Welcome to AIRAH’s WA Division Event

Presented by: David Coe, M.AIRAH, Regional Contracts Chilled and and Engineering Manager (WA), Tower Envar Engineers and Contractors and Design Lindsay Turner, Affil.AIRAH, Managing Director, Airskill

Thank you to our Sponsor

Upcoming AIRAH WA Events airah.org.au/calendar

Wednesday, October 21 • 12 - 3pm

AIRAH WA Members’ Centenary Lunch

Ascot Racecourse, Ascot

Wednesday, November 18 • 4 - 7pm

AIRAH Perth Industry Night

HBF Stadium Join AIRAH

airah.org.au/join AIRAH is celebrating its Centenary

Attend our Explore the See the Share photos Join us at Centenary “100 Faces” timeline, from and memories Outlook 2020 events of AIRAH 1920 to today

GET INVOLVED + FIND OUT MORE AT AIRAH100.ORG.AU

Leading HVAC&R for 100 years Presenting: Kim Cramer, M.AIRAH, Trustee and Past Chairman of The Alan Robert Memorial Fund Board and Director, Reliable

The Alan Robert Memorial Fund proudly offers financial support for training in and .

For more information or to apply, visit:

www.armfwa.org.au Presenting:

David Coe, M.AIRAH, Regional Contracts and Engineering Manager (WA), Envar Engineers and Contractors and Lindsay Turner, Affil.AIRAH, Managing Director, Airskill SYSTEM PRESENTATION HVAC design is not black and white.

There are numerous methodology's and ideologies that can achieve the same result.

Good design is based around determining and implementing an efficient, cost effective and robust system to service the application. Good design goes hand in hand with best installation practices.

This presentation will focus on understanding the suitability of plant and equipment and installation best practice for HVAC Chilled water systems. It will reference commonly used systems employed to service office and commercial applications. Many of the principles employed in this presentation can be applied in other areas of HVAC applications. Chilled Water air-conditioning systems are commonly used in HVAC applications, particularly in medium to large commercial installations such as Office Blocks, Hotels, Shopping Centre’s, Airports and industrial situations that need large scale cooling capacity. plants act as a centralized cooling system that can service individual or multiple buildings. Chiller plant configurations can range from single to more complex multiple Chiller applications. Central plant provides simplified service access and provides greater efficiencies. Chilled Water systems provide coolingto an application by using chilled water to absorb heat. Chilled water systems are a closed loop system, the chilled water circuit consists of a series of pipes, , valves and fittings that form a loop. Chillers provide chilled water that is pumped to various heat exchange systems such as Air Handling, Coil units, process plant and equipment. Chilled water passes though heat exchange equipment where it absorbs heat and returns to the Chillers, the Chiller then removes heat from the water by means of a refrigeration cycle and returns the chilled water to the loop to repeat the process. The refrigeration circuit is made up of four main components: 1 The 2 The 3 (TX valve) 4 The condenser

The compressor takes and compresses the refrigerant to high pressure high gas. The refrigerant travels to the condenser (which can be air or water cooled) where the heat is rejected and the gas condenses to a liquid. The refrigerant then passes through a thermal expansion valve (TX valve), which meters the amount of refrigerant passing into the evaporator. The TX valve takes the high pressure liquid and changes it to a low pressure, cold saturated gas. This saturated gas enters the evaporator and the gas then changes state to a dry gas (no liquid present) within the evaporator. As a process of changing of state, heat is absorbed within the evaporator from the fluid circuit thus cooling the water. The cool dry gas re-enters the compressor where the cycle is then repeated. :

Compressors used in chilled water plant are generally of four types:

1 Centrifugal 2 Screw 3 Scroll 4 Reciprocating Centrifugal Compressors:

The centrifugal type compressor is quite easy to spot as the compressor is above the Chiller with a large volute shaped pipe curling around into the condenser. Centrifugal compressors are the most common compressors used in large chilled water system applications. The refrigerant flows in through the suction line, hits into the centre of the impeller where it will be directed by the blades. The blades rotate and that imparts an angular velocity onto the particles of the refrigerant. This angular velocity makes the refrigerant particles fly out at high velocity, in all directions, and collects in the volute (the outer curl) where it increases in pressure from the kinetic energy, it then passes down into the condenser. Turbocor Compressor:

A variation of the centrifugal type is the Turbocor compressor. Turbocor compressors are much smaller units mounted also to the top of the Chillers. These work very similar to the centrifugal type, but they have two stage compressors inside. The refrigerant flows in through the front, passes through the two different compressors and then the refrigerant exits and travels down into the condenser. These usually have magnetic bearings and electronic motors inside, which make these units very efficient. Turbocor are becoming much more common and they are set to continuethis trend. Screw Compressors:

Screw compressors are used in both water cooled and air cooled Chillers. With the water cooled type, the compressor is on top of the chiller and with the air cooled type, the compressors is under the Chiller. Inside the compressor are two interconnecting screws. The refrigerant will enter into a void between the two screws, as the screws rotates they push the refrigerant further into the compressor and squeeze it into a small space. The refrigerant exits at high pressure high temperature. Reciprocating Compressors:

Reciprocating type compressors are becoming less common because newer, more efficient, technology has been replacing it so these are slowly being phased out, however they are still quite popular in industrial refrigeration. They are very strong and reliable compressors and with the right maintenance these compressors just seem to work forever. Noting there are a lot of moving parts though so they can be expensive to operate and generally serve lower capacityinstallations. In reciprocating types, the refrigerant will often pass over the electrical motor to proving cooling to the electrical coils and then head into the compression chamber. The compression chamber is simply a number of piston and chambers which the refrigerant will flow into. The piston is on a crank which moves it up and down. As it moves it will compress the refrigerant into the chamber and at a timed interval the refrigerant will exit at a high pressure. Scroll Compressors:

The is used mostly on air cooled Chillers but you can also find them on water cooled. Usually one compressor isn’t enough to meet the cooling load so several will be joined together in a bank. In the example above the black cylinders under the Chiller are the compressors which are joined to form a bank. Once again these chillers generally serve lower capacity installations With these type of compressors, the refrigerant usually enters via the bottom and is fed into the compressor discs. One disc will be stationary whilst the other is rotated to compress the refrigerant into a tighter space. The refrigerant is forced around the spiral as the disc moves which causes it to compress, and exits the compressor at high pressure. Chillers:

Air and water cooled Chillers are fundamentally the same in operation, other than the medium they use for heat exchange within the condenser section of the Chiller. Air Cooled Chillers:

Air cooled Chillers exchange heat from the condenser to the surrounding air by running ambient fan forced air across the condenser coils the condenser consists of a series of tubes that are fitted with fins the hot refrigerant gas enters the condenser and exchanges heat as the gas passes through the condenser the gas condenses to a liquid. Water Cooled Chillers:

Water cooled Chillers exchange heat from the condenser by running water (condenser water) that is derived from a evaporative type through the condenser vessel.

The condenser consists of a series of tubes contained within the vessel (shell and tube) that the condenser cooling water passes through, the hot refrigerant gas enters the condenser and exchanges heat to the condenser water as the gas passes through the condenser the gas condenses to a liquid. Selecting a Chilled Water System

Which system type is best for your application: Air cooled, or Water cooled? There’s no single answer, HVAC system designers need to ask a lot of questions before advocating one type of system over another. The obvious equipment choice is sometimes over-ruled by unique project factors including: • Available space • Capacity • Maintenance/running costs. • Acoustic considerations • Ambient conditions • Energy efficiency • Longevity • Water availability, conservation & cost Considerations: Spacial

Air Cooled: Air cooled chilled water plant requires a reduced plant footprint when compared to water cooled systems. Air- cooled systems require plant space exposed to the atmosphere with enough ventilation space to accommodateseparated intake and discharge airstreams.

Water Cooled: Water cooled chilled water plant requires additional plant footprint in comparison to air cooled systems. Water cooled systems require an enclosed plant room to house chillers and plant space exposed to atmosphere to accommodatecooling towers with enough ventilation space for separated intake and discharge airstreams. Capacity:

Air-cooled: Typically available in sizes ranging from 25 to 2000 kW.

Water-cooled: Typically available in sizes ranging from 35 to 15,000 kW. Maintenance Costs:

Air-cooled Chillers: Have substantially reduced maintenance costs in comparison to water cooled. This is due to reduced plant and equipment required to operatesystem.

Water-cooled Chillers: Require additional pumps and independent Cooling Towers. They have additional maintenance demands: water treatment, chiller condenser-, tower mechanical maintenance. Systems that use open cooling towers must have a water treatment program to prevent contaminantssuch as bacteria and algae. Acoustic Considerations:

Air-cooled : Air cooled plant needs to be located in external plant areas and compressor and fan noise can be an issue to surrounding neighbours with strict guidelines in force with regards to maximum noise levels that can be generated noise can be treated by incorporating acoustic louvres attenuators and acoustic screening however this can be costly

Water-cooled : Water cooled plant is generally contained within plantroom with only cooling towers external to the plantroom noise from cooling towers can be treated once again with acoustic screening discharge attenuators and specialised low noise fan selections Ambient Conditions:

Air Cooled: Air cooled condensers performance is directly related to dry bulb temperature. Standard design conditions for air cooled chillers is 35°C. Chillers can operate up to 46°C with options available to introduce high ambient selections up to 55°C which incorporate sub coolers, oversized electrical equipment ventilation to switchboards and controls It should be noted that capacity of chillers will be derated as temperature rises above 35°C

Water Cooled: Cooling Tower efficient operation is directly affected by the wet bulb temperature. The amount of , and hence , depends on the wet bulb temperature. Cooling Towers are generally selected with a 24°C wet bulb temperature in Perth. Note cooling tower performance will be further covered in section 2 of presentation Energy Efficiency:

Chillers plants are often a significant portion of a buildings energy usage, with 15-20% of total energy used in standard buildingoperation being for cooling. Water-cooled chillers are typically more energy efficient than air-cooled chillers. The refrigerant condensing temperature in an air-cooled chiller is dependent on the ambient dry-bulb temperature. The condensing temperature in a water-cooled chiller is dependent on the condenser-water temperature, which is dependent on the ambient wet-bulb temperature. Since the wet-bulb temperature is often significantly lower than the dry-bulb temperature, the refrigerant condensing temperature (and pressure) in a water-cooled Chillercan be lower than in an air-cooled Chiller. The lower condensing temperature, and therefore lower condensing pressure, means that the compressor needs to do less work and, subsequently, consumes less energy. This efficiency advantage may lessen during night time operation because the dry-bulb temperature tends to drop faster than the wet-bulb temperature. Longevity:

Air-cooled Chillers last 15 to 20 years. Air-cooled Chillers operate outdoors, at higher condenser pressure.

Water-cooled Chillers last 20 to 30 years. Water-cooled Chillers are typically installed indoorsand operateat lower condenser fluid pressure

The above estimates are subject to hours of use and maintenance regimes Water Availability / Conservation:

Water availability, cost, quality and environmental requirements as as potential additional construction complexity, all play a role in system selection. Water cooled systems use cooling towers which consume large quantities of water through the heat exchange process (evaporation) and bleed rates to control concentrations of total dissolved (TDS) that result due to evaporation process Since air-cooled Chillers do not require water, they are often a preferred choice in locations where there is a water shortage, low quality water or the water is very expensive . In Summary:

Air-cooled system advantages include: • Lower maintenance costs • A prepackaged system for easier design and installation. • No ongoing water supply requirements

Water-cooled system advantages include: • Greater energy efficiency • Larger capacities • Longer equipment life.

It’s important for system designers to take all factors into consideration to make sure the Chiller type and configuration that ultimately gets selected, balances all the objectives over the long term. Chiller Efficiency

Chiller efficiency has steadily increased mainly due to improvements in compressor and technology, along with better controls. Below graph shows improvement in chiller efficiency from 1970’s to present.

To optimise chiller selection for high performance buildings, the most accurate method is to carry out a thermal simulation of a building to determine the annual cooling under different ambient conditions. Co-efficient of Performance:

Co-efficient of performance (COP) is a measure of the energy efficiency of a system. Calculation of Chiller co- efficient of performance (COP) is determined by dividing the refrigeration capacity (in ) by electrical input power (in Watts) to gain a more accurate analysis of energy performance. An assessment of system COP includingchiller and pumps, provides a more reflective outcome. Variable Speed Variable flow Chillers:

High levels of energy efficiency that are being achieved in modern chiller plants are largely being achieved by improved vessel design, compressor design, the introduction of variable speed compressors and variable chilled and condenser water flow strategies. Given that the chiller plant rarely if ever operates at peak load the ability of systems to ramp down and operate efficiently at capacity's below is essential to achieving an energy efficient system Variable frequency drives fitted to the compressor enables chillers to be efficiently turned down to 20% of capacity and as low as 10% when hot gas bypass is introduced. Peak chiller COP’s are generally achieved in the operating range of 40 - 80% in the case of multiple chiller system staging of chillers to operate chillers within these ranges achieves optimum energy efficiency. Chillers selected with variable chilled and condenser water flow enables pumps to ramp down relative to chiller loadingthe reduced water flows result in considerable energy savings

Chiller sizing and Configuration: Chillers are selected to: • meet peak load requirements as determined via the heat load calculations • part load requirements determined via energy modelling The importance of considering part load operation cannot be underestimated as the majority of the time chillers will in a building operating within normal working hours will operate below 50% of load • Chiller configuration required to meet redundancy requirements in critical applications such as hospitals chiller configuration will be N + 1 ie failure of any chiller will maintain 100% of capacity. in commercial building application to achieve PCA premium grade buildings must maintain 60% of capacity on failure of largest chiller

Chiller Staging:

Chiller staging is vital in establishing optimum system performance. Tabulating of system co efficient of performance (COP) across chiller configurations facilitates initial optimum stage up and stage down set points for commissioning purposes During the first year of operation staging should be reviewed and tuned in to actual building performance

Minimum Chilled Water Loop Volume:

At low load operation chiller capacity at minimum turndown may exceed building load which if not addressed in the design will result in chillers short cycling Chiller manufacturers nominate maximum starts per hour and minimum run time. System should be designed to incorporate a total system water volume (inertia) that provides minimum requirement to facilitate maximum starts per hour and run time. system volumes can be addressed is by the use of buffer tanks or Locating bypass valves remote from chillers and using volume of flow and return pipework to increase total volume

Calculation of minimum water volume

V = (N x 60 x Z) / (4.18 x dt)

V = total water volume (Litres) N = Capacity of the chiller’s minimum turndown (kW) Z = Minimum allowable running time (minutes) dt = Temp difference at minimum part load condition

Buffer Tanks:

Installation of Buffer tanks to return line of chilled water system increase system total volume

Plant Layout:

System design must take into account cornerstones of best practice plant layout:

• Ergonomic considerations • Service and maintenance access • Plant failure / end of life replacement • Service Walkways

Cooling Tower 101

• Types of Cooling Towers • Water Usage • Sound • Locating Cooling Towers • Requirements of AS 3666 Cooling Tower 101 Definition of a Cooling Tower

An enclosed device for cooling a fluid or refrigerant by evaporation; used in water cooled refrigeration, air conditioning, and industrial process systems Open Circuit Or Closed Circuit? Open Circuit:

• Use plastic fill, to create a large surface area to evaporate water by mixing with an air stream. • Most common type of cooling Tower • Cheapest • Lightest • Most efficient (smallest/kW) • The water used for the cooling process is in direct contact with the air, called open circuit. Closed Circuit:

• Instead of fill, towers contain a coil. Air and water evaporating on the outside cool the fluid or refrigerant inside the coil. • Contains refrigerant = Evaporative Condenser • Rarely used as a pure fluid cooler. • More often as a condenser. • Expensive • Heavy • Approximately three times larger for same capacity Cooling Tower Selection Criteria

• Quantity of water to be cooled l/s or • Heat of Rejection kW • Entering water temp (°C) • Leaving water temp (°C) • Ambient entering air wet bulb temp (°C) Cooling Tower Typical Selection Criteria - Perth

• Quantity of water to be cooled l/s = ?? • Entering water temp (°C) = 35 °C • Leaving water temp (°C) = 29.5 °C • Entering air wet bulb temp = 24 °C Range and Approach

Two important terms:

Range (K): Difference between entering and leaving water

Approach (K): Difference between leaving water and ambient wet bulb temperatures The Effect of Approach on Cooling Tower Size

Source AIRAH Application Manual DA17 Tower water usage

• The evaporation and water usage of a tower is directly proportional to the heat of rejection.

• It is calculated by Heat of rejection / of vaporisation of H2O (2402 kJ/litre).

• Quick and easy way is 1.5 x Heat Rejection = Litres / Hour Types of Mechanical Draft Towers

Forced Draft Tower • One or more fans are located at the air inlet to force air into the tower. • Fans are high volume, high static but use a lot of power. • Suited to towers located inside plantrooms.

Induced Draft Tower • One or more fans are located in the air outlet to induce air flow through the air inlets • Axial fans, high volume, low static, low power. Crossflow and Counterflow Axial Fan Cooling Towers Two Cooling Tower Fluid Paths • Crossflow - Air flows horizontally Water through the cooling tower and Air interfaces perpendicularly with the falling hot water

• Counterflow - Air enters at the base of Water the cooling tower, flows upward and interfaces with the falling hot water Air Water Cross-flow Principle of Operation Air

Air Pathway

Moist Warm Air Out Air Entry Hot Water In Hot Water In

Dry Air In Dry Air In Plenum

Cold Water Air Entry Out Cross-flow Configuration

Gravity Feed Hot Water Axial Fan with belt, Basin & Nozzles Gearbox or Direct Drive

Open Direct, Plenum Belt or Space Gearbox Drive

Crossflow Fill Sloping Cold Basin Incorporating Eliminator & Connections Advantages • Lowest sound • Ease of maintenance • Easy, safe, simple access AS/NZS 3666 Compliance • Lower energy • Fill cleanable in place • Tolerance to water flow variation

Disadvantages • Large footprint • Cost Water Counter-flow Principle of Operation Air

Typical* Moist Warm Air Pathway Air Out

Air Entry Plenum Hot Water In

Air Entry Air Entry

Air Entry Dry Air In Dry Air In

Cold Water Out

* Alternate configurations are available which may effect thermal capacity Counter-flow Configuration

Axial Fan with belt, Gearbox or Direct Drive Hot Water Spray Nozzles

Counter-flow Eliminators

Counter-flow Fill

Sloping Cold Basin & Connections Advantages • Efficient Heat Transfer • Reduced Footprint • Lowest Cost

Disadvantages • Access for maintenance • Increased energy due to pump head/spray nozzles • High static pressure losses Access Inspection Sound Side challenges of challenges space confined traverse the easily lessening large enough to stand and center is The area plenum and maintenance inspection Easy access splash noise No frequency CWB. high fill continual path to with Water gravity by distribution - Cross by - to side side Comparison - flow fill fill for . A counterflow counterflow . towerA nature by has. maintenance making accessfor to accessvital components Very space limited is available be removed. difficult. fill to Blocks need of and maintenance be can Accessfor to fill inspection waterwith silencers water. Partial compensation production to falling due frequency High noise Counter - flow Footprint Hygiene Energy Side cooling towerscooling footprint the increase the of area plenum Larger needs drift and reduce aid coalescence increases water droplet size to Spray and distribution path cost operational head lower pumping and for water allows distribution Gravity flow through nozzles - Cross by - side side Comparison - flow small small areas economical forand beneficial counter overall size cost, and making Smaller reduce the plenums droplet size promote can harmful drift of the high in velocity path air Spray distribution mist located across fill nozzles correctfor distribution atomisation of water through required Pumping for Counter - flow flow towers very - flow Sound Considerations

Fan Noise Fan Noise

Water Cascade High High Water Water Low Noise Noise Water Water Noise Fall

Crossflow Counterflow Sound Attenuation - Fan Noise Fan Noise • Fan Options • Standard Fan • Low Sound Fan • Whisper Quiet Fan • Sound Attenuation Sound Attenuation – Water Noise Crossflow vs Counterflow

Intake Sound Attenuation Water Splash Mats Sound Attenuation or Larger Tower?

It is generally a lot cheaper to use a standard fan in a larger tower and slow it down than to add Whisper Quiet fans and/or attenuators.

You also get the added advantage of lower power and running costs, plus spare capacity if you need it. Tower layout

• Manufacturers provide guidelines for space requirements between and louvred walls.

• Don’t forget to allow access for maintenance

• Make sure the top of the tower discharge is equal too or higher than any surrounding walls.

• If towers need to be pushed hard against one another the losses can be over come with custom towers with increased louvre height.

• When towers are located in a well, we would like the downward air velocity around the tower, to be less than 1.5 m/s. AS 3666

• Cooling towers shall be fabricated from corrosion-resistant materials and for ease of maintenance, particularly cleaning fill, water distribution, basin and sumps.

• Internal surfaces shall be smooth faced and constructed to facilitate cleaning. “Cooling towers that undergo retrofit of components such as fill, basins or eliminators • Provision shall be made for quick draining and refill. or any upgrade for performance shall be required to meet all requirements associated with cooling towers, of this Standard.” • Drains and basins shall be graded to prevent collection of water.

Source AS 3666.2011.1 • Drift shall be less than 0.002% of the recirculating flow rate. Questions? Thank you for attending; please stay for refreshments in the foyer.

Thank you to our Sponsor