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5/26/2020
AAR - Webinar - Date : 26.05.2020 1
Bhaskar Paddala
Area Sales Manger
BAC (Baltimore AirCoil Company)
Contact : +91 7506696586
Email : [email protected]
Selection of Evaporative Condenser for
Energy Efficient Refrigeration
Agenda
Introduction – Refrigeration Cycle
Types of Refrigeration Condensers
Condenser Selection & Effect on plant efficiency
Modern Evaporative Condenser - Technology
Water Quality & Condenser Maintenance
Q&A
AAR - WEBINAR 2
Basic Refrigeration Cycle Refrigeration System Components
AAR - WEBINAR 4
Methods of Condensing
Air cooled
Dependent on
ambient
(dry bulb)
temperature
Evaporative cooled
(Water + Air)
Evaporative cooling,
dependent on wet bulb
temperature
Water cooled
Water cooled systems
performance, dependent
on cooling water outlet
temperature
5
Shell & Tube
Condensers
Shell & Tube
Condensers
Atmospheric CondensersAtmospheric Condensers ConceptConcept
Plate type CondensersPlate type Condensers
AAR - WEBINAR 6
Types of Condensers
1 2
3 4
5 6
5/26/2020
AAR - Webinar - Date : 26.05.2020 2
• Performance NOT consistence as it is linked with the natural
air flow which varies throughout the day and from season to
season.
• Occupies large space, huge wastage of water due to drift
losses. Space can be commercialize by cold storage owners.
• To be located in area where free air flow is available.
• Refrigerant charge will be considerably high. Almost double to
evaporative condensers.
• Civil construction cost is hidden for the customer.
• Expansion of these type of condensers are difficult.
AAR - WEBINAR 7
Atmospheric Condensers
Pre
ssu
re
Heat Content
Subcooled
Liquid
Mixture of liquid and vapor
Superheated
Vapor
Effect of condensing pressure
Suction
Pressure
Discharge
Pressure
Greater RE less flash
gas
Lower Condensing can
reduce work done by
compressor
Effect of condensing pressure
• Maximum Discharge
Pressure safety:
Compressor will react to high discharge
pressures:
Stop loading ~ 210 psig
Force unload ~ Based on Compressor
Amperage
Shut down ~ 230 psig
Note : Different plants will have difference
settings.
Compressor safeties
Maximum design CT
15.8 kg/cm2 g
14.06 kg/cm2 g
12.3 kg/cm2 g
10.54 kg/cm2 g
8.78 kg/cm2 g
17.57 kg/cm2 g
14.76 kg/cm2 g
16.17 kg/cm2 g
Effect of condensing pressure
• Condensing Pressure :
System Design – SDT & WBT.
40 °C 14.8 kg/cm2 g ( 211 psig )
39°C 14.4 kg/cm2g ( 205 psig )
38 °C 13.9 kg/cm2g ( 198.5 psig )
37 °C 13.5 kg/cm2g ( 192.6 psig )
36 °C 13 kg/cm2 g ( 186.8 psig )
35 °C 12.7 kg/cm2 g ( 181 psig )
Case study - Required condenser Capacity
SI Units : • 2 Stage – Screw compressors – 3 No’s.
• SST – Minus 40° C
• SDT – 40° C
• Condenser Heat rejection Load :
• Compressor cooling load = 471 kW.
• Motor Bkw = 291 kW
• Total heat rejection =471+291= 762 kW + ** Safety Factor.
• For 3 Compressors = 762 X 3 Nos = 2286 kW.
• ** Based on manufacturer’s suggestion / plant designer suggestion.
Design considerations while selection
AAR - WEBINAR 1126-05-2020
Condenser Selection S&T :• Condensing temperature required (TC) : 40 ° C
• Cooling water inlet temperature (tci ) : 32 ° C
• Cooling water outlet temperature (tco ) : 36 ° C
• Heat rejection in kcal /Hour = kW X 860 = 2286 X 860 = 1965960 kcal/hr
• Calculate the condenser water flow rate using :
Heat rejection in kcal/hr
Flow rate(m3/Hr) =
3024 X Water temperature rise in ( ° C)
Design considerations while selection
AAR - WEBINAR 1226-05-2020
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9 10
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5/26/2020
AAR - Webinar - Date : 26.05.2020 3
Condenser Selection S&T :• Condensing temperature required (TC) : 40 ° C
• Cooling water inlet temperature (tci ) : 32 ° C
• Cooling water outlet temperature (tco ) : 36 ° C
• Heat rejection in kcal /Hour = kW X 860 = 2286 X 860 = 1965960 kcal/hr
Find out the heat transfer area as :
Heat rejection in kcal/hr
Area =
LMTD X U
U – Value varies from metal to metal. Customer to insist for heat transfer area
as per calculation with positive margin.
Design considerations while selection
AAR - WEBINAR 1326-05-2020
Design parameters – SI Units : • Heat rejection either SI units
• Condensing temperature in ° C
• Wet bulb temperature in ° C of site location.
What is so great about Wet Bulb Temperature?• It is suggested to use a 0.4% day – not the hottest day ever recorded – just a
temperature that 99.6% of the time is safe.
• Total working hour= 24 X365 days = 8760 hour = 35 hour (0.4%)
• For Pune – The numbers from ASHRAE – 2017 are :
Design considerations while selection
AAR - WEBINAR 1426-05-2020
Design considerations while selection
AAR - WEBINAR 1526-05-2020
Design considerations while selection
AAR - WEBINAR 1626-05-2020
Method of moving air through a Evaporative Condensers
How air and water mix - direction of air and direction of water
Principle of Operation Evaporative
Condenser
Induced Draft
Crossflow Counterflow
90° interaction of air and water 180° interaction of air and water
Air
Air
Air
Water Water Water
Pushes Air Pulls Air
Forced Draft
AAR - WEBINAR 17
Axial fansAxial fans
Centrifugal fansCentrifugal fans Radial fansRadial fans
AAR - WEBINAR 18
Principle of Operation Evaporative
Condenser
13 14
15 16
17 18
5/26/2020
AAR - Webinar - Date : 26.05.2020 4
• Combined flow
• Axial fan
• Induced draft
CONFIGURATION
Latest Evaporative Condenser Technology
AAR - WEBINAR 1926-05-2020
Combined flow technology in
Evaporative Condensers
Prime Surface
Coil
Evaporative Wet
Deck Surface
AAR - WEBINAR
Evaporation occurs primarily in wet deck
• Sensible heat transfer coil section
• Latent heat transfer 70 –80% of evaporation wet deck
• Minimizes scaling potential in the coil section
Combined Flow Technology
AAR - WEBINAR 2126-05-2020
134 TR X 3 Nos – Screw compressors running for butter deep freezer
10.2
21.6
32.7
46.5
54
0
10
20
30
40
50
60
70
4 0 ° C 3 9 ° C 3 8 ° C 3 7 ° C 3 6 ° C 3 5 ° C
Po
we
r S
av
ing
in
kW
h f
or
ea
ch d
eg
ree
red
uct
ion
in
co
nd
en
sin
g t
em
pe
ratu
re
Condensing temperature in °C
421 TR EVAPORATIVE CONDENSER AT DIFFERENT CONDENSING
TEMPERATURES, CONSTANT SST MINUS 40°C AND WBT 28°C.
Power savings ( kW ) vs Condensing
Temperature
Case Study of Dairy in Gujarat - Converted from PHE + Cooling
tower to Evaporative Condenser AAR - WEBINAR 2226-05-2020
6 Lacs
13 Lacs
19 Lacs
27 Lacs
32 Lacs
40 Deg C 39 Deg C 38 Deg C 37 Deg C 36 Deg C 35 Deg C
Cu
sto
me
r S
av
ing
s in
IN
R-L
ac f
or
ea
ch
de
gre
e
ch
an
ge
in C
on
de
nsi
ng
te
mp
era
ture
Condensing Temperatures in °C
463 TR Evaporative condensers at different SDT, constant SST
Minus 40°C and WBT 28°C.
Lower condensing temp means lower operating costs !
Customer Benefits
Considered 8 Rs/ kwh as power cost & 20 Hours a day operation of
Condenser through out the year
AAR - WEBINAR 2326-05-2020
Shield for your healthy
condenser sump
Combined Inlet Shields
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AAR - Webinar - Date : 26.05.2020 5
Reduced Refrigerant
Charge – Compared to
ATM Condenser
Combined heat transfer requires less
coil surface
AAR - WEBINAR 2526-05-2020
Suggested Fan/motors for each
unit to be minimum - 2
In case of failure of one motor at least some portion of plant can run.
AAR - WEBINAR 2626-05-2020
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Water contains impurities
26-05-2020 AAR - WEBINAR 28
Typical water analysis report
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Critical water chemistry elements
1. Total Dissolved Solids (TDS)– Ca, Mg, Na, iron,..
– measured by the Conductivity
2. Hardness (TH)– the amount of Ca & Mg ions dissolved in
water
– typical measure: Total Hardness
3. Alkalinity (TAC)– Carbonate (CO3) or Bicarbonate
(HCO3)
4. pH
5. Chlorides and Sulfates– Salts can be corrosive to metals at high
levels26-05-2020 AAR - WEBINAR 30
Evaporative cooling
Evaporation –
pure waterWater drift loss
Water with added
minerals (concentrated
dissolved solids &
suspended particles)
Water bleed with
added minerals
Only water evaporates, not minerals26-05-2020
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AAR - Webinar - Date : 26.05.2020 6
AAR - WEBINAR 31
Makeup = bleed + evaporation
Example:
Makeup water TDS = 500 mg/l
Cooling water TDS = 2500 mg/l
Cycles of concentration = 2500/500 = 5 cycles
Bleed ( B ) = E / ( N-1 )
What is cycles of concentration
Cycles of concentration(N) = TDS in recirculation spray water
TDS in the makeup water
Evaporation ( E ) = Total Heat rejection in kW/ 2322 = in l/s
26-05-2020 AAR - WEBINAR 32
Impact of bleed on CoC
Constant evaporation
6
5
4
3
2
1
With zero bleed
Tim
e >
Solids build up
over time
6
5
4
3
2
Constant evaporation
With continuous bleed
maintaining set cycles
Tim
e >
Solids levels stay balanced
with proper bleed
26-05-2020
AAR - WEBINAR 33
Impact of bleed on CoC
Cycles of concentration
Makeup
Water
Usage Good Balance between
water usage and scale
risk
26-05-2020 AAR - WEBINAR 34
Water Treatment for Condenser
26-05-2020
• G235 Galvanized Steel : Low Cost / Higher Water Usage
• Special Hybrid Polymer Protection : Value for money / Less Water Usage
• Water Touched Stainless Steel: Medium Cost / Less Water Usage + High
protection to Chlorides
• Stainless Steel: High cost / Less Water Usage + Highest resistance
against Chlorides
• * Please follow guidelines of manufacturer suggestion.
Materials of Construction
AAR - WEBINAR 3526-05-2020
Climatic Data : 2017 ASHRAE HAND BOOK
FUNDAMENTALS.
Special thanks to Mr.Anil Gulanikar, Mr.Haresh
Rupchandani and Mr.Vaidyanatha Swamy for helping
with this presentation.
Courtesy :
AAR - WEBINAR 3626-05-2020
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AAR - Webinar - Date : 26.05.2020 7
Q&A
AAR - WEBINAR 37
37