最新刊期
卷 38 ， 期 2 ， 2017
- 摘要：Plenty of low-grade heat is produced duringindustrial energy consumption. Waste heat reuse significantly contributesto energy-savings ifhigh-efficiency technologies are employed for heat recovery. Heat pump technology allowsfor temperature upgrading and capacity expansion of industrial waste heat. The recovered heat can then be supplied to industrial processes orused in district heating and cooling. In this paper, the characteristics and development trends of vapor compression heat pumps, sorption heat pumps, and chemical heat pumpsare introduced. These three heat pump technologies have been greatly improved interms of working fluid, cycle optimization,and system innovation. Nonetheless, there are some incompatible optimizing targetsassociated with capacity, energy efficiency, temperature lift, and stability. Moreover, the applications and characteristics of industrial waste heat vary depending on its category and temperature grade. Design guidelines suitable for different waste heat conditions are lacking for heatrecoveryequipment and systems. Further research should focus on heat pump technologies characterized as high efficiency, large capacity, and high thermal adaptability, stability, and reliability. In addition, general design principles should be developed for mutually complementary applications of different heat pumps. Meanwhile, the high-quality integration of heat recovery systems can be accomplished to realize the highly efficient use of industrial waste heat by means of energy network utilization, including heating, power generation, cooling, and storage and transportation technologies.关键词：industrial waste heat;vapor compressed heat pump;sorption heat pump;chemical heat pump;network utilization2609|2501|10发布时间：2024-07-18
- 摘要：In order to improve the stability and coefficient of performance of the air source heat pump, a scroll compressor refrigeration / heat pump system with flash tank was proposed using R134a, and the experiment platform was built. The compressor’s discharge temperature, power input, cooling capacity, heating capacity, coefficient of performances of the refrigeration/heat pump system were studied. Results showed that, under the condition of condensing temperature 45 ℃ and evaporating temperature from ﹣20 ℃ to 0 ℃, the discharge temperature of the vapor injection system was 6.2 ℃ lower than that of the single stage compression system, power input increased only 1.4% to 2.8%, the cooling capacity and cooling COPc are 19.8% and 17.6% higher than that of the single stage system, the heating capacity and heating COPh are 15.3% and 13.2% higher, respectively.关键词：R134a;vapor injection;heating performance;COP2261|2239|9发布时间：2024-07-18
- 摘要：Natural convection heat transfer is experimentally investigated for a porous medium, water-saturated copper foam, in a square cavity. The effects of porosity, pore density (PPI) and angle of inclination on natural convection heat transfer are discussed. The experimental results show that natural convection heat transfer rate increases with the decrease of porosity. For a given porosity, the heat transfer rate is found to be lower at higher pore densities. The Nusselt number decreases with the angle of inclination. According to the theory of similarity, the dimensionless heat transfer correlation, including porosity, pore density (PPI) and angle of inclination, is developed, and deviation is within ±7.5%.关键词：natural convection heat transfer;porous media metal foam;porosity;pore density2037|2235|1发布时间：2024-07-18
- 摘要：Many correlations have been proposed about R404A condensation heat transfer and pressure drop, but all of them apply for smooth tubes or microfin tubes with big diameter. Some correlations are based on 5 mm diameter tube, but the refrigerant is not R404A. Up to now, there is no correlation for R404A condensation heat transfer and pressure drop with 5 mm diameter tube. In this paper, a number of correlations were selected by variable-controlling and giving priority to refrigerant with similar properties, combining experimental test and theoretical calculation, deviation between the calculated and experimentally measured values have been compared through a large amount of data to demonstrate the applicability and revisability of the correlations. The research results indicate that modified Dobson and Chato condensation heat transfer correlation (multiplied by the correction factor 2.13) shows good predictability of condensation heat transfer coefficient of R404A in small diameter microfin tube within a deviation of ﹣14.13% to +15.51%. The friction pressure drop correlation proposed by Huang Xiangchao can well predict the friction pressure drop of R404A in small diameter microfin tube within a deviation of ﹣13.58% to +12.56%. Both correlations can provide more accurate theoretical guidance for the calculation and design of heat exchanger.关键词：correlations;small diameter tube;condensation;heat transfer coefficient;pressure drop;R404A2144|1961|2发布时间：2024-07-18
- 摘要：The heat transfer performance of a heat pipe using acetone as working fluid is experimentally studied and discussed in this paper. A novel heat pipe array was designed and expected to be utilized in integrated waste heat recovery equipment with higher heat transfer efficiency at lower temperature heat sources. The device is composed of five vertical evaporation sections which are connected at the bottom, and a horizontal concentric tube condensing section. The heat transfer performance of a new type of thermosiphon waste heat recovery unit was analyzed by theoretical and experimental methods, and the structural parameters of the device were optimized. The influence of inclination angle of 15°~90°, operation temperature of 40~80 ℃ and cooling water temperature of 10~30 ℃ on heat transfer performance of the device was studied. It is found that the new gravity heat pipe waste heat recovery device has good isothermal performance and operation stability. When the liquid filling ratio is 15%, the inclination angle is 60°, the cooling water temperature is 30℃, the heat exchanger reaches the best working state. The maximum heat transfer rate is about 1 700 W, and the average thermal resistance is 0.042 ℃/W.关键词：gravity heat pipe;waste heat recovery;heat transfer characteristic2078|2274|2发布时间：2024-07-18
- 摘要：Incomplete wet compression can sharply reduce the discharge temperature of compressors. However, the challenge of the application is how to control the real-time suction refrigerant quality of compressor within the appropriate range. A method using quasi saturation isentropic compression discharge temperature (QSICDT) to control suction refrigerant quality of compressor was proposed in the paper. The performance change of refrigeration system with R22, R32, R134a and R410A is theoretically analyzed under AHRI (air-conditioning heating and refrigeration institute) air conditioning and refrigeration applications when this method is used to control the suction refrigerant with a small liquid, and the method is verified by R32 experimental data. The results show that using QSICDT can control compressor suction with a small amount of liquid refrigerant; the capacity and COP all can reach the maximum for wet compression refrigeration system with R32 by using QSICDT to control suction refrigerant quality at 0.96 to 1.关键词：wet compression;suction refrigerant quality;discharge temperature;experimental research2220|2275|1发布时间：2024-07-18
- 摘要：In recent years, high temperature is increasingly frequent, which has a serious effect on the health of workers. Thus, it is necessary to develop a cooling garment to improve work conditions. The cooling performance of thermoelectric cooling garment is experimentally investigated in the paper. The studies show that: under working conditions of only one element of thermoelectric cooler, the temperature is basically equal at the same radius as the center of P0, and as the distance increases, the temperature difference of each measuring point reduces rapidly first and then slows down; under working conditions of three elements of thermoelectric cooler, the temperature exhibits some differences, and as the distance increases, the measuring point temperature difference of P5-P8 and P9-P12 first decrease and then rise, which has a significant turning point at the distance of 3cm; the overlap effect scope of thermoelectric cooling garment is a circle, the radius of 4cm at the center of P0, and at the same distance of two adjacent elements of thermoelectric cooler, the overlap effect is more obvious when the cooling center is located in the same horizontal line. This study provides some guidance for the application of thermoelectric cooling garment.关键词：thermoelectric cooling;cooling garment;overlap effect2149|2091|7发布时间：2024-07-18
- 摘要：In the liquid desiccant air conditioning system, the dehumidifier is a core component of the system. An experimental platform is built to be used for the dehumidifier performance test in the liquid desiccant air conditioning system. The measuring points are arranged in the dehumidification tower with LiCl solution as the desiccant, where the diameter of is 300 mm, and packing height is 800 mm. A heat and mass transfer model for the dehumidifier is established based on the Mercel theory, the heat and mass balance and the effective model of D. I. Stevens. The influence of various parameters on the performance of dehumidifier is analyzed from both experimental and theoretical results. The results show that the simulation results are in good agreement with the experimental ones, which shows that the model has good adaptability and can be used to simulate the performance of the dehumidifier. After analyzing the experimental and theoretical results, it can be seen that the inlet solution temperature, concentration and mass flux have greater impact on the dehumidification in the range of experimental conditions. The lower the inlet temperature of the solution, the better dehumidification effect of the desiccant; the lower the concentration of the solution, the better effect of removing moisture. And the inlet mass flux of the solution must be controlled in a certain range so that the performance of the dehumidifier can be improved. The air inlet velocity, dry bulb temperature and moisture content have little effect on the outlet air condition of the dehumidifier.关键词：liquid desiccant air conditioning;dehumidifier;heat and mass transfer model;test conditions2190|2079|5发布时间：2024-07-18
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- 摘要：An adsorption refrigeration system with two beds is designed and developed, which uses hot water of 85~100℃ as the driving heat source. Through the alternating adsorption and desorption of the refrigerant by two adsorption beds, the system can realize continuous refrigeration. The adsorbent beds use fin and tube structure, and the surface of the fin is coated with adsorbent, which is composited by 13X and CaCl2. The coating thickness of the absorbent is only 0.15mm, which can accelerate the adsorption / desorption rate and the heat transfer rate. The evaporator uses coil and water plate structure, and they are stepped with interval and distributed from top to bottom. This structure can ensure that the water is boiling on the surface of the heat exchangers tube. The condenser adds a non-condensable gas discharging device, and the device can discharge non-condensing gas during the system’s operation, which can ensure the high efficiency of the condenser. At the same time, the structure of the cylinder block is optimized from the aspects of strength, sealing and assembly structure. In addition, the mass recovery and heat recovery are added to the adsorption refrigeration cycle. Based on this cycle model, the performance of the system is tested，it is found that when the desorption heat source is 85 ℃ hot water, the system cooling power is 7.7kW, the coefficient of performance is 0.467, the SCP is 380W / kg, and the average power consumption is 1.23 kW.关键词：adsorption refrigeration;composite adsorbent 13X/CaCl2;refrigeration capacity;coefficient of performance;SCP;power consumption1876|2050|0发布时间：2024-07-18
- 摘要：The principle of bubble pump is introduced briefly and a number of bubble pumps that apply to single pressure absorption refrigeration system are summarized and discussed. Configuration, operating parameter and working fluid are presented as the important parameters influencing the performance of the bubble pump. The theoretic and experimental research on bubble pumps with diffusion-absorption refrigeration cycle and Einstein refrigeration cycle are provided. The factors that influence the performance of the bubble pump and research in other aspects are classified. Finally, more further research on different types of working medium and the multiplication of lifting capacity formed are pointed out in the future.关键词：refrigeration system;bubble pump;reviews;absorption refrigeration1984|2048|2发布时间：2024-07-18
- 摘要：The control of ice nucleation temperature during the freezing stage has significant influences on quality uniformity of freeze-dried products and drying rate of later stages. For active depressurization to induce ice nucleation of supercooled water in vials, the effects of depressurization rate, final pressure level and supercooling degree on the nucleation phenomenon were studied experimentally and theoretically here. The following results were obtained: under atmospheric pressure the range of releasing supercooling degree(RSD) was 9-17 ℃,while during depressurization the range of RSD became 8-11 ℃; in the range of 5-20 kPa/s the depressurization rate had little effect on the nucleation of supercooled water; in the range of 100-400 Pa, lower final pressure led to lower RSD. Through numerical calculation and analysis it was indicated that the lowest temperature of surface water during depressurization maybe the key factor influencing ice nucleation.关键词：freeze drying;pre-freezing;nucleation;depressurization;supercooled water2121|1900|0发布时间：2024-07-18
- 摘要：Compared with the traditional vapor compression air conditioner, the pump-driven two phase cooling unit has a great potential in energy saving of data centers for it consumes less power and has a higher energy efficiency ratio when air temperature is low. However, insufficient control strategies not only hinder the improvement of performance, but also influence the accuracy of indoor temperature controlling, which limits the practical application. For a better application on small data centers, this paper designs a control system for the pump-driven two phase cooling unit, and studies its operating performance using in a small data center. This paper also fits the operating characteristic curves and makes an energy saving analysis. The results show that when the set point of indoor temperature is 22 ℃, the pump-driven system can fit the heat load well and get a good energy saving effect under the condition of an outdoor temperature of 10 ℃ or lower, and it can achieve at least a ratio of 26.77% on energy saving comparing with the existing air conditioner of the data center.关键词：air conditioning;energy saving;data center;pump-driven;natural cooling2028|2105|2发布时间：2024-07-18
- 摘要：To study the influence of the temperature of chilled water on the exergy loss of the double cooling source refrigerating unit, the model of exergy analysis on the unit that adopts the large temperature glide zeotropic mixture R32/R236fa (60%/40%) as refrigerant is established, and the experimental platform of the double cooling source refrigerating unit was set up for experimental exergy analysis in this paper. The theoretical exergy loss and the experimental exergy loss of the refrigeration unit are studied when the condensation temperature is 32 ℃ and the temperature of chilled water is 18 ℃/8 ℃, 17 ℃/6 ℃, and so on respectively. The results show that the minimum exergy destruction occurs when the inlet water temperature of the condenser is 32 ℃, higher and lower outlet water temperatures of the evaporator are 8 ℃ and 17 ℃. At the same time, the maximum exergy loss of the unit is compressor, followed by the condenser.关键词：zeotrope;chiller;test conditions;exergy analysis1997|2102|1发布时间：2024-07-18
- 摘要：The homogeneous phase flow model was established to analyze gravity recirculating evaporators in the condition that four kinds of refrigerants are used respectively. The experimental device of gravity recirculating refrigeration system was set up, and the experimental results were compared with the theoretical calculation results under different working conditions. Taking R404A as an example, when the air temperature in heat insulation decreased from 0 ℃ to -25 ℃, the deviation of the experimental value from the theoretical value of the heat transfer coefficient lowers from 15.91% to 3.01% gradually. The deviation of the experimental value from the theoretical value of the cooling capacity decreases from 14.43% to 2.07%. The lower the air temperature in heat insulation is, the smaller the deviation becomes, which indicates that the running state of the gravity recirculating refrigeration system is in better agreement with the theoretical operating state in lower temperature. This model was used to predict the running states of the four refrigerants. And it shows that comparing with the other three refrigerants, the heat transfer coefficient and cooling capacity of the R407C are the highest when the supplying height is in a relatively low level.关键词：gravity recirculation evaporator;comparison;theoretical analysis;experimental research1980|2074|3发布时间：2024-07-18
- 摘要：In this paper, vacuum freezing drying was selected as the research of whole books processed by deacidification. Liquid nitrogen pre-freezing and slow-rate pre-freezing were compared in terms of brightness, color, tensile strength, tearing strength, folding strength and sensory evaluation of books. The results showed that slow-rate freezing shortened drying time. Liquid nitrogen freezing was better than slow-rate freezing in terms of optical quality and appearance, while slow-rate freezing was better in terms of mechanical quality. Considering economical efficiency and long-term conservation of books, slow-rate pre-freezing is recommended.1959|2000|0发布时间：2024-07-18
- 摘要：Ultrasound can promote the formation of crystal nucleus, shorten the freezing time and get a higher quality freeze, but the technology is currently used for the liquid samples or immersion freezing process, and solid samples were barely taken into account. In this paper, the contact ultrasonic assisted vibrating plate was designed and set up, which is used for the freezing process of solid fruits and vegetables. The effects of ultrasound power, exposure time and phase stage on the freezing rate of the carrot were investigated. The experiments are divided into three groups: 1）applying ultrasound with different powers (0,122.6,178.7,229.8 W) for 10s at -1 ℃; 2）applying 178.7 W ultrasound at -1 ℃ for 0,5,10,15 s respectively; 3）applying 178.7 W ultrasound for 10 s during different phase stages. The results showed that the optimum condition is applying 178.7 W ultrasound for 10 s during transition phase，which can significantly reduce the tcf (characteristic freezing times) and ttf ( total freezing times) and increase the freezing rate of samples.关键词：ultrasound;plate freezing;freeze rate;carrot1880|2043|2发布时间：2024-07-18
- 摘要：In order to solve the problem of the probable wet compression and temperature fluctuation of cold storage after liquid refrigerant defrosting operation, the method of fan delayed running is proposed. Taking the delayed time of fan running as a variable parameter, the experiment has conducted under the condition of ﹣20 ℃ cold storage temperature and 3 kg weight of frost with the delayed time of fan running from 0 s to 180 s after the finish of defrost. The system parameters such as temperature fluctuation of cold storage after the finish of defrosts, defrosting time and the suction parameters of the compressor after system returning to work are analyzed and compared for different delay time of fan running. The result shows that running the fan without delay after defrosting, the cold storage temperature will sudden rise 5 ℃ and wet compression occurs for the first 4 min after refrigeration is resumed; the best delay time of fan running is 140 s to 180 s after defrosting and the rise of temperature in cold storage is 3 ℃ lower than that in the condition without fan delaying, and the temperature fluctuation of cold storage is within 5 ℃.The defrosting time is about 12 min, and the probable wet compression is completely avoided after refrigeration system returns to work.关键词：cold storage;liquid refrigerant defrosting;temperature fluctuation;wet compression2303|2191|2发布时间：2024-07-18
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