最新刊期
卷 41 ， 期 5 ， 2020
- 摘要：Flat plate micro heat pipe array (FPMHPA) is a new type of high-efficiency heat transfer element, and its introduction solves the problem of limited heat flux and heat transport capacity of a single micro heat pipe. Furthermore, it improves the overall reliability of the heat pipe. Given its superior flat plate, the FPMHPA overcomes the limitations of small contact area, shape, and contact thermal resistance of a conventional circular heat pipe in typical applications. In this study, the internal structure of the FPMHPA, type of wick, and manufacturing and packaging processes are summarized. Furthermore, theoretical research, mathematical model for performance, and experimental tests of the FPMHPA are introduced. Additionally, the application status of FPMHPA in many fields is expounded. Hence, this review provides focus areas for future research and reference for the development of the FPMHPA.关键词：flat plat micro heat pipe array;groove;wick structure;heat transfer1756|2231|2发布时间：2024-07-18
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Research on Dehumidification Performance of a Cooling Dehumidifier with a MultistageMatrix Structure
摘要：A multi-stage structure packing tower dehumidifier for feed air dehumidification in compressors is proposed to reduce the power consumption of compressors in cryogenic air separation systems. A multi-stage cooling and dehumidification experimental bench was built, and the dehumidification performance of the dehumidifier was examined experimentally. Experimental results indicated that when the air flow rate increased from 0.48 kg/s to 0.78 kg/s, the moisture content at the air outlet increased from 7.1 g/(kg dry air) to 7.7 g/(kg dry air) with the inlet moisture content and temperature maintained at 11.7 g/(kg dry air) and 24.4 °C, respectively. When the cooling water temperature increased from 6.9 °C to 11.9 °C, air outlet moisture content increased from 7.1 g/(kg dry air) to 9.4 g/(kg dry air) with the inlet air flow rate and temperature maintained at 0.53 kg/s and 25.2 °C, respectively. A steady-state numerical model of heat and mass transfer process in the dehumidifier was established and verified using the experimental data. A performance study of the multi-stage structure dehumidifier and single-stage cross-flow structure dehumidifier was conducted based on the numerical model. The results indicated that the dehumidification rate and dehumidification efficiency can be increased by 4.3% and 2.5%, respectively with the inlet air flow rate and water flow rate maintained at 0.53 kg/s and 0.3 kg/s, respectively. Additionally, the dehumidification performance can be improved by increasing the length of the packing module. The volume of the packing module was fixed at 0.054 m3.Hence, when the module length increased from 0.14 m to 0.28 m, the mass transfer coefficient increased from 4.3 g/(m2?s) to 6.5 g/(m2?s), and the dehumidification efficiency increased from 66.4%to 79.2%.关键词：cooling dehumidification;packing tower;numerical simulation;dehumidification efficiency1586|1743|1发布时间：2024-07-18 - 摘要：To avoid deterioration in the performance of air conditioner heat exchangers after prolonged operation, the dust deposited on the fin surfaces should be removed in a timely manner. In this paper, the frosting–defrosting process of heat exchangers was used to realize the dust removal, and the effect of fin surface coatings on dust removal process was experimentally evaluated. Four test samples, including an uncoated aluminum plate, an uncoated copper plate, a hydrophilic copper plate, and a hydrophobic copper plate, were evaluated in the experiment. The hydrophilic copper plate and hydrophobic copper plate were prepared via a self-assembly method. A visual experimental apparatus was fabricated to observe the dust removal on various samples via the frosting–defrosting process. The dust removal rate and remnant dust weight were obtained. The frosting condition involves a surface temperature of -10 °C, frosting time of 1 h, air temperature of 27 °C, and relative air humidity of 50%. Furthermore, the defrosting condition corresponds to a surface temperature of 5 °C. The dust removal on the hydrophobic surface exhibits the best performance when compared to other samples. The remnant dust weight on the hydrophobic surface is only 1.9% of that on the aluminum surface, 2.0% of that on the copper surface, and 5.9% of that on the hydrophilic surface.关键词：heat pump;defrosting;frosting;coating;dust1590|1799|0发布时间：2024-07-18
- 摘要：A theoretical model for annular flow of R1234ze(E) flow boiling in micro-tubes was proposed in this paper. The surface coefficient of heat transfer and pressure drop were calculated using the model. The variation in the liquid film thickness profile due to the gravitational effect, surface tension, and liquid-vapor interfacial stress was considered. The effect of the variation in the liquid film thickness profile on the heat transfer was analyzed. Furthermore, certain existing surface coefficients of heat transfer and empirical correlations of two-phase friction pressure drop were compared with the numerical results, and the comparison revealed deviations within 30%. The numerical results indicated that the variation in the liquid film thickness profile is evidently affected by gravity in the initial flow area, and the gravitational effect starts to weaken with the flow boiling process. The surface coefficient of heat transfer of annular flow with gravity was higher than that without gravity. Hence, the mean surface coefficient of heat transfer increased with gravitational acceleration. Furthermore, surface coefficient of heat transfer and pressure drop increased as the mass flux increased. Conversely, surface coefficient of heat transfer and pressure drop decreased as the diameters increased.关键词：micro-tube;flow boiling;annular flow;R1234ze(E)1486|1695|0发布时间：2024-07-18
- 摘要：R1234ze(E)(1,1,1,3-tetrafluoropropene) is extremely environmental-friendly and is currently considered as one of the alternative refrigerants. In this paper, the solubility of R1234ze(E) in two polyol ester oils was measured at temperatures ranging from 40 °C to 80 °C and pressures ranging from 0.123 MPa to 0.360 MPa. Additionally, the experimental data was correlated using the PR equation of state with MHV2 mixing rules and the NRTL activity coefficient model to calculate the interaction coefficient at different temperatures. Furthermore, the average absolute relative deviation between calculated value and experimental data was calculated. The results indicated that the solubility of R1234ze(E) in two polyol ester oils decreased as temperature increased. Additionally, a numerical calculation model for the equilibrium pressure and solubility was proposed using a cubic function with acceptable accuracy. In the two polyol ester oils, the deviations between calculated value and experimental data were 1.68% and 1.11% respectively. Thus, the results can better describe the phase equilibrium behavior of R1234ze (E) in the two polyol ester oils.关键词：R1234ze(E);solubility;zeotropic mixture;GWP;ODP1674|1608|1发布时间：2024-07-18
- 摘要：To measure the vapor-liquid equilibrium (VLE) of refrigerants/lubricants, a refrigerants/lubricants VLE experimental system with high precision was developed based on the cycle method. The circulation system was equipped with a detachable sample tank. It combined the cycle method and weighing method and eliminated the systematic error of isochoric saturation method due to the assumption. Furthermore, it could measure the VLE of refrigerants/lubricants at a temperature range of 263.15 K to 373.15K. The saturated vapor pressure of R290 was measured from 293.35 K to 323.33 K. The relative deviation of the pressure was less than -0.18% when compared to NIST REFPROP9.1. Additionally, the phase equilibrium values of R290 and squalane were measured at 303.35 K. The experimental data and literature data were correlated with the Peng–Robinson (PR) equation of state and one-fluid van der Waals mixing rules in Aspen Plus, and the results indicated maximum relative deviation of pressure of-0.37% and0.76%, respectively.关键词：refrigerant;lubricant;vapor-liquid equilibrium;cycle method1538|1856|1发布时间：2024-07-18
- 摘要：Pore structure in-situ-regulation of activated carbons for adsorption refrigeration is conducted via an innovative procedure involving precursor blending, catalytic carbonization, CO2 oxidation, and multi-step activation. New carbon higher total pore volume (GHUM)simultaneously realized well-developed mesopores (0.881 9 cm3/g) and micropores (0.295 5 cm3/g) with a high total volume (1.177 4 cm3/g). After depth-activation in SX-100, higher volume of mesopores (1.183 2 cm3/g) was observed with higher total volume (1.183 2 cm3/g). The effects of pore structure distribution regulation on the adsorption/desorption and refrigeration efficiency of activated carbon–methanol working pairs were examined and compared with those on microporous carbon GDWK-02. The results indicated that condensation and diffusion of refrigerants can be well-promoted by carbons with simultaneously well-developed mesopores and micropores with GHUM. Adsorption and desorption capacities of GHUM for methanol were （368.04±4.64）mg/g and （375.92±7.38）mg/g, respectively. Furthermore, GHUM (299.32±123.16) realized higher surface diffusion coefficient (15Dso/Rp2) than SX-100 (242.18±149.33) and GDWK-02 (0.338 7±0.125). When the desorption temperature was 100 ℃, the temperature difference of heat exchange in GHUM type adsorption bed was as high as 50 ℃.Hence, the average temperature of refrigeration room was maintained at 23±1 ℃.Furthermore, the system reached are frigeration capacity (286.12 kJ/kg) and refrigeration power (357.65 kJ/(kg?h)) that can maintain the indoor constant temperature of the cooling air-conditioning system in summer and exhibit good heat transfer and refrigeration performance.关键词：adsorption refrigeration;adsorption working pair;activated carbon-methanol;pore structure distribution;refrigeration performance1636|1589|3发布时间：2024-07-18
- 摘要：The gas–liquid two-phase flow characteristics in the riser of the bubble pump directly affects its working substance lifting performance. A high-speed camera system was set-up to visualize the lifting process of multiple tube bubble pump under different heating power values (400, 600, 800, 1000, 1 200, 1 400 W), and the liquid lifting process of the multiple tube bubble pump was compared with that of the single-tube bubble pump. The research results indicated that multiple tube bubble pumps exhibit an increase in total lifting capacity and liquid lifting rate as heating power increases. When the heating power was 1400 W, the total lifting capacity increased by 15.16 kg and liquid lifting rate increased by 5.08 g/s when compared to that under a heating power of 1200 W. The lifting effect was optimal when the number of bubbles in the lifting tube at the center of the multi-tube bubble pump was higher. With respect to single-tube bubble pumps, when the heating power was 400 W, the increase in the number of riser tubes could not improve the liquid lifting performance of the bubble pump when compared with that of multiple tube bubble pumps. When the heating power was 400 W, the increase in the number of riser tubes could not improve the liquid lifting performance of the bubble pump. Furthermore, when the heating power was 600–800 W, the single-tube bubble pump liquid lifting performance was approximately similar to that of multiple tube bubble pump. When the heating power was 1000–1400 W, the total lifting capacity, maximum lifting rate, and pump efficiency of the multiple tube bubble pump were significantly improved when compared with the corresponding performance of a single-tube bubble pump.关键词：single-pressure absorption refrigeration;bubble pump;gas-liquid two-phase flow;visualization experiment;riser1325|1580|0发布时间：2024-07-18
- 摘要：Most of the existing data-driven fault diagnosis methods are based on the black box model. Although their accuracy is high, it is difficult to explain the diagnosis process and result. In view of the aforementioned problems, this paper proposes a method for fault diagnosis of chillers and the interpretation of diagnosis mechanism based on associative classification. This method, on the premise of high accuracy, performs reverse analysis of diagnostic process based on the rule library in the diagnostic model and explains the mechanism of the faults and process of diagnosis, and thereby increases reliability of the method for diagnosis based on a data-driven mechanism. Experimental data from ASHRAE research project 1043 (ASHRAE rp-1043) was used for model validation of the system. The results indicated that this method, based on associative classification, can effectively identify seven typical chiller faults, and the average accuracy is as high as 90.84%. The important rules extracted in this study coincide well with refrigeration principles and the knowledge of thermodynamic cycles. Thus, the rules can be used for conducting further studies on fault mechanism analysis and fault diagnosis.关键词：fault diagnosis;chiller;associative classification;knowledge discovery1560|1613|3发布时间：2024-07-18
- 摘要：To comprehensively consider temperature and humidity requirements, this paper proposed a room air conditioning system with adjustable temperature and dehumidification functions. Furthermore, the performance of the system in air conditioning and dehumidification modes were examined. The results indicated that the device can realize the air conditioning mode, dehumidification mode with rising temperature, and dehumidification mode with regulated temperature. In the dehumidification mode, under all test conditions, the outlet temperature of the dehumidification mode with regulated temperature was approximately 7% lower than that of the dehumidification mode with rising temperature, and the relative humidity of the outlet was approximately 27% lower. Furthermore, the former mode exhibited a dehumidification amount of approximately 2.8 times of that in the latter mode, and the unit power of dehumidification was approximately 2.6 times of that in the latter mode. Hence, dehumidification mode with rising temperature should be used when the outdoor temperature is lower than 18 ℃, and the compressor can be adjusted via variable frequency. Dehumidification mode with regulated temperature should be used when the outdoor temperature is between 18 ℃ and 26 ℃, and the compressor can be controlled with the "capacity adjustment + variable frequency" method. The system can effectively solve the problem of lower supply air temperature owing to the dehumidification in the middle and lower reaches of the Yangtze River.关键词：room air conditioning;dehumidification;dehumidification with regulated temperature;specific dehumidification1614|1616|0发布时间：2024-07-18
- 摘要：To solve the problems involving insufficient liquid supply in the low-condensation temperature of the vapor compression air-conditioning refrigeration system and the low utilization rate of natural cold energy in the cold season, an air-conditioning system based on refrigerant pump boosting was designed, and the operating characteristics of the system was experimentally studied in this paper. The system can be operated in three modes: vapor compression, refrigerant pump boost, and single refrigerant pump drive in hot summer, transitional season, and cold winter. The results show that the traditional compression vapor refrigeration system using a capillary tube and an electronic expansion valve in the experiment suffers from insufficient liquid supply and reduced cooling capacity when the outdoor temperature is below 25 ℃and15 ℃, respectively. Furthermore, it can achieve a rated cooling capacity of more than 100% and a COP of 3.96 to 6.25 in the working conditions with an outdoor temperature of 25 ℃ to -5 ℃.This satisfies the operating requirements of the transition season. When the outdoor temperature is lower than -5 ℃, the use of a single refrigerant pump drive can satisfy the rated cooling capacity and exhibit a COP of more than 19.关键词：data center;air conditioning system;refrigerant pump;natural cold energy;refrigeration performance test1554|2025|0发布时间：2024-07-18
- 摘要：A ground source heat-pump system for a residential community in Yangzhou was designed and tested under winter conditions. The operating performance was evaluated and ground thermal imbalance problem was also analyzed based on the annual energy consumption of the air conditioning system of the community. The results showed that the ground source heat pump system requires 1087 vertical wells for heat transfer, the water temperature at the outlet of the buried pipe was 8.5–9.0 ℃, the coefficient of performance (COP) of heat pump unit was 3.67–4.17, and the system COP was 2.66. Based on the test data, it is concluded that the main reason for the low system COP is that the system operates at low temperature differences between inlet and outlet and large flow rate at low partial load rates, and thereby resulting in higher pump power consumption. Conversely, based on the combined annual air-conditioning energy consumption data of the community, it is concluded that the system's heat extraction in winter and the heat release in summer are unbalanced, and thereby resulting in a decrease in soil temperature.关键词：ground-source heat pump;system design;performance analysis;thermal imbalance;residential community1458|1621|3发布时间：2024-07-18
- 摘要：In order to match the best state point of air-conditioning performance, this paper selects an air conditioning unit with a refrigerating capacity of 5.15 kW as a research object. The influence of the charging capacity, the subcooling degree and the superheat degree at the evaporator outlet of the air conditioning system on the refrigerating capacity and energy efficiency of the system is experimentally studied. The theoretical matching curves of SH-Q, SC-EER, SC-Q, SH-EER are proposed, and the best state point of the air conditioning system is matched through the curve. The way to achieve the best state point matching can be divided into two parts: 1) the first charge amount of refrigerant should be based on the matching curve to find the most suitable evaporation superheat degree and condensation subcooling degree of the system; 2) according to the evaporation superheat degree and condensation subcooling degree, the charge amount and throttling intensity are then adjusted to match the best state point of refrigeration efficiency of the air conditioning system. According to the matching curve, the best matching state points of the system are obtained, that is, the most suitable superheat degree and subcooling degree is 1.3 ℃ and 6 ℃, respectively, and the corresponding refrigeration energy efficiency is 2.94, which is 11.4% higher than the minimum value of 2.64 during the experiment.关键词：optimal state;performance matching;air conditioning;energy efficiency ratio;superheat1588|1644|0发布时间：2024-07-18
- 摘要：A liquid recirculating refrigeration system, with ejector as a throttling device, was proposed in this paper. Furthermore, a gas–liquid separator was set after the evaporator in the system. By using the pressure difference between high-pressure refrigerant and liquid refrigerant in the vapor–liquid separator to inject the liquid, the evaporator can form a super-feeding without consuming additional energy, which can improve the cooling capacity of the system. An experimental bench of the system was set up to conduct experimental studies on the changing conditions of the system's ejection ratio and system performance, and they were compared with that obtained via the two phase flow injection method. The experimental results indicated that under the condition of evaporation temperature in the range of -13 to -6 ℃ or condensation temperature in the range of 36–42 ℃, the cooling capacity of the ejector liquid recirculation method is 24.6%–45.9% higher than that of the two phase flow injection method, and the maximum COP of the system increases by 14%, while the COP of the system slightly decreases when the evaporation temperature is lower than -13 ℃ or the condensation temperature exceeds 42 ℃. At the same time, it was determined that the pressure difference between the ejector inlet and outlet was the main factor that affected the ejection ratio of the liquid recirculating refrigeration system.关键词：liquid recirculating system;ejector;ejection ratio;variable conditions performance1557|1646|2发布时间：2024-07-18
- 摘要：In this study, a new independent type B liquefied natural gas (LNG) mock up tank with an inner volume of 40 m3 and an insulation thickness of 400 mm was examined. After reasonable simplification, two-phase flow and phase change heat transfer of a cryogenic fluid in the mock up tank were simulated by unsteady three-dimensional computational fluid dynamics(CFD). The volume of fluid model was selected to track the vapor-liquid interface. The Lee model was used as the phase change model, and the influence of the static pressure on the phase change model was considered. The temperature distribution and the staticboil-off-gas (BOG) generation rate of the mock up tank were calculated, and the characteristics of the simulated tank under different liquid levels and partial insulation damage were discussed. The pressurization characteristics of the mock up tank with a closed vent was also studied. By comparing the simulation results with the experimental results, it was evident that the deviation between the simulation and experimental results was less than 10%. This shows that this model can effectively simulate the evaporation process of cryogenic liquids in the mock up tank, which provides an important reference for the design and improvement of the new independent type B LNG ship.关键词：new independent type B LNG ship;two-phase flow simulation;static evaporation rate1408|1510|1发布时间：2024-07-18
- 摘要：Reasonable temperature distribution within a carriage guarantees the quality of transported cargo and improves energy efficiency. Thus, it is important to develop a refrigerated truck with a uniform temperature distribution to improve its transport capacity. Therefore, a cascade air supply mode was presented to improve the uniformity of the temperature field of the single-temperature refrigerated truck. When there is no cascade air supply system, the cold air forms a circulation in the refrigerated truck. The flow of the cold air is in a specific direction, which is not conducive to the overall cooling of the carriage. In a cascade air supply system, fans are added at the top of the carriage. The velocity of the cold air is increased, and the flow direction is more diverse, which is beneficial for improving the speed of overall cooling and uniformity of the temperature field. A simulation model of a single-temperature refrigerated truck was established to optimize the temperature distribution within the refrigerated carriage. The influence of cascade air supply system on the temperature field of the refrigerated truck was investigated via computational fluid dynamics (CFD). Subsequently, a contrast experiment was conducted to verify the results of the simulation. The average temperature of the jet region, global average temperature, non-uniformity coefficient of temperature field, and the difference between the highest temperature and lowest temperature were used as the evaluation criteria. The results indicated that the cascade air supply system can effectively reduce the average temperature of the jet region, global average temperature, non-uniformity coefficient of temperature field in the refrigerated truck, the difference between the highest temperature and lowest temperature. Furthermore, it can increase the cooling velocity. The decrease in average temperature and increase in cooling velocity were evidently optimized because of the cascade air supply system, especially within the area of the jet region. The decrease in temperature in the corner of the rear carriage was not obvious. However, the cooling velocity was evidently increased.关键词：refrigerated truck;computational fluid dynamics (CFD);numerical simulation;cascade air supply;temperature field1478|1444|2发布时间：2024-07-18
- 摘要：A part of the refrigerant of the air-source heat pump (ASHP) system is used for mechanical subcooling of the freezer in the combined air-source heat pump and freezer system. This can improve the performance of the system. In this paper, the outdoor heat exchanger of the ASHP system and condenser of the freezer was designed as an integrated heat exchanger, which can retard the frost formation and growth in winter. The performance of the combined ASHP-freezer under frosting condition was studied experimentally, and the performance of ASHP system and freezer under combined operating conditions was compared with that under separated operating conditions. The performance of the combined system and the frosting characteristics on the outdoor heat exchanger were analyzed under different cooling mass flow ratios. The experimental results indicated that the frosting period of the integrated outdoor heat exchanger under combined working conditions of ASHP-freezer is prolonged as2.17 times as that under separated operating conditions, when the outdoor heat exchanger is severely frosted. The average heating capacity and average COP of the ASHP system under combined working condition were increased by approximately 5% and 4.8%, respectively, when compared with that under separated operating conditions. The average refrigerating capacity and average COP of the freezer increased as the cooling mass flow ratio increased. With respect to the cooling mass flow ratio in the range of 0–12%, the frosting period, average heating capacity, and average COP of the ASHP system slightly changed as the cooling mass flow ratio increased. Conversely, in range exceeding 12% of cooling mass flow ratio, the frosting period was reduced as the cooling mass flow ratio increased, and the average heating capacity and average COP exhibited a downward trend.关键词：combined ASHP-freezer;frosting characteristics;integrated heat exchanger;cooling mass flow ratio1507|1582|2发布时间：2024-07-18
- 摘要：A water-cooled compressive CO2 hydrate cold storage system was designed to examine the hydrate cold storage characteristics with different initial charge pressure values (from 3.5 MPa to 4.0 MPa). Furthermore, cold storage capacity and cold storage velocity are calculated based on the experimental data. The results indicated that as the initial charge pressure increases, the cold storage characteristics are improved. This is because as the initial charge pressure increases, the dryness degree of CO2 at the reactor inlet decreases and the cold capacity of the unit mass CO2 increases. When the initial charge pressure was 4.0 MPa, the cold storage characteristics were optimal: the cold storage time was the shortest (11.33 min), the average cold storage velocity was the highest (5.19 kW), the hydrate generating mass was of the maximum value (3.96 kg), and the ratio of hydrate cold storage capacity to total cold storage capacity was the highest (57%). When the initial charge pressure was 3.5 MPa, the cold storage characteristics were the worst: the cold storage time was the longest (37.50 min), the average cold storage velocity was the lowest (1.07 kW), the hydrate generating mass was of the minimum value (1.58 kg), and the ratio of hydrate cold storage capacity to total cold storage capacity was the lowest (34%). When compared with air-cooled compressive cold storage system, the cold storage characteristics of the water-cooled compressive cold storage system were significantly improved: the maximum increase in hydrate formation mass was 38.6%, and the maximum increase in total cold storage was 13.24%.关键词：compression refrigeration cycle;cold storage characteristics;cold storage system;CO2 hydrate;water-cooled1430|1765|4发布时间：2024-07-18
- 摘要：Phase change material slurry (PCS) can serve as cold storage material and secondary refrigerant to transport cold energy with the advantages of good flow ability and high energy density. Ice slurry is a safe and efficient cold storage medium, which has been widely used in cold storage air conditioning. However, the low temperature of ice slurry preparation limits its efficiency in terms of energy utilization in air-conditioning systems. The urea slurry can be prepared by cooling the high mass concentration urea solution, and the phase change temperature range covers the air-conditioning condition. Furthermore, the phase change latent heat is high, and thus the urea slurry can be potentially used in several applications. In this paper, the thermos-physical properties of urea solution and the fluidity of urea slurry are experimentally studied. The results indicated that the phase transition temperature of urea solution with a mass concentration of 43%–48% is 5–12 ℃,and the latent heat is in the range of 213.7–223.2 J/g. Furthermore, the density of urea solution (mass concentration was higher than 32.5%) at the liquids increased with solution mass concentration, while the tendency of kinematic viscosity was opposite. Additionally, the flow characteristics of urea slurry were affected by the solid fraction and Re; thus, it can be regarded as a dilatant fluid under different working conditions.关键词：cold storage slurry;urea solution;thermos-physical properties;flow characteristics1492|1598|1发布时间：2024-07-18
- 摘要：A novel type of radial combined sealing structure was proposed to improve the end-face sealing of wraps between fixed and orbiting scrolls. Geometry and engineering fluid mechanics were considered to develop an algorithm for determining leakage from the tooth top of the base circular involute oil-free scroll compressor with a smooth clearance tip seal, labyrinth tip seal, and combination tip seal. A simulation platform to test adjacent compression chambers for scroll compressors was established to measure the gas leakage of three sealing structures under the same pressure difference. The experimental and theoretical calculation results were compared, and the theoretical calculations were identical to the measured results. The amount of leakage from the smooth seal and labyrinth seal increased as pressure difference increased, while the leakage amount of the combined seal was inversely proportional to the pressure difference. However, the wear amount of the seal increased. The measured leakage of the labyrinth seal was 80% that of the smooth seal, and the measured leakage of the combined seal was 63% that of the smooth seal. Thus, we can confidently conclude that the combination sealing structure is more suitable for large compression ratio scroll compressor applications. Furthermore, the radial leakage of these three sealing structures decreases as the speed of the moving scroll increases. This tends to be stable when the rotational speed exceeds 4000 m/s.关键词：oil free;scroll compressor;seal structure;leakage rate1587|1621|1发布时间：2024-07-18
- 摘要：Insect screens are always installed outside windows to prevent insects in most buildings in China. This in turn negatively impacts the natural ventilation performance. Small-scaled wind tunnel experiments were conducted in an environmental cabin to determine the effect of insect screens on natural ventilation performance. A combination of statistical analysis and data calculation was used to obtain the resistance characteristics of four different insect screens, and the effect of screens on ventilation rates were obtained via experiments. An insect screen resistance model was utilized to inspect the effect of porosity and validate field measurements. Furthermore, the accuracy of the precise model and simplified model exceeded 80%. The results indicated that the discharge coefficient of insect screens increases as the air velocity increases and finally tends to be constant. As the porosity increased, the discharge coefficient increased to a higher stable value because the air velocity increased. The accuracy of the new model improved by approximately 34% when compared with that of the model in the literature.关键词：model research;wind tunnel experiment;insect screens;natural ventilation;discharge coefficient1464|1878|0发布时间：2024-07-18
- 摘要：Efficient cryopreservation of cell samples on microfluidic chips can significantly shorten the cycle of cell experiments on chips, reduce the cost of experiments, which will contribute to the wide application of cell experiments on chips. In this paper, the cryopreservation of the attached HepG2 cells on PDMS-glass microfluidic chip was examined. Furthermore, the cooling rate, cryoprotectant, storage time and temperature, and the cryopreservation protocol of the attached HepG2 cells on the chip was determined. The results indicated that a cooling rate of 0.36–35.12 ℃/min can be realized in the chip microchannel by using different cooling environments and cooling mediums. There is an optimal cooling rate of 0.5–1.5 ℃/min in cryopreservation of HepG2 cells. Furthermore, at -20 ℃ or 40 cm above the surface of liquid nitrogen cooling environment combined with -80℃cooling environment can significantly increase the viability of7d frozen HepG2 cells on chip. Additionally, DMSO with a volume concentration of 20% combined with 0.1 mol/L trehalose can significantly enhance the activity of cryopreserved HepG2 cells on chip. After optimization of the aforementioned cryopreservation conditions, the attached HepG2 cells on chip were successfully stored for 7d with a viability of more than 90%.关键词：microfluidic chip;cryopreservation;attached HepG2 cells1330|1546|2发布时间：2024-07-18
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