最新刊期
卷 34 ， 期 4 ， 2013
- 摘要：In order to get the cooling temperature to the liquid hydrogen temperature and guarantee the temperature stability at the same time, experimental investigation on single-stage high frequency multi-bypass pulse tube cryocooler (PTC) without double-inlet is carried out. A criterion that determines whether the opening of the multi-bypass is optimum or not, is achieved by numerical simulation firstly. At present, the cooler has reached the lowest temperature of 23.6K with an electric input power of 220W, which is the reported lowest temperature for single-stage high frequency PTC without double-inlet. The fluctuations are below 0.1K after reaching its stable state, which is much smaller than that of other double-inlet PTCs. The cooler typically provides 0.516W at 29.2K and 1.0W at 34.1K with the input power of 220W.关键词：pulse tube cryocooler;experimental research;Multi-bypass1711|1791|0发布时间：2024-07-18
- 摘要：Corrosion character is one of the main characters of Al microchannel heat exchanger. In the present study, standard seawater acidified test (7 and 14 days) were carried out on microchannel heat exchangers with Zn-coated extruded tube and Si-coated extruded tube, and the performances of the test samples before and after the corrosion were tested in order to compare the change of capacity, air side pressure drop and thermal resistance. The result showed that, the long-term performance of the sample with Si-coated extruded tube was much better than the sample with Zn-coated extruded tube.关键词：Corrosion, Microchannel heat exchanger, Zn-coated, Si-coated, Long-term performance1742|1799|0发布时间：2024-07-18
- 摘要：Theoretical analysis is made for a freeze dryer driven by low-grade heat source. Its condenser utilizes LiCl solution which is continuously regenerated, and its refrigeration system adopts ammonia-water absorption type. Through thermodynamic analysis, it is demonstrated that 13573~20747kJ heat is needed for the removal of 1kg water from the material which eutectic temperature varies between -10 and -35℃, if the freeze dryer is used in summer in east China. The energy saving potential is thus significant.关键词：Low-grade heat source;freeze drying;energy saving;LiCl solution1729|1836|0发布时间：2024-07-18
- 摘要：The cool-down performance of a miniature mixed refrigerant J-T refrigerator was experimentally investigated. A miniature mixed refrigerant J-T refrigerator driven by an Aspen mini-compressor was developed, and preliminary test results were presented. The miniature J-T cryocooler was constructed with stainless steel capillary tubes with specific inner diameter of 0.3mm. By using multicomponent mixed refrigerant, the miniature J-T refrigerator can reach no-load temperature of 180K. Driven by the mini-compressor, such miniature J-T cryocoolers have good perspective in such applications as mobile biomaterials preservation, cryosurgery and electronic devices cooling, etc.关键词：Miniature J-T refrigerator;mixed refrigerant;Mini-compressor1819|1799|0发布时间：2024-07-18
- 摘要：To study the effects of Hydroxyapatite (HA) nanoparticles on devitrification of different cryoprotectant solutions, the crystallization of Glycerol(60%,w/w) and PEG-600(50%,w/w) solutions with HA nanoparticles of different particle size(20nm、40nm、60nm）and concentrations（0.1%、0.5%）were observed under a cryomicroscope. Experimental results showed that the morphology of Glycerol and PEG-600 solutions is dendritic and spheric respectively, and both structures are not changed by adding nanoparticles. The ice fraction of Glycerol solution containing 0.5% HA with the particle size of 60nm is 1/7 of that of Glycerol solution without nanoparticles. The ice fraction of PEG-600 solution increased drastically between -64℃ and -52℃, and the ice fraction of PEG-600 solution containing 0.5% HA with the particle size of 40nm increased by 90%. Ice growth rate has two maximum normally, however, there is only one maximum in Glycerol solution containing 0.5% HA with the particle size of 40nm, PEG-600 solution with the particle size of 60nm, and PEG-600 solution without nanoparticles.关键词：cryomicroscope,devitrification,morphology,ice fraction,ice growth rate1852|1760|0发布时间：2024-07-18
- 摘要：The paper reported two-phase flow pressure drop results of R22 during condensation in a horizontal stainless steel rectangular microchannel with the hydraulic diameter of 0.952 mm. Tests were conducted with saturation temperatures of 40-50oC, mass fluxes of 200-800 kg/m2 s and vapor qualities from 0 to 1. The results show that pressure drops in the test section account for more than 95% of the measured pressure drops while the fractions of the expansion pressure drops at the outlet of the test section are small enough to neglect. Pressure gradients of R22 increase with mass flux and vapor quality especially in high vapor quality regions while decrease with the saturation temperature. Pressure gradients of R152a are lower than the data of R22 when compared with the same experimental conditions.关键词：pressure drop;microchannel;condensation;experimental investigation1796|1860|0发布时间：2024-07-18
- 摘要：The air infiltration though the cold chain transport equipment directly affects the safety during transport and the energy consumption. The existing standards on the cold chain transport equipment adopt the differential pressure method and the resulting value of air infiltration is difficult to characterize the actual running situation. To solve this problem, the mechanism of air infiltration through the cold chain equipment is analyzed and the relationship between the running speed, the aging conditions and the equipment status is gained. The computational model of the air infiltration through the vehicles is found and the definition method of relevant parameters such as air infiltration index and the equivalent infiltration area is gained through the experiment. The study showed that the model can reflect the air infiltration characteristics of refrigerated transport equipment well and provide a reference to the overall evaluation on the air tightness and optimal control of the vehicles.关键词：Refrigerated transport equipment;Air infiltrated model;Mechanism;Calculated model1792|1779|0发布时间：2024-07-18
- 摘要：The coefficient of thermal conductivity of glycerin solution was measured by the transient hotline method, in which the concentration was 10%, 20%, 30%, 40%, 50% respectively with the SiO2 nano powder. And the relationship of thermal conductivity with nano content, concentration of glycerin solution and measuring temperature was investigated. The results indicated that, with the increase of the nano-particles` additional amount(0.5g/L-1g/L), glycerin solution coefficient of thermal conductivity increase; when the glycerol concentration increased from 10% to 50%, the thermal conductivity increased from 0.4% to 6.8%; and the nano-cryoprotectant thermal conductivity decreases with decreasing temperature. If the temperature is lower than 260K, nanoparticles had no effect on the thermal conductivity of nano-cryoprotectant.关键词：Nanoparticles;thermal conductivity;cryoprotectant;Measuring Temperature1851|1992|0发布时间：2024-07-18
- 摘要：Theoretical analysis of a heat pump with an economizer have been presented in this paper. The mathematic models of the heat pump system have been developed and experiments have been conducted to investigate the impacts of the gas injection on heat pump performance under low ambient temperatures. The results indicate that the heating capacity and the power consumption go up when the amount of gas injection increases under low ambient temperatures. The discharge temperature declines with the increment of gas injection, while the COP of the heat pump rises first and then descends. According to the test results, the optimal amount of gas injection is about 10%-14% of the total mass flow rate in the heat pump system.关键词：heat pump;Gas injection;energy efficiency ratio1849|1933|0发布时间：2024-07-18
- 摘要：Prediction and optimization of product quality is the key to product design. A model-based quality prediction and optimization method of refrigeration products was proposed to take into account uncertainties and parameter variations in refrigeration product manufacturing. Product quality (performance and its variation) can be therefore predicted in the early design phase. Moreover, a new method was proposed to get the quality-loss function, specifically a response surface model of design capability index varying with the component tolerances was developed by the Center Composite DOE method and Monte Carlo simulation. Taking the quality-loss function as constraints and minimizing cost as the objective, the product quality and cost were optimized in the end. It turns out that better product quality and lower cost can be achieved with the proposed approach.关键词：Refrigeration and cryogenics engineering;Product quality;model;simulation;optimization1793|1900|0发布时间：2024-07-18
- 摘要：The simulation platform of the variable flow air conditioning system is setup based on TRNSYS software platform. To accelerate simulation speed to ensure it can be used for control analysis, the fast and explicit expression models for R410a thermodynamic properties are corrected to ensure their repeatability in calculation of changing phase. The results show that corrected model still maintains high accuracy and the stability of control of superheating in suction can be improved significantly.关键词：VRF Air-conditioning system;simulation of control;corrected model of thermodynamic property1802|1965|0发布时间：2024-07-18
- 摘要：A test rig of the R134a/CO2 cascade supermarket refrigeration system has been built up to get a comprehensive understanding of its performance. The results show that the maximum COP of the system occurred when the condensing temperature of the CO2 cycle was about -2℃, the condensing temperature of R134a and the evaporating temperature of CO2 was settled at 48℃ and -30℃ respectively with a temperature difference of 3℃. Moreover, the COP remained stable while the condensing temperature varied within a certain range of ±5℃. Results also show that the maximum deviation of the compressor adiabatic efficiency is within 4%, the main factor affecting the system cooling capacity is the compressor volumetric efficiency. And the performance of the cascade system could be 3% higher compared with that of conventional R404a refrigeration system at the same condition.关键词：cascade refrigeration system;experimental research;R134a/CO21815|1839|0发布时间：2024-07-18
- 摘要：In order to understand the heat transfer and pressure drop mechanisms of fin and tube heat exchanger under dehumidifying conditions, a model of condensate water droplets moving on fin surface should be established firstly. Based on the force analysis of the condensate water droplet on fin surface, a critical condition of the water droplet motion is obtained. With the surface tension is taken into account, which is defined by the contact angle and VOF method, a numerical model of condensate water droplet moving on fin surface is developed. Then an experiment is carried out to verify the numerical model. The average deviation between simulation results and experimental data for the contact angle is 2.11% and the maximum deviation is 2.51%, and the average deviation for water droplet velocity is 6.5% and the maximum deviation is 10%, which show the accuracy of the model.关键词：Numerical model;Condensate water droplet motion;contact angle1830|1767|0发布时间：2024-07-18
- 摘要：Water is heated to 60℃ by refrigerant in heat pump water heater, which results serious fouling . Studying the precipitation characteristics are the first step to find anti-fouling technology. CaCO3 is precipitated on stainless steel 304 and 316 coupons from 0.5 and 1.0 mmol/l CaCO3 solution by static reaction. By weighing the coupons before and after experiments the mass of fouling is obtained and the morphology of different grown time coupon surfaces can be got using SEM. The results show that at the same condition there was more fouling on ss304 than ss316 and more aragonite on ss304 and more calcite on ss316. Higher Ca2+ concentration formed more nuclei but the sizes of the nuclei was decreased and less fouling was formed for each nuclei, and the proportion of aragonite and calcite wasn’t changed. Higher pH promoted formation of calcite and both homogeneous and heterogeneous nucleation rate, but the former increased more, so the fouling mass decreased. The main mechanism of fouling formation on heat exchanger surfaces was insoluble salt crystallization to form fouling particles in solution and then precipitate on surface, reaction and adsorption of insoluble salt directly to surface is the secondary mechanism.关键词：CaCO3 crystallization fouling;Coupon test;Crystal morphology;Nucleation rate1769|1822|0发布时间：2024-07-18
- 摘要：A method integrating the condensing heat recovery technology with the heat pump technology to produce sanitary hot water was put forward. According to the characteristics of domestic air conditioner, the condensation heat was recovered and reused to heat the sanitary hot water. A prototype was set up for experiment which can achieve the function of heat pump water heater, heat pump air conditioner and condensing heat recovery. The system operating performance in simultaneously cooling and hot water supply was tested. The relationship among the quantity of hot water supplied, COP of the system and water temperature were discussed.关键词：condensing heat recovery;air-conditioner;thermal storage;energy saving1806|1790|0发布时间：2024-07-18
- 摘要：Aiming at the control problems of evaporator superheating in the household Variable frequency air conditioner, the Electronic Expanded Valve (EEV) control system was investigated based on a dead band integral-separation PID control algorithm and the STC89S52 single-chip microcontroller as the control core. And the control system principle, the hardware circuit and the software design are expounded too. The experimental results of household air conditioning showed that the EEV control system had the characteristics of static accuracy, adaptability, reliability, and anti-interference.关键词：Automatic control;Single-chip microcontroller;PID control;EEV;superheat1834|1918|0发布时间：2024-07-18
- 摘要：A Parallel-Connected AGMD system was designed, which uses thermoelectric refrigeration instead of mechanical refrigeration to provide refrigeration capacity for membrane distillation. With the analysis of matching method between membrane distillation and thermoelectric refrigeration, the basic requirements of the optimum matching mode have been given out. A thermoelectric refrigeration membrane distillation cold chamber with water cooled heat dissipation components was built to research the refrigeration performance of a TEC with air-cooled model in its cold side. The results show that the cryogenic temperature of the thermoelectric refrigeration membrane distillation cold chamber can meet the membrane distillation operation requirement under constant intensity of heat dissipation. Under the experimental conditions of inlet water of 20℃ and 100L/h and air flow rate of 660m3/h, when the working current of TEC is 5.5 A, the thermoelectric refrigerating capacity is 87.1 W and cooling efficiency is 1.3, which reaches the maximum of both. The corresponding theoretical distillation flux is calculated to be 40 kg/(m2?h). This investigation establishes the foundation for the theoretical research and practical application of solar air gap membrane distillation system with thermoelectric refrigeration.关键词：membrane distillation;thermoelectric refrigeration;Matching Theory1910|1847|0发布时间：2024-07-18
- 摘要：In order to study on the heat transfer performance of Cacl2/ENG, the solidified composite adsorbents with 4 different molding pressure and 3 different kinds of ratio between Cacl2 and expanded natural graphite have been developed. Meanwhile thermal conductivity of samples is tested with Nai Chi LFA447 conductivity Meter. The experiment results show that: in a certain range, the thermal conductivity increases with the increase of molding pressure under the same ratio and the thermal conductivity decreases with the ratio increases under the same molding pressure. In all the test samples, the thermal conductivity of consolidated composite adsorbents is reached its highest 2.7 W/ (m?K) when molding pressure is 1.7KN and the ratio of Cacl2/ENG is 2:1.关键词：thermal conductivity;Composite adsorbents;Molding pressure1757|1799|0发布时间：2024-07-18
- 摘要：The structural characteristic of the open cell metal foams is presented. In four application areas, compact heat exchangers, phase change energy storage systems, heat pipe and catalytic reactor, research of open-cell foam metal thermal transport performance is discussed and analyzed, respectively. Application prospects and problems are analyzed in these areas. The research and application direction of open-cell foam metal thermal transport performance are pointed out in the future.关键词：metal foams;thermal transport;compact heat exchanger;phase change thermal storage;heat pipe;reactor1743|1998|0发布时间：2024-07-18
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