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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Performance of R-410A Alternative Refrigerants in a Reciprocating Compressor Designed for Air Conditioning Applications

In response to environmental concerns raised by the use of refrigerants with high Global Warming Potential (GWP), the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) has launched an industry-wide cooperative research program, referred to as the Low-GWP Alternative Refrigerants Evaluation Program (AREP), to identify and evaluate promising alternative refrigerants for major product categories. After successfully completing the first phase of the program in December 2013, AHRI launched a second phase of the Low-GWP AREP in 2014 to continue research in areas that were not previously addressed, including refrigerants in high ambient conditions, refrigerants in applications not tested in the first phase, and new refrigerants identified since testing for the program began. Although the Ozone Depletion Potential of R-410A is zero, this refrigerant is under scrutiny due to its high GWP. Several candidate alternative refrigerants have already demonstrated low global warming potential. Performance of these low-GWP alternative refrigerants is being evaluated for Air conditioning and heat pump applications to ensure acceptable system capacity and efficiency. This paper reports the results of a series of compressor calorimeter tests conducted for the second phase of the AREP to evaluate the performance of R-410A alternative refrigerants in a reciprocating compressor designed for air conditioning systems. It compares performance of alternative refrigerants ARM-71A, L41-1, DR-5A, D2Y-60, and R-32 to that of R-410A over a wide range of operating conditions. The tests showed that, in general, cooling capacities were slightly lower (except for the R-32), but energy efficiency ratios (EER) of the alternative refrigerants were comparable to that of R-410A.

Alternative Refrigerants↗
DOE OSTI2017

Evaluation of Alternative Refrigerants for Mini-Split Air Conditioners

The phase-out of hydrochlorofluorocarbons (HCFC) refrigerants in developing countries is currently underway according to the Montreal Protocol. R-22 is one of the most commonly used HCFCs in the developing nations. It is extremely well suited for air conditioning and refrigeration (AC&R) in high ambient temperature environments. Non-Article 5 countries have already gone through the phase-out of HCFCs and settled on using R-410A as the refrigerant of choice for AC applications. Previous studies have shown that R-410A results in significant capacity and performance degradation at higher ambient temperature conditions. As such, there is a growing concern on finding alternative refrigerants to R-22 that would have zero ODP, lower GWP, and at the same time maintain acceptable performance at higher ambient temperatures. Furthermore, the developed world s transition through higher global warming potential (GWP) refrigerants like HFC and HFC blends resulted in significant direct CO2 equivalent emissions. It is imperative to develop a bridge for developing nations to avoid the transition from HCFC to HFC and then from HFC to alternative lower GWP refrigerants. This paper summarizes data from an experimental campaign on alternative refrigerant evaluation for R-22 and R-410A substitutes for mini-split air conditioners designed for high ambient environments. The experimental evaluation was performed according to ANSI/ASHRAE Standard 37 and the performance was rated at test conditions specified by ANSI/AHRI 210-240 and ISO 5151. Additional tests were conducted at outdoor ambient temperatures of 52 C (125.6 F) and 55 C (131 F) to evaluate their performance at high ambient conditions. Alternative refrigerants, some of which are proprietary, included R-444B, DR-3, N-20b, ARM-20b, R-290, and DR-93 as alternatives to R-22 and R-32, DR-55, L41-2, ARM-71A, and HPR-2A as alternatives to R-410A. The units performances were first verified using the baseline refrigerant and then drop-in refrigerant evaluation followed including soft optimization to ensure refrigerant performance is adequately represented. The soft optimization included: 1) charge optimization, 2) lubricant change, and 3) flow control. The paper presents the relative performances (efficiency and capacity) of the alternative refrigerants compared to the baseline refrigerants at the different operating conditions. Paper concludes with remarks about the suitability of alternative refrigerants for R-22 and R-410A applications in high ambient temperature regions.

Alternative Refrigerant↗
DOE OSTI2016

Alternative Refrigerant Evaluation for High-Ambient-Temperature Environments: R-22 and R-410A Alternatives for Rooftop Air Conditioners

The Oak Ridge National Laboratory (ORNL) High-Ambient-Temperature Evaluation Program for Low-Global Warming Potential (Low-GWP) Refrigerants aims to develop an understanding of the performance of low-GWP alternative refrigerants relative to hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC) refrigerants in packaged or Rooftop Unit (RTU) air conditioners under high-ambient-temperature conditions. This final report describes the parties involved, the alternative refrigerants selection process, the test procedures, and the final results.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2015

Alternative Refrigerant Evaluation for High-Ambient Temperature Environments: R-22 and R-410A Alternatives for Mini-Split Air Conditioners

The Oak Ridge National Laboratory (ORNL) High-Ambient Temperature Testing Program for Low-GWP Refrigerants aims to develop an understanding of the performance of low-Global Warming Potential (low-GWP) alternatives to Hydrochlorofluorocarbon (HCFC) and Hydrofluorocarbon (HFC) refrigerants in mini-split air conditioners under high ambient temperature conditions. This interim working paper describes the parties involved, the alternative refrigerants selection process, the test procedures, and the preliminary results.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

Extending ORNL HPDM Capabilities for Design and Optimization of New Refrigerant Blends – FY18 1st Quarterly Milestone: Perform literature review to collect heat transfer, pressure drop correlations and compressor mapping method for alternative refrigerants

Through a comprehensive literature survey, we identified heat transfer and pressure drop correlations for two-phase evaporation and condensation in fin-and-tube coils using microfin tubes and micro-channel heat exchangers. We also developed a compressor mapping method to convert the maps originally developed for R-22 or R-410A to be used by the alternative lower GWP refrigerants. The correlations and method will be implemented in HPDM for design and optimization of air conditioners and heat pumps using the new refrigerants/blends.

42 ENGINEERING↗
DOE OSTI2017

Compare optimized performance results for packaged RTU using all alternative refrigerants FY17 1st Quarter Milestone Report

Based on the laboratory investigation in FY16, for R-22 and R-410A alternative low GWP refrigerants in two baseline rooftop air conditioners (RTU), we used the DOE/ORNL Heat Pump Design Model to model the two RTUs and calibrated the models against the experimental data. Using the calibrated equipment models, we compared the compressor efficiencies, heat exchanger performances. An efficiency-based compressor mapping method was developed, which is able to predict compressor performances of the alternative low GWP refrigerants accurately. Extensive model-based optimizations were conducted to provide a fair comparison between all the low GWP candidates by selecting their preferred configurations at the same cooling capacity and compressor efficiencies.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2016

Evaluating alternative refrigerants for high ambient temperature environments

According to the Montreal Protocol, developing countries have started the phase out schedule of the ozone depleting substances, including HCFC refrigerants, in 2015 and expect them to reach 35% reduction in 2020. This commitment to the start the phase out of HCFC refrigerants, especially R-22, in developing countries is seen as an opportunity to introduce lower Global Warming Potential (GWP) refrigerants. Furthermore, this paper summarizes an investigation into the performance of lower GWP refrigerants in high ambient temperature environments, experienced in some of the developed countries, in mini-split air conditioning units.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Analysis of Environmentally Friendly Refrigerant Options for Window Air Conditioners

This paper presents a technical assessment of environmentally friendly refrigerants as alternatives to R410A for window air conditioners. The alternative refrigerants that are studied for its replacement include R32, a mixture of R32/R125 with 90%/10% molar concentration, R600a, R290, R1234yf, R1234ze and R134a. Baseline experiments were performed on a window unit charged with R410A. The heat pump design model (HPDM) was modified and calibrated with the baseline data and was used to evaluate the comparative performance of the WAC with alternative refrigerants. The paper discusses the advantages and disadvantages of each refrigerants and their suitability for window air conditioners. Among all the refrigerants studied, R32 offers the best efficiency and the lowest Global Warming Potential (GWP), and hence its use will result in the overall environmental friendliness.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1993

COP improvement of refrigerator/freezers, air-conditioners, and heat pumps using nonazeotropic refrigerant mixtures

With the February, 1992 announcement by President Bush to move the deadline for outlawing CFC (chloro-fluoro-carbon) refrigerants from the year 2000 to the year 1996, the refrigeration and air-conditioning industries have been accelerating their efforts to find alternative refrigerants. Many of the alternative refrigerants being evaluated require synthetic lubricants, are less efficient, and have toxicity problems. One option to developing new, alternative refrigerants is to combine existing non-CFC refrigerants to form a nonazeotropic mixture, with the concentration optimized for the given application so that system COP (Coefficient Of Performance) may be maintained or even improved. This paper will discuss the dilemma that industry is facing regarding CFC phase-out and the problems associated with CFC alternatives presently under development. A definition of nonazeotropic mixtures will be provided, and the characteristics and COP benefits of nonazeotropic refrigerant mixtures will be explained using thermodynamic principles. Limitations and disadvantages of nonazeotropic mixtures will be discussed, and example systems using such mixtures will be reviewed.

Westra, Douglas G.↗
DOE OSTI2018

Investigation of low GWP Flammable Refrigerant Leak from Rooftop Units

One of the recent global trends in the air conditioning industry is to replace the high global warming potential (GWP) refrigerants such as R410A and R134A with alternative refrigerants that have lower GWP. However, most of these alternative refrigerants are classified as slightly flammable (classified by ASHRAE as A2L) which impose a potential fire risk. Therefore, research efforts have focused on the study of flammable refrigerants and their potential risk. In this paper, we present a numerical investigation to study one R32 (ASHRAE A2L) leak scenario from a 5 ton rooftop unit into a conference room with the dimensions of 40 × 30 × 8 ft (12.2 × 9.1 × 2.4 m). A catastrophic rupture of a Â-inch refrigerant line was simulated. A total charge of 15lb (6.8 kg) was leaked in 31.5 seconds. A mixture of air and refrigerant is diffused from four air diffusers mounted in the ceiling. The ducting system was simulated first to predict the air/refrigerant mixure entering the room from the four air diffusers.The total simulation time was 10 minutes to study the refrigerant diffusion and dispersion of the flammable refrigerant in the room after the inception of the leakage. The volume fraction is presented as a function of time at different monitoring points inside the room. The total room volume where the R32 concentration exceeds its LFL is quantified and presented as an indication of the risk of ignition.

Elatar, Ahmed↗
DOE OSTI2018

Evaluation of flammable volume in the case of a catastrophic leak of R-32 from a rooftop unit

With the effort to use alternative refrigerants with lower global warming potential (GWP), the majority of these alternative refrigerants are classified as slightly flammable. Here in this paper we report on the numerical evaluation of a catastrophic leak scenario of R-32 refrigerant from a 3-ton roof top air conditioning unit (RTU) which serves a 12.2 × 9.14 × 2.4 m room. A full rupture of a 6.35 mm (¼ inch) pipe downstream of the evaporator coil is simulated. Two separate cases with refrigerant releases of 1.81 kg and 3.62 kg charge have been studied. The two charges are released in 10.2 and 20.4 s, respectively, just after the end of a unit cooling cycle. The flammable volume inside the room existed only for about 40 s with a maximum flammable volume inside the room of 1.12% of the total room volume for the 3.62 kg charge case.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2016

Preliminary Analysis of a Fully Solid State Magnetocaloric Refrigeration

Magnetocaloric refrigeration is an alternative refrigeration technology with significant potential energy savings compared to conventional vapor compression refrigeration technology. Most of the reported active magnetic regenerator (AMR) systems that operate based on the magnetocaloric effect use heat transfer fluid to exchange heat, which results in complicated mechanical subsystems and components such as rotating valves and hydraulic pumps. In this paper, we propose an alternative mechanism for heat transfer between the AMR and the heat source/sink. High-conductivity moving rods/sheets (e.g. copper, brass, iron, graphite, aluminum or composite structures from these) are utilized instead of heat transfer fluid significantly enhancing the heat transfer rate hence cooling/heating capacity. A one-dimensional model is developed to study the solid state AMR. In this model, the heat exchange between the solid-solid interfaces is modeled via a contact conductance, which depends on the interface apparent pressure, material hardness, thermal conductivity, surface roughness, surface slope between the interfaces, and material filled in the gap between the interfaces. Due to the tremendous impact of the heat exchange on the AMR cycle performance, a sensitivity analysis is conducted employing a response surface method, in which the apparent pressure, effective surface roughness and grease thermal conductivity are the uncertainty factors. COP and refrigeration capacity are presented as the response in the sensitivity analysis to reveal the important factors influencing the fully solid state AMR and optimize the solid state AMR efficiency. The performances of fully solid state AMR and traditional AMR are also compared and discussed in present work. The results of this study will provide general guidelines for designing high performance solid state AMR systems.

Abdelaziz, Omar↗
DOE OSTI2016

Model validations for low-global warming potential refrigerants in mini-split air-conditioning units

To identify low GWP (global warming potential) refrigerants to replace R-22 and R-410A, extensive experimental evaluations were conducted for multiple candidates of refrigerant at the standard test conditions and at high-ambient conditions with outdoor temperature varying from 27.8 C to 55.0 C.. In the study, R-22 was compared to propane (R-290), DR-3, ARM-20B, N-20B and R-444B in a mini-split air conditioning unit originally designed for R-22; R-410A was compared to R-32, DR-55, ARM-71A, L41-2 (R-447A) in a mini-split unit designed for R-410A. To reveal physics behind the measured performance results, thermodynamic properties of the alternative refrigerants were analysed. In addition, the experimental data was used to calibrate a physics-based equipment model, i.e. ORNL Heat Pump Design Model (HPDM). The calibrated model translated the experimental results to key calculated parameters, i.e. compressor efficiencies, refrigerant side two-phase heat transfer coefficients, corresponding to each refrigerant. As a result, these calculated values provide scientific insights on the performance of the alternative refrigerants and are useful for other applications beyond mini-split air conditioning units.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Potential emission savings from refrigeration and air conditioning systems by using low GWP refrigerants

Refrigeration and air conditioning systems have high, negative environmental impacts due to refrigerant charge leaks from the system and their corresponding high global warming potential. Thus, many efforts are in progress to obtain suitable low GWP alternative refrigerants and more environmentally friendly systems for the future. In addition, the system’s life cycle climate performance (LCCP) is a widespread metric proposed for the evaluation of the system’s environmental impact.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1995

The Oak Ridge Refrigerant Management Program

For many years, chlorofluorocarbons (CFC's) have been used by the Department of Energy's (DOE) Oak Ridge Y-12 Plant in air conditioning and process refrigeration systems. However, Title 6 of the Clean Air Act Amendments (CAAA) and Executive Order 12843 (Procurement Requirements and Policies for Federal Agencies for Ozone Depleting Substances) signed by President Clinton require, as policy, that all federal agencies maximize their use of safe, alternate refrigerants and minimize, where economically practical, the use of Class 1 refrigerants. Unfortunately, many government facilities and industrial plants have no plan or strategy in place to make this changeover, even though their air conditioning and process refrigeration equipment may not be sustainable after CFC production ends December 31, 1995. The Y-12 Plant in Oak Ridge, Tennessee, has taken an aggressive approach to complying with the CAAA and is working with private industry and other government agencies to solve tough manufacturing and application problems associated with CFC and hydrochlorofluorocarbon (HCFC) alternatives. Y-12 was the first DOE Defense Program (DP) facility to develop a long-range Stratospheric Ozone Protection Plan for refrigerant management for compliance with the CAAA. It was also the first DOE DP facility to complete detailed engineering studies on retrofitting and replacing all air conditioning and process refrigeration equipment to enable operation with alternate refrigerants. The management plan and engineering studies are models for use by other government agencies, manufacturing plants, and private industry. This presentation identifies some of the hidden pitfalls to be encountered in the accelerated phaseout schedule of CFC's and explains how to overcome and prevent these problems. In addition, it outlines the general issues that must be considered when addressing the phase-out of ozone depleting substances and gives some 'lessons learned' by Y-12 from its Refrigerant Management Program. Discussion topics include requirements for developing a refrigerant management plan and establishing priorities for cost-effective compliance with the CAAA, as well as ways in which employees can be empowered to develop a comprehensive refrigerant management plan. The result of this employee empowerment was a cooperative labor-management effort that is beneficial for Y-12, DOE, and the environment.

Kevil, Thomas H.↗