENGINEERING
2
Close control air conditioning

• Basics of air conditioning for critical rooms
• Application engineering

3
Basics of air conditioning for critical rooms

• 1. Needs of equipment
• 2. Comparison between precision and comfort air
  A/C-units
• 3. Cost comparision

4
Needs of equipment
Most of all equipment provider declare
temperature and humidity ratings as follows
5
Needs of equipment
Workable conditions for temperature and relative
humidity
Optimum operating conditions
6
Needs of equipment
return air
Recommendation for return air / room
conditions Min. limitation 20C 55
r.H. or 24C 55 r.H. and supply
conditions Min. limitation 12C 90
r.H. or 16C 90 r.H.
rack
heat load Q
?T
raised floor
? only reachable by ?T of max. 8K
supply air
7
Needs of equipment
return air
Design air volume
VL Air volume m³/s Q heat load kW rA
density kg/m³ cpA specific. heat
capacity of air kJ/kgK DT differenct
between discharge and supply temperature K
rack
heat load Q
?T
raised floor
supply air
reference value approx.
8
Needs of equipment
In order to prevent printed circuit boards
against electrostatics the relative humidity has
to have at least 30.
Caution ! Very important in winter time !
air stream
9
Needs of equipment
return air
Filtration of the air volume is
required. Equipment has to be prevented against
dust from outside air, walls, ceiling and the
raised floor.
rack
heat load Q
?T
raised floor
For example EU4
supply air
10
Needs of equipment
The equipment declares the following
parameters for the air conditioning system
gt
Heat load
Air volume
Grade of filtration
Room temperature deviation
Room humidity deviation
11
Precision and comfort A/C-units comparison
The same needs ?
12
Precision and comfort A/C-units comparison

• Requirements for a comfort A/C-unit
• Temperature
• Relative humidity
• Air quality
• i.e. fresh air 30m3/h per person
• Air velocity
• i.e. cmax.? 0,15 m/s
• Sound pressure level
• i.e. Lp(A) 45 ??55 dB(A)

13
Precision and comfort A/C-units comparison
Total Cooling Capacity

Latent Cooling Capacity

Sensible Cooling Capacity
14
Precision and comfort A/C-units comparison
Insufficient air distribution of a comfort
A/C-unit will result in hot spots in the room /
equipment
Comfort Air Conditioning Units Cooling capacity
100 m³/h per kW
15
Precision and comfort A/C-units comparison
Perfect air distibution of a precision
A/C-unit even in remote areas of the room
Precision Air Conditioning Units Cooling capacity
300 m³/h per kW
16
Precision and comfort A/C-units comparison
Operation of a comfort A/C-unit means
continuous dehumidification
Comfort Air Conditioning ??t ? 15 k Separate
humidifier is necessary.
17
Precision and comfort A/C-units comparison
Operation of a precision A/C-unit means only
controlled dehumidification
Precision Air Conditioning ??t ? 15 k
18
Precision and comfort A/C-units comparison
5
50
Precision Air Conditioning Units
Difference in the relative humidity level of
the room
Comfort Air Conditioning Units
Permanent dehumidification
10
19
Precision and comfort A/C-units comparison
Precision Temperature Control
1 K
24 C
- 1 K
t
1 C
Difference in the control accurancy
Comfort Temperature Control
3 K
24 C
- 3 K
t
3 C
20
Precision and comfort A/C-units comparison
Difference in the operation time
21
Precision and comfort A/C-units comparison
Operation mode
22
Precision and comfort A/C-units comparison
Comfort Air Conditioning
Precision Air Conditioning
Cold climate operation
10
0
0
-15
Optional winter operation - 20 C - 45
C - 60 C
Crash
Ok
23
Precision and comfort A/C-units comparison
Requirements STULZ Precision System Comfort
Cooling System
Cold weather operation High sensible heat
ratio Operating standards Humidification
and dehumidification control
Good to -15.0 C, on special request down to
-50.0 C. Also free cooling systems
available. Typically 0.85-1.1. Up to 58
higher efficiency on sensible cooling, plus
minimal humidification costs. 8,760 hours per
year. Standard
Not available or good only to 15C. These units
are designed for summer cooling, and are subject
to liquid slugging and evaporator
freeze-up. Typically 0.6-0.7. Designed to cool
people. Will waste energy removing humidity
unnecessarily, requiring rehumidification.
1,200 hours per year, i.e. office hours during
the cooling season. Not available. Additional
systems needed.
24
Precision and comfort A/C-units comparison
Requirements STULZ Precision System Comfort
Cooling System
Air movement Filter Service Spare
parts
300 m³/h per kW of sensible cooling. Continuous
fan operation. High efficiency - EU 4 up to EU
6. Available 24 hours a day, 365 days a
year. Available with service from local stocks.
Typically 100 - 150 m³/h with intermittent fan
operation. Standard throw away furnace
filter,not classified, max. EU
2. Various Various
25
Cost comparison
Precision vs. comfort air conditioning (Operating
Costs per 1 unit)
precision comfort Total cooling
capacity 4.4 kW 4.66 kW Sensible cooling
capacity 4.4 kW 2.34 kW Latent
cooling capacity 0.0 kW 2.32 kW Air
volume 1950 m³/h 840 m³/h Temperature
difference 7 K 17 K Compressor capacity
(nominal) 1.2 kW 1.5 kW Fan capacity
(nominal) 0.25 kW 0.04 kW Operating
time 8,760 hours 8,760 hours Operating cost
per year 3650 DM 3780 DM
...to achieve 4.0 kW of sensible cooling, a
second comfort unit will be necessary.
But...
26
Cost comparison
Precision vs. comfort air conditioning
precision comfort 1 precision A/C unit
vs. 2 comfort A/C units 3650 DM 7560 DM
...as comfort units dehumidify the air
constantly, humidification is required for
these units.
But...
Operating costs for humidification (1 unit)
0 DM 1470 DM Total operating costs same
sensible cooling capacity and constant humidity 1
precision unit vs. 2 comfort units 3650 DM
7560 DM Operating costs for humidification (2
units) 0 DM 2940 DM Total
costs 3650 DM 10500 DM
...at the same sensible cooling capacity the
operating costs are about 7000 DM higher.
But...
27
Application engineering

• 1. Site survey
• 2. Load estimation
• 3. System design
• 4. Air conditioning unit selection

28
Site survey
A proper site survey will indicate

• 1. The true cooling and heating requirements
• 2. The possiblities of greatest load reduction at
  least cost
• 3. The most economical equipment selection and
  location
• 4. The most efficient air distribution

29
Site survey
DETAILS OF SITE SURVEY
30
Site survey
DETAILS OF SITE SURVEY
31
Site survey
Advice for site survey

• Physical plans and elevations of the critical
  rooms
• Declaration of equipment heat load and its
  diversity
• Essential datas for heat transfer calculations
• i.e. construction of walls and ceiling
• orientation and location of the critical room
• Data of lighting load
• Consideration of occupancy and diversity
• Supplies

32
Load estimation
Qload Qequ Qtrans Qsolar Qlight
Qperson Qfresh
Qload total heat load Qequip heat load of
equipment Qtrans heat transmission Qsolar
solar heat gain Qlight lighting load Qperson
heat load of persons Qfresh load of fresh air
intake
33
System design
34
System design example 1
35
System design example 2
36
System design example 3
37
System design example 4
38
Type A
1. Compressor 2. Discharge line 3. Evaporator 4.
Air cooled condenser 5. Liquid line 6. Liquid
receiver 7. Condenser pressure switch 8. Terminal
box
Refrigerant liquid lines and hot gas discharge
lines are connected to remote air cooled
condensers. The condensers are independant one
per air conditioning module, thus reducing
dependence on common components.
,
39
Type A - Aircooled system
Advantage
Disadvantage

• 1. Most economical system for an application
  which allows short distances between A/C-unit and
  condenser unit
• 2. No water pipes in the critical room necessary
  (except water for humidifier)

1. Limited distance between A/C-unit and
condenser unit possible 2. Refrigerant pipe work
has to be carried out by specialists 3. Condenser
can be only 3m lower than A/C-unit







40
Type G
1. Drycooler 2. Pump 3. Expansion tank
Heat from the room is rejected to the stainless
steel plate condenser, water/glycol solution is
circulated through the condenser and the heat is
rejected into the atmosphere via the
drycooler Glycol is added to the water to act as
an antifreeze to protect the drycooler in winter.

.


41
Type G - Water or glycol cooled system
Advantage
Disadvantage
1. Long distance between A/C-unit and drycooler /
cooling tower possible 2. Several A/C-units can
be combined to one dry cooler /cooling tower 3.
Plumbers work for the water pipes only 4. Dry
cooler can be lower than A/C-unit
1. Additional heat exchanger and pumps are
necessary 2. Water pipes in the critical room 3.
High maintenance effort for the cooling tower
plant







42
Type GE
1. Free-cooling coil 2. Dry cooler 3. 3-way
control valve 4. Expansion tank 5. Condenser 6.
3-way head pressure control valve 7. Pump

43
Type GE - Free cooling system
Advantage
Disadvantage
1. Energy saving due to reduced compressor
operation time 2. Several A/C-units can be
combined to one dry cooler 3. Plumbers work for
the water pipes only
1. Efficient in cold climate onlyi.e. North
europe 2. Additional heat exchanger and pumps are
necessary







44
Type A/CW
1. Compressor 2. Discharge line 3. Add.
chilled water coil 4. Air cooled condenser 5.
Liquid line 6. Liquid receiver 7. Condenser
pressure switch 8. Terminal box 9. Chilled
water flow line 10. Chilled water return line 11.
Central chiller 12. 3-way modulating valve








45
Type A/CW - Aircooled / chilled water system
Advantage
Disadvantage
1. Integrated cooling redundancy means safety
operation 2. Add-on cooling capacity for heat
load peaks possible 3. Shut down the building
chiller during the weekends means energy saving

1. Higher effort for the pipe work (refrigerant
chilled water pipes) 2. Central building chiller
necessary







46
Type CW
1. Central chiller 2. Central pump set 3.
Chilled water - return pipework 4.
Chilled water - supply pipework 5.
MODULAR-LINE CW - units


47
Type CW - Chilled water system
Advantage
Disadvantage
1. Especially for large installations less effort
for the pipe work 2. Centralised chilled water
plant 3. No refrigerant pipe work in the
building 4. Plumbers work for the water pipes
only
1. Central building chiller necessary 2.
Centralised chilled water plant 3. Only
economical for large installations







48
Air conditioning unit selection

• Crucial parameters
• Summery of site survey
• Result of heat load estimation
• Finalised system design

Selection of the air conditioning unit
49
Which criterion is crucial for you ?
Cooling capacity kW
Airflow m³ /h
12000
10000
Air veloc. m/s
41.640,-
39.760,-
37.100,-



31.810,-
29.910,-















Footprint m²
1,62
1,25
1,25
1,87
1,5
50
Aspects of redundancy
while assuring 35 kW
Cooling capacity kW
77.820,-


59.950,-
60.180,-
58.120,-
55.140,-






























Footprint m²
2,43
2,5
2,5
2,8
2,96
51
Which criterion is crucial for you ?
Cooling capacity kW
28000
Airflow m³ /h
24000
64.360,-
64.580,-


58.830,-


Air veloc. m/s
















Footprint m²
2,45
3,6
3,12
52
Aspects of redundancy
while assuring 90 kW
Cooling capacity kW
115.960,-


95.120,-
95.690,-






























4,9
Footprint m²
5,5
4,67