Research Article
Research on High Temperature Cascade Heat Pump System for Vapor Production Employing Scroll Compressors and Multi-stage Preheat Cycle
Haihan Yu*
,
Zhaorui Zhao
Issue:
Volume 10, Issue 4, December 2025
Pages:
78-84
Received:
9 September 2025
Accepted:
22 September 2025
Published:
10 October 2025
Abstract: Water vapor production is an essential process in industrial fields such as dyeing, food processing, and pharmaceutical manufacturing, yet it is characterized by substantial power consumption. Against the backdrop of global carbon neutralization initiatives, high-temperature heat pumps have emerged as a promising alternative to traditional boilers, owing to their environmental friendliness and cost-saving advantages. However, developing and manufacturing such vapor production systems poses significant technical challenges: compressors must withstand extreme high pressures, heat exchangers suffer from low effectiveness during high-temperature condensation, suitable working fluids balancing low evaporation and high condensation temperatures are scarce, and components face issues like heat exchanger incrustation and insufficient compressor lubrication at high discharge temperatures. In this study, a cascade high-temperature heat pump system integrated with a flashing circulation and multi-stage preheating cycle was developed for water vapor production. The system comprises three core cycles: an R134a low-temperature heat pump cycle, an R245fa high-temperature heat pump cycle, and a two-stage preheat-evaporation water cycle. Theoretical simulations were conducted to evaluate component performance (compressors, heat exchangers, etc.) and optimize system parameters. An experimental testbed was constructed with scroll compressors (3.5kW for R134a, 5kW for R245fa) and plate heat exchangers, verifying system reliability under varied operating conditions. Results demonstrate the system efficiently produces 135°C/0.3MPa water vapor, with a Coefficient of Performance (COP) ranging from 2.1 to 3.5. COP increases with evaporation temperature and decreases with condensation temperature, with an optimal intermediate-stage temperature of 70–75°C. This system proves to be an efficient, eco-friendly industrial alternative to conventional boilers.
Abstract: Water vapor production is an essential process in industrial fields such as dyeing, food processing, and pharmaceutical manufacturing, yet it is characterized by substantial power consumption. Against the backdrop of global carbon neutralization initiatives, high-temperature heat pumps have emerged as a promising alternative to traditional boilers,...
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Research Article
Magnetic Vortex Dynamics and I-V Characteristics in Type-II Superconductors
Issue:
Volume 10, Issue 4, December 2025
Pages:
85-94
Received:
7 September 2025
Accepted:
25 September 2025
Published:
28 October 2025
DOI:
10.11648/j.wjap.20251004.12
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Abstract: We study the dynamics of flux vortices and I-V characteristics of a type-II superconductor in which the flux-pinning centers are randomly distributed with various contents and applied with a transport current and an external magnetic field. When an external magnetic field and transport current are applied to a superconductor, the vortex dynamics inside the superconductor is very complex. This is especially true if the flux-fixing centers are randomly distributed. We have performed simulations by choosing the transport current through the type-II superconductor in which the first vortex motion is observed and the value of the applied external magnetic field. The simulation results of vortex dynamics inside superconductors are analyzed through electric field profiles and E-t curves. We emphasize here that the electric field profile and total energy have a very close relationship. We found that the change in total energy is the most significant at ω=0.2, in terms of the content of the flux-pinning centers distributed inside the superconductor. This indicates that the distribution of flux-pinning centers plays a very large role in the properties of the type-II superconductor. We also found from our study of the I-V characteristics of superconductors that when a superconductor transitions from a superconducting state to a normal conducting state, the I-V characteristics are linearized, especially as the content of the flux-pinning centers increases faster.
Abstract: We study the dynamics of flux vortices and I-V characteristics of a type-II superconductor in which the flux-pinning centers are randomly distributed with various contents and applied with a transport current and an external magnetic field. When an external magnetic field and transport current are applied to a superconductor, the vortex dynamics in...
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