Track: Heat Exchange Equipment
Sponsor: MTG.LowGWP Lower Global Warming Potential Alternative Refrigerants, 1.3 Heat Transfer and Fluid Flow, TCs 1.3, 3.1, 8.4, 8.5, 8.11, The American Society of Thermal and Fluids Engineers (ASTFE) and the U.S. National Committee of the International Institute of Refrigeration (IIR).
Chair: Lorenzo Cremaschi, Ph.D., Member, Auburn University, Auburn, AL

This session introduces the audience to heat transfer characteristics, energy performance, safety and trade-off aspects of the low GWP refrigerants used in heat exchange equipment of air conditioning and refrigeration systems. The speakers provide an overview of several case-studies with low GWP refrigerants and with natural refrigerants, and they discuss modeling, simulation and laboratory performance testing. Real world applications and performance under field type conditions are presented. This session provides the background information for the follow up forum panel discussion of Part 2 of this session.

1. Simulated Thermal Performance of Flooded Evaporators with R1234ze (and others) Vs. R134a with Oil Effects
John Thome, Ph.D., Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
This presentation describes a new simulation code for flooded evaporators, which is a fully-incremental code along the length of the bundle and also tube row by tube row from bottom to top. This code handles enhanced boiling tubes, new and existing refrigerants, adverse oil effects locally within the bundle and the onset of dryout and dry tube rows along the top of the bundle. Presently, the code is used to make and present some case studies on thermal performance between new and existing refrigerants, focusing on local and total performance of the bundle with and without oil effects.

2. Low Environmental Impact Refrigerants for Air-Conditioning, Chiller and Refrigeration Applications
Ankit Sethi, Associate Member, Honeywell International, Buffalo, NY
R410A refrigerant is used widely for residential and commercial air-conditioning, heat pump applications and air-cooled direct expansion chillers and R404A refrigerant is widely used for various refrigeration applications. The first part of this presentation discusses an evaluation of low GWP replacements for R410A in air-conditioning and chiller applications. The second part presents an evaluation of low GWP replacements for R404A in refrigeration applications. Thermal properties as well as experimental results in representative systems and components are presented, showing the benefits of using these new working fluids.

3. Recent Developments in Low GWP Refrigerants for Refrigeration and Air Conditioning
Joshua Hughes, Member, Chemours, Wilmington, DE
Blended HFO-based refrigerant compositions have been developed and optimized to provide improved overall safety and performance, while retaining significant environmental sustainability properties versus the legacy refrigerants. The trade-offs that exist between refrigeration capacity, energy efficiency, temperature glide, GWP value and flammability in optimized HFO-based refrigerant blends have been explored and assessed. Data presented will include thermodynamic properties and modeling results, heat transfer results and system performance results. These new refrigerant blends should provide useful options to help maintain quality of life and health benefits from air conditioning and refrigeration, but in an energy efficient, cost effective and environmentally sustainable manner.

4. Comparative Analysis of Conventional Shell Side Ammonia Flooded Evaporator versus New Concept Direct ExpansionEvaporator
Zahid Ayub, Ph.D., P.E., Fellow ASHRAE, Isotherm, Inc., Arlington, TX
Extensive experimental study was conducted on direct expansion of ammonia on a plain tube bundle at saturation temperature range of -1.7 to -20C and heat flux range of 5 – 45 kW/m2. Heat transfer coefficient showed a classic behavior of increase with both saturation temperature and heat flux. The effect of exit superheat and inlet quality on the overall performance and pass to pass bundle effect was also investigated. The results are compared with such type chillers currently installed world-wide and conventional flooded evaporator operating at the same operating conditions. This concept has advantages over the flooded systems.

5. Heat Exchanger Performance of Low GWP Refrigerants in Chillers
Kenneth Schultz, Ph.D., Member, Ingersoll Rand, La Crosse, WI
This presentation provides an overview of the thermodynamic and heat transfer properties of the new low GWP refrigerants being considered for replacing R123, R134a and R410A in chillers. Fortunately, the thermodynamic and heat transfer properties of fluids to replace R123 in low pressure chillers are quite good. On the other hand, the characteristics of the medium and high pressure fluids present some challenges to maintaining the efficiencies of chillers using R134a and R410A today.

Presented: Tuesday, January 23, 2018, 8:00-9:30 AM
Run Time: 90 min.

This is a zip file that consists of PowerPoint slides synchronized with the audio-recording of the speaker (recorded presentation), PDF files of the slides, and audio only (mp3) for each presentation.