An Overview of Environment-Friendly Refrigerants for Domestic Air Conditioning Applications

Abstract

Low global warming potential (GWP) refrigerants for the next-generation air conditioning systems have been investigated with target domestic applications. High-GWP refrigerants are mostly used in climate control applications such as heating, ventilation and air conditioning (HVAC) and refrigeration systems. The majority of refrigerants are responsible for significant environmental issues such as ozone layer depletion and global warming. The Montreal Protocol and the Kyoto Protocol have been implemented to address such issues. In the meantime, authorities in many countries have taken the initiative to phase out the usage of environmentally harmful refrigerants in vapor compression refrigeration systems. Following the global warming mitigation scheme by many signatory countries, research interest has been focused on finding alternative refrigerants with low or ultra-low GWP. This study considered the research trend and development of low-GWP refrigerants while examining system performance, safety issues, and the equivalent environmental impact as the critical assessment parameters. Here, the focus is primarily set on the potential of refrigerant blends (HFCs + HFOs) where the GWP value of 300 is set as the threshold value. Targeted for domestic heat pump systems, the performance of such systems using various refrigerant blends is collated and discussed. Many blends offer innovative drop-in replacements for R410A-conforming F-gas regulations. The technical difficulties and realistic remedies for the existing refrigerants are also discussed.

Engineered Nanoporous Frameworks for Adsorption Cooling Applications

“…Although GWP can potentially be reduced down to a threshold value of 300 via mixture strategies, temperature glide increases the possibility of refrigerants leaking and makes the ratio of components in the mixtures uncontrolled. These uncertainties are neutralized via optimizing the compressor and heat exchanger structure during the vapor-compressor process. , The following discussion puts more focus on the single fluorocarbon-based working pairs for adsorption cooling applications given the scope of this review.…”

“…These uncertainties are neutralized via optimizing the compressor and heat exchanger structure during the vapor-compressor process. 164,167 The following discussion puts more focus on the single fluorocarbon-based working pairs for adsorption cooling applications given the scope of this review.…”

“…Given the downward regulation of HFC production and consumption, HFOs being characteristic of near-zero GWP and zero-ODP are viewed as new and environmentally benign refrigerants. However, the usage of HFOs must reckon with their undesirable concerns, including higher potential risks toward flammability (higher ratio of C–H and C–F bond), toxicity, cost ineffectiveness, and a possible olefinic bond in HFO reacting with ozone to produce long-lived greenhouse gas as a byproduct , For example, Ye et al proposed Maxsorb III/HFO-1234ze­(E) as a promising working pair for adsorption cooling, although it has a much lower cooling efficiency than R32 or R134a–Maxsorb III pair. , For example, Ye et al proposed Maxsorb III/HFO-1234ze­(E) as a promising working pair for adsorption cooling, although it has a much lower cooling efficiency than R32 or R134a–Maxsorb III pair. Current trends for HFC replacement generally employ dual or ternary mixtures of HFCs and HFOs with/without carbon dioxide.…”

Potential of Energy Saving of Propane Heat Pump as replacement of gas boilers with low and high temperature emitters

“…The performance of heat pumps and air conditioning systems is considerably influenced by the thermo-physical properties of the working fluids. Thermodynamic properties (e.g., latent heat of vaporisation, heat transfer coefficients, density…), toxicity, flammability, environmental impact, cost and availability are crucial to ranking refrigerants and defining the best fluids [3]. Unfortunately, the refrigerants deployed currently in commercial ASHPs are harmful to the environment.…”

Modeling Liquid Thermal Conductivity of Low-GWP Refrigerants Using Neural Networks

“…Since environmental constraints and regulations [1,2] aim to limit the production and utilization of several high-global warming potential (GWP) refrigerants, worldwide research is underway to find low-GWP alternatives, known as "fourth generation" refrigerants [3]. Currently, few low-GWP synthetic working fluids, mainly hydrofluoroolefins (HFOs) and hydrochlorofluoroolefins (HCFOs), have been identified as refrigerants having appropriate safety, environmental, and thermodynamic characteristics for different HVAC&R applications [4][5][6][7]. However, since a limited number of measurements for their thermodynamic and transport properties are available in the literature, it is necessary to develop models that estimate the properties of the potential low-GWP alternatives with sufficient accuracy.…”