2022 IIAR Technical Papers

Savannah, GA
44th Annual Meeting

CFD-based Design Basis for Avoidance of Hydraulic Shock in Ammonia Pipework Systems

Chidambaram Narayanan
Principal Engineer, AFRY Switzerland AG
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Incidents of ammonia releases due to hydraulic shock in the refrigeration pipework have been reported in the past and could occur in the future. Such shock events carry significant commercial risks and are a concern for the health and safety of humans. Two locations where hydraulic shock occurs frequently are, (a) in the evaporator coil headers at the beginning of a hot gas defrost sequence, and (b) in the wet suction piping from the evaporator at the end of the hot gas defrost sequence. Research on experimental and numerical characterization of hydraulic shocks in ammonia systems was carried out through two impactful projects funded by ASHRAE. In the latter project a validated CFD model was developed using the experimental data as a basis. This CFD model was subsequently applied to a real incident where a shock amplitude of 4,000 psia was predicted as expected from forensic analysis. The validated CFD model was used in this study to simulate a large set of conditions related to generic hot gas defrost piping, to establish a design basis prevent hydraulic shock.

Proper Installation and Maintenance Practices for Variable Frequency Drives

Paul Jasczynski
Sales Marketing Manager, Logic Technologies
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The use of a variable frequency drive (VFD) to control the speed of an AC induction motor has numerous benefits, including energy savings, improved reliability, reduced equipment wear and tear, and more precise control of motor speed. When operating, VFDs generate heat, and the output voltage waveform is not a true, clean sinewave. These characteristics present challenges when installing a VFD. However, following a few proper installation practices can help ensure successful operation. Most VFDs fail because of an improper installation and not because of a poor-quality product.

Managing Your Energy Costs: It Can Be Done!

James Majsak
Construction Manager, CrossnoKaye
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All too often, energy management projects with good potential will fail for any number of reasons. Most of these failures will be a result of the project not addressing key requirements for success, or not meeting the expectations of all users throughout the organization. This report is intended to provide a 10,000-foot view on taking a holistic approach to energy management and reduce the risk of project failure.

Benefit of Ammonia Heat Pump Implementation in the Industry and for District Heating

Kenneth Hoffmann
Application Manager Heat Pumps, GEA Heating and Refrigeration Technologies
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Over the last 15 years the market for high-temperature ammonia heat pumps has been growing in Europe and now it is also taking off in North America. That period in Europe has yielded many lessons as higher pressure and temperature present new challenges in refrigerant design. This paper explains where heat pump installation differs from refrigeration installation through three case studies of installations in Europe. The favorable thermodynamic properties of ammonia and good system design lead to high efficiency and short payback, which the three cases will describe. With many heat pumps being installed into the district heating market new challenges also arise regarding ammonia handling and safety as the installations are now closer to the public than traditional industrial settings for ammonia refrigeration systems. The paper will describe how these challenges have been overcome. With the phasedown of fluorinated greenhouse gases (F gases), incentives to go for natural refrigerants for these solutions have increased, and as this paper shows financial and environmental incentives to employ ammonia heat pumps are also large.

Oil Management Design Considerations for Industrial Transcritical CO2 Systems

Alessandro Silva, Senior Application Engineer
Joe Sanchez, VP Engineering
BITZER US
Application Manager Heat Pumps, GEA Heating and Refrigeration Technologies
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Carbon dioxide as a refrigerant is becoming increasingly more popular on a global scale. The industrial refrigeration market is also finding applications for transcritical CO2 systems. Unlike ammonia systems, oil in CO2 systems is typically miscible and can create unique challenges in its management. With thousands of commercial transcritical systems running worldwide, much knowledge and experience has been gained on this topic. Certainly these systems can be employed in many industrial environments. However, some industrial systems have increased complexities; not just larger capacities, but also longer pipe runs and/or more dramatic load shifts. These factors should drive an industrial transcritical CO2 system designer to consider additional measures.

Absorption Applications for Residential-Light Commercial Space Conditioning and Water Heating

Michael Garrabrant, President & CEO
Stone Mountain Technologies, Inc.
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Absorption cycles using the ammonia-water refrigerant pair have a long track record of commercial applications ranging from industrial-size cooling using waste heat as the energy source, to gas-fired residential air-conditioners and small refrigerators for recreational vehicles using propane fuel. However, the heating side of the cycle (as a heat pump) has not seen widespread use. With a Coefficient of Performance (COP) ranging from 1.4 to 2.0 for space and water heating, ammonia-water absorption heat pumps have potential to provide significant CO2 emission reductions for residential and light commercial applications, which are historically very difficult to decarbonize. In this paper, methods of applying gas-fired absorption heat pumps to heating applications normally served by furnaces, boilers or commercial water heaters are reviewed, including the potential energy and CO2 emissions reductions compared to both conventional and electric vapor compression appliances.

Transcritical CO2 Compressors: Technical Challenges in Industrial Refrigeration Applications

Giacomo Pisano, M. Eng.
DORIN USA
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Carbon dioxide (CO2) has today become the standard refrigerant of choice for many applications, often enabling better coefficient of performance (COP) than the previously adopted technologies based on other refrigerants. This trend is progressively leading to both a lower usage of high global warming potential (GWP) refrigerants and sensible energy expenditure reductions in several industrial sectors. However, specific components and appropriate system design are mandatory when approaching CO2 technology, due to the unique thermodynamic characteristics of this refrigerant.

Simple Equations for Determining Mass Flow in Refrigeration Systems

Don Faust, Training Manager
FRICK, a Johnson Controls Company
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The goal of any industrial refrigeration system is to remove heat. Therefore, the total heat load is the design engineer’s first calculation, which is then used to size and select the evaporators. Unfortunately, this heat load is often also applied to the sizing of other components in the system, which can result in errors. However, heat load should only be used to size components that exchange heat. This paper introduces a methodology and develops simple equations for determining mass flows in industrial refrigeration systems. The proposed methodology involves the mass balance technique, which assumes a steady-state condition in which the sum of the mass flows into a machine or system equals the sum of the mass flows out. The mass balance technique can help quantify mass flows that may be difficult to calculate using other methods. The mass flow equations apply to any refrigerant in a typical vapor compression cycle. Modern industrial refrigeration systems often employ multiple temperature and pressure levels to maintain various conditions in processing and storage facilities. Mass balances enable the accurate sizing of various pieces of equipment, and this technique can reveal strategies for saving energy and initial cost.

Don’t Curse the Purger

Don Tragethon CIRO, CRST, RAI
Regulatory Liaison, Western Precooling
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The goal of operators, contractors, and design engineers is to operate a closed loop refrigeration system as close to design intent as possible. The owner wants maximum value from the equipment and personnel employed at the facility. The presence of gases that do not liquify within the operating conditions add cost to the running of the system.

Liquid Overfeed Ammonia Refrigerating Plant and Energy Efficiency

Stefan S. Jensen, Managing Director
Scantec Refrigeration Technologies Pty. Ltd
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The global HFC phase-down and the proposed restrictions on PFAS (per- and polyfluorinated alkyl substances) have accelerated the transition towards natural refrigerants. The requirements of the Paris Agreement, the European CBAM (Carbon Border Adjustment Mechanism) initiative, and ESG (Environmental, Social, Governance) have combined to elevate the ranking of system energy efficiencies in decision-making processes. Energy performance benchmarking for certain refrigeration applications is emerging in various polities and sectors. The benchmarking is often technology- agnostic and challenges long-held conventions and energy-efficiency engineering capabilities. This will continue and will force critical reviews of all refrigeration system design conventions. One such system is the liquid overfeed concept that will celebrate its centenary in 2025. This paper presents energy performance records from refrigerating plants servicing several refrigerated warehouses and provides evidence that the presence of high-density liquefied refrigerant in complex suction line networks of expansive plants may cause more energy waste than previously thought. This paper seeks to quantify the energy performance penalties associated with liquid overfeed through comparisons of near-identical practical installations where the only significant difference is the presence (or not) of liquefied refrigerant in the suction line network. Finally, this paper presents a small selection of practical business cases that demonstrate the economic viability of design interventions targeting maximization of energy efficiency

Machinery Room Ventilation and Ammonia Release Computational Fluid Dynamics (CFD) Study

Scott Davis, PhD, PE;
Derek Engel, PE;
and John Pagliaro PhD, PE;
Gexcon US, Inc.
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The ammonia refrigeration industry has a historically good safety record and hence there have been few instances of ammonia release resulting in ignition events. To continue and improve upon safe practice, computational fluid dynamics (CFD) modeling was undertaken in the present study to evaluate the effectiveness of various emergency ventilation designs and emergency ventilation flow rates in protecting against accidental ammonia releases in ammonia refrigeration machinery rooms. The study was specifically limited to only consider ammonia releases from full-bore ¾"" diameter line failures containing: 1) high temperature, high pressure liquid (i.e., saturated liquid); 2) low temperature, high pressure liquid (i.e., subcooled liquid); and 3) high pressure vapor (i.e., superheated vapor). The study did not evaluate the rationale behind, nor the likelihood associated with a full-bore ¾"" diameter release, hence, as mentioned above, the study was specifically limited to this condition. Note, while larger hole sizes are possible, they do not arise frequently in this industry.