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B. Srinivasa RajkumarSales Manager (HVAC)
Commercial Building ServicesGrundfos India
Optimization of Pumping System in HVAC
ACREX 2012
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All system operated as variable flow systemPrimary variable pumping
Use of thermal storageCombination of active and passive systemsUse of tertiary pumps (zone dividing)
Challenges in condenser water pumpingRemote monitoring of pumping systems
HVAC pumping schemes
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All system operated as variable flow system
Constant flow system:Constant flow systems will use three way val-
ves and will give a variable flow in distribution
net and variable flow in the load.
Variable flow system:Variable flow systems will use two way valvesand give a variable flow in both the load and inthe distribution net.
By using Tertiary pumps the flow in load canbe held constant but with a variabletemperature.
MAB A
B
Variable flowConstant temperature
Constant flowVariable temperature Load
M
Constnt flowVariable temperature
Variable flowConstant temperature Load
M
Constnt flowVariable temperature
Variable flowConstant temperature Load
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The way to - Primary variable flow
Improvedperformance
Chiller
Chiller
Chiller
Load
Load
Load
Load
Load
Load
Load
Load
Load
Constant flowThree way valvesConstant speed pumps
Chiller
Chiller
Chiller
Load
Load
Load
Load
Load
Load
Load
Load
Load
Commonpipe
Constant flow (primary)
Variable flow (secondary)Two way valvesConstant/variable speed pumps
Chiller
Chiller
Chiller
Load
Load
Load
Load
Load
Load
Load
Load
LoadBuffer tank
Constant flow (primary)Variable flow (secondary)Two way valvesConstant/variable speed pumps
Chiller
Chiller
Chiller
Load
Load
Load
Load
Load
Load
Load
Load
Load
Variable flowTwo way valvesVariable speed pumps
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Primary variable flow
Also the using primary variable flow has been discussion inleading technical magazines like The ASHRAE Journal.The conclusion often end up in favour of:Primary variable flow
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Primary variable flow
Advantages:Lower first costLess space required (less pumps)Reduced pump power designLower energy consumption
Between a flow at50% to 80% we havethe highest numberof operation hours,and here the saving
is significant.
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Primary variable flow
Primary/tertiary dedicated pumps:
If there is a demand for standby pumps
there has to be installed one standby per
chiller. The pump controller has to be
able
take out the pump of control sequence
when the chiller is switches off.Primary/tertiary common pumps:
There is a demand for control valves on
each chiller to be able to control the flow
in the chiller, and there is only demand
for one standby pump for all the chillers.
Load
Load
Load
Load
Load
Load
Load
Load
Load
Chiller
Chiller
Chiller
Load
Load
Load
Load
Load
Load
Load
Load
Load
Chiller
Chiller
Chiller
For both system types there is a demand for controlled bypass tosecure the minimum flow.
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Use of thermal storage tanks
Chillerplant
Charge mode flow Discharge mode flow
Stage storage tank
Distribution net
Basis thermal storage tank principal
Reduced refrigeration equipment investmentLess expensive than chiller capacity in large systemsLess inefficient part-load operation of plantCapacity for emergencies and growth
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Capacityhandle bychillers
Capacityhandle by
chillers andstorage
Load
24 hours
Use of thermal storage tanks
Use of thermal storage provide a good opportunities tocover the peak load instead of installing more capacity, alsoin situation where the system is expanded.
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Combination of active and passive systems
To reduce the size of the air part (ducts and AHUs) passive systems areoften used it could be cooling ceilings or cooling floors. The passivesystem also has an advantage in operating with a higher flowtemperature (15-17oC) which fit with alternative cooling sources andmake it possible to operate with a higher system Dt.The big challenge is to avoid condensation on floors and ceilings.
M
M
M
15oC
18oCCooling Ceiling/floors as apart of the building
construction
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Typical buildings where passive system can be use arebuildings with large public areas like:
Air portsHotel receptions
MuseumsOpera housesetc.
Passive systems always has to combined with chilled airsystem to provide fresh air.
Combination of active and passive systems
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Use of tertiary pumps
Chiller
Chiller
Chiller
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Chiller
Chiller
Chiller
De-coupling
Load
Load
Load
Load
Load
Load
Load
Load
Load
De-couplingChiller
Chiller
Chiller
No matter if the system design is a Primary variable flow or Primarysecondary flow tertiary can be used larger systems. The mainpurpose is to increase the hydraulic balancing and to lower the headof the Primary/Secondary pumps and there by reduce the operationcost.The system will be much more flexible easier to make changes.
Load
Load
Load
Load
Load
Load
Load
Load
Load
Chiller
Chiller
Chiller
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Indirect connection
with flowtemperature control,
and and heatexchanger
Indirect connection
with flowtemperature control,and by-pass control
Indirect connectionwith flow
temperature control
Connection with
booster pumpand high pressure
bypass
Connection withbooster pump
Connection withcontrol valve
Direct connection
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
Load
The tertiary system/pumps can be connected to thedistribution net in different ways depending on the individualconditions.
Use of tertiary pumps
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Potential Challenges in Condensers Circuit
Condensers circuit are Primarily a much easier to manage. However,troubles still persist occasionally in some system. Lets have a brief look
at
some of the potential challenges:
1. Pump Cavitations due to insufficient inlet pressure
2. Air entering pumps due to the formation of vortex at collection basinor incorrect setting of bypass
3. Over sizing of pump due to over estimation of frictional losses in thecircuit
4. Fouling of pipes and condenser tube
5. Changes in operating condition for circuit with bypass line
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Closed Loop and Open Loop system
In a large chilled water system consists two difference kind of circuit
Closed loop system- Distribution circuit
Closed systems are characterized as systems with pumps that onlyhave to overcome the sum of friction losses, which are generated by
all the components Open loop system- Heat rejection circuit
Open systems are systems, where the pump is used to transportliquid from one point to another
Thing to note between these two type of circuit while sizing the pump is
Static head consideration.
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System Curve for Closed/ Open Loop system
Closed Loop system Open Loop system
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Typical Heat Rejection Circuit
Chiller
Condenser Pump
Cooling Tower
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Points to note to avoid cavitations on Condenserpump
Condenser side is an open loop system, the only positive pressure to the
pump suction are the elevation of cooling tower and atmospheric
pressure, therefore, here are a few notes;-
Always locate the condenser pumps as close as possible to the tower
Design the pumps below As much as possible below the collection basinwater level
Locate the condenser pumps before Condenser to avoid large pressuredrop of this component
Ensure sufficient NPSHA.
Avoid using high pressure drop strainer, check Valve and balancing Valveat pump suction line
(If strainer has to be installed, try to use large mesh opening up to 3/16 atthe suction, propose is just to protect the pump and install a fine meshstrainer at the pump discharge to protect all other equipments)
Avoid Overhead suction piping
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Vortex at Collection basin Exit
Vortex at Collection basin iscreated when, there is insufficientwater level above the collectionbasin exit for the velocity that thewater is exiting.
Facts contributing to the vortexing:-1. Sudden decrease in exit pipe
size (Suction line) causes thewater velocities above themaximum allowable limit,vortex created
2. Over sizing of pumps due toover estimation of frictionallosses
3. In correct setting of bypassline (If any)
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Points to note to avoid formation of Vortex
Cooling Tower exit pipe follows collection basin exit at least for thelength of 10x the diameter before reducing it to the pump suctionsize
Throttle valve to control flow (energy consideration)
Modifying impeller diameter
Speed control
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Remote monitoring of pumping systems
Why to own when you can rent theservices ?
World is moving towards cloudcomputing. So does the buildingservices
No hassles of maintaining a localnetwork
All devices talk to each other and to acentral network
Nominal charges for web servicemaintenance to the use
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Remote monitoring of pumpingsystems
Easy-to-install, low-cost monitoring andmanagement of pumping systems.
Web access to reports and trend data for all relevantemployees.
Automatic event log and service log for all pumpsin the system.
Plug n
Play integration with Controls
monitoring of all pumps and sensors.
Centrally hosted database andapplication server.Users only need an Internet PC.
Alarms on SMS and Email distributed according tobuilt-in week schedule.
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Cloud Overview
Pump LogicControllers
Data logger
Internet
GSM
Central Web Server
Users
Users
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Online monitoring of pumpingsystem efficiency
Close monitoring of specificenergy consumption
Immediate course correction inevent of any performancedegradation
Get access to data andperform basic functions suchas acknowledge alarms,start/stop pumps, reset
controllers from your mobilephone / PDA
Business model could coverAMC or 24/7 operation supportto benefit users
Remote monitoring of pumping systems Userbenefits
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Focus on energy saving (Carbon footprint)
Energy saving:To reduce operation costTo reduce CO2 emissionUtilizing energy sources better
The use of Life Cycle Cost more and more common
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How to evaluate the most efficient pump solution
The best way to evaluate theefficiency of a pump system is touse:Life Cycle Cost Analysis (LCC)LCC shows the total life time cost of
a pump system.The lifetime of a quality pumpsystem will be no less than 20years.When used as a comparison toolbetween possible design oroverhaul alternatives, the LCCprocess will show the most cost-effective solution within the limits ofavailable data.
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The LCC equation
Normally only 3 elements in theequation will add value whencalculating HVAC systems inCommercial Buildings :
Initial costMaintenance costEnergy cost
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B. Srinivasa Rajkumar
Manager Sales (HVAC)
Commercial Building Services
Grundfos Pumps India
Direct: (+91) 44 4596 6891Mobile: (+91) 99406 79196
Mail: [email protected]
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