最新刊期
卷 33 ， 期 1 ， 2012
- 摘要：In order to simulate different types of refrigerators under the same platform, an integrated simulation platform for multi-type refrigerators is introduced. Firstly, the general model for compressor model, heat exchanger model and cabinet model is built separately, and then the method of data interaction and integration of system control algorithm is put forward. The experimental validation results show that the integrated simulation platform for multi-type refrigerators is able to simulate the commonly-used types of refrigerators, and the deviations of energy consumption and on-off ratio are within 10%.关键词：refrigerator;Multi-type;Simulation Model2028|2701|0发布时间：2024-09-26
- 摘要：Absorber is the key component of Ammonia-water absorption refrigeration. This study simulate the falling film adiabatic absorption to analyse the characteristics of mass absorption and compare the simulated result with the experiment result. The error of the simulated value of mass transfer rate comparing to the experiment value is less than 20%.Besides the experiment shows that subcooling of weak solution before absorption can promote the mass absorption. In experiment, cooled absorption with subcooling improve the mass absorptive rate by 132%.关键词：engineering thermophysics;Ammonia-water falling film absorption;Adiabatic absorption;subcooling1998|2103|0发布时间：2024-07-18
- 摘要：Utilizing cold energy of LNG would bring good economic benefits. A combined system of Stirling engine and gas turbine for recovering LNG cold energy is put forward. Based on the first and second laws of thermodynamics, the combined system is analyzed in detail. The results show that in the 35℃ environment, the output power of combined system is 5715.48kW, the thermal efficiency is 31.62%, and the exergy efficiency is 43.65%. Compared with the gas turbine system and the direct cooling inlet air system, the output power of combined system will respectively increase 7.84% and 0.78%, the thermal efficiency will increase 3.16% and 1.63%, and the exergy efficiency will increase 4.23% and 1.63%. At different environment temperatures, the inlet air temperature will decrease about 10℃ in the combined system, and the output power and efficiencies will increase with the decreasing of inlet air temperature.关键词：pyrology;LNG;thermodynamic analysis;Stirling engine;Gas turbine2011|2683|0发布时间：2024-07-18
- 摘要：Ice slurry has been widely used in many fields because of its thermal properties, and ice-making technology has become a focus of study. Dynamic ice-making with supercooled water is one of the most promising method in making ice slurries, but the major defect of this method is that the ice blocking easily take place in the supercooled heat exchanger. Based on the theory of water crystallization and the analysis of the influence factors of ice blocking, a nano-fluorocarbon coating was used to improve the surface conditions of the supercooled heat exchanger and to restrain water from freezing. It is concluded that the nano-fluorocarbon coating will effectively restrain crystallization on the wall and improve the efficiency of the ice-making unit, which results in the decrease of ice blocking and the energy consumption. The investigation will benefit in developing and improving anti-icing techniques.关键词：engineering thermophysics;Ice blocking;Crystallization;Nano-fluorocarbon coating;Super-hydrophobic surface;contact angle2150|2027|0发布时间：2024-07-18
- 摘要：This paper analyzed theoretically the change of refrigerant system after replacement of R410 with R32. Such replacement led to the increase of the discharge temperature of the system. The method of gas refrigerant injection was proposed to reduce the discharge temperature. Some experiments were made to investigate the variation of refrigerant system on charging rate, capacity,COP, discharge temperature after the replacement of R410A with R32. The results showed that, comparing with R410a system,the capacity, COP and discharge temperature of R32 were increased, and the R32 system with gas refrigerant injection can reduce effectively the discharge temperature, andincrease the capacity and COP. It can be concluded that R32 is a promising refrigerant candidate, and the limitation brought by high discharge temperature of R32 can be broken with the gas refrigerant injection system.关键词：pyrology;R32;Gas injection;discharge temperature;COP2031|3132|0发布时间：2024-07-18
- 摘要：Low-temperature heat steam, as heat source of organic Rankine cycle ( ORC ), is used to simulate waste heat, and Organic Rankine Cycle (ORC)power generation system is established. Software of Engineering Equation Solver (EES) is utilized to solve the mathematical modeling of ORC system with refrigerant R134a. Predicted result is compared with experimental result. It is shown that the electricity generation efficiency is 8% with R134a working substance. The thermal efficiency and power rate can increase along with the increase of inlet pressure when inlet condition of expansion machine is saturated or overheated. Moreover, the system's irreversible loss is high and system efficiency will reduce greatly when the pressure of system is low.关键词：pyrology;Organic Rankine Cycle(ORC);Thermal analysis;Waste heat power generation;Low-Grade Energy2133|3098|0发布时间：2024-07-18
- 摘要：Due to the large energy compensation caused by the fixed dew point on the cooling coil (CC) in the conventional constant temperature and humidity air-conditioning system, a new system employing a temperature and humidity independent control device(THIC device) in the CC and a method of PID split-range control, is developed in this paper. Based on the experiment verification,the operation states and the energy saving effects of the system under different heat and moisture loads have been simulated by TRNSYS 16 software. The results show that under different working conditions, the system can automatically control air temperature and humidity independently with a high precision, by adjusting the mass flow rate and the temperature of the chilled water into the CC, and the output of the heater or the humidifier. In the design of such CC, the heat transfer area should be calculated under a higher inlet temperature of the chilled water (for example, 12℃ instead of the usual 7℃). The system is energy-efficient with a rate of 30% under low temperature high humidity condition and about 50% under high temperature and low humidity condition, compared with the conventional system.关键词：pyrology;Constant temperature and humidity air-conditioning system;Temperature and humidity independent control device;PID split-range control;TRNSYS;energy saving1923|2651|0发布时间：2024-07-18
- 摘要：The compressor model used in the dynamic simulation of refrigeration system should not only be applicable in the case that the state of the sucked refrigerant varies in a wide range of vapor to two-phase, and also be quick enough in predicting the major dynamic characteristics of the compressor. In order to meet these requirements, a quasi-dynamic hermetic compressor model covering the suction state from vapor to two-phase was presented in this paper. According to its thermodynamic process, the compressor model includes, a dynamic model for the mixing process of refrigerant inside compressor and sucked two-phase or vapor refrigerant, a dynamic model for the compressor shell heat transfer model, and a steady state model for the polytropic compression.The compressor model overcomes the flaw of unreasonable mass flow of the existing models caused by neglecting the mixing process of refrigerant inside of compressor. The maximum differences of steady state mass flow rate and input power of a hermetic compressor between the experimental data and the predicted results are less than 5%, while the deviations of the predicted transient mass flow rate and input power from the experimental data are within 10%.关键词：pyrology;simulation;Hermetical compressor;Models;Quasi-dynamic;Two-phase1834|2183|0发布时间：2024-07-18
- 摘要：The thermodynamic properties of saturated liquid ammonia were modeled by molecular dynamics simulation. The densities and the specific enthalpies of saturated liquid ammonia are modeled with the site-site potential model. The maximum relative deviations between the simulated results and the database of NIST are less than 1.5% for the density and less than 3.2% for specific enthalphy. The results show that the simulation method is feasible to predict the thermodynamic properties of the single component substance by using the reasonable potential model and parameters.关键词：engineering thermophysics;molecular dynamics simulation;Thermodynamic properties;ammonia1840|2022|0发布时间：2024-07-18
- 摘要：The shutdown reason of parallel condensers dehumidifier was analyzed. It is shown that the unbalance of the pressure in the two condensers is the main reason for shutdown, which leads to the accumulation of refrigerant and fluctuations of pressure.The advantages and shortcomings of several methods to improve the performance were discussed. The reheat condenser is proposed to be changed to evaporator when the mode turns to freezing dehumidifier. Test bench was set up and experiment was carried out.The result shows that the mode could resolve the shutdown incident. Moreover, the EER and dehumidification capacity of double evaporator mode are better than the traditional dehumidifier with one evaporator.关键词：engineering thermophysics;Dehumidifier with temperature control;Refrigerant accumulating;Double-evaporator1809|2317|0发布时间：2024-07-18
- 摘要：Based on the two phase natural convection, a system with R22 for the hot-swappable communication cabinet is built and tested for its heat dissipation capability. The result shows that this system can handle more than 3000W with the cooling water at about 28℃, meanwhile, it keeps the temperature of the electronic module to be lower than 65℃. Moreover, the tests of unbalance heat load start up and varying during operation are carried out to simulate cases of the heat load changing and hot swapping in a real cabinet. The result tells that the system operates stable with unbalance heat load and meets the requirement for hot swapping.关键词：pyrology;Two-phase natural convection;Hot-swappable communication cabinet1829|1952|0发布时间：2024-07-18
- 摘要：EES software was used to simulate the flow of refrigerant and oil in underground U-tube of the Direct Expansion Ground Source Heat Pump. The results show that: the pressure of refrigerant/oil mixture first increases and then decreases along the U-tube;the temperature of refrigerant/oil mixture increases firstly and then decreases, in superheat region, the temperature rises sharply; the refrigerant/oil mixture exits in U-tube mainly as annular flow; the minimum refrigerant/oil return velocity is increasing when the U-tube diameter increases; comparing the simulation results with the experimental results find that the oil in the U-tube of the experimental system can return normally.关键词：engineering thermophysics;ground source heat pump;Numerical analysis;U-tube heat exchanger;Minimum oil return velocity1747|2036|0发布时间：2024-07-18
- 摘要：Cryopreservation of enzyme-labeled methamidophos was studied using the composite protective agent (2.0mol /L NaCl,4.0mol/L xylitol and 1.25mol/L glycerol) obtained from accelerated test. The results show that the relationship between enzyme activity loss rate and storage temperature meet arrhenius equation. After 6 months, the retention rate of enzyme activity is 77.13%(without protective agents) and 97.44% (with protective agents) under the storage conditions of -18℃. Comparing to theoretical prediction value according to chemical kinetics, the relative standard deviation was 3.10% (without protective agents) and 0.51% (with protective agents), respectively. The result will lay the foundation for the development of thermal pesticide residue biosensor.关键词：Enzyme-labeled pesticides;Protective agent;stability;Cryopreservation1787|2091|0发布时间：2024-07-18
- 摘要：The effect of pre-cooler on performance of evaporator was investigated on a mid-temperature vertical open-type display cabinet. And an experimental investigation was undertaken in the test room (temperature of 25℃ and relative humidity of 60%) to characterize the effect of pre-cooler on performance of evaporator in display cabinet. The results showed that: the condition of the air inlet evaporator were changed, and temperature of the air inlet evaporator was reduced by 2.4℃; the accumulation rate of frost on the evaporator was dropped and the defrost time was reduced by 28%; and the use of pre-cooler could lead to significant decrease in the cooling load by 19.2%.关键词：food storage technology;display cabinet;pre-cooler;evaporator1959|2199|0发布时间：2024-07-18
- 摘要：To improve the vacuum degree requirement of the vacuum ice slurry making equipment, the intermediary substance was proposed to add to water. A performance test system was established to study vacuum evaporation characteristics experimentally using ammonia water with concentration of 26% as the intermediary substance solution and the influence of ammonia on ice slurry production was analyzed. The results show that the cooling rate and temperature’s drop range of ammonia water are significantly higher than distilled water with the same initial temperature and vacuum degree. Moreover, ice crystal can be formed above the pressure of water’ triple point in ammonia water. With the decrease of vacuum degree, the temperature’s decreasing scope of ammonia gradually diminishes, but still much larger than that of distilled water, which indicates that ammonia water’s requirement for the vacuum degree to achieve the same evaporation temperature is much lower.关键词：pyrology;Vacuum ice slurry making;vacuum degree;Intermediary substance;ammonia1774|2462|0发布时间：2024-07-18
- 摘要：Effective vacuum cooling simulation has the advantage of low cost and short period, and therefore is important in theory and application. Based on the theories of unsteady heat transfer and mass conservation, a mathematical model developed by CFD software is used to predict the variation process of temperature and mass during vacuum cooling for cabbage. The simulative result matches well with the experimental data. The error between simulation and test result is no more than 4 percent for temperature, and no more than 6.5 percent for weight. So the mathematical model can benefit for the practical application of vacuum cooling.关键词：pyrology;vacuum cooling;heat and mass transfer;CFD simulation;Cabbage1932|2199|0发布时间：2024-07-18
- 摘要：Applying air-bearings supporting structure to the compressor turbine expander refrigeration system, the thermodynamic parameters of the test equipment was analyzed by means of system performance experimental investigation. The experiment results show that when the refrigerator rotating speed runs from 40000 r/min to 60000 r/min, the refrigerating performance improved greatly; the flow rate at 60000 r/min was twice as much as that at 40000 r/min, the temperature difference of the compressor and the turboexpander were doubled, while the power was increased five times as much. This test results provided reference_articles to the advanced optimization of compressor turbine expander.关键词：pyrology;Thermodynamic performance;experimental investigation;Compressor turbine expander refrigerator;Hybrid air-bearings1887|2263|0发布时间：2024-07-18
- 摘要：The effect of different final pressures(400~800Pa) on the vacuum cooling performances of sliced dragon fruits was studied. The cooling rate, weight loss and typical property changes (water binding capacity, pH value, hardness, colour and luster)during the storage period of 72 hours at 4℃. The results indicate that effects of final pressures on cooling rate and weight loss were not significant. However, increasing final pressure in the certain range can delay the changes of water binding capacity, pH value,hardness, colour and luster. The conclusion was drawn that 700~800Pa is considered as the best final pressure interval since the sliced dragon fruit cooled under thses pressures can be stored for 60 hours at 4℃ without significant quality change.关键词：Sliced dragon fruit;Vacuuming cooling;Final pressure;cooling performance1948|2642|0发布时间：2024-07-18
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