High Temperature Heat Pumps (HTHPs) are increasingly recognized as a key technology for decarbonizing industrial heating processes. This study presents a comprehensive thermodynamic and exergy analysis of various Low-GWP Refrigerants used in HTHP systems operating under different temperature lifts and condensation temperatures. The refrigerants evaluated include R718 (water), R600 (butane), R123, R1234ze(Z), R1233zd(E), R1224yd(Z), and R245fa. Results show that R718 consistently outperforms other refrigerants in terms of COP and exergy efficiency. At a temperature lift of 40 ◦ C and a condensation temperature of 150 ◦ C, R718 achieves a COP of 6.9 and an exergy efficiency of 49%. Even at an 80 ◦ C lift, its COP remains at 3.0, with exergy efficiency rising to 55%, indicating strong thermodynamic resilience. However, R718 also exhibited the highest discharge temperatures, requiring larger compressors and advanced system configuration. In contrast, R600 exhibits the lowest COP and highest exergy destruction, making it unsuitable for high-lift applications. Exergy destruction analysis identified the compressor as the dominant source of irreversibility, contributing more than 50% of total exergy destruction under all conditions. Total exergy destruction increased sharply with higher temperature lifts, ranging from 5 to 12% at 40 ◦ C to 10–30% at 80 ◦ C. Component-level analysis highlighted that improvements in compressor design and refrigerant selection are critical to minimizing system losses. Notably, R1233zd(E) and R1234ze(Z) showed lower compressor and condenser irreversibilities compared to other synthetic refrigerants. These results provide valuable guidance for refrigerant selection and system optimization in the development of efficient and sustainable HTHP technologies.

High-temperature heat pumps (HTHPs) are a promising solution for reducing carbon emissions in industrial heating by upgrading low-grade waste heat to temperatures above 100 °C. A key challenge in designing efficient and practical HTHP systems is choosing the right refrigerant. This study presents a comprehensive thermodynamic analysis of seven low-global-warming-potential (GWP) refrigerants R718 (water), R600, R123, R1234ze(Z), R1233zd(E), R1224yd(Z), and R245fa for high-temperature heat pump (HTHP) applications. The refrigerants were evaluated under temperature lifts of 40 °C and 80 °C and condenser temperatures between 100 °C and 150 °C. Key performance metrics including coefficient of performance (COP), volumetric heating capacity (VHC), compressor pressure ratio (PR), discharge temperature, volumetric flow rate, power consumption, and second-law efficiency were analyzed to identify optimal working fluids. Results show that R718 achieved the highest COP, up to 6.9 at 40 °C lift and 3.0 at 80 °C lift, along with the highest second-law efficiency, reaching 55% at 80 °C lift, due to its superior thermodynamic properties. However, R718 also exhibited the lowest VHC (1900  kJ/m³ at 40 °C lift) and the highest discharge temperatures (>520 °C at 80 °C lift), requiring larger compressors and advanced materials. Conversely, R1234ze(Z) and R600 demonstrated higher VHC (>7000  kJ/m³ at 40 °C lift) and moderate discharge temperatures (<180 °C), enabling more compact and cost-effective designs but at a reduced COP (5.5 at 40 °C lift). This study highlights that R718 has clear advantages in HTHP applications. In industrial heat recovery, an R718-based HTHP can provide the required high output temperatures while achieving better overall performance. These findings provide practical guidance for engineers and designers working on next-generation heat pumps for industrial heating applications.

High-temperature heat pumps (HTHPs) are emerging as a cornerstone technology for industrial decarbonization, enabling efficient recovery and upgrading of low-grade waste heat to supply process heat and steam above 100 °C. Operating at temperatures between 120 °C and 200 °C, HTHPs address the heating demands of energy-intensive sectors such as chemicals, food processing, and metals. This review consolidates recent advancements in HTHP design, refrigerant selection, and integration strategies. Current systems achieve coefficients of performance (COP) of 2.5–4.0 for 100–150 °C outputs, while advanced configurations using low-GWP refrigerants report COPs up to 6.10. Environmental benefits are significant: HTHPs can reduce CO₂ emissions by 60–98% compared to gas boilers, with case studies demonstrating annual savings exceeding 30,000 tCO₂. Economic analyses indicate payback periods as short as 1.9–3 years for optimized designs. Key challenges include the development of low-GWP refrigerants, high initial investment costs, and maintaining efficiency under large temperature lifts. Future research should focus on advanced cycle configurations, integration with thermal storage and renewables, and innovative compressor technologies to accelerate adoption. Overall, HTHPs represent a critical pathway for low-carbon industrial heating, offering substantial energy recovery and a proven potential to reduce the carbon footprint of high-temperature processes.

Solar energy is a clean, abundant, and sustainable power source that forms the foundation of energy sustainability. Researchers have focused on examining various factors affecting solar energy generation and storage to improve the efficiency of solar collectors. They have evaluated different design criteria, considering environmental elements such as wind speed, solar radiation, and ambient temperature. Both experimental methods and numerical simulations, including Computational Fluid Dynamics (CFD), have been used. ANSYS-Fluent CFD modeling, in particular, provides a cost-effective alternative to experiments by simulating fluid flow and heat transfer within solar collectors. This article reviews recent advances in numerical modeling of concentrating solar systems, using ANSYS-Fluent, detailing the models and methods employed while discussing current challenges. It covers various solar concentrators, including evacuated tube collectors (ETC), Linear Fresnel reflectors (LFR), Compound Parabolic Collectors (CPC), and Solar Towers (ST). Summaries of previous studies are tabulated, highlighting different CFD models, techniques, and assumptions. The main goals and results of these studies are outlined. The article also discusses validation techniques and compares experimental data with simulation outcomes, assessing the employed numerical models and methods. It emphasizes common physical models, solution strategies, and assumptions used in analyzing different solar concentrating systems. Additionally, it identifies current challenges, suggests future research directions, and offers perspectives to help advance understanding. This work aims to support researchers in understanding current trends in the numerical simulation of high-concentration solar collectors. Scholars can use this resource to select appropriate models and methods, leveraging their strengths and avoiding common pitfalls in CFD analysis of solar collectors with ANSYS-Fluent.