Hydrofluorocarbon Refrigerants Research Articles

What Data Are Most Valuable to Screen Ionic Liquid Entrainers for Hydrofluorocarbon Refrigerant Reuse and Recycling?

What Data Are Most Valuable to Screen Ionic Liquid Entrainers for Hydrofluorocarbon Refrigerant Reuse and Recycling?

Coordinating to promote refrigerant transition and energy efficiency improvement of room air conditioners in China: Mitigation potential and costs

Implementing the Kigali Amendment to the Montreal Protocol has imposed certain restrictions on the production and consumption of hydrofluorocarbons (HFCs). Taking this opportunity to promote the alternatives of high global warming potential (GWP) HFC refrigerants in the room air conditioner (RAC) sector as well as improve the energy efficiency can bring double benefits. With the RAC sector as an example, a demand-emissions-cost model is developed to assess the potential and costs of emission reductions in different regions of China under different scenarios. The model includes three scenarios: a business as usual (BAU) scenario, a Kigali energy efficiency (KAE) scenario with simultaneous energy efficiency improvements following the Kigali amendment, and an accelerated transition energy efficiency (ATE) scenario with accelerated HFCs reduction and energy efficiency improvements. The results show that under the KAE and ATE scenario, the GHG emissions of the RAC sector will peak in 2025 at 389.8–393.9 Mt CO2-eq and 378.8–382.8 Mt CO2-eq in China. The main contribution to this result is the alternative of low GWP refrigerants. From 2021 to 2060, the cumulative direct emission reductions are about 6.4–7.4 Gt CO2-eq and 8.5–9.5 Gt CO2-eq in KAE and ATE, and the cumulative indirect emission reductions for both scenarios are 1.6–1.8 Gt CO2-eq. The cumulative abatement costs are $286–321 billion and $288–322 billion (prices in 2020). Under the ATE scenario, direct emissions from refrigerants in the RAC sector are near zero in 2060, and indirect emissions depend on the power system structure. The RAC sector's average abatement cost varies significantly in diverse climatic environments. Given the variation in average abatement cost, it is critical to tailor mitigation policies to local conditions to ensure maximum benefits.

Decomposition mechanism of hydrofluorocarbon (HFC-245fa) in supercritical water: A ReaxFF-MD and DFT study

In this work, the concept of using supercritical water to treat Hydrofluorocarbons (HFCs) refrigerants waste is proposed. Taking 1,1,1,3,3-Pentafluoropropane (HFC-245fa) as the research object, based on the ReaxFF reactive force field molecular dynamics method and density function theory, the decomposition mechanism of HFC-245fa in supercritical water, the effects of temperature, HFC-245fa mass concentration and oxygen addition on the decomposition of HFC-245fa in supercritical water and decomposition mechanism were studied. The results show that the main stable products of HFC-245fa decomposition in supercritical water are HF, CO2, CO and H2. In supercritical water, ·F radicals can easily combine with H2O molecules and then rapidly decompose to generate HF molecules and ·OH radicals. The hydrogen extraction reaction of ·H radicals with H atoms in HFC-245fa molecules and H2O molecules has relatively low energy barrier. ·OH radicals can also participate in the dehydrogenation reaction, promoting the further dehydrogenation of HFC-245fa molecules and their molecular fragments. Moreover, it can combine with carbon-containing molecular fragments to promote the conversion of C element to CO and CO2. The lower concentration of HFC-245fa promotes the conversion of C element and generation of H2. The addition of oxygen facilitates the generation of ·OH radicals and promotes the conversion of C element to CO2, but reduces the generation of CO and H2. Under the condition of HFC-245fa mass concentration of 13.0%, the calculated formation apparent activation energies of HF, CO and CO2, H2 are 196.3, 368.5 and 249.0 kJ·mol−1, respectively.

Resource utilization of waste HFC-134a refrigerant by supercritical gasification method: A reactive molecular dynamic study

Effective treatment of HFCs (hydrofluorocarbons) waste refrigerants is of great significance for reducing greenhouse gas emissions. In this study, the supercritical water gasification method was applied to the treatment of waste HFCs refrigerants in order to realize the harmless treatment and resource utilization at the same time. Taking widely used HFC-134a (1,1,1,2-Tetrafluoroethane, CF3CFH2) refrigerant as the research object, the gasification mechanism of HFC-134a in supercritical water was studied by the ReaxFF-MD, and the effect of temperature, reactant concentration and pressure on gasification was studied. The results show that the main products of HFC-134a gasification in supercritical water are HF, H2, CO and CO2. HF is mainly generated by the hydrogen extraction reaction between F radicals and H2O molecules, and the energy barrier is only 31.3 kJ·mol−1. H2 is mainly generated by the hydrogen extraction reaction between H radicals and H2O molecules and H atom-containing molecules or radicals. When the F, H radicals and H2O undergo hydrogen extraction reaction, a large number of OH radicals are generated, and the carbon-containing radicals combine with OH radicals to undergo a reforming reaction. After further removal of H and F atoms, CO and CO2 are ultimately generated. Parametric analyses show that higher reaction temperature can speed up the reaction rate and improve the yields of CO and H2; Lower reactant concentrations help to increase the yields of CO2 and H2 and have little effect on the yields of HF and CO; Higher pressure boosts the reaction rate to increase CO2 and CH4 yields but decrease the yields of HF, CO and H2.

Separation of Azeotropic Hydrofluorocarbon Refrigerant Mixtures: Thermodynamic and Kinetic Modeling for Binary Adsorption of HFC-32 and HFC-125 on Zeolite 5A.

Hydrofluorocarbons (HFCs) have been used extensively as refrigerants over the past four decades; however, HFCs are currently being phased out due to large global warming potentials. As the next generation of hydrofluoroolefin refrigerants are phased in, action must be taken to responsibly and sustainably deal with the HFCs currently in circulation. Ideally, unused HFCs can be reclaimed and recycled; however, many HFCs in circulation are azeotropic or near-azeotropic mixtures and must be separated before recycling. Previously, pure gas isotherm data were presented for both HFC-125 (pentafluoroethane) and HFC-32 (difluoromethane) with zeolite 5A, and it was concluded that this zeolite could separate refrigerant R-410A (50/50 wt % HFC-125/HFC-32). To further investigate the separation capabilities of zeolite 5A, binary adsorption was measured for the same system using the Integral Mass Balance method. Zeolite 5A showed a selectivity of 9.6-10.9 for HFC-32 over the composition range of 25-75 mol % HFC-125. Adsorbed phase activity coefficients were calculated from binary adsorption data. The Spreading Pressure Dependent, modified nonrandom two-liquid, and modified Wilson activity coefficient models were fit to experimental data, and the resulting activity coefficient models were used in Real Adsorbed Solution Theory (RAST). RAST binary adsorption model predictions were compared with Ideal Adsorbed Solution Theory (IAST) predictions made using the Dual-Site Langmuir, Tóth, and Jensen and Seaton pure gas isotherm models. Both IAST and RAST yielded qualitatively accurate predictions; however, quantitative accuracy was greatly improved using RAST models. Diffusion behavior of HFC-125 and HFC-32 was also investigated by fitting the isothermal Fickian diffusion model to kinetic data. Molecular-level phenomena were investigated to understand both thermodynamic and kinetic behaviors.

Performance evaluation of graphene-enhanced LPG in a vapour compression refrigeration system: An experimental approach

Hydrofluorocarbon refrigerants will be phased out of domestic refrigeration shortly, by the Montréal and Kyoto Protocols, due to their high global warming potential (GWP), making them environmentally unfriendly. This study looked into the possibility of using graphene-nanolubricant in a domestic refrigerator system to improve liquefied petroleum gas (LPG) of propane and butane mixtures. In a 50–70 g charge of LPG refrigerant, the graphene-nanolubricant was investigated. To monitor the temperature of the system, four Type K thermocouples were connected to the refrigerator components. Two pressure gauges were also mounted in the compressor to assess the domestic refrigerator’s suction and discharge pressure. With graphene-nanolubricant concentrations, the COP was found to be higher. The refrigerator system’s compressor input was reduced by 13.1 % to 32.5% and refrigerating effect increased by 3.5% to 17.2%. As a result, graphene-enhanced LPG is capable of replacing LPG with the base lubricant in a vapour compression refrigeration system.

Scenarios for future Indian HFC demand compared to the Kigali Amendment

Demand for hydrofluorocarbon (HFC) refrigerants used as substitutes for ozone-depleting substances is growing in India and is estimated to continue growing at a high rate through the middle of this century. HFCs, although not directly ozone-depleting, are highly potent greenhouse gases subject to a global phasedown under the 2016 Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer. As of 20 January 2022, 130 Parties have ratified the Kigali Amendment, including India. This analysis evaluates scenarios for India’s HFC demand trajectory compared to likely control obligations under the Kigali Amendment. It is based on current and projected markets for HFC-using equipment and types of refrigerants utilized now and likely to be used in the future. Sectors considered in this work include mobile air conditioning, stationary air conditioning, refrigeration, and foam blowing agents. Results suggest that India’s annual HFC demand under current market trends could reach 76 MMT CO2-equivalent (CO2e) in 2030 and 197 MMT CO2e in 2050, from 23 MMT CO2e in 2020, making no changes to the current mix of HFCs in use. The Kigali Amendment requires for compliance that India freeze its HFC consumption in 2028 at a projected level of 59–65 MMT CO2e and phase down progressively over the following 29 years; in that case, annual Indian HFC demand would peak in 2030 at a projected 57 MMT CO2e and fall to 8 MMT CO2e by 2050. This trajectory would avoid cumulative HFC use of 2.2 GT CO2e through 2050 versus the current market trends. If actions are taken to accelerate the refrigerant transition in stationary air conditioning by five years, India could peak its annual HFC demand by 2028 at 40 MMT CO2e and avoid additional cumulative HFC demand of 337 MMT CO2e between 2025 and 2050, exceeding its obligations under the Kigali Amendment.

Drop-in Replacement of Conventional Automotive Refrigeration System to Hybrid-Ejector System with Environment-Friendly Refrigerants

Ejector refrigeration system (ERS) is a propitious cooling skill for automobiles with a reduced fuel consumption along with structural simplicity, low cost, and driven by engine waste heat. Conversely, the lower coefficient of performance (COP) of standalone ERS is the major drawback for automotive applications, which can be overcome by hybridizing with a conventional compression system. Therefore, an indigenously designed hybrid cooling system is proposed to switch in three different cooling modes based on required thermal comfort— compressor, ejector, and hybrid. A real gas property-based theoretical model of this hybrid system is established under critical and sub-critical modes with a variable area ejector for a better entrainment ratio. In parallel, the performance of the proposed system is explored with two environment-friendly hydrofluorocarbon (HFC) refrigerants R152a, R440a and four extremely low global warming potential (GWP) hydrofluoroolefin (HFO) refrigerants R1234yf, R1243zf, R1234ze(E) and R513a, as an immediate replacement of commonly used R134a. The thermodynamic performance variation is compared for an extensive choice of the evaporator, generator, and condenser temperatures. Due to the conversion of waste heat into work in the hybrid mode, the compression ratio reduces maximum by 54% and cooling capacity increases by almost 22% more than in the conventional compressor mode. Moreover, compared with the standalone ejector system, the hybrid system improves the cooling capacity and COP by up to 4 times. Irrespective of the circumstances, the maximum entrainment ratio and COP are achieved with refrigerant R1234yf in hybrid mode, claiming ideal replacement of R134a for automotive air conditioning applications.

Potential reduction in emissions after replacement of automobile air conditioning refrigerants in China

For more than a decade, R134a has been the most widely used refrigerant in automobile air conditioners in China. Although R134a does not damage the ozone layer, it contributes to the greenhouse effect. In 2021, China officially announced its decision to accept the Kigali Amendment, which mandates the gradual replacement of hydrofluorocarbon refrigerants used in automobile air conditioners. Focusing on the replacement of R134a with R1234yf and R744 — two environment-friendly refrigerants that are currently popular in the industry — this study predicted how refrigerant replacement could impact China’s emissions under different scenarios in the future. The results showed that with automobile electrification in China, emissions from automobile air conditioners could peak in 2030 and drop to 58,300 tons of CO2 equivalents by 2045. Through relevant policy interventions, the emissions from automobile air conditioners could be reduced to 27,500 tons of CO2 equivalents by 2045 — a decrease of 52.8%. Thus, policy interventions could have a great impact on automobile air conditioner-related emissions. The research results of this study provide basic data for the subsequent formulation of relevant policies, so as to better promote the development of non-carbon greenhouse gas emission reduction in China.

A DIRECT CONTRIBUTION OF MARINE REFRIGERATION TO ANTHROPOGENIC GREENHOUSE GASES EMISSION - A SHORT REVIEW

The problem of reducing greenhouse gas (GHG) emissions in the maritime sector are currently important. The share of shipping emissions in global anthropogenic emissions was 2.89% in 2018 [1]. The main contribution to GHG emissions (indirect emission) on the marine fleet generates the main and auxiliary engines, and boilers during fuel combustion as well as incinerators [1, 2]. However, marine merchant and passenger ships have another significant source of direct GHG emissions, which is currently not directly regulated and considered as not mandatory inventory – hydrofluorocarbons (HFCs) refrigerants emissions from refrigeration and air conditioning systems. It should be highlighted, that reduction of the direct GHG emissions for marine refrigeration systems is the most difficult among all types of refrigeration systems.

Controversial Analyzing of a Vapor-Compression Cycle in Various Climatic Conditions Using Various Refrigerants

Abstract This research is about “controversial analysis of a refrigeration vapor-compression cycle,” using R22, and environmentally friendly hydrofluorocarbon (HFC) refrigerants such as R134a, R407c, and R410a in various climatic conditions. For initiation, a complete database was provided for thermophysical properties of the refrigerants’ performances. Then, P–h, s–T, s–h equations are derived in matlab and Excel with the maximum R2. Meanwhile, five climatic conditions (from hot to cold state) are assumed. Consequently, temperature, pressure, enthalpy, and entropy of the cycle states are illustrated for aforesaid conditions as per working fluids properties in the form of quadripartite diagrams. Subsequently, the cycle was analyzed thermodynamically. The coeffcient of performance (COP) was performed for refrigeration (cooling procedure), heat pump (heating procedure), and both heating and cooling for both standard and actual conditions. Afterward, the calculation was performed for parameters like energy efficiency ratio (EER), heat rejected ratio (HRR), capacity, energy, exergy, irreversibility, and exergy destruction ratio (EDR) of each system component according to the first and second laws of thermodynamics, individually. Derived and calculated values in each session illustrated in 3D diagrams on which TEvap s, TCond s and working fluids for each assumed climatic condition can be distinguished easily. A concise analytic study was performed for the increasing and decreasing in values. Forecast for two steps upper and lower than all values derived for trending. Making a trend for indicating either positive or negative inclines of the values and proposing a development for all similar cycles can be considered as the novelty of this research.

Data‐driven approximation of thermodynamic phase equilibria

AbstractWe present a new data‐driven approach for both accurate and computationally efficient approximation of vapor liquid equilibria (VLE) models. Our method is able to provide guaranteed enclosure to limit the approximation errors over the entire domain of interest, all just by sampling only at select points. The approximation relies on a mixed‐integer linear programming (MILP) formulation that exploits vertex polyhedral properties of theoretically guaranteed lower and upper bounds to enclose nonlinear and nonconvex equations of state (EOS) and empirical models. Another advantage is that, unlike traditional full simulation‐based data‐driven approaches, we do not solve nonlinear system of equations (f(x) = 0) for sampling. Instead of looking for only feasible samples, we evaluate f(x) over x‐domain. This functional evaluation eliminates the need for computationally‐demanding full‐scale simulations and the associated convergence issues. We demonstrate excellent performance of the proposed MILP formulation in predicting the solubility of hydrofluorocarbon (HFC) refrigerants in ionic liquids (IL).

Exergy investigation of home air conditioner working with different environment friendly refrigerants

In this paper, the performance of various alternative refrigerants were compared to find the replacement for R22, the widely used hydrochlorofluorocarbon (HCFC) refrigerant in home air conditioning systems in most developing countries. This study include the environment friendly hydrofluorocarbon (HFC) refrigerants such as R-134a, R-410A, R-407C and R- 404A. A steady state thermodynamic modelling and simulation of a home air conditioner as an actual vapor-compression system was developed. The model predicted the performance of the system with the mentioned alternative refrigerants in terms of energy and exergy. Based on design conditions, operating parameters, such as coefficient of performance (COP), energy efficiency rating (EER), exergy efficiency (η11) and exergy destruction ratio (EDR) were evaluated. The results obtained showed that R-134a, R-410A, R407C, and R-404A are better substitute to replace R22, as they are more environment friendly air conditioning cooling applications.

A review of fluorocarbon sorption on porous materials

Fluorocarbons have commonly been used for refrigerants, coolants, fire-suppressants, propellants, semiconductors, fluoropolymers, and other applications since the early 20th century. However, starting in the late 1980s these chemicals have been highly regulated due to environmental concerns over ozone depletion potential (ODP) and global warming potential (GWP). Porous materials such as zeolites, activated carbons, and metal-organic frameworks (MOFs) are among the current sorbents being studied to reduce emissions of greenhouse gases (GHGs) including fluorocarbons and carbon dioxide. Recent legislation now requires the reduction of hydrofluorocarbon refrigerants over the next two decades to reduce global warming which makes environmental remediation a relevant issue. An extensive literature search has been conducted for fluorocarbon sorption in porous materials to better understand current and prior separation technologies that can reduce climate change. This review article discusses applications for which fluorocarbon sorption is reported and encompasses both academic and patent literature from the late 1940s to present. Pure gas sorption of straight-chain paraffinic and olefinic fluorocarbons as well as zeotropic, azeotropic, and isomeric mixture separations is reviewed. Additional topics including molecular interactions, reactivity, and molecular modeling are discussed in detail. • Comprehensive review of fluorocarbon sorption with 367 sources from 1947 to present. • Discusses capture, purification, separation, adsorption-refrigeration, nanofluids, catalysis, and fundamental studies. • More than 10 sorbents mentioned including zeolites, activated carbons, and metal-organic frameworks (MOFs). • Includes over 100 fluorocarbons consisting of CFCs, CFOs, HCFCs, HCFOs, HFCs, HFOs, PFCs, and PFOs. • Highlights the use of over 15 adsorption isotherms for modeling fluorocarbon sorption with different sorbents.

Manipulating Pore Topology and Functionality to Promote Fluorocarbon-Based Adsorption Cooling

ConspectusWith the worldwide demand for refrigeration and cooling expected to triple, it is increasingly important to search for alternative energy resources to drive refrigeration cycles with reduced electricity consumption. Recently, adsorption cooling has gained increased attention since energy reallocation in such systems is based on gas adsorption/desorption, which can be driven by waste/natural heat sources. Eco-friendly sorption-based cooling relies on the cyclic transfer of refrigerant gas from a high to low energy state by the pseudocompression effect resulting from adsorption and desorption. The driving force for energy transfer relies on heat rather than electricity. The performance of a sorption chiller is primarily influenced by this cyclic sorption behavior, which is characterized as the working capacity of the porous sorbent. Thus, increases in this working capacity directly translate to a more compact and efficient cooling system. However, a lack of highly effective sorbent/refrigerant pairs lowers cooling performance and therefore has limited applicability. To this end, synthetic metal-organic frameworks (MOFs) and covalent organic polymers (COPs) possess higher porosity and greater tunability leading to more substantial potential benefits for adsorption, compared to traditional sorbent materials. Similarly, hydrofluorocarbon refrigerants have more favorable applicability given the ease of operation above atmospheric pressures due to suitable saturated vapor pressures and boiling points. For these reasons, our work focuses on an ongoing strategy to promote sorption cooling via improvements in the sorbent/refrigerant pair. Specifically, we target the interaction of hydrofluorocarbon refrigerants with MOF/COP materials at a molecular level by interpreting the host-guest chemistry and the role of framework pore topology. These molecular-level differences translate to cooling performance, which is described herein. These strategies include engineering framework porosity (i.e., pore size, pore volume) by using elongated organic linkers and stereochemistry control during synthesis; manipulating the sorbate/sorbent interaction by introducing functional moieties or unsaturated metal centers to enhance working capacities in narrow pressure ranges; varying pore topology/morphology to impact adsorption isotherm behavior; and leveraging defective sites within the frameworks to further enhance adsorption capability. This atomic level understanding of sorbate-sorbent interactions is conducted using various in situ experimental techniques such as synchrotron-based X-ray diffraction, X-ray absorption spectroscopy, in situ Fourier transform infrared spectroscopy, and direct sorption energies determinization with calorimetry. Moreover, the experimentally studied interactions and the corresponding adsorption mechanism are corroborated by computational studies using density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulations. Using this approach, we have made strides toward engineering designed frameworks with precise molecular control to target refrigerant molecules and thereby enhance the performance of desired working pairs for sorption-based cooling.

Realization of near-less friction of ta-CNx coating under R32 refrigerant environment

Diamond-like carbon (DLC) has attracted attention from refrigeration industry due to their excellent tribological behaviors. This study focused on high friction-efficiency in hydrofluorocarbon (HFC) refrigerant, however, DLC coatings have not been achieved in previous research. We evaluated friction behavior of tetrahedral amorphous carbon nitride under difluoromethane (R32) and R32/polyolester (POE) mixture environment, respectively. Friction coefficients of 0.02 and 0.03 were recorded under R32 and R32/POE atmosphere, respectively. These results emphasize an importance of the tribofilm consisted of graphite-and polymer-like carbon, terminated with R32 components (C, H, and F).

Flammability inhibition effects of R227ea, R125, R134a, and R744 on 3,3,3-trifluoropropene (R1243zf)

3,3,3-trifluoropropene (R1243zf or HFO-1243zf) has low global warming potential, which is expected to be an excellent alternative to hydrofluorocarbon refrigerants in air conditioning and refrigeration systems, but its flammability hinders the practical applications. This paper reports the experimental results of the flammability inhibition effects of carbon dioxide (R744), 1,1,1,2,3,3,3-heptafluoropropane (R227ea), pentafluoroethane (R125), and 1,1,1,2-tetrafluoroethane (R134a) on R1243zf. The measured critical suppression ratios decrease in the order: R744 (3.1) > R134a (1.42) >R125 (0.68)> R227ea (0.58), which are also predicted by group contribution method. The flammability limit range of R1243zf was estimated as per three methods, and the closest estimation values to tested data was obtained by using the Jones’ method (the stoichiometric concentration for combustion method). Finally, the mechanisms of flammability inhibition effect differences of R744, R227ea, R125, and R134a on R1243zf were analyzed, from the views of the combustibles or oxidants dilution, combustibles and oxidants isolation, and/or free radical production and consumption. A hydrofluorocarbon flame retardant that has the big F/H ratio and produces much free radical CF3 during its thermal decomposition, exhibits the good flammability inhibition efficiency to R1243zf.

Greenhouse gas mitigation and electricity saving potential from replacing refrigerants in Thai refrigerator

Refrigerant leak from refrigerator production and operation is one of major sources that causes greenhouse gases (GHG) emission due to the high global warming potential (GWP) from existing Tetrafluoroethane (R-134a) which is hydrofluorocarbon (HFC) refrigerants in Thailand. There are three factors to leakages, production, operation & maintenance and disposal of the refrigeration system. Therefore, replacing the refrigerant with a new lower GWP one will reduce GHG emissions from refrigerant leaks. For that reason, producers have started to use Isobutane (R-600a) refrigerants replacing R-134a by 97% from lower GWP. However, R-600a contains flammability competence which causes relatively small amount usage not more than 150 gram per refrigeration unit. This research provides a method to evaluate the greenhouse gas reduction from refrigerant modifications measured from 2016–2020,​ which reduced by 499,818 tons of carbon dioxide equivalent (tCO 2eq) furthermore, increased energy efficiency from refrigerant modifications reduced greenhouse gas 808,677 tCO 2eq. In the absence of statistics indicating the amount of refrigeration equipment disposed, an estimation of such is required. Provided that an appropriate base year of collected data is defined.

플레인 핀을 사용한 플레이트 핀 열교환기 내 HFO-1234yf의 흐름 비등 열전달 특성

Interest in hydrofluoroolefins (HFOs) based refrigerants, which have significantly lower global warming potential compared to currently used hydrofluorocarbons (HFCs) refrigerants, is increasing. However, heat transfer experiments of HFO refrigerants are limited in double-tube heat exchangers and square channels. Therefore, in this study, the flow boiling heat transfer characteristics and pressure drop of HFO-1234yf in a plate-fin heat exchanger were analyzed. The main results are as follows. The flow boiling heat transfer coefficient increases as the vapor quality increases; however, at certain point of high vapor quality, it decreases rapidly. As the mass flux, heat flux and saturation temperature increase, the flow boiling heat transfer coefficient increases.

Fault detection of low global warming potential refrigerant supermarket refrigeration system: Experimental investigation

As one of the most energy-intensive end-uses in the commercial buildings sector, supermarkets consume around 50 kWh/ft2 (or 537.6 kWh/m2) of electricity annually, or more than 2 million kWh of electricity per year for a typical store. The biggest consumer of energy in a supermarket is its refrigeration system, which accounts for 40–60% of its total electricity usage and is equivalent to about 2–3% of the total energy consumed by commercial buildings in United States, or around 0.5 quadrillion Btu (or 0.53 quadrillion KJ). Also, the supermarket refrigeration system is one of the biggest consumers of refrigerants. Current supermarket refrigeration systems rely on high global warming potential hydrofluorocarbon refrigerants. Reducing refrigerant usage or using environment friendly alternatives can result in significant climate benefits. The refrigeration system can also be adapted to handle flexible building loads and be integrated into grid response transactive control to balance the supply and demand of the electric grid. Even minor improvements in the efficiency and operational reliability of supermarket refrigeration systems can create significant value in terms of saving energy, improving food quality, protecting the environment, reducing carbon footprint, and enhancing electric grid resilience. Fault detection and diagnostics (FDD) techniques can be used to support refrigeration system operators in achieving these benefits. However, compare to FDD of other building heating, ventilation and air-conditioning and refrigeration (HVAC&R) equipment and systems which has attracted extensive FDD studies for decades, FDD of supermarket refrigeration systems, especially for low GWP refrigerant supermarket refrigeration system, has not gained enough attention from researchers. One of the key challenges is lack of available testing datasets to benchmark the system performance and record the faulted performance for system FDD research. This study selects several common faults of supermarket refrigeration systems, including display case door open, ice accumulation, expansive valve failure, and fan failure, to conduct experimental study to identify their fault characteristics, benchmark their faulted performance, then create a FDD characteristics matrix to support next step research on the development of supermarket refrigeration system FDD methods and field automated FDD implementation.