chilled water installations, dubai, uae 23.05.2016

7/26/2019 Chilled Water Installations, Dubai, UAE 23.05.2016

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Office 2107, Jafza View 19,PO Box 262611, Jafza, Dubai,U.A.E

Tel +971 (0) 4 8864500Fax +971 (0) 4 8864500

www.imi-hydronic.com

IMI Hydronic EngineeringTechnical report

CONTROL PHILOSOPHYFOR CHILLED WATER

INSTALLATIONS

23rdof May 2016


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DISTRICT COOLING CONNECTION (ETS ROOM):

Most of the current District Cooling Systems are variable flow, thus subject to differential pressurevariations which occur at partial load conditions. In this report we refer to DC systems with IndependentBuilding Connection, where each load (building) is connected with the set of Plate Heat Exchangers

(PHEX).

While manual balancing, as a typical solution shown on Fig. 1, is essential and effective in order toachieve PHEX design flow rate, it is important to note that the same cannot be obtained at partial loads.The static balancing valves (DRV) do not compensate for any stabilization of differential pressuresoccurring at partial and varying load conditions.

Fig. 1. Typical PHEX arrangement

Thats why DC system is subject to overflow and underflow scenarios during most part of the year. Thisleads to supply & return water temperature fluctuation and poor indoor conditions of the building resultingon low system delta T, hence increase in energy cost apart from many other limitations.

Recommendations:

We recommend use of Pressure Independent Balancing & Control Valves (PIBCV) with adjustable Kvsand EQM characteristic (TA-FUS1ON-P model) on the primary side of each Plate Heat Exchangerinstead of typically proposed control valve and DRV, as shown on Fig. 2. Each valve shall be equippedwith modulating actuator.

PIBCV selection shall be based on design flow rate, available differential pressure. Actuator selection

shall be based on required closing force of the PIBCV, power supply voltage, control and feedbacksignals provided by BMS supplier.

Once selected and installed, the Kvs value of PIBCV should be adjusted to required value in order toregulate design flow rate and maintain it at valves fully open position and design load conditions.Differential Pressure Controller of PIBCV maintains a constant differential pressure across the controlpart of the valve, thus provides good valves authority at any load conditions.

We recommend equipping of the hot (secondary) side of each PHEX with Balancing valve (VODRV) forproportional balancing of the plate heat exchangers and on/off Motorized Butterfly Valve (MBTV) toconnect/disconnect each PHEX.


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Fig. 2. PHEX arrangement with PIBCV

If the flow rates for each Plate Heat Exchanger are higher than 50 l/s, we recommend 2 or 3 numbers of

Pressure Independent Balancing & Control Valves to be installed in parallel for each PHEX, as shown onFig. 3.

Fig. 3. PHEX arrangement with set of PIBCVs

Primary side of PHEX to be controlled by set of connected in parallel 2-way Pressure IndependentBalancing & Control Valves. PIBCV valve shall be equipped with modulating actuator in order to provideenough closing force at maximal available differential pressure.

Both PIBCVs will be controlled simultaneously to work as a pair in order to avoid distortion of the totalEQM characteristic.

The final number of valves in parallel shall be evaluated as a division of the total flow rate for PHEX by50-55 l/s (as a maximum recommended flow rate for the PIBCV).

The use of few PIBCVs in parallel gives:

much accurate modulating control especially at the partial load conditions, better rangeability of the set of the valves compared to only one device,

control redundancy (backup),

easy service & maintenance without system shut down.


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Operation sequence:

The BMS shall take over the operations of the secondary pumps and Pressure Independent Balancing &Control Valves in Auto mode. Temperature sensors shall be located in the supply and return water linesof the Primary and Secondary sides of each PHEX. The temperatures shall be continuously monitored

and controlled by PLC/DDC controller.

The Pressure Independent Balancing & Control Valve should be set to maintain the differentialtemperature in the primary circuit.

When demand chilled water flow in the secondary circuit is less than supply flow rate from the primaryside and the temperature difference will decrease the set limit, BMS shall send a signal to the actuatorsin order to close the Pressure Independent Balancing & Control Valves in sequence until primary delta Treaches the set value.

When the demand chilled water flow in the secondary circuit is more than supply flow rate from theprimary side and the temperature difference will increase the set limit, BMS shall send a signal to theactuators in order to open the Pressure Independent Balancing & Control Valves in sequence untilprimary delta T reaches the set value.

The set point of the secondary pumping station to be controlled by the signal from differential pressuresensor (DPS) installed on the index circuit/branch (to be submitted with Hydronic Calculation).Temperature difference between T3 and T4 equal to 9oC has to be considered in the control sequence ofthe secondary pumping station and maintained by BMS.

Balancing valves should be equipped with test points in order to provide flow, differential pressure,temperature and power (cooling load) measurement on site. They can be proportionally balanced duringcommissioning using TA Hydronics Methodology (TA Diagnostics, TA Wireless) with TA-SCOPEbalancing instrument.

TERTIARY PUMPING STATIONS:

In order to avoid interactivity between Secondary and Tertiary pumping stations, we recommendmodification of the direct connection to the auto adapting variable flow decoupling circuit (as shown onFig. 4).

Fig. 4. Connection details for the Tertiary pumping station

The Differential Pressure Control Valve (DPCV) keeps constant and very low flow (1% of design flowrate for the load) through the bypass. Secondary flow rate is automatically adapted to the tertiary flowvariations. Both secondary and tertiary flow rates are variable. This circuit was designed for supply watertemperature preserving (secondary supply water temperature will remainunchanged).


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Auto adapting variable flow decoupling circuit is entirely self-acting. It has to be equipped with robustDifferential Pressure Control Valve for accurate control and long lifetime. We recommend pilot operatedDPCV model TA-PILOT-R.

Differential pressure stabilized through the bypass (PAB) can be deducted from needed pump head in

the tertiary side. This circuit provides optimization of the Tertiary pumping station since availabledifferential pressure from the Secondary pumping station is directly transferred to the Tertiary side.

Available differential pressure for connection of each Tertiary station can be calculated during theHydronic calculation with the help of HySelect software.

Balancing valve (VODRV) in the bypass should be sized for qBthat is 1% of the design tertiary flow rateqT.

SMALL TERMINAL UNITS:

Each Fan Coil Unit to be controlled by 2 port Pressure Independent Balancing & Control Valve (modelTBV-CMP or KTCM512) as shown on Fig. 5 with the following features:

stroke of 4 mm, EQM characteristic, modulating actuator in order to satisfy required indoor climate conditions at any system load

variations, direct flow measurement based on Kv-methodology.

Fig. 5. Connection details for group of FCUs.

Design flow rates will be adjusted on every valve based on presetting given in the PIBCV selection andactual flow rate is measured with TA-SCOPE balancing instrument in order to provide design flow ratefor each FCU at full load conditions and avoid over/under flows in the consumption/dissipation chilled

water side.

MEDIUM AND LARGE TERMINAL UNITS:

Air Handling Units (and also secondary plate heat exchangers or other medium terminal units) to becontrolled by 2 port Pressure Independent Balancing & Control Valves (model TA-FUS1ON-P) withadjustable Kvs and EQM characteristic (as shown on Fig. 6). PIBCV will be equipped with MC55/MC100Modulating actuator in order to provide accurate flow control and enough closing force at maximalavailable differential pressure.


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Fig. 6. Connection details for AHU.

Design flow rates will be adjusted on every PIBCV based on presetting given in the PIBCV selection andactual flow rate is measured with TA-SCOPE balancing instrument in order to provide design flow rate

for each AHU at full load conditions and avoid over/under flows in the consumption/dissipation chilledwater side.

Pressure Independent Balancing & Control Valves from IMI Hydronic Engineering are combining and notcompromising functions of control valve, balancing valve and differential pressure controller in one body.The Kvs value of PIBCV will be adjusted to required value in order to regulate design flow rate andmaintain it at valves fully open position and design load conditions. Differential Pressure Controller ofPIBCV maintains a constant differential pressure across the control part of the valve, thus provides goodvalves authority at any load conditions, even in circumstances where the inlet pressure is very unstable.

FUTURE CONNECTIONS:

If CHW system commissioning and balancing require flow rate and differential pressure limitation forfuture connections and also verification that installed pumping stations can deliver required flow rate toevery part of the entire installation, we recommend the following arrangement for stub out connections.

Future extensions can be equipped with balancing valve (VODRV) installed on the supply line anddifferential pressure control valve (DPCV) installed on the return (as indicated on Fig. 7).

Fig. 7. Connection details for future loads

VODRV has to be sized as per design flow rate for future extension and P = 3kPa with presetting closeto full opening. DPCV has to be sized as per design flow rate and Pmin = 5kPa, DPCV spring rangehas to be selected with respect to expected circuit (future load) pressure drop.

Commissioning of the Shall & Core will be done in two steps:

1) VODRV has to be adjusted to presetting which, at design flow has the pressure drop equal to sum ofretail unit (load) pressure drop and pressure drop across balancing valve at fullyopen position and design flow (at least 3 kPa). Isolation valve (IV) has to be fully


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open. DPCV has to be adjusted to design flow using balancing valve as a flow measuring device.

2) When the retail tenant will be connected balancing valve (VODRV) has to be adjusted to hand wheelsetting which, at design flow provides pressure drop equal to 3kPa. Isolation valve should be closed.Retail unit flow rate will be maintained dynamically regardless of other circuit activity or pump speed

changes.

When future loads get connected to existing buildings, installed PIBCVs and DPCVs will see thevariation in differential pressure and will dynamically move to adjust to the new situation. Hence thebalancing of the branches will not be affected and thereby do not require any re-adjustment.

PRESSURIZATION EQUIPMENT:

Each individual CHW Zone should be equipped with the pressurization unit containing expansionvessel(s), buffer vessel, pumps, break tank and all controls, interlocks and ancillary equipmentnecessary to maintain the system static pressure in accordance with the operating conditions (as shownon Fig. 8). The pressurization unit shall be connected to the suction side of the pumping station if it ispossible, however other locations are also acceptable, but requires detailed selection for correct staticpressure maintenance.

Each unit shall be provided with sufficient number and capacity of expansion vessels. These shall handlethe full expansion volume of the system from normal cold fill or ambient conditions to normal workingtemperature and minimal water reserve. We recommend the use of expansion and buffer vessels withbutyl rubber bladder.

Fig. 8. Pressurization unit and Vacuum Degasser

The actual system water contents and the capacity of the expansion vessels, buffer vessel and breaktank shall be calculated by the contractor to achieve and accept the total system contraction/expansionvolume of water.

Instead of indicated on the drawings air separators, we recommend the use of pressure-step Vacuumdegasser as a standalone device or integrated part of the pressurization unit in order to remove air froma closed water system.

The vacuum degasser shall be selected based on the system volume. Where a single degassing unitcannot deal with the system volume separate multiple degassers shall be installed in parallel. The feedline to the deaerator shall be provided with dirt separator.


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The pressure step degasser works on the basis of exposing part of the system water to a vacuum whichforces all dissolved gases from the water. These gases then will be expelled via an automatic air vent.Once the water sample has been deaerated it will be fed back in to the main system. This cycle will berepeated every 30 seconds to gradually remove all air from the system.

IMI Hydronic Engineering has a wide range of pump based pressurization units with combined functionof water make-up and vacuum degassing called Transfero TV Connect and Transfero TI (fig. 9.)

Fig. 9. Pump based pressurization units Transfero TV Connect and Transfero TI

Transfero is a precision pressure maintenance device recommended in high rise installations where highperformance, compact design and precision within 0.2 bar are required. In the medium performancerange they can also be used as combination devices with integrated degassing and water make-up.

The pressure is measured on the water side with the pressure transducer PIS and compared to thecalculated target value of the BrainCube control. If the pressure falls below this target value, the pump(P1) switches on, and if the pressure exceeds the target value, the spill valve (V1) opens. In systemswith 2 pumps and 2 spill valves, switching occurs alternately depending on the load, but with the samelevel of precision.

The water level is measured by the measuring foot LIS, analyzed in the BrainCube and displayedgraphically. If it is signaled that the water level has dropped below the minimum, then the pumps arelocked.

If the temperature in the system increases, then the pressure also rises. The spill valve opens when thetarget value is exceeded, and system water flows into the airproof butyl bag of the primary vessel. Theair between vessel wall and the bag is displaced to the atmosphere through an open vent.

If the temperature in the system falls, the pressure also decreases. When the pressure drops below thetarget value, the pump switches on and pumps the expanded water back into the system.

So that the smallest volume changes do not immediately run the pump or spill valve, a small pressurebuffer vessel is integrated into the Transfero range.

Transfero consists of a TecBox, a primary vessel and optional secondary vessel(s), supplemented by apressure buffer vessel from the Statico range.

The TecBox includes hydraulics and the BrainCube which controls and monitors all processes ofprecision pressure maintenance, fillsafe water make-up and oxystop degassing.

The hydraulics of the Transfero are housed in a steel case and installed on the basement plate. All thehydraulic connections to the primary vessel needed for assembly are included inthe delivery scope.


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The necessary vessel volume can be shared between a primary vessel and optional additionalsecondary vessel(s). The primary vessel is equipped with a measuring foot for content measurement.The content is indicated on the graphical display of the BrainCube. The primary vessel is connected tothe TecBox on the water side.

Air sides of both primary and secondary vessels are open to atmosphere. Water is accommodated inairproof butyl bag with extraordinary diffusion tightness that has been proven in countless practicalapplications and laboratory tests. The vessel can be filled up to 90% of its total volume. If it is signaledthat the water content has reached the maximum, then the spill valves are locked. Both primary andsecondary vessels are available from 200 up to 5000 l and have maximal operating pressure equal to 2bar. They are used as open water storage vessels in principle and hydraulically protected againstexceeding of pressure higher the maximal limit. In addition to BrainCube protection there is pressuresafety valve which protects the vessels in case of failure or leakage of spill valve(s). That is whyTransfero stations can be used in HVAC applications with different operating pressures up to 25 bar.

Benefits:

Precision pressure maintenance with tight pressure tolerances 0.2 bar.

Compact design. Almost the entire vessel volume is available for water acceptance.

Speed control permits elastic starting and stopping of pumps, smooth pump operation andsystem protection against abrupt pressure variations.

The pump switching frequency is minimized due to buffer vessel.

Smaller Vessel size compared to conventional solution.

Simple integration of water make-up and degassing.

Almost unlimited performance.

The BrainCube guarantees fully automatic self-optimizing operation and control of systemparameters, shows on graphical display all relevant parameters as well as the digital andanalogue display of pressure and water content, sends feedback to BMS via RS 485 interfaceor 2 volt-free outputs in case of any alarm, stores alarm messages.

ENGINEERING SUPPORT CENTER:

Engineering Support Centre (ESC) is a part of IMI Hydronic Engineering. ESC is a centralized technicalteam to support with complex, intensive and precise HVAC engineering to enhance IMI HE value to ourcustomer and stakeholders. IMI Hydronic Engineering, as leading global provider and expert in hydronicdistribution systems and room temperature control, has experience in more than 100,000 projectsworldwide, delivering significant energy savings, extending the longevity of the system and ultimatelyincreasing the building value to our customers.

ESC covers everything within: Product selection;

Detailed Hydronic calculation; HVAC design & redesign; System re-engineering; Reducing installation, maintenance and life cycle costs; Optimization of the energy consumption in the HVAC installation.


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The expertise of the Engineering Support Center was used in many projects where IMI HydronicEngineering provided efficient solutions and our products were successfully installed and commissioned.In 2014 2015 we have extended our support through ESC to the following projects in the Middle EastRegion:

City Walk Phase 1, Dubai, UAE

City Walk - The Avenue Phase 2, Dubai, UAE Nikki Beach Resort, Dubai, UAE Four Season Hotel, Abu Dhabi, UAE

Musheirab, Doha, Qatar

Al Bandary, Doha, Qatar IMG Theme Park, Dubai, UAE Sulaiman Al Habib Hospital, Dubai, UAE Sheikh Khalifa Medical City, Abu Dhabi, UAE Kingdom Tower, Jeddah, KSA Government Agencies Compound, Riyadh, KSA

Dubai Mall Fashion Avenue, Dubai, UAE

Manazir Al Khor, Dubai, UAE King Fahd Medical City, Riyadh, KSA

King Abdul Aziz International Airport, Jeddah, KSA Al Suwaidi Hospital, Riyadh, KSA

World Trade Center Residences, Dubai, UAE Madinat Jumeirah Phase 4, Dubai, UAE Lusail Marina, Doha, Qatar Sky Views, Dubai, UAE


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PROPOSED PRODUCTS:

TA-MODULATOR (shown in Fig. 10) is Pressure Independent Balancing and Control Valve for Fan CoilUnits combining the key hydronic functions of control and balancing in one valve with differentialpressure controller. EQM characteristic of TA-MODULATOR allows compensation of non-linear coil

characteristic and provides stable and accurate temperature control. The Measuring points enableaccurate measurement of flow, differential pressure, temperature, cooling power and availabledifferential pressure.

Fig. 10 TA-MODULATOR with TA-SLIDER actuator

KTCM 512 (shown on Fig. 11) is a high differential pressure model of Pressure Independent Balancingand Control valve for Fan Coil Units combining the key hydronic functions of control and balancing in onevalve with differential pressure controller. KTCM 512 valve has EQM characteristic, measuring points forflow measurement based on Kv-methodology. Maximal differential pressure for the KTCM 512 is 800kPa (8 bar).

Fig. 11. KTCM 512


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TA-FUS1ON-P (shown in Fig. 12) is innovative Pressure Independent Balancing and Control Valve forchilled water applications combining the key hydronic functions of control, balancing and differentialpressure control in one valve. Adjustable Kvs and inherent independent EQM characteristics allowcorrect valve sizing and optimum system controllability. The Measuring points enable accuratemeasurement of flow, differential pressure, temperature, cooling power and available differential

pressure. This will simplify system commissioning and also offer key diagnostic feature for troubleshooting. TA-FUS1ON-P valve is equipped with pressure balanced cone that gives possibility to useactuators with smaller closing force. Maximal differential pressure for the TA-FUSION-P is 800 kPa(8 bar).

Fig. 12. TA-FUS1ON-P with MC55 and MC100 actuators

KTCM 512 and TA-FUSION-P valves have special inline design, robust construction and durablematerials (AMETAL, Ductile Iron and Stainless Steel) in order to assure:

High system performance. Stable and precise control at any load conditions and differential pressure variations.

Accurate flow measurement, easy system commissioning and troubleshooting. Compact installation. Low noise generation.

Differential pressure control valves from IMI Hydronic Engineering are compact controllers withadjustable set-point for cooling applications. Those DPCVs are particularly effective in situations

requiring high differential pressure up to 8 bar and even 16 bar with low noise generation.

Differential pressure controllers are required to protect control valves and system branches from largedifferential pressure variations experienced at varying load on the system. This will give better authorityand controllability of control valves which provide a stable and accurate room temperature controlthroughout the system, whatever the control mode and Dp sensor location were selected. DPCVs help toreduce the risk of noise and cavitation in control valves and other equipment, decrease requiredactuation close-off force for the control valves that depends on: differential pressure applied on the plug;tension of the return spring if available; frictions in O-rings, seals, etc.


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Fig. 13. TA-PILOT-R and DA 516

Balancing valves from IMI Hydronic Engineering deliver accurate hydronic performance in cooling &heating applications. All balancing valves are equipped with measuring points that provides accuratemeasurement of flow, differential pressure, temperature, cooling power and available differentialpressure and simplifies the balancing procedure with TA-SCOPE balancing instrument and IMI HydronicEngineering Methodology (TA Diagnostics, TA Wireless), increases its accuracy and enablestroubleshooting and delivers desired differential pressure ensuring accurate balancing.

Fig. 14. STAD & STAF

TA-SCOPE is a tough, effective, accurate and easy-to-use balancing instrument for measuring andlogging of differential pressure, flow, temperature and power in hydronic systems. TA-SCOPE deliversquicker, more cost-efficient balancing with new TA-Diagnostics and TA-Wireless methods and enablesrapid troubleshooting. TA-SCOPE links effortlessly to the HySelect PC software gaining the maximumbenefit from recorded data and enabling professional report writing and automatic software upgrades.


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Fig. 15. TA-SCOPE

We trust this information is of use when evaluating IMI Hydronic Engineering as a reputable and highquality supply partner.

Should further information or clarifications be required, please do not hesitate to contact the

undersigned.

Your Faithfully,

Roman Yerema

Regional Technical Manager - Middle East

chilled water installations, dubai, uae 23.05.2016

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