最新刊期
卷 46 ， 期 1 ， 2025
- 摘要：Heat pump technology is an energy-saving solution that could potentially combat global warming and reduce carbon emissions. Industrial heat pumps recover waste heat from the heating process to heat water or air, thereby reducing electricity consumption and carbon emissions. Industrial heat pumps are energy-saving, environmentally friendly, and provide stable heating. They have been widely used at all stages of production and life. This study analyzes the compressor types and characteristics of domestic and international high-temperature heat pumps (HTHP) that recover industrial waste heat and analyzes their application and technical status with a focus on twin-screw and centrifugal compressors. Twin-screw heat pump compressors should adopt an open structure when the evaporation temperature is high, and high-speed and oil-free design can be used when the condensation temperature is high. In addition, centrifugal heat pump compressors should prioritize highly efficient impellers, high-temperature-resistant motors, and oil-free lubricated bearings. Screw steam compressors need to solve the problems of rotor thermal deformation and shaft seal, and target for large temperature lifts.关键词：high-temperature heat pump;twin-screw compressor;Centrifugal compressor;steam compressor284|112|0更新时间：2025-01-23
- 摘要：HP-1 is an eco-friendly hydrofluoroolefin (HFO) refrigerant with favorable thermodynamic and environmental properties. The critical parameters and saturated vapor pressure of HP-1 are similar to those of R245fa, with HP-1 serving as a potential replacement for R245fa, which has a high global warming potential (GWP) in high-temperature heat pumps. The flammability, solubility, and material compatibility of HP-1 were mainly determined experimentally, with the results demonstrating that HP-1 has a flammability range of 9.75%-16.1%, exhibiting excellent solubility with MK220 lubricating oil at elevated temperatures, and good compatibility with materials used in high-temperature heat pump systems. When HP-1 is applied to high-temperature heat pump units, the condensing temperature of the unit can reach up to 125 ℃ when the evaporating temperature ranges between 50 ℃ and 70 ℃, with a heating capacity of 99.27-153.14 kW and a coefficient of performance (COP) of 2.25-4.85.关键词：high-temperature heat pump;refrigerant replacement;HFO refrigerant;physical property160|101|0更新时间：2025-01-23
- 摘要：Achieving low-carbon combined cooling and heating supply in distributed areas away from centralized cooling and heating networks is highly significant in the context of carbon neutrality. This study proposes a combined cooling and heating system based on an absorption heat pump, which uses a variety of clean and renewable energies, such as solar heat, geothermal, waste heat, biomass, and air-source energy, to achieve the combined cooling and heating in a wide temperature range from -20 ℃ to 90 ℃. Such systems are suitable for distributed areas, such as villages, cities, and industrial parks. The system model was constructed based on Aspen, and a prototype was developed. The prototype uses a vacuum tube collector to capture solar thermal energy and introduces natural gas as a supplementary heat source to balance fluctuations of solar energy. Multiple sets of indoor heating and cooling terminals can be driven through medium circulation and valve switching using a single set of absorption heat pumps and outdoor units. The environmental test of the prototype was performed in Jinan, and the solar thermal ratio reached 35% during the testing period. An all-weather stable energy supply was achieved by proportional control of natural gas. Moreover, a wide range of concentration adjustments was achieved by controlling the liquid level in the solution tank, enabling efficient system operation in a wider temperature range. The coefficient of performance (COP) of cooling reached 0.30-0.43 at -20 ℃ and 0.70-0.78 at 7 ℃, with cooling water temperatures varying from 30 ℃ to 20 ℃; the COP of heating reached 1.40-1.90 at 45 ℃ and 1.35-1.56 at 80 ℃, with evaporation temperature varying from -15 ℃ to 20 ℃. The study results demonstrated that introducing solar thermal energy and ambient energy recovery increased the fraction of renewable energy in the system to over 50%. Compared with the traditional method of gas furnace plus air conditioning, the annual operating cost and carbon emissions of the proposed system were reduced by over 54.3% and 44%, respectively, which has significant application potential.关键词：absorption heat pump;multi-energy complement;combined cooling and heating;renewable energy;carbon emission reduction135|52|0更新时间：2025-01-23
- 摘要：The application of latent thermal energy storage with heat pumps has been extensively studied in recent years. The combination of phase change heat storage and a heat pump can improve the performance of the heat pump and the utilization of renewable energy; however, further cost reduction and efficiency increase are required. Therefore, this study reviews the progress of heat pumps coupled with solid-liquid phase change materials and summarizes the applicable conditions and characterization methods for phase change materials applied to heat pumps. The optimization approaches for the performance of the heat pump system are summarized, including the selection and improvement of phase change materials, the optimal setting of the heat exchanger, and the dynamic optimization control strategy of the system. The outstanding performance of heat pumps with cascade heat storage in improving the supply-side comfort and utilization rate of renewable energy indicates the broad prospect of cascade heat storage being applied to heat pump energy storage systems. Herein, mixed, non-eutectic phase change materials are proposed as alternative materials for cascade heat storage. Notably, summarizing and developing new methods for adjusting the thermophysical properties of phase change materials for energy storage is necessary for adapting the selection and improvement of phase change materials to the optimization of the thermodynamic cycle of cascade heat storage devices and further improving the heating decarbonization ability of latent heat storage heat pumps.关键词：heat pump energy storage;latent heat thermal storage;phase change material;cascade heat storage116|102|0更新时间：2025-01-23
- 摘要：The air-source heat pump capillary radiant floor heating system directly heats the floor using a refrigerant as the heat transfer fluid, which employs a simple system and promotes good heat transfer. This study developed an experimental device for capillary floor radiant heating with an air-source heat pump, and a heating experiment with parallel capillary floor radiant terminal was conducted at different outdoor ambient temperatures. The experimental results demonstrate that a longer time is required for the temperature of the capillary floor radiation terminal to reach steady as the outdoor temperature decreases. When the outdoor temperature was -5 ℃, the required time was 120 min. The temperature difference between the discharge inlet end and the condenser outlet end on the same capillary wall was large. The temperature difference on the capillary wall reached 6.40 ℃, while that on the surface of the 20 mm-thick cement floor reached 4.20 ℃. Conversely, the vertical temperature difference from the capillary wall to the cement floor surface was small, not exceeding 0.40 ℃, and the vertical heat transfer effect of the floor was good. The temperature difference at the same position of different capillaries was within 0.80 ℃, and the temperature uniformity was good. When the outdoor temperature was -5 ℃, the heating coefficient of performance of the unit reached 4.61 with good heating performance.关键词：air-source heat pump;capillary;floor radiation;heating performance113|84|0更新时间：2025-01-23
Heat Pump Technology
- 摘要：Microchannel cooling, with its high heat transfer efficiency, low thermal resistance, and light weight advantages, is one of the most effective technologies for solving the problem of heat dissipation with high heat flux; however, it faces the issue of increased pressure drop. The microchannel structure determines the thermal-hydraulic performance. This study describes the research progress on single-phase liquid-cooled microchannel heat sinks in terms of domestic and international structural design to address this problem. Among them, single-phase heat dissipation structures are divided into variable cross-sectionals, flow disruption, pin-fin, double-layered, bionic, and hybrid-reinforced structures. The advantages and disadvantages of the heat transfer coefficient, pressure drop, comprehensive performance, and temperature uniformity were analyzed based on the principle of enhancing heat transfer in various structures. A cost analysis of the commonly used matrix materials and processing methods for microchannel heat sinks was conducted. Finally, we provided the prospect and development direction of microchannel heat sinks from an application perspective. The application of composite structures, integration of simulation and experimentation, advances in material science and processing technology, and the nexus of disciplines are noted as the focus of future structural research.关键词：microchannel;heat transfer coefficient;single-phase flow;structural design134|111|0更新时间：2025-01-23
- 摘要：A compressor outlet tube is a transmission component of sound power, and its sound power loss directly affects the performance of pulse tube cryocoolers. Flexible bellows can adjust the relative positions of compressors and cold fingers in applications compared with traditional rigid smooth tubes. This study analyzed the flow characteristics of two types of connected pipes by simulation, and the influence of different types of connected pipes on the performance of the entire machine was verified experimentally to determine the influence of flexible bellows on the cryocooler. The simulation results demonstrated that mixed flow appears at the ripple of the bellows, resulting in greater resistance loss, when compared with a rigid smooth pipe. Under the same inlet parameters, the outlet mass flow and pressure amplitude were lower, and the sound power loss was greater. The experimental results demonstrated that the input power required by the bellows was higher when the cooling capacity was the same. When the cooling temperature was 37.5 K and the cooling capacity was 0.5 Wthe input power of bellows and smooth tubes was 119 W and 112 W, respectively; when the cooling capacity was 3.0 W, the input power of bellows and smooth tubes was 279 W and 259 W, respectively.关键词：Pulse tube cryocooler;Flexible bellows;flow characteristics;Sound power transmission54|64|0更新时间：2025-01-23
- 摘要：The low-carbon transformation of data centers is highly significant for achieving carbon peaking and carbon neutrality. This study compared and analyzed the overall situation of data centers in China. Three variables—energy efficiency improvement rate, proportion of non-fossil energy—and negative emission technology intensity were introduced based on the CO2 emission and intensity targets of China in key years, and the total CO2 emissions of the data centers were projected via scenario analysis. The results demonstrated that the power consumption of the data centers increased gradually; the carbon emissions first increased and then decreased, and the power usage effectiveness (PUE) of the data centers decreased gradually. The carbon peak time of the three scenarios is 2030, and the expected times to achieve carbon neutrality are 2059, 2057, and 2055 in the three scenarios. In light of the goal to achieve carbon neutrality by 2060, the data center industry should further improve the energy efficiency utilization rate, increase the proportion of non-fossil energy, strengthen the technological innovation of carbon capture and storage, and enhance the level of carbon sinks.关键词：data center;carbon neutrality;scenario analysis;emission reduction paths86|68|0更新时间：2025-01-23
- 摘要：A CO2 data center cooling and heating system integrated with dedicated mechanical subcooling and dual-temperature evaporation technology (DMS-DE) is proposed to realize green and efficient cooling for data centers and improve comprehensive energy efficiency. A thermodynamic and carbon emission performance system model was established and compared with the basic CO2 system (Base) and a single evaporating-temperature CO2 system with dedicated mechanical subcooling (DMS-SE). The results demonstrated that the DMS-DE system had the maximum coefficient of performance (COP), optimal subcooling degree, and discharge pressure. Therefore, adopting the DMS-DE can significantly increase the system COP and exergy efficiency. Compared with Base and DMS-SE, COP increased by 14.1% and 9.0%, and the exergy efficiency increased by 13.24% and 4.31%, respectively. The life cycle carbon emissions of the DMS-DE system were reduced by 16.1% and 9.3% compared with Base and DMS-SE, respectively. This study can provide a technical reference for the highly efficient and clean operation of combined heating and cooling utilization for data center scenarios.关键词：mechanical subcooling;dual-temperature evaporation;data center;CO2 system;combined heating and cooling67|23|0更新时间：2025-01-23
- 摘要：Drying of Lentinus edodes is an effective method to prevent problems such as rotting and browning. During the drying process, the loading density has a significant impact on system performance and drying quality. Based on a newly designed quasi-two-stage enhanced vapor injection heat pump closed drying system, the effects of different loading densities of Lentinus edodes on moisture ratio, drying rate, coefficient of performance of the system (COPsys), specific moisture extraction rate (SMER), drying capacity per unit energy consumption, and rehydration ratio were experimentally investigated. The results showed that when the drying air supply temperature was 55 ℃ and the circulating air volume was 580 m3/h, the drying rate of Lentinus edodes decreased gradually with the loading density in the drying chamber, from 1.5 kg/m2 to 3.0 kg/m2. Meanwhile, the average COPsys, average SMER, drying capacity per unit energy consumption, and rehydration ratio increased first and then decreased. When the loading density was 2.4 kg/m2, the average SMER, drying capacity per unit energy consumption, and rehydration ratio reached the maximum values of 0.320 kg/(kW·h), 0.391 kg/(kW·h), and 3.6, respectively. When the loading density was 2.4 kg/m2, the average COPsys reached its maximum of 4.22.关键词：heat pump;drying;Lentinus edodes;Loading density;performance54|33|0更新时间：2025-01-23
- 摘要：The two-phase flow pattern of hydrocarbon working fluids on the shell side of a helically baffled heat exchanger for liquefied natural gas determines its heat transfer performance. This study tested the two-phase flow patterns of propane and ethane/propane mixtures on the shell side of a helically baffled heat exchanger using a visualization experimental method. The test results demonstrated that with the increase in vapor quality, the experimental observations sequentially included stratified flow, stratified-spray flow, and spray flow; as the mass flux of propane increased from 20 kg/(m2·s) to 40 kg/(m2·s), the transition vapor quality from stratified flow to stratified-spray flow decreased from 0.7 to 0.3, while the transition vapor quality from stratified-spray flow to spray flow decreased from approximately 1 to 0.7; when the proportion of ethane increased from 0 to 50%, the transition vapor quality from stratified flow to stratified-spray flow increased from 0.30-0.45 to 0.43-0.55, while the transition vapor quality from stratified-spray flow to spray flow increased from 0.69-0.85 to 0.83-close to 1. The existing flow pattern map for water-air mixtures was inadequate for predicting the flow patterns of hydrocarbon working fluids. A new set of flow pattern transition criteria was established with prediction deviations of approximately 6.5%, 5.5%, and 4.2% for the experimental stratified flow, stratified-spray flow, and spray flow, respectively.关键词：mixed refrigerants;two-phase flow;flow pattern;shell side;helical baffle48|82|0更新时间：2025-01-23
- 摘要：An energy-saving optimization operation strategy based on maintaining the high-energy-efficiency operation of chillers is proposed to address the prevalent issue of increased energy consumption in the application of cold-storage technology for economic optimization in the current air-conditioning industry. This strategy involves the storage and release of cooling using small cold-storage tanks to actively control the load ratio of the water chiller, thus ensuring that the unit operates efficiently for an extended period to achieve energy savings. A physical model of the air-conditioning system is established and simulated using operational data from the central air-conditioning system of a hospital. Performance curves of the water chiller under different environmental conditions are obtained to accurately depict the high-efficiency operational states of the unit at each moment. On a typical day with a peak cooling load of 9 979 kW, using an active chilled-water storage system, as compared with using the conventional chiller operation strategy without active storage, can reduce 2 777 kW·h of daily electricity consumption, which constitutes 6.0% of the daily electricity usage of the central air-conditioning system. Over the entire cooling season, this approach can save 2.35% of the total electricity consumption of the central air-conditioning system and 4.45% of the electricity consumption of the chiller.关键词：load distribution;water thermal storage;chiller sequencing control;energy-saving operation strategy65|76|0更新时间：2025-01-23
- 摘要：The refrigeration systems in high- and low-temperature test chambers face challenges of high energy consumption and low efficiency. This study developed an enhanced vapor injection system in a test chamber and conducted experiments using R448A and R404A refrigerants to improve the system efficiency and ensure its alignment with low-carbon environmental goals. The impact of refrigerant charge amounts and compressor frequencies on system performance was analyzed. The results demonstrated that the cooling capacity and coefficient of performance (COP) of the R404A and R448A systems initially increased and then decreased with increasing refrigerant charge amounts. The R448A system demonstrated an 11.3% higher maximum cooling capacity and a 10.4% higher COP than the R404A system. In addition, the compressor power consumption of the R448A system was lower than that of the R404A system. At a refrigerant charge amount of 2.0 kg, the R448A system consumed 7.5% less power than the R404A system. The refrigeration capacity of the R448A system exhibited a 7.7% higher increase compared with that of the R404A system, whereas the compressor power consumption increase was 1.9% lower than that of the R404A system.关键词：high- and low-temperature test chamber;enhanced vapor injection;R448A;compressor frequency;refrigerant charge63|96|0更新时间：2025-01-23
- 摘要：Motor cooling is critical for ensuring the high reliability of linear compressors. This study established a linear oscillating motor loss model based on experimental operating parameters and temperatures. The trends of the copper loss, iron core loss, and eddy current loss of the motor with temperature were analyzed, coupled with a three-dimensional flow field model of the linear compressor to analyze the temperature distribution characteristics of the motor coils and permanent magnets under different operating conditions. The research results demonstrated that, for every 0.2 g/s increase in mass flow rate, the motor temperature can be reduced by 4-20 ℃, and the variance of temperature distribution decreases by 0.5-1.2 under the same intake temperature. Furthermore, for every 5 ℃ decrease in intake temperature, the motor temperature decreases by 4-6 ℃ under the same mass flow rate. The maximum temperature difference of the permanent magnet was 7.3 ℃ at a mass flow rate of 0.6 g/s and 6.9 ℃ at a mass flow rate of 1.4 g/s. The optimized intake structure reduced the variance of motor temperature distribution by 5.521, the highest temperature decreased by 4.1 ℃, and the maximum temperature difference decreased by 4.55 ℃.关键词：linear compressor;motor power loss;temperature distribution;linear oscillating motor39|84|0更新时间：2025-01-23
- 摘要：This study employed a validated computational fluid dynamics (CFD) model to investigate the influences of the mixer length and diffuser angle on the ejector pressure-recovery performance. The results demonstrated that an optimal combination of mixer length and diffuser angle exists at which the ejector has the highest performance. The effects of these two geometrical parameters on the ejector performance were highly consistent. When the mixer length was sufficiently long, the mixing was sufficient, and the mixed flow was not subjected to separation during pressure recovery. Under these circumstances, the effect of the diffuser angle on the ejector performance was relatively trivial, varying between 0.5° and 3°. However, when the mixer length was short, the flow was prone to turbulent losses near the diffuser wall. In this case, the effect of the diffuser angle was significant. In addition, the optimal geometries were affected by the operating conditions. The optimal mixer length increased as the nozzle inlet pressure and temperature decreased, whereas the optimal diffuser angle decreased. Under the conditions and nozzle configuration investigated in this study, the optimal mixer length was approximately 38 mm and the optimal diffuser cone half angle was between 1° and 1.5°.关键词：two-phase flow;CO2 ejector;mixer;diffuser61|38|0更新时间：2025-01-23
- 摘要：In an occupied enclosure space formed by multiple opposing jet outlets, understanding vortex structures is crucial in controlling the spread of viruses and pollutants. In this study, a scaled model of an occupied enclosed space with opposing jet flows was constructed by incorporating a heated floor as a heat source to create thermal plumes under cooling conditions. A particle image velocimetry (PIV) system was employed to measure the flow field under isothermal and cooling conditions. The identification performance of different vortex identification algorithms was compared by studying the turbulent characteristics of the flow field from the perspective of the vortex. The Liutex vortex identification method was applied to analyze the vortex motion within one oscillation period, revealing distinct strengths in counterclockwise and clockwise directions, with maximum intensities of 50 s-1 and 110 s-1, respectively. The study concluded that the motion, merging, and annihilation of vortices influenced the flow field structure with a jet oscillation period of approximately 3.67 s. Owing to the trapping effect of vortices on pollutants, areas of pollutant accumulation can be represented using relative frenquency distribution maps of vortex cores. Despite the unsteady flow field, the vortex distribution remained relatively stable. Specifically, on the left side of the CS4 cross-section, the vortex core appeared at the same point up to 21 times. Under cooling conditions, pollutants are confined to smaller regions, which aids in containing the spread of pollutants.关键词：enclosed space;ventilation flow field;opposed impinging jet;vortex identification45|84|0更新时间：2025-01-23
- 摘要：Circulating water is used as the working medium in water-based chillers. Salt ions, such as calcium in circulating water, may precipitate during long-term operation, resulting in the attenuation of heat transfer performance. The application of small-diameter tubes in heat exchangers may lead to more prominent fouling problems. This study developed an accelerated fouling method to evaluate water fouling risk. The most typical operating conditions for water-based chillers were selected as the experimental conditions. The test samples included small diameter (5 mm) smooth tubes, with 7 mm smooth tubes selected for the control experiment. The experimental conditions include a circulating water inlet temperature of 60 ℃, a flow rate of 1 m/s, a foulant mass concentration of 800 mg/L, and a test time of 0-400 h. The results revealed that the total fouling mass was 39.5% higher and required fouling time was 17.6% shorter when comparing the 5 mm and 7 mm smooth tubes; the small diameter tubes had a larger total fouling mass and higher fouling rate. The heat transfer coefficients of the 5 mm and 7 mm tubes after fouling decreased by 12.5% and 9.7%, respectively, and the pressure drops increased by 50.6% and 10.4%, respectively, demonstrating a more severe heat transfer performance deterioration of small diameter tubes after fouling. The microscopic observation results of the fouling layer morphology demonstrated that the fouling layer in 5 mm tubes is a form of compact lamellar scaling, which is more difficult to remove compared with the 7 mm tube; therefore, the fouling risk should be considered when promoting the application of small diameter tubes in chillers.关键词：chiller;small diameter;accelerated fouling method;crystallization fouling;experimental research63|91|0更新时间：2025-01-23
- 摘要：Microencapsulation technology based on sodium alginate hydrogels can be used to optimize freezing and rewarming procedures and to reduce cryo-damage to cells and tissues. This study first observed the morphology of oocytes of sodium alginate hydrogels at different volume fractions (0.5%, 1.0%, 1.5%, and 2.0%) to determine the safe concentration for their encapsulation. Second, the crystallization temperature and crystallization behavior of sodium alginate hydrogels with different volume fractions were systematically investigated using cryo-microscopy, and the morphology and crystallization of oocytes were compared when they were cooled down/retempered in the base solution (cryoprotectant solution). Finally, the freezing effects of the sodium alginate antifreeze hydrogel-encapsulated oocytes prepared by solvent replacement and physical mixing were compared. The results revealed that oocytes maintained their overall morphology and volume better in sodium alginate gels at volume fractions of 0.5% and 1.0%. Furthermore, oocytes in both the 1.0% sodium alginate group and the cryoprotectant solution group of 12.5% DMSO + 12.5% EG + 0.5 mol/L trehalose did not produce intracellular ice during the cooling process. Additionally, compared with the physical mixture, oocytes in the hydrogel solvent replacement group did not produce intracellular ice during the cooling process, and the cells retained their normal morphology after rewarming.关键词：Alginate;oocyte;Microencapsulation;Crystallization temperature63|75|0更新时间：2025-01-23
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