new benchmark - airah

DECEMBER 2019 · VOLUME 18.11

RRP $14.95

PRINT POST APPROVAL

NUMBER PP352532/00001

New benchmarkAn AIRAH Awards finalist shows the way.

ANNUAL

AIRAH

AWARDSSPECIAL

F E A T U R E

22 DECEMBER 2019 • ECOL IBR IUM

Small but mighty

As a leading distributor in the Australian food service industry, Bidfood operates distribution centres (DCs) across the eastern seaboard as well as in South Australia, the Northern Territory, Western Australia and overseas.

With refrigeration critical to its business operations, Bidfood has shared a long

history with Brisbane-based refrigeration specialist Scantec Refrigeration Technologies. Over the years, Scantec has designed and installed various refrigeration systems for Bidfood including HFC-based systems, conventional liquid overfeed systems, and the first centralised, low-charge ammonia (NH3) system in Perth.

This system would become the first of 20 centralised, low-charge NH3 refrigeration systems that Scantec has since designed and installed for a variety of clients, purposes and capacities around Australia.

“These systems deliver specific energy consumption values (SEC-values) in kWh/m³a that are in line with the latest best-practice energy performance for refrigerated warehouses, as proposed by Dr Andy Pearson at the International Congress of Refrigeration held in Montreal Canada last August,” says Scantec managing director, Stefan Jensen, F.AIRAH.

Featuring a three to five times lower NH3 inventory (charge) than conventional liquid overfeed systems, it is believed that Scantec is now responsible for the largest installed base of centralised, low-charge NH3 systems of this particular design in the world.

“There are other centralised low-charge NH3 refrigeration system developments in the US and Europe,” Jensen says. “But none of these competing developments have the same installed base, in terms of plant numbers, as found in Australia.”

The installation of a small-scale packaged centralised low-charge ammonia refrigeration system at a Queensland distribution centre is the culmination of almost three decades of development and field testing by an Australian company. Sean McGowan reports.

Interior of pre-fabricated low charge ammonia engine room (ScanPAC) Stainless steel evaporative condenser and ScanPAC

ScanPAC interior showing three compressors - two duty and one standby

DECEMBER 2019 • ECOL IBR IUM 23

What sets the design apart from others is a number of features including the complete elimination of NH3 pumps, combined superheat/quality-based refrigerant injection control, demand-based hot gas defrost, and dry expansion feed glycol/NH3 heat exchangers.

Jensen says the difficulties pertaining to dry expansion feed for low-temperature air coolers (evaporators) are well known, and have been for more than a century.

“New knowledge relating to boiling NH3 refrigerant behaviour in horizontal tubes, and the factors affecting this behaviour, has emerged during the past decade,” he says. “The implementation of this new knowledge in practical, commercially operating installations remains rare, however.”

The main reason for this is the unique set of challenges facing system designers with respect to evaporator designs.

“When Dr Dermot Cotter presented part of his thesis at the Gustav Lorentzen Conference in Copenhagen in 2008, video recordings revealed the impact of the thermal conductivity of the tube material on refrigerant behaviour in return bends.”

It seems that the lower the thermal conductivity of the tubes, the greater

the probability of stratification between liquid and vapour phases inside the tubes.

“Lack of exposure of the internal tube surfaces to the boiling refrigerant causes significant reductions in the utilisation of the tube surface area,” explains Jensen. “The result is a significant reduction in evaporator performance.”

Cotter’s findings were subsequently confirmed by similar video recordings conducted by Dr Pega Hrnjak and presented at the annual IIAR conference in the US.

THREE DECADES OF DEVELOPMENTJensen’s packaged, centralised low-charge NH3 refrigeration system represents the culmination of three decades of development and practical field testing carried out in Australia.

Despite dry-expansion NH3 refrigeration plants generally having a poor reputation around the world, the Scantec design challenges this perception.

WINNER

Building exterior, offices to the left,

ScanPAC to the right

Industrial ammonia compressor with water cooling and variable frequency drive


“The elements that are essential for a successful dry-expansion ammonia installation are evaporator (air cooler) design, and the control system that controls the refrigerant injection and manages the automatic hot gas defrost,” says Jensen.

He says his firm specifically designs every air cooler in a centralised, low-charge NH3 refrigeration system based on first principles that consider the operating envelope, operating

temperatures, liquid subcooling, gravity, oil content, orientation, materials of construction and the defrost method.

“For consistency, and to broaden the field of prospective evaporator suppliers, the evaporator design uses a coil rating software developed and refined … over the last three decades,” Jensen says.

This software is capable of rating most commonly used tube and fin geometries, and materials.

“The centralised PLC-based control systems used for the control of low-charge NH3 plant have been developed and refined since 2012/13,” Jensen says. “The use of combined superheat/quality (refrigerant wetness) based injection control is considered novel.”

FUTURE-PROOFINGFollowing the introduction of the carbon-equivalent HFC levy in 2012, Scantec advised Bidfood that the time had come to future-proof its refrigeration systems at all sites. This position was only further crystallised by Australia’s subsequent signing of the Kigali Amendment to the Montreal Protocol four years later, which initiated the phase-down of HFCs in Australia from January 2018.

These events led to the consideration of a natural-refrigerant-based solution to replace the existing air-cooled HFC 404A based systems with electric defrost operating at Bidfood Mackay’s distribution centre.

LESSONS FROM THE REFRIGERATION SPECIALISTScantec Refrigeration’s managing director, Stefan Jensen, F.AIRAH, shares some of the lessons from the installation of the packaged, centralised low-charge NH3 (ammonia) system at Bidfood Mackay.

1. Centralised low-charge NH3 systems are a very viable option even for refrigeration capacities this moderate. The additional capital cost over and above that of a transcritical CO2 system with adiabatically assisted air-cooled gas cooler and electric defrost is returned in four years based on energy savings alone.

2. Where a transcritical CO2 system designed to replace the existing R404A systems would have delivered an energy performance improvement of no better than

20 per cent and probably less, the centralised low-charge NH3 system has delivered a recorded reduction in the SEC-value of up to 71 per cent compared with the HFC systems it replaced.

3. The concept is highly suitable for a utility financing model where the end-user does not own the plant but only pays for the conversion of electrical energy to cooling. Due to the superior energy efficiency, the cost of this conversion for a centralised, low-charge NH3 system is very attractive to end-users compared with alternative, less capital-intensive solutions that do not deliver energy efficiencies comparable with those of the centralised low-charge NH3 concept.

F E A T U R E

EUROPEAN ENERGY EFFICIENT PRODUCTS

FIRST CLASSBlauberg Ventilation is a market leader in the innovation, design and manufacture of modern, highly efficient ventilation products.

Turbo ECInline mixed flow fans with EC motor

Air flow: up to 1995 m³/h 554 l/s

Power: from 32 W

Noise level:from 21 dB(A)

Heat recovery efficiency:up to 93%

Iso-Mix ECSound insulated inline mixed flow fans with EC motor

Air flow: up to 1995 m³/h 554 l/s

Power: from 30 W


VENTO Expert A50-1 S10 W V.2Energy recovery single-roomunits with EC motor

Air flow: up to 50 m³/h

Power: from 4.45 W


KOMFORT EC S(B)Wall-mounted heat and energy recovery air handling units with EC motor

Air flow: up to 750 m³/h

Heat recovery efficiency:up to 98%

Inline mixed flow fans

Decentralised energy recovery units Heat and energy recovery air handling units

Phone: 1300 475 504 Email: [email protected] Web: blaubergventilation.com.au

WINNER

Refrigerant piping between building and ScanPAC

Evaporative condenser fans

ScanPAC interior


“The requirements at the Bidfood Mackay site are quite typical of hundreds, perhaps thousands, of other refrigerated distribution centres in Australia and elsewhere,” says Jensen. “There are low- and medium-temperature services of a certain mix ratio, the facility is used for storage of a variety of food products, and product movements vary on a daily and yearly basis.”

The climatic conditions at Mackay are challenging, however, and characterised by high wet bulb and dry bulb temperatures. This places the application of some natural refrigerant-based solutions at a substantial disadvantage, and made the use of the packaged, centralised low-charge NH3 refrigeration system more attractive.

“A transcritical CO2 system was considered,” says Jensen.

“This would have featured considerably lower capital cost (around 40 per cent lower than the centralised low-charge NH3 refrigeration system) but there would have been limited to no energy

performance improvement compared to the existing air-cooled HFC 404A systems with electric defrost being replaced.”

Modelling forecast a simple pay-back period of less than five years based on the energy savings associated with the application of the packaged, centralised low-charge NH3 system. The site installation commenced in mid-2018.

BIDFOOD MACKAYThe installation of the packaged, centralised low-charge NH3 refrigeration system at Bidfood Mackay was completed in August 2018.

The recorded improvement in SEC-value during the first period after commissioning (up to and including January 2019) was considerable.

“The energy consumption of the HFC 404A-based refrigeration systems for the same summer period during the years 2013/14 was recorded at an average of 1,794kWh/day, or 206kWh/m³a when corrected for the light and power reticulation included in the general kWh meter reading,” Jensen says.

“Following the conversion to ammonia, the specific energy consumption reduced to 88kWh/m³a. This represented a recorded SEC-value reduction of 57 per cent.”

Since then, the system’s energy efficiency has gradually improved as a result of adjustments made to sub-floor heating temperature settings and the compressor capacity control.

As well as delivering a significant energy consumption reduction, the Bidfood Mackay installation challenges

F E A T U R E

A full range of brochures, manuals, and technical and specification information is available from the Bosch website www.bosch-industrial.com.au or call 1300 30 70 37 for assistance.

Bosch, a global leader in heating boiler technology, has now introduced a range of commercial and industrial heating boilers to the Australian market. For commercial heating applications, Bosch can offer steel fire tube, cast iron, modular condensing (AlSi heat exchanger), and stainless steel condensing boiler technologies. For industrial heating applications, Bosch has packaged hot water and steam boilers in capacities up to 20 MW in both Fire Tube and Water Tube technology.

Bosch Commercial & Industrial Boilers

GE

RM

AN TECHNOLOG

Y

GE

RM

A N T E C H N O

LOG

Y

NEW

PROJECT AT A GLANCE

The personnel

▲ Client: Bidfood

▲ Electrical contractor: Claxton Electrical

▲ Refrigeration contractor: Scantec Refrigeration Technologies

▲ Refrigeration Engineer: Scantec Refrigeration Technologies

The equipment

▲ Compressors: SABROE

▲ Electronic Controls: Allen Bradley

▲ Evaporators and air coolers: Thermofin

▲ Heat exchanger: Alfa Laval

▲ Low-charge NH3 refrigeration system: Scantec Refrigeration Technologies

▲ Mechanical controls: Danfoss

▲ PLC control system and SCADA: Scantec Refrigeration Technologies

▲ Sensors: HB Products + Danfoss

Variable frequency drive

Building interior

the general industry consensus that NH3 is only suitable for large refrigeration plants.

Rather, the low- and medium-temperature design capacities at Mackay are 45kW and 48kW respectively.

“This is in the same capacity category as a small-to-medium size retail refrigeration system,” says Jensen.

With the HFC phase down triggering an unprecedented technology transition globally, and an estimated 100,000 cold storage facilities operating in Australia alone, the experience at Bidfood Mackay might well change perceptions about the application of ammonia across the broader refrigeration industry. ❚

Scantec’s Bidfood Mackay installation earned the 2019 AIRAH Award for

Excellence in Refrigeration.

LOWERING THE AMMONIA INVENTORYMany jurisdictions around Australia, including councils, stipulate risk-mitigation measures as a function of ammonia (NH3) inventory. The latest AS/NZS 5149 refrigeration standard nominates a limit of 4,500kg, beyond which additional safety measures are required.

And similar safeguards are in place around the world. For instance, in the US, NH3 inventories exceeding 10,000lbs (approximately 4,536kg) trigger the PSM/RMP regulatory requirements causing significant compliance costs for plant owners. In France, NH3 inventories beyond 1,500kg trigger significant compliance issues.

In Germany, inventories above 3,000kg trigger the safety measures required under the German Störfallverordnung – again significant and ongoing compliance costs for owners is the result. In Switzerland, the limit is 2,000kg.

The ability to operate an NH3 refrigeration system with a significantly lower refrigerant inventory enables owners to have more refrigeration capacity without the associated compliance costs.

“And aside from regulatory issues, lower NH3 inventories are in the interests of public and employee safety,” says Scantec’s Stefan Jensen, F.AIRAH.

WINNER

new benchmark - airah

Documents