最新刊期
卷 47 ， 期 3 ， 2026
- 摘要：ObjectiveTo support complex aerospace missions including manned spaceflight， Mars exploration and space station construction， it is critical to conduct deep-space exploration research for solar-system planets and even extrasolar space. High-specific-impulse cryogenic fluids such as liquid hydrogen-liquid oxygen （LH2-LOX） and liquid oxygen-liquid methane （LOX-LCH4） are primary propellant for deep-space missions. During flight， cryogenic fluids in propellant tanks undergo gravity changes， leading to interface relocation. Owing to low surface tension and viscosity， their interfaces easily deform and break up， resulting in complicated flow behaviors. Meanwhile， increased interfacial and contact areas enhance heat transfer， triggering intense phase change due to low boiling points and latent heats， making thermal states unpredictable. This study aims to reveal the evolution of interface dynamics and thermal behavior during relocation， which is essential for the design of on-orbit propellant management devices.MethodsIn this study， a drop-tower experimental platform for LOX reorientation was constructed. The setup， housed in a stainless‑steel vacuum chamber with sapphire windows for optical access， uses multilayer insulation and combined LED lighting to enable high‑speed visualization. A liquid nitrogen cooling circuit connected via copper braids provides stable precooling and suppresses boiling. The test cell， made of sapphire with high pressure resistance， is instrumented with multiple temperature sensors. LOX is condensed and stabilized at a height of 18.5 mm until thermal drift is below 0.000 1 K/s. The system is then installed in the drop tower tube， adjusted for center‑of‑mass， and released from 83 m to generate nearly 3.5 s of microgravity at approximately 0.004 4 g₀. High‑speed images are recorded and processed using a MATLAB edge‑detection algorithm to analyze interface evolution during the relocation process. Meanwhile， the vapor-phase temperature and pressure were measured. During the drop-tower process， the overload environment transitioned from normal gravity to microgravity.Results and DiscussionsThe LOX propagated along the inner wall and formed a liquid layer. The motion of this liquid layer was decoupled from that of the bulk liquid， and the interface center oscillated continuously. Owing to the ascend of the contact line， the gas-liquid interface area increased， and LOX evaporated continuously at the contact line. The emergence of the liquid layer resulted in a pressurization rate of 3 227 Pa/s at the first oscillation of the contact line， which is approximately 1.8 times higher than the final stabilized pressurization rate. During the entire 2.5 s reorientation process， the pressure in the gas-phase region increased by 4 217 Pa. The temperature variation at 15.2 mm from the interface was affected by not only heat transfer from the solid wall but also disturbances from the low-temperature gas flow induced by interface oscillations. Additionally， the temperature at this measurement point increased by only 0.351 K during the entire reorientation process.ConclusionsThis study concludes that the evolution of the LOX interface， temperature and pressure in the ullage in the interface reorientation process. This experiment provides the cryogenic fluid data for simulation validation and guidance for the configuration and design of cryogenic-propellant management devices.关键词：liquid oxygen;drop tower;micro-gravity;interface242|358|0更新时间：2026-06-01
- 摘要：Ortho-para hydrogen conversion is a key process in hydrogen liquefaction that reduces energy consumption and improves storage efficiency. Understanding the catalytic reaction kinetics and achieving real-time concentration monitoring are crucial for optimizing liquid hydrogen production. Among available techniques， Raman spectroscopy enables rapid， accurate， and efficient in situ measurement of ortho-para hydrogen concentration. Compared with traditional indirect methods that use gas chromatography， this technique meets the dynamic detection needs of the process and provides precise measurements， such as reaction kinetics， making it an advanced measurement technique. This study reviews the Raman scattering spectroscopy-based ortho-para hydrogen concentration measurement technique. Accordingly， the principle and composition of the optical detection system for this measurement technique are systematically explained. This study highlights the advantages and disadvantages of Raman spectroscopy compared with the methods of gas chromatography， nuclear magnetic resonance， and sound velocity by reviewing the development and evolution of the ortho-para hydrogen conversion measurement technique from its early use for macroscopic thermal conductivity measurements to its use for modern， in situ spectroscopic analyses. Finally， the study highlights the advantages of Raman spectroscopy in terms of its self-calibration and nondestructive， in situ， and rapid response capabilities. Overall， this study provides a theoretical basis and technical reference for the high-precision monitoring of ortho-para hydrogen in large-scale applications of hydrogen energy.关键词：Raman scattering spectroscopy;hydrogen liquefaction;ortho-para hydrogen catalytic conversion;in-situ measurement techniques;quantitative measurement para-hydrogen125|673|0更新时间：2026-06-01
- 摘要：ObjectiveTo satisfy the optimization and design requirements of small-scale hydrogen liquefaction systems cooled by cryogenic refrigerators， this study investigates the flow-condensation heat-transfer process of hydrogen in a small-diameter helical tube. The objective is to reveal the condensation behavior and key factors influencing hydrogen under cryogenic conditions. Owing to its low viscosity， surface tension， and two-phase density ratio， the heat-transfer mechanism of hydrogen differs significantly from that of conventional refrigerants. However， existing experimental data and correlations for hydrogen flow condensation remain limited. Therefore， in this study， the effects of mass flux， saturation pressure， and temperature difference on the flow condensation heat-transfer performance of hydrogen were investigated， thus providing experimental evidence and theoretical references for the structural design and performance optimization of small-scale hydrogen liquefaction systems.MethodsAn experimental setup for hydrogen-flow condensation was established using a Gifford–McMahon refrigerator. The condenser comprises a stainless-steel helical coil （inner diameter： 1.75 mm） welded onto a copper block in close contact with the refrigerator to ensure efficient heat transfer. Experiments were conducted at three saturation pressures （495 kPa， 665 kPa， and 850 kPa） with mass fluxes ranging from 15 kg/（m2·s） to 40 kg/（m2·s）. The temperature， pressure， and flow rate were measured， and the hydrogen-condensation heat-transfer coefficient was calculated using a thermal-resistance model and the heat-balance method. Prior to the hydrogen-condensation experiments， the refrigerator performance was tested， and a fitted function relating the cooling capacity to the cold-head temperature was obtained. Additionally， computational fluid dynamics （CFD） simulations were performed to verify the uniformity of the internal temperature distribution of the copper block. The results confirmed that the measured temperature represented the refrigerator cold-head temperature， thus ensuring the reliability of the heat-transfer calculations.Results and DiscussionsThe condensation heat-transfer coefficient increased with mass flux， with a higher growth rate at low mass fluxes and a more gradual increase at high mass fluxes. This behavior is primarily due to the thinning of the liquid film， enhanced convective heat transfer， and reduced thermal resistance as the two-phase flow velocity increased. At low mass fluxes， increasing the saturation pressure decreases the condensation heat-transfer coefficient， which is attributed to liquid-film thickening， reduced thermal conductivity， and weakened film fluctuations. However， at high mass fluxes， turbulence dominates heat transfer， thereby diminishing the effect of pressure， and the heat-transfer coefficients stabilize at different saturation pressures. The condensation heat-transfer coefficient decreased with increasing temperature difference. A larger temperature difference thickened the liquid film， increased the liquid viscosity， and increased the gas-liquid density ratio， thereby increasing the thermal resistance. This trend aligns with the data reported by Ohira et al.， thereby verifying the reliability of the experimental results.ConclusionsWithin the experimental range， the hydrogen-condensation heat-transfer coefficient increased significantly with mass flux， with an overall enhancement of 74%-133%. Moreover， the increase was more pronounced under low mass fluxes. Additionally， at low mass fluxes， when the saturation pressure increased from 495 kPa to 850 kPa， the condensation heat-transfer coefficient decreased by 47%， whereas the effect of pressure weakened at high mass fluxes. Under the present experimental conditions， the condensation heat-transfer coefficient ranged from 594 W/（m2·K） to 1 388 W/（m2·K）.关键词：hydrogen;flow condensation;heat transfer characteristics;cryogenic refrigerator152|405|0更新时间：2026-06-01
- 摘要：Low-temperature superconductivity and space exploration urgently require compact， highly reliable， and long-lifespan cooling technologies that operate at the liquid-helium temperature. Multistage Stirling-type pulse tube cryocoolers are a promising solution. In this study， a thermally coupled three-stage Stirling-type pulse tube cryocooler was designed and constructed. The system employs a two-stage high-frequency （70 Hz） Stirling cryocooler （model TC3130， Lihan） to precool the third stage， thus providing cooling capacities of 5 W and 2 W at 70 K and 32 K， respectively. For the third stage， simplified models were first established using Sage to determine the key operating parameters， including the operating frequency， average pressure， and precooling temperature. The third stage was fully simulated， followed by the final design and experimental set up. Experimental results show that under an average pressure of 1.4 MPa， a frequency of 21 Hz， and a total input power of approximately 370 W， the lowest no-load temperature reached 5.16 K， with typical cooling capacities of 50 mW and 102 mW at 6 K and 7 K， respectively.关键词：three-stage;liquid helium;regenerator;Pulse tube cryocooler211|734|0更新时间：2026-06-01
- 摘要：Liquid-hydrogen tank containers have received increasing attention for hydrogen storage and transportation applications owing to their high hydrogen storage density and relatively low system cost. However， maintaining a high vacuum environment of 10-2 Pa in the interlayer of liquid-hydrogen containers remains challenging， with residual hydrogen contributing significantly to vacuum failure. Thus， high-performance， low-cost hydrogen adsorption materials and their corresponding vacuum maintenance mechanisms must be developed urgently. In this study， the adsorption characteristics of HKUST-1—a metal-organic framework—and its application mechanism in 40-foot （length： 12 192 mm， width： 2 438 mm， height： 2 591 mm） liquid hydrogen tank containers were investigated. The results show that the self-synthesized HKUST-1， with a specific surface area of 1 426 m2/g and a bimodal pore structure， exhibited excellent physical adsorption potential. The material demonstrated reversible hydrogen adsorption in the liquid-hydrogen temperature range and maintained effective adsorption at extremely low pressures， thus serving dual functions for both cryogenic and ambient-temperature adsorption. Dynamic vacuum model results reveal that using a small amount of HKUST-1 at the cold end of the interlayer reduced the required amounts of both cryogenic and ambient-temperature adsorbents， thereby effectively enhancing the physical adsorption of residual hydrogen and retarding the increase of H₂ partial pressure under extreme vacuum conditions. This study provides a new material solution for vacuum maintenance in liquid-hydrogen storage and transportation equipment， as well as offers valuable insights into the safety design and operation of liquid-hydrogen tank containers.关键词：hydrogen adsorbent;metal-organic framework;adsorption performance;vacuum multilayer insulation150|579|0更新时间：2026-06-01
- 摘要：To provide accurate design guidance for multilayer insulation （MLI） combined with vapor-cooled shield （VCS） structures in liquid hydrogen storage tanks， a three-dimensional steady-state MLI/VCS model was established. The temperature distribution within the VCS was analyzed for parallel and spiral arrangements. The effects of VCS tube diameter， number/length， radiation shield thickness， and vapor mass flow rate on the thermal insulation performance of the tank were systematically investigated. Comparative analysis of the thermal insulation performances of the two arrangements was conducted. The results show that for the parallel arrangement， increasing the tube diameter， number of tubes， and mass flow rate improved the insulation performance of the tank. For the spiral arrangement， increasing the tube diameter and flow rate achieved the same effects as those observed for the parallel arrangement. However， the effect of tube length on insulation performance depends on the vapor mass flow rate. Radiation shield thickness had a minor impact on insulation performance. The relative superiority of the two VCS pipe configurations in terms of insulation performance is influenced by the venting vapor mass flow rate. An appropriate VCS pipe arrangement should be selected for practical engineering applications， based on the venting method and capacity.关键词：multilayer insulation;vapor-cooled shield;liquid hydrogen tank;three-dimensional model;thermal insulation performance584|1127|0更新时间：2026-06-01
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Review of the Non-Uniform Frosting/Defrosting Characteristics of Air-Cooled Refrigerator Evaporators
摘要：Non-uniform frost accumulation on evaporator coils is a significant feature in air-cooled refrigerators. It is also one of the important causative factors leading to evaporator performance degradation. This paper reviews related research in three distinct areas： non-uniform frost characteristics of air-cooled refrigerator evaporators， defrost optimization based on these characteristics， and frost detection optimization. A concise introduction is provided into the formation mechanism of non-uniform frost on air-cooled refrigerator evaporators， the influencing factors， and their impact on refrigerator performance. Frost-heat matching defrosting and frost suppression strategies for the evaporators of air-cooled refrigerators are systematically summarized. The complex challenges and solutions of direct and indirect frost detection techniques under non-uniform frost conditions are analyzed. The performance degradation of air-cooled refrigerator evaporators is summarized and discussed. Finally， this study identifies shortcomings in the research field of non-uniform frost on air-cooled refrigerator evaporators and proposes potential future development directions. This study aims to provide a framework for the efficient operation and energy-saving optimization of air-cooled refrigerators.关键词：Air-cooled refrigerators;Non-uniform frosting;defrosting;return air duct;Frost detection445|1924|0更新时间：2026-06-01 - 摘要：In this study， a new method for passive thermal management of lithium-ion batteries based on paraffin/expanded graphite/bamboo charcoal composite bilayer phase-change materials is proposed. To solve the problem of the limited temperature-control range of existing phase-change materials， a dual phase-change temperature （30 ℃/50 ℃） gradient structure is constructed， and a composite phase-change system with dual phase-change temperature regulation is developed by combining the high thermal conductivity of expanded graphite with the porous adsorption properties of bamboo charcoal. Based on these results， at 40 ℃ ambient temperature and under 5 C large multiplication rate， the temperature increase of the battery constructed using the double-layer phase-change material was 37.8% lower than that of the non-phase-change material group （43.3 ℃ vs. 69.6 ℃， respectively）； at low ambient temperatures （-10 ℃ and 0 ℃）， the double-layer phase-change material extended the battery's effective working temperature range through the synergistic effects of the latent heat release of the phase change materials and the heat storage in the pores. The composite phase-change system realized intelligent thermal management across a broad temperature spectrum （-10 - 40 ℃） via the dual-phase-change mechanism， providing an innovative solution for the thermal safety regulation of batteries， which has significant engineering application value.关键词：dual-layer phase change material;battery thermal management;paraffin/expanded graphite/bamboo charcoal;broad-spectrum temperature regulation537|4331|0更新时间：2026-06-01
- 摘要：The temperature and humidity distributions in a pharmaceutical warehouse affect the efficacy of the medicine stored in the warehouse. For a stereoscopically-monitored high-rack medical cold-storage unit in Tianjin， the influence of shelf layout on the temperature and humidity distributions is examined. The internal airflow distribution of the cold storage unit is optimized. Using the field synergy theory， the temperature and humidity distributions， temperature and humidity uniformity， and refrigeration effect are systematically discussed. Based on the findings， the field synergy angle can be effectively used to evaluate the performance of a high-rack cold storage unit. Increasing the spacing between the shelf layers optimized the unit's thermal performance. At a shelf-layer spacing of 0.6 m， the average temperature， the temperature inhomogeneity coefficient （Kt）， average relative humidity， relative humidity inhomogeneity coefficient， and the average field synergy angle （αp） were 4.56 ℃， 0.039， 55.21%， 0.015， 57.47°， respectively， resulting in a more uniform and reasonable temperature field.关键词：high-rack cold-storage unit;field synergy principle;thermal performance;airflow distribution;shelf arrangement strategy467|844|0更新时间：2026-06-01
- 摘要：Given that measurements made under steady-state laboratory conditions cannot fully reflect the actual performance of air conditioners， the dynamic measurement of room air conditioner performance based on virtual buildings has become a research hotspot. This study determines the key parameters for the dynamic measurement of room air conditioner performance via simulation and model analysis methods， focusing on the heat load of the building， the zero-load point， the heat-to-cold ratio， the sensible-heat ratio， the selection coefficient， and the room's effective heat capacity and moisture capacity. The feasibility of this dynamic performance-measurement method is experimentally verified. The results show that for air conditioners applicable to average buildings in China， the selection coefficient for the cooling season was 1.33. For rooms equipped with an air conditioner with 2.4 kW nominal capacity （12-20 m2）， the effective heat capacity was 240-300 kJ/K， and the moisture capacity was 50-100 kg. Based on these parameters， a dynamic performance test of a 3.5 kW air conditioner was conducted in the laboratory. These parameters resulted in a dynamic energy efficiency 31.8% lower than the steady-state energy efficiency， thus more accurately reflecting the actual performance of the air conditioner.关键词：air conditioners;virtual building;dynamic testing;key parameters520|1648|0更新时间：2026-06-01
- 摘要：The annual operating characteristics of a photovoltaic/thermal （PV/T）-coupled ground-source heat-pump （GSHP） system with cross-seasonal heat storage for an office building in Jinan were investigated via on-site testing combined with TRNSYS and GeoStar simulations. For a ten-year operation period， the ground temperature and energy efficiency of the coupled and single GSHP systems were compared and analyzed. The results showed that the integrated energy efficiency ratio （IEER） of the coupled system exceeded 1.5 during the heating/cooling seasons， peaking at 2.21. The renewable energy fraction contributed by the PV/T components was highest during the transition season， peaking at 0.9 in April. In summer， the injected heat from PV/T inhibited the performance of the heat pumps， and the coefficient of performance （COP） and the IEER were 10.5% and 4.97% lower than those in winter. Over the ten-year operation period， for the coupled system， the soil temperature decreased by 0.13 ℃， IEER decreased from 1.24 to 1.22， and the renewable heat fraction decreased from 0.459 to 0.443. For the standalone GSHP system， in contrast， the soil temperature decreased by 0.7 ℃ and the IEER decreased from 1.195 to 1.15. The PV/T-coupled ground source heat pump system achieved soil thermal balance regulation and coordinated optimization of cooling， heating， and power， thus providing an efficient and sustainable clean energy solution for cold regions.关键词：photovoltaic/thermal;ground-source heat pump;ground thermal balance;cross-season heat storage659|1791|0更新时间：2026-06-01
- 摘要：To address the issues of poor air quality and the lack of fresh air in traditional variable refrigerant flow （VRF） systems， fresh air units are commonly supplemented in practical engineering applications. However， these systems are typically controlled independently. To achieve coordinated operation between VRF systems and heat-recovery fresh-air units， a new integrated VRF fresh-air system was developed， with the aim of reducing system energy consumption and improving indoor comfort and air quality. Based on the full-condition performance model of the VRF system and the characteristics of the heat-recovery unit， simulations were conducted to evaluate the energy-saving effects of conventional VRF systems and of three types of integrated VRF fresh-air systems in residential buildings in Nanjing and Beijing. The results indicate that， compared with conventional VRF fresh-air systems， the system equipped with a constant air volume heat-recovery unit significantly reduced the operational energy consumption， achieving annual energy savings of 20.7% and 30.6% in Nanjing and Beijing， respectively. The energy-saving performance was positively correlated with the severity of cold-climate conditions. During the heating season， the new integrated system prioritizes the use of the heat-recovery mode and minimizes the fresh air volume. During the cooling season， the energy-saving performance can be further improved by introducing a bypass branch and combining it with a variable air-volume control strategy. Compared to the primary baseline system， the combined VRF fresh-air system achieved cooling-season energy-saving rates of 2.77% and 15.31% for Nanjing and Beijing， respectively.关键词：heat recovery;Fresh air unit;variable refrigerant flow system;optimized control;climate zone218|1188|0更新时间：2026-06-01
- 摘要：The optimization of regenerator geometries to enhance the performance of active electrocaloric regenerators （AERs） has attracted significant attention. In this study， corrugated and tapered structures were applied to a parallel-plate AER， and the effects of electrical field parameters on device performance were compared. The results indicated that the tapered structure better balanced the flow resistance and heat transfer efficiency， thus achieving the best refrigeration performance under the same operating conditions， followed by the corrugated AER structure. Short or long device cycle periods resulted in poor refrigeration performance. The electrical field should be switched when the transferred heat reaches 63%-66% of its maximum value. For the same cycle period， each device exhibited an optimal polarization duration （0.2 s）， during which the refrigeration capacities of the parallel-plate， corrugated， and tapered AERs were 4.16 W， 4.35 W， and 4.71 W， respectively， with corresponding coefficients of performance of 1.76， 2.04， and 3.17. As the electrical field intensity increases， the refrigeration capacity of the device increases exponentially. The greater the field intensity， the greater the improvement in the refrigeration capacity of the gradually shrinking AER. When the field intensity increased from 50 MV/m to 225 MV/m， the refrigeration capacity of the tapered AER increased from 0.68 W to 10.06 W， an improvement of approximately 13.79 times.关键词：structural optimization;active electrocaloric regenerator;enhanced heat transfer;tapered structure;corrugated structure439|867|0更新时间：2026-06-01
- 摘要：The novel refrigerants R474A and R479A have demonstrated superior performance in terms of environmental friendliness， safety， and thermodynamic properties. However， their solubility in refrigeration oils remains unknown. This study investigates the miscibility and solubility of R474A and R479A in the lubrication oils RB68 and RB100EV. The critical miscibility temperatures of R474A and R479A in RB68 and RB100EV were tested within a temperature range of -20 ℃ to 20 ℃. The findings reveal that within the experimental temperature range， R474A is miscible in RB68 and RB100EV solutions at different oil contents， and the critical miscibility temperature is lower than -20 ℃. R479A maintains a homogeneous transparent state in both refrigeration oils， with critical miscibility temperatures below -20 ℃. Based on the isochoric saturation method， the solubility of R474A and R479A in RB68 and RB100EV was tested within a temperature range of -20 ℃ to 60 ℃. The solubility of both novel refrigerants in RB68 and RB100EV increased with pressure and decreased with temperature. Based on these findings， for a given temperature range， the enhancing effect of pressure on solubility increases significantly as the pressure increases.关键词：R474A;R479A;lubrication oils;miscibility;solubility808|1101|0更新时间：2026-06-01
- 摘要：To address the limitations of magnetic refrigeration and magnetic heat pump systems near room temperature， this study establishes a one-dimensional numerical model of a cascade active magnetic regenerator and examines the key parameters influencing heating performance. The simulation results indicate that a higher flow rate of the heat transfer fluid accelerates the attainment of a steady-state temperature at the hot end. Furthermore， as the flow rate increases， the no-load temperature span initially increases and then decreases， while the heating capacity increases. Reducing the （de）magnetization time and flow time can significantly enhance both the heating capacity and no-load temperature span， achieving values of up to 55.2 W and 29.9 K， respectively， under a 1-1-1-1 s operating sequence. When the Curie temperature interval of LaFeSiH increases， the no-load temperature span first increases and then decreases， reaching a maximum of 40.2 K at a Curie temperature interval of 6 K. Among the four filling length ratios， the optimal heating performance is achieved at a ratio of 2∶2∶2∶2∶7， resulting in a maximum no-load temperature span of 31.2 K and a maximum heating capacity of 64 W.关键词：Magnetic heat pump;cascade active magnetic regenerator;Numerical model;heating performance374|655|0更新时间：2026-06-01
- 摘要：The use of large-scale water-pit thermal energy storage （PTES） systems can increase the share of renewable energy sources in district heating systems. Currently， the available models for PTES systems are mostly based on numerical models that are not amenable to fast calculation， lacking accurate analytical models. Accordingly， this study proposes a analytical model suitable for PTES. The model solves for the water and soil domains separately and then couples them through the pit sidewall， bottom temperature， and boundary heat fluxes. For water domain heat transfer analysis， a "three-zone" model is proposed， dividing the cross-section into central， transition， and edge zones. Compared to simple one-dimensional models， this "three-zone" model considers horizontal water flow， thereby providing a more accurate dynamic simulation of water temperature. In the heat transfer analysis of the soil domain， the finite cylindrical source model used in the field of ground-source heat pumps was improved to make it suitable for modeling PTES. Furthermore， the semi-analytical model was validated using 10 years of measured data from a 60 000 m³ PTES in Denmark. The average temperature errors at the top， upper-middle， middle， lower-middle， and bottom positions were 0.233%， 0.44%， 0.445%， 0.316%， and 1.27%， respectively， all less than 1.5%， indicating that the model exhibits high accuracy and reliability.关键词：seasonal thermal energy storage;large-scale water pit thermal energy storage system;Numerical model;analytical model276|574|0更新时间：2026-06-01
- 摘要：A new type of air-source heat pump system is proposed， combining domestic hot water and waterless floor heating that is achieved by the direct condensation of the refrigerant in buried pipes. The high-temperature refrigerant is exchanged in the wrapped coil water heater to produce domestic hot water. The prototype was assembled and tested in three modes： standalone floor heating， dual supply， and standalone domestic hot water. The experimental results show that in all three cases， the surface temperature of the floor was maintained between 25 ℃ and 33 ℃， and the air temperature was maintained between 18 ℃ and 22 ℃. Due to the heat storage effect of the capillary floor， the air temperature in the room remained above 18 ℃ within 113-245 min after terminating the system. At an ambient temperature of -5 ℃， after 572.3 min， the water temperature of the water heater rose to 45 ℃. The minimum system heating capacity and energy efficiency ratio （EER） can reach 2.70 kW and 3.55， respectively.关键词：air-source heat pump;waterless floor heating;external coil water heater;heating performance286|991|0更新时间：2026-06-01
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Response Analysis and Thermal Performance Evaluation of Pulsating Heat Pipe with Surfactant Solution
摘要：Appropriate addition of the surfactant cetyltrimethylammonium bromide （CTAB） can significantly reduce solution surface tension and promote boiling heat transfer. In this study， it was applied to a pulsating heat pipe （PHP）， and the experimental study was guided using response surface methodology （RSM）. The influence of heating power （Q=10-105 W）， filling ratio （α=25%-75%）， and CTAB concentration （ω=0-0.29%） on the heat transfer performance of PHP was studied. The results show that the proper addition of CTAB （e.g.， ω=0.145%） at a moderate filling ratio （α=50%） can effectively improve the operation of PHP， reduce thermal resistance， and transform temperature fluctuation characteristics at lower powers. In terms of influencing factors， the heating power had the greatest influence， followed by the filling ratio， whereas concentration had the least influence. The interaction between heating power and filling ratio was the most significant， whereas that between the filling ratio and concentration was not significant. The minimum thermal resistance was predicted as approximately 0.32 ℃/W， and a relatively wide optimal operating condition area existed， which makes the overall thermal resistance of PHP relatively small. This is beneficial for the practical application and performance optimization of PHP in engineering.关键词：pulsating heat pipe;response surface methodology;surfactant;operating factors;evaluation123|305|0更新时间：2026-06-01 - 摘要：In the operational diagnosis of air-source heat pumps， the conventional coefficient of performance has limitations in distinguishing environmental effects from equipment performance degradation because of its dependency on the operating conditions. To address this issue， this study proposes a performance consistency index based on the second law of thermodynamics. By normalizing the second law efficiency under actual operating conditions against its value under rated conditions， a diagnostic method is established for energy efficiency based on this index， with operational robustness and design benchmarking capabilities. The study demonstrates that the performance consistency index inherits the stability and comparability of second-law efficiency， effectively decoupling the effects of environmental parameter fluctuations and equipment performance degradation. It is independent of the operating conditions and accurately characterizes the equipment status. With a design benchmark based on performance consistency index PCI = 1， the deviations between the actual performance and design objectives were quantified. Validation through operational diagnosis of four units confirmed that the performance consistency index successfully identified the degradations in partial-load energy efficiency and low-temperature performance. The performance consistency index provides a theoretical tool for the long-term energy efficiency monitoring of air-source heat pumps， enabling the precise identification of inefficient units through threshold settings and supporting scientific decision-making for equipment renewal in "coal-to-electricity" projects.关键词：air-source heat pump;performance consistency index;thermodynamic perfectibility;long-term energy efficiency conservation;operational diagnosis365|1061|0更新时间：2026-06-01
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