Hydrofluoroolefin Refrigerants Research Articles

Surface functionalization enabling highly effective phase-change heat transfer of R1234yf: A molecular dynamics study

Phase-change heat transfer has been demonstrated to be an effective thermal management approach for high-power electronics and power generators. In this work, we propose a strategy using surface functionalization to enhance the phase-change heat transfer of an environmentally friendly refrigerant, i.e., hydrofluoroolefins (HFO)-based R1234yf. Using molecular dynamics simulations, we find that the evaporation (condensation) heat transfer coefficient (HTC) at self-assembled monolayer (SAM) functionalized gold (Au) surfaces can be increased by ∼7 (∼5) times compared to that at the planar Au surfaces. The improvement in phase-change heat transfer of R1234yf at functionalized Au surfaces arises from the high thermal conductance across functionalized Au/R1234yf interfaces and the strong vibrational couplings between SAM molecules and R1234yf molecules. On the one hand, the introduced SAM layer can increase the interfacial thermal conductance (ITC) between Au and R1234yf owing to the strong bonding between Au and the SAM molecules, as well as the strong vibrational couplings at low-frequency modes (0–6 THz) among Au, SAM, and R1234yf. On the other hand, the thermal energy exchange during the evaporation (condensation) process can be improved by surface functionalization through the vibrational couplings between SAM and R1234yf at high frequency (∼12 and ∼30 THz) regions. This dual vibrational coupling will then allow the SAM layer to work as an intermedia to bridge the vibrations between Au and R1234yf molecules, which in return benefits the phase-change heat transfer. By further characterizing the evaporation and condensation processes, we find that the evaporation rate of R1234yf is increased by ∼50% at most at the wall superheat <70 K when the Au surfaces are functionalized using SAMs. When the wall superheat is above 70 K (i.e., 100 K for the planar Au surface), the evaporation of R1234yf becomes like film evaporation in which clusters of R1234yf molecules move off the surface together, which limits the enhancement (i.e., ∼100% at most) of evaporation HTC at the functionalized Au surfaces. At the same time, the condensation rate at functionalized Au surfaces is found to be increased by 15%–100% compared to that of the planar Au surfaces. By elucidating the mechanisms governing phase-change heat transfer on functionalized surfaces, our results provide an efficient strategy to enhance the cooling efficiency of the HFO refrigerants, which may benefit the design of surfaces with high phase-change heat transfer capabilities.

A new comprehensive model of thermal conductivity for hydrofluoroolefins refrigerants using feed-forward back-propagation neural networks

A new comprehensive model of thermal conductivity for hydrofluoroolefins refrigerants using feed-forward back-propagation neural networks

Modeling the Ground- and Excited-State Unimolecular Decay of the Simplest Fluorinated Criegee Intermediate, HFCOO, Formed from the Ozonolysis of Hydrofluoroolefin Refrigerants.

Hydrofluoroolefins (HFO) are fourth-generation refrigerants designed to function as efficient refrigerants with no ozone depletion potential and zero global warming potential. Despite extensive studies on their chemical and physical properties, the ground- and excited-state chemistry of their atmospheric oxidation products is less well understood. This study focuses on the ground- and excited-state chemistry of the simplest fluorinated Criegee intermediate (CI), fluoroformaldehyde oxide (HFCOO), which is the simplest fluorinated CI formed from the ozonolysis of HFOs. HFCOO contains syn- and anti-conformers, which have Boltzmann populations of, respectively, 87 and 13% at 298 K. For both conformers, the calculated ground-state reaction energy profiles associated with cyclization to form fluorodioxirane is lower than the equivalent unimolecular decay path in the simplest CI, H2COO, with anti-HFCOO returning a barrier height more than half of that of H2COO. The excited-state dynamics reveal that photoexcitation to the bright S2 state of syn-HFCOO and anti-HFCOO is expected to undergo a prompt O-O fission─with the former conformer expected to dissociate with an almost unity quantum yield and to form both O (1D) + HFCO (S0) and O (3P) + HFCO (T1) products. In contrast, photoexcitation of anti-HFCOO is expected to undergo an O-O bond fission with a non-unity quantum yield. The fraction of photoexcited anti-HFCOO that dissociates is predicted to exclusively form O (1D) + HFCO (S0) products, which is in sharp contrast to H2COO. The wider implications of our results are discussed from both physical and atmospheric chemistry perspectives.

Molecular dynamics evaluations of homogeneous condensation and thermophysical properties of (R-1234ze(E)+R-134a) binary blends

Environmental concerns demand prioritizing the development of eco-friendly refrigerants and prompting the replacement of conventional working fluids. The HFCs (hydrofluorocarbon) will be banned soon, and HFOs (hydrofluoroolefin) have been indicated as an alternative. In this study, numerous blends were attained by mixing two refrigerants, R-1234ze(E) and R-134a. Few blends are proposed as substitutes for high Global Warming Potential (GWP) fluids and are employed in refrigeration systems. The homogeneous condensation and thermophysical properties of nine binary blends of R-1234ze(E) + R-134a by varying composition with increment and decrement, respectively of 10% for each in a sequence were investigated using a molecular dynamics simulations scheme. The density, isobaric heat capacity, mean square displacement, internal potential energy and radial distribution function were investigated at constant pressure and different condensation temperatures (273.15 K to 328.15 K). The present study aims to check how the mass ratio of different refrigerants can affect mentioned properties. The current outcomes are compared, analyzed and discussed with earlier available simulation data for pure and mixtures of refrigerants and along with REFPROP data. The computed results show that Blend 4, with a 60.0+40.0% mass ratio composition and R-450A, has similar condensation behavior and thermophysical properties. The properties of Blend 5 with a composition 50.0+50.0% mass ratio are nearly equal to Blend 4 and R-450A. The R-450A has a good inclusive performance as a pure alternative refrigerant. The physical properties of pure R-1234ze(E), R-134a and its nine binary blends were investigated and these results may be helpful for new HFO refrigerants based on these blends.

Green ground source heat pump using various low-global-warming-potential refrigerants: Thermal imbalance and long-term performance

Ground source heat pump is a promising technology for achieving carbon neutrality in the building sector owing to its high energy efficiency in heating and cooling applications. To mitigate global warming, low-global-warming-potential refrigerants are explored as long-term substitutes for ground source heat pumps. However, few studies have examined the long-term characteristics of green ground source heat pump systems using low-global-warming-potential refrigerant. This work fills this gap by comparing the long-term performance of ground source heat pump systems using typical low-global-warming-potential hydrofluorocarbon and hydrofluoroolefin refrigerants, with the conventional R134a as a baseline. Results show that the ground source heat pump system with R161 has the smallest thermal imbalance ratio, while the ground source heat pump system with R1234ze(E) suffers from the largest. Compared to R134a, R161 and R1234yf relieve the soil thermal imbalance, while R152a and R1234ze(E) exacerbate the imbalance. After 10 years of operation, the average soil temperature decreases from 10.40 °C to 9.82 °C, 9.58 °C, 9.41 °C, 9.16 °C, and 9.09 °C for R161, R1234yf, R134a, R152a, R1234ze(E), respectively. R1234ze(E) yields the highest annual average coefficient of performance of 4.16–4.20, while R161 shows the lowest value of 3.55–3.56. Compared to R134a, R152a and R1234ze(E) improve the annual coefficient of performance, while R161 and R1234yf degrade it. This work could guide the rational development of green ground source heat pump technologies using promising low-global-warming-potential refrigerants to achieve low environmental impact and high energy efficiency.

Evaluation of ionic liquids as absorbents for absorption refrigeration systems using hydrofluoro-olefin refrigerant

In this study, we evaluate the use of ILs as absorbents in a double effect absorption refrigeration system using HFO refrigerant. By examining the properties of various refrigerant/absorbent mixtures, we identify the most efficient refrigerant/absorbent pair for the aforementioned absorption refrigeration system. First, we identify a suitable HFO refrigerant for the system. Among the candidates in this study, R1336mzz(Z) and R1234ze(Z) can be used in the absorption refrigeration system because both have low flammability and high critical points. Then, we analyze the characteristics of ILs as absorbents in the absorption refrigeration system. Imidazolium ILs have relatively low viscosities of approximately 20 mPa s at temperatures exceeding 50 °C and high stability. Next, we analyze the characteristics of refrigerant/absorbent pairs. When R1336mzz(Z) and R1234ze(Z) are used as the refrigerant, [OMIM][BF4] have the highest solubilities in oprating conditions. The solubility value of R1234ze(Z) with [OMIM][BF4] is 0.256 at 289.89 kPa and 80 °C, while the solubility value of R1336mzz(Z) with [OMIM][BF4] is 0.154 at 128.02 kPa and 80 °C. Finally, we analyze the performance of the refrigeration system. When the R1234ze(Z)/[OMIM][BF4] is used in the absorption refrigeration system, the COP and cooling capacity of the system exhibit the values of 0.516 and 0.549 kW, respectively.

On Integrated Fluid Screening and Turbomachinery Design for Optimized Industrial Heat Pumps

Abstract This work presents an approach to the contextual integration of fluid selection and compressor design for the cycle design of efficient industrial heat pumps. The vapor-compression cycle of an air–water heat pump operated at 42 °C source and 82 °C target temperature is investigated as a theoretical case study. An optimization study is performed, which includes the assessment of suitable refrigerants. Besides well-known single-component refrigerants, various binary mixtures are considered. The cycle optimization aims at simultaneously providing high cycle coefficient of performance and volumetric heating capacity. Cycle operation with the mixtures R-41/trans-2-butene (10, 90 mol. %) and CO2/R-161 (40, 60 mol. %) yields the highest values of these parameters, respectively. For further evaluation, centrifugal compressors operated with each of the two promising mixtures are designed with an in-house meanline program. In addition, the compressor design for the hydrofluoro-olefin refrigerant R-1234ze(Z) is considered as a reference. All designs are reviewed with respect to cycle as well as compressor design criteria and the applied methodology will assist designers in identifying key decision variables. The comprehensive design assessment suggests that CO2/R-161 (40, 60 mol. %) provides the best overall solution for an efficient cycle with a compact compressor design.

Solubilities of 3, 3, 3-trifluoropropene in pentaerythritol tetrahexanoate and pentaerythritol tetraoctanoate from 278.15 K to 343.15 K at pressures to 1 MPa

Due to the very low GWP and good thermodynamic properties, 3, 3, 3-trifluoropropene (R1243zf) was considered as a promising substitute for R134a. The phase behavior of R1243zf with lubricant oils is essential for the optimization of the refrigeration cycle. In this work, the solubility of R1243zf in pentaerythritol tetrahexanoate (PEC6) and pentaerythritol tetraoctanoate (PEC8), which are the two pure components of polyol ester (POE) oil, was determined at temperatures from 278.15 K to 343.15 K and pressures up to 1.0 MPa using isochoric saturation method. The experimental data were regressed by means of non-random two liquid (NRTL) model and Krichevsky-Kasarnovsky (K-K) model, respectively. Both of the two models present good correlation results with the absolute average relative deviations lower than 3.0 %. Moreover, the solubilities of different hydrofluoroolefin refrigerants (R1234yf, R1234ze(E) and R1243zf) in the studied PECs were compared. Results show that the molar fraction of HFOs dissolved in the same PECs follows: R1234ze(E) > R1243zf > R1234yf. In addition, the dissolution thermodynamic properties including the mixing enthalpy, mixing Gibbs energy and mixing entropy of R1243zf in PEC6 and PEC8 were calculated according to experimental solubility data and the NRTL model, and the dissolution process was analyzed.

Film thickness and heat transfer characteristics of R1233zd(E) falling film with nucleate boiling on an inclined plate

Falling film evaporation is an effective heat transfer method for achieving high heat flux and wide-area cooling with less refrigerant. As the film thickness and wall superheat increase, nucleate boiling occurs in the liquid film. In this case, the superficial liquid film thickness becomes thicker due to the existence of vapor bubbles. Although such superficial film thickness is an important parameter for expressing the film structure, the liquid film thickness of hydrofluorocarbon and hydrofluoroolefin refrigerants under nucleate boiling conditions has not yet been reported. This study experimentally investigated the liquid film thickness and heat transfer coefficients on an inclined plate with the width of 50 mm and the length of 75 mm. R1233zd(E) was used as the working fluid at a saturation temperature of 20°C. The film Reynolds number at the inlet was varied from 4.4 × 102 to 2.7 × 103, and the heat flux was varied from 5.6 to 138 kW/m2. As a result, the mean film thickness under adiabatic conditions increased when the flow rate increased or the inclination angle decreased from 30° to 15°, and ranged from 0.14 to 0.37 mm. The values were in good agreement with preexisting theories and correlations. Under heating conditions without boiling, the film thickness was almost equal to that under adiabatic conditions, and the heat transfer coefficients were slightly higher than the typical heat transfer correlation of the saturated falling film of water. With nucleate boiling in the high heat flux range, the superficial film thickness reached 1–3 mm at the location where vapor bubbles existed. The frequency of the thickness exceeding 1 mm increased with the heat flux as nucleate boiling became more active; thus, the average thickness also increased. The heat transfer coefficients under the developed nucleate boiling conditions were dominated by heat flux and were in good agreement with the existing pool boiling correlation.

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.

Solubility determination and mixing thermodynamic properties of R1243zf in two 1-butyl-3-methyl-imidazolium based ionic liquids

3,3,3-Trifluoropropene (R1243zf), as a new-type hydrofluoro-olefin refrigerant with extremely low GWP and thermophysical properties similar to R134a, has received more and more attention. Ionic liquids (ILs) with 1-butyl-3-methyl-imidazolium ([BMIM]+) cation are a promising kind of absorbent in absorption refrigeration cycle (ARC) owing to their low viscosity level and good stability. Towards better understanding the phase behavior of R1243zf/[BMIM]+ IL mixtures and promoting their application in ARC, the solubilities of R1243zf in [BMIM][TFO] and [BMIM][PF6] were experimentally determined using isochoric saturation method in this work. The non-random two liquid (NRTL) and Krichevsky-Kasarnovsky (K-K) model were utilized to correlate the experimental data, and both models exhibited reasonable results. In addition, the dissolution thermodynamic properties (enthalpy, entropy and Gibbs energy) and Henry’s law constants of R1243zf in the two ILs were calculated, and the variation with solubility was analyzed. Furthermore, the absorption capacities of [BMIM][TFO] and [BMIM][PF6] to different refrigerants were compared based on the reported data in the literatures.

The Characteristic of High-Speed Centrifugal Refrigeration Compressor with Different Refrigerants via CFD Simulation

This study used Computational Fluid Dynamics (CFD) to simulate and analyze the working fluid in magnetic centrifugal refrigerant compressors using R-134a to mixed refrigerant: R-513A and HFO (Hydrofluoroolefins) Hydrofluoroolefin refrigerant: R-1234yf, and the impact on integrated part-load performance, Integrated Part Load Value (IPLV) and internal flow field. This study used a single-stage 280 USRT maglev centrifugal refrigerant compressor as a simulation model. Three different refrigerants were used: R-134a, R-513A, and R-1234yf, as presented in the National Institute of Standards and Technology (NIST) real gas database. The refrigerant was used to set the IPLV working conditions and change the compressor speed and mass flow rate to simulate the compressor’s characteristic curve after replacing the refrigerant. The compressor working conditions were the fixed refrigeration cycle condensation and evaporation following the same capacity standards. This study used the CFD software by Ansys software company to simulate the flow field. The k-omega turbulence software was used to model the turbulence. The results show that the maglev centrifugal refrigerant compressor efficiency dropped significantly when the refrigerant was directly replaced. Based on R-134a, the full load efficiency of R-1234yf dropped 13.21%, the full load efficiency of R-513A dropped 9.97%, and the partial load efficiency was similar to R-134a.

Exergy assessment of a multistage multi-evaporator vapor compression refrigeration system using eighteen refrigerants

The use of lower global warming potential refrigerants as an alternative to hydrochlorofluorocarbons and hydrofluorocarbons from an environmental perspective is the need of an hour. The feasibility and possibility of alternative refrigerants in the existing refrigeration system can be recognized using exergy assessment. This will lead to improving the thermal performance of the refrigeration systems. In this paper, exergy assessment of a multistage multi-evaporator vapor compression refrigeration system is performed using the Simulink model. A total of eighteen refrigerants are considered for the analysis from the environmental perspective, safety considerations, etc. The evaporator-1, evaporator-2, and condenser temperatures are varied from 0 °C to 15 °C, −15 °C to −5 °C, and 25 °C to 33 °C respectively. The highest exergy destruction among all the components is found for both the compressors, followed by the condenser, evaporators, expansion devices, and internal heat exchanger. Refrigerants R141b, R123, R245ca, R245fa, and R152a showed better thermal performance than hydrofluoroolefins refrigerants, but have high GWP values. R1234ze(E), and R1234yf are environmentally friendly and achieved similar performance to conventional refrigerants.

Universal parameters of the extended corresponding states (ECS) model for hydrofluoroolefin refrigerants

• New universal parameters of the ECS model are presented for HFO refrigerants. • They are based on the saturation properties of well-studied eight refrigerants. • Typical deviations are within 1% for vapor pressures and within 3% for saturated liquid densities. • They are sufficient accuracies for the preliminary evaluation of novel refrigerants. New universal parameters of the extended corresponding states (ECS) model are presented for hydrofluoroolefin (HFO) refrigerants. The ECS model employing the universal parameters successfully represents the saturation properties. For well-studied HFO refrigerants, which were used to determine the universal parameters, typical deviations between estimations with the ECS model and calculated values with accurate equations of state are within 1 % for vapor pressures and within 3% for saturated liquid densities at reduced temperatures from 0.6 to 0.9. Similar deviations are expected for other HFO refrigerants if reliable experimental values for the critical parameters and acentric factors are available. If these values are less reliable, larger deviations could be observed, up to 3 % and 8 % for vapor pressures and saturated liquid densities, respectively. The ECS model presented here is readily implemented and provides reasonable accuracies; therefore, it is suitable for the preliminary evaluation of novel refrigerants.

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.

Experimental absorption solubility and rate of hydrofluoroolefin refrigerant in ionic liquids for absorption chiller cycles

An absorption chiller cycle using HFO-1234yf (2,3,3,3-tetrafluoropropene) as an environmentally friendly refrigerant could allow for the efficient utilization of waste heat. In this study, we tested ionic liquids as absorbents for HFO-1234yf, and measured their experimental absorption equilibrium solubilities using a volumetric method. At 50°C, the solubility of HFO-1234yf in ionic liquids increased in the order: [BMIM][Tf2N]>[BMIM][BF4]>[EMIM][PF6]. We calculated the experimental solubility of the [BMIM][Tf2N] system using the non-random two-liquid (NRTL) model and evaluated its Dühring diagram. This confirmed that the absorption chiller cycle allowed heat exchange at 0°C with a generation temperature of 80°C. The absorption rate was measured via a volumetric method, and increased following the absorption equilibrium solubility when the experimental temperature and pressure conditions were changed. The absorption solubility obtained at the absorber outlet was equivalent to 25–33% of the absorption equilibrium solubility in the lab-scale falling-film absorber. To improve the absorption performance, it will be necessary to investigate heat exchanger tubes with higher wettabilities to reduce the thickness of the absorbent flowing on the heat exchanger surface.

Effect of subsurface tunnel on the nucleate pool boiling heat transfer of R1234ze(E), R1233zd(E) and R134a

Nucleate pool boiling heat transfer of R1234ze(E), R1233zd(E) and R134a were investigated outside two reentrant cavity tubes. The two tubes have different fin density while the size of subsurface tunnel width and fin height are almost the same. In the experiment, the pool boiling heat transfer is tested at the saturation temperature of 6 °C and heat flux of 10–80 kW/m 2 . A brief summary of pool boiling experimental data of Hydrofluoroolefins(HFO) refrigerants on different enhanced tubes from recent work is also provided. It is found that the combinations of tube and refrigerant: R134a and R13234ze(E) outside Tube-B1 shows almost equivalent boiling heat transfer performance. The two combinations also yield the highest averaged overall heat transfer coefficient. At the lower heat flux less than 60 kW/m 2 , for the tube with larger fin density and thinner fin thickness, the number of nucleation cavities is found to be more than that with larger fin thickness. At the heat flux more than 40 kW/m 2 , the boiling heat transfer coefficient of R134a and R1234ze(E) for the two enhanced tubes nearly merges into a single curve. At the higher heat flux, boiling heat transfer shows weak dependence on the surface structures. The boiling heat transfer coefficient of R1233zd(E) is more than 40 percentages lower than R134a for the two tubes at the nearly identical conditions. The research is helpful for the designer to summarize the boiling heat transfer performance of some typical HFO refrigerants.

HFO refrigerants: A review of present status and future prospects.

• Various HFO refrigerants have been reviewed and discussed. • Main emphasis is on the research published in the last 5 years. • Flammability and oil-compatibility of HFO refrigerants is also discussed. • HFOs can be regarded as suitable environment-friendly alternatives to HFCs. HFCs (Hydrofluorocarbons) are one of the most widely used refrigerants worldwide. But, HFCs are heading towards complete phase out in the near future due to environmental concerns. A high global warming potential (GWP) of HFCs is the main reason for its phase-out. As a result, researchers, engineers and technicians associated with the refrigeration sector are looking for a suitable environment-friendly alternative. Recent past has witnessed the emergence of a new group of environment-friendly refrigerants known as the HFOs (Hydrofluoro-olefins). The present review is focussed on addressing various aspects of HFO refrigerants such as the thermodynamic and transport properties, flammability and oil compatibility, boiling and condensation heat transfer performance and their performance in actual vapour compression refrigeration systems. Few suggestions for future research work related to HFO refrigerants are also discussed.

Viscosity and Density of a Polyol Ester Lubricating Oil Saturated with Compressed Hydrofluoroolefin Refrigerants

Hydrofluoroolefins (HFOs) are currently being developed to replace hydrofluorocarbons (HFCs) with high global warming potential (GWP) in air-conditioning and refrigeration systems. The development ...

Effect of enhanced surfaces and materials in boiling heat transfer with HFO Refrigerants: A review

The boiling heat transfer of refrigerants on these surfaces generates more active nucleation sites and it depends on the properties of refrigerants and surface materials. Heat improvement consequence within the boiling heat transfer mainly depends on thermo-physical features of material & the working fluid, modification of surface techniques, thin-film (nano-scale, micro-scale, macro-scale surfaces, and hybrid scale), coating method, working fluid (water or refrigerants) and additives for fluids. This paper describes the current investigations on hydrofluoroolefin (HFO) refrigerants in pool boiling heat transfer. In boiling heat transfer process, a heat enhancement depends on the solid surfaces materials (surface design, surface geometry, surface material, surface finish condition), working fluid (water and refrigerants) and fluid additives, etc. Heat transfer enhancement improves the system performance of the thermal system and reduces the size of heating applications parts. In recent years, refrigerant emissions have become a serious concern as it is responsible for depleting the ozone layer. Under this circumstance, HFO refrigerants are considered as an alternative of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). Hydrofluoroolefin (HFO) refrigerants have some excellent properties such as zero ozone depletion potential (ODP), low global warming potentials (GWP), low toxicity, mild flammability (manageable) and same system performance as HFCs for any surface tested. Based on the literature review, this paper proposed a brief future study to identify existing shortcomings.