Low-GWP alternative refrigerant blends for HFC-134a :

Abstract

This project addresses the objectives of the Statement of Need number WPSON-17-20 "No/Low Global Warming Potential Alternatives to Ozone Depleting Refrigerants." Its goal is to identify and demonstrate performance of low global-warming-potential (GWP), nonflammable refrigerants to replace HFC-134a in military environmental control units (ECUs). This project is a follow-on to the limited-scope project WP-2740, which used thermodynamic cycle simulation models alone to screen over 100 000 refrigerant blends and identified over 20 candidate HFC-134a replacements. In this study we narrow the pool of blend candidates down to three 'best' fluids, verify experimentally their flammability behavior, demonstrate their performance through tests in a military ECU in environmental chambers over a wide range of operating conditions, and extrapolate the laboratory-measured performance to ECUs equipped with optimized heat exchangers through first-principles-based simulations combined with machine-learning optimization methods. This Interim Report documents the work leading to the selection of three 'best' blends. This work included refrigerant blend tests in a laboratory mini-breadboard heat pump apparatus, fundamental measurements and modeling of thermophysical properties, two-phase heattransfer performance, and flammability behavior.

Validation of and optimization with a vapor compression cycle model accounting for refrigerant thermodynamic and transport properties

“…For example, the model was used to evaluate replacements for high global-warming-potential (GWP) refrigerants, whose future use is limited by regional and global regulations [17], [18]. Domanski et al [19] used CYCLE_D-HX to evaluate low-GWP options for medium and high-pressure applications, and Bell et al [20] and Domanski et al [21] used the model to select candidates for non-flammable R-134a replacements, which were later extensively tested in [22]. The referenced simulationbased low-GWP refrigerant screening studies are supported by the experimental validation presented in this work.…”

“…Tested 'medium-pressure' refrigerants included R-134a, and five lower-GWP replacements including: R-1234yf (A2L classification) and four of the 'best' non-flammable candidates from [21], R-513A, R-450A, Tern-1, and R-515B. Tern-1 is a ternary blend developed by NIST for [22]. Tested 'high-pressure' refrigerants included R-410A, and three lower-GWP replacements with 'A2L' safety classification: R-32, R-454B, and R-452B.…”

Update of legacy NIST horizontal micro-fin tube convective boiling measurements and model with current fluid property values

“…NIST (2021) provides an online database that contains the complete corrected flow boiling heat transfer measurements of the Hamilton et al (2008), the Kedzierski and Park (2013), the Kedzierski and Kang (2016), and the Kedzierski and Kang (2018). The data presented in Domanski et al (2021) is also included in the database; however, it did not require correction. The online database shows the expanded measurement uncertainty (U) of the various measurements along with the range of each test parameter in the four studies in Table 1.…”

“…Finally, the fourth NIST study (Kedzierski and Kang, 2018) contains the refrigerants R1234yf, R134a, and R450A. The fifth study are measurements for R513A, R515B, and R450A that were analyzed with the current REFPROP and presented without the raw measurements in Domanski et al (2021).…”

Vapor and Liquid (p–ρ–T–x) Measurements of Binary Refrigerant Blends Containing R-134a, R-1234yf, and R-1234ze(E)

“…The measurements presented here were part of a larger project aimed at identifying and experimentally demonstrating the performance of several candidate nonflammable refrigerant blends to replace R-134a in military environmental control units. 19 In this work, we report pressure−density−temperature−composition (p−ρ−T−x) measurements in the singlephase and supercritical regions for three binary refrigerant blends: R-1234yf + R-134a, R-134a + R-1234ze(E), and R-1234yf + R-1234ze(E). Overall, these measurements covered temperatures from approximately 230 to 400 K and pressures up to 21 MPa, and sample compositions were approximately (0.3/0.7) and (0.7/0.3) mole fraction for each blend.…”