最新刊期
卷 37 ， 期 1 ， 2016
- 摘要：Refrigerant is the blood of refrigeration systems. Since the synthetic refrigerants were developed, refrigeration technology has experienced a rapid development. However, this also brings environment problems, such as ozone depletion and global warming, which turns into the main challenges for traditional synthetic refrigerants. Based on the new version of the Montreal Protocol 2014 Assessment Report written by UNEP RTOC, the proceedings of the 25th International Congress of Refrigeration 2015 and the 11th IIR Gustav Lorentzen Conference on Natural Refrigerants 2014, a review of the latest research and development of refrigerants was presented in this work. Different aspects were discussed including current situation of refrigerants in different types of refrigeration units, properties of novel low-carbon refrigerants, latest development of international standard for flammable refrigerants, issues that need concerning in the application of novel low-carbon refrigerants and the possible trends for alternative refrigerants.关键词：low-carbon refrigerants;performance;international standard;current situation13986|12528|16发布时间：2024-07-18
- 摘要：Chiller fault detection based on neural network is a data-based analysis method. The fault detection efficiency relies on the quality of the training data and the mesasured data.The wavelet transfer method which can remove the measurement nosise is used to improve the detection efficiencies of chiller.The results show that wavelet transfer make the detection efficiencies of fault level improved, especially the first level. The increase of the first level detection rate will be able to timely identify the chiller fault, and take the measures to prevent further deterioration of chiller fault, which is of important significance to reduce energy consumption and improve the reliability of the air-conditioning system and ensure the indoor thermal comfort. The FDD (fault detection and diagnosis）strategy is validated through using ASHRAE Project data, which shows that the detection rate is improved obviously.关键词：chiller;fault detection and diagnosis;BP neural network;wavelet denoising;bayesian regularization3268|3746|10发布时间：2024-07-18
- 摘要：In order to get the thermophysical properties of mixed refrigerants R1234yf/R134a, the PVT properties of mixture refrigerant R1234yf/R134a with mass fraction 55%/45%, 50%/50%,45%/55% in the range of 268 ~ 323 K were measured by using high-precision PVTx apparatus which is based on the Burnett method.The gas virial equation of these mixed refrigerants was fitted based on the measured data. It turned out that the experimental data agreed well with the equations.关键词：mixed refrigerants;R1234yf/R134a;PVTx;virial equation3601|3834|2发布时间：2024-07-18
- 摘要：Vapor compression refrigeration and heat pump systems, which use the natural refrigerant R718 as refrigerant, usually work at sub-atmospheric pressure. In order to study the water boiling heat transfer characteristics at sub-atmospheric pressure, one test system was built, and the heat transfer performance was studied under the pressures of 1.8~3.3 kPa. The results show that the coefficient of heat transfer increases with the increase of pressure and heat flux. Experimental data were compared with the calculated results by cooper correlation at the same conditions. Regression equations of the coefficient of heat transfer, which apply to the conditions of this experiment, were fitted using the least square method for the sake of practical application. This experiment can offer a useful reference for the study of evaporator heat transfer and heat transfer enhancement in water vapor compression refrigeration and heat pump systems.关键词：refrigerant;coefficient of heat transfer;evaporator;sub-atmospheric pressure;water3120|3278|0发布时间：2024-07-18
- 摘要：Recently, more attention have been paid to the new refrigerant R1234ze(E), which is supposed to be the most promising alternative of R134a in heat pump system. In this paper, the saturated flow boiling frictional pressure drops characteristics of R1234ze(E) and R134a inside an 8 mm ID horizontal tube were investigated. The experiment were carried out at the saturation temperature of 10 ℃ with heat flux ranging from 5.0 kW/m2 to 10.0 kW/m2 and mass flux ranging from 300 kg/(m2?s) to 500 kg/(m2?s). The influence of mass flux and heat flux on the frictional pressure drops were examined and discussed. The results show that, the frictional pressure drops of R1234ze(E) are slightly greater than those of R134a. Meanwhile, the experimental data of the frictional pressure drops are compared with four well-known empirical correlations.关键词：R1234ze(E);R134a;horizontal tube;flow boiling;frictional pressure drops3322|3746|2发布时间：2024-07-18
- 摘要：In view of the imperfection of present efficiency region of multi-split air conditioning system based on energy efficiency ratio at nominal working condition, a concept and a determination method of seasonal efficiency region of multi-split air conditioning system based on seasonal energy efficiency (SEER) and annual performance factor (APF) were proposed. The construction approaches of full condition performance models of multi-split air conditioning system and air-cooled water chiller & heater unit plus fan-coil air conditioning system based on experimental data were illustrated. Using the building load model and air conditioning hours at various temperatures in cooling and heating season in GB/T 18837 (draft for approval), the seasonal efficiency region of multi-split air conditioning system with different nominal energy efficiency ratio (EER and COP) in office building in Nanjing was calculated as an application example. The proposed concept and determination method of seasonal efficiency region of multi-split air conditioning system can not only provide an option to improve the code for engineering design of multi-split air conditioning system, but also offer guidance for the selection of air conditioning system and equipment in a practical project.关键词：multi-split air conditioning system;air-cooled water chiller& heater unit;full condition performance;seasonal efficiency region3319|3903|2发布时间：2024-07-18
- 摘要：The performance of air coolers with different flow distribution was simulated after establishing the model of air cooler evaporator with different kinds of flow distribution, and the air cooler with optimal flow distribution which adopted R717 as refrigerant was tested using the refrigerating capacity test method with liquid feed pump in this paper. The results indicate that the performance of air cooler was optimal with the flow distribution of two circuits in a single row. The refrigerating capacity was 44.3 kW at evaporating temperature ﹣25 ℃ as the pumping ratio increased to 3.5 which was the optimum value to the air cooler. The heat transfer coefficient was enhanced by 25.5% from 27.4 W/(m2?K) to 34.4 W/(m2?K) with the evaporating temperature varying from ﹣25 ℃ to 0 ℃ and the refrigerating capacity increased from 44.3 kW to 64.3 kW which achieved a 45.15% enhancement at the same range of evaporating temperature. The experimental data also verified that the cooling capacity of experimental values were approximately 5% lower than that of simulation values, which indicated the validity of air cooler model.关键词：air cooler;test conditions;refrigerating capacity;pumping ratio;heat transfer characteristics3288|3206|3发布时间：2024-07-18
- 摘要：Research and development of organic phase change materials (PCMS) and inorganic-organic PCMS are reviewed. The method of using the formula to guide the ratio of low eutectic phase change thermal storage material is discussed, and a method is presented to improve thermal conductivity of organic phase change materials. The application of phase change materials in the fields of solar energy utilization, electricity peak shift, air conditioning energy conservation and refrigerated transport is stated. It is pointed out that performance characteristics, theoretical model of heat transfer, phase transition mechanism and composite technology of PCMs should be focused on, and organic composite phase change thermal storage material is the key development direction of organic phase change materials in the future.关键词：phase change materials;thermal conductivity;cooling energy storage technology;application13684|13210|33发布时间：2024-07-18
- 摘要：The composite phase change material (PCM) used in thermal energy storage with phase change temperature of 5-15 ℃ are proposed in this paper. The material consists of lauric acid (LA), decanoic acid (DA), tetradecyl alcohol (TA) and dodecane (DD), and the mass ratio of its ingredients is 27.1:28.5:29.6:14.8, respectively. The composite was prepared by ultrasonic oscillations. The properties of the composite were characterized by cooling process, DSC (differential scanning calorimety), thermal cycling test and so on. The results show that degree of superheat of the composite is close to zero so that it can be ignored; phase change temperature and latent heat of the composite are 5.13 ℃and 154 J/g at 5 ℃/min under a constant and steady stream of nitrogen atmosphere at a flow rate of 10 mL/min, respectively; the composite after 600 cycles deviates the eutectic point without phase separation, so it has better thermal stability; basic physical properties and thermal properties of the composite were gained by a series of property test. Hereby, the composite shows large potential in thermal energy storage, especially in air-conditioning systems, because of high latent heat, suitable phase change temperature, good thermal stability and low cost.关键词：thermal energy storage;phase change materials;differential scanning calorimety;thermal properties3159|3425|7发布时间：2024-07-18
- 摘要：A novel type of adsorption chiller with synthetic zeolite-water was proposed, in which the zeolite FAMZ01 was chosen as the adsorbent and coated adsorber with fin as adsorber. The effects of heat source temperature and chilled water inlet temperature on cooling power and coefficient of performance (COP) were obtained experimentally. The results showed that the adsorption chiller can supply the chilled water steadily at driven heat source temperature of 55℃, and is with better performance at the driving heat source temperature about 65 ℃.2430|2932|1发布时间：2024-07-18
- 摘要：Erythritol with transformation temperature of 119 ℃ has huge potential in application according to temperature range of mobile heating, but it is also limited by its disadvantage of low thermal conductivity, unstable heat releasing, bigger supercooling. Nanometer materials as nucleating agents were putted into erythritol in order to improve its thermal properties, and the composite can be used as phase change materials (PCMs). The properties of nanotitanium-erythritol with different mass ratio have be gained by time-temperature curve, differential scanning calorimetry (DSC),thermal conductivity test and other properties testing. The results show that Nanometer materials can decrease the supercooling of erythritol in a large degree, and it can also increase its thermal conductivity in small extent; Nanometer titania can decrease the composite’s coefficient of cubical expansion, and the composite’s density will fluctuate over a little range with 0.02~0.08 g/cm3; Nanometer titania of 0.1% mass ratio has a drop of 37.91 percent in erythritol’s supecooling, 1.09 percent in its latent heat and a growth of 3.67 times in solid thermal conductivity.关键词：energy storage technology;erythritol;PCMs;thermal property2583|2739|13发布时间：2024-07-18
- 摘要：The non-uniformity of frost distribution on evaporator of indirect cooling refrigerator will increase the defrosting time and decrease the defrosting efficiency. Therefore, based on the optimization of defrosting this paper proposes an optimization method for return air duct of indirect cooling refrigerator. Firstly, the surface temperature distribution of the defrosting heater is measured through experiments, and the heat distribution of defrosting heater is calculated accordingly, thus the frost distribution on the evaporator that matches the defrosting heat distribution is obtained. Then the optimal air flow rate distribution of return duct is determined by the frost distribution on the evaporator. Finally, the optimal air flow rate distribution is achieved by designing the return air duct of refrigerator compartment to improve the defrosting performance. An optimization case shows that the optimized return air duct can make the air flow rate distribution in accordance with the defrosting heat distribution, which decreases the defrosting time by 38.9%, and increases the cooling capacity of the refrigerator by 3.43%.关键词：indirect cooling refrigerator;defrosting;return air duct;optimization design3270|4199|1发布时间：2024-07-18
- 摘要：Based on water spraying technology, the characteristics of CO2 hydrate formation in spray reactor were investigated experimentally. The effects of temperature and pressure in the reactor, the coolant temperature in entrainment and the use of buffer tank on CO2 hydrate formation characteristics were studied. Compared with CO2 hydrate formation under static conditions, the pressure drop in the spraying process was larger, and CO2 hydrate was formed much faster. The water was sprayed into gas, providing much more gas-water contact surface. The experimental results showed that the duration of CO2 hydrate formation was about 20 minutes in the presence of a buffer tank. However, under the same working condition, the duration of CO2 hydrate formation was about 40 minutes without a buffer tank. The buffer tank sent CO2 into the spraying system evenly and stably, which enhanced the spraying effect and doubled the CO2 hydrate formation rate. The experimental results provide an important reference for the analysis of CO2 hydrate formation and engineering applications.关键词：cool storage;CO2 hydrate;spray enhancement;growth rate;buffer tank2703|2708|5发布时间：2024-07-18
- 摘要：Two phase thermosyphon loop has a good potential of application in cooling of electronic equipment with high power source because of its relatively high efficiency of heat dissipation performance. To solve the cooling problem of a DAM with four channels, this paper designs a prototype of two phase closed thermosyphon cooling system. The starting characteristic of the system, the influence of the refrigerant charge and working inclination angle on its heat dissipation performance are investigated experimentally in this paper. The results show that the structure and heat dissipation performance of the system match the requirement. It also can be found that the starting characteristic and the working performance of the system are very good. In addition, a 1600W module with local heat flux near 100W/cm2 is cooled very well by the system in this paper.关键词：thermosyphon loop;cooling system;electronic equipment;experiment research;R134a2665|3500|1发布时间：2024-07-18
- 摘要：Moisture condensation appears on enclosure structure especially on the inner face of glass curtain walls due to high humidity and high temperature. Through analysis of condensation on the envelope surface with high temperature and high humidity by field measurement and combination of theoretical calculation and numerical simulation, the distance between the air vent and curtain wall and the outlet angle of the supply air are concluded as key influential factors. When the distance ranges from 0.2 m to 1.1 m and the outlet angle is between 30° to 45°, large area of condensation on glass curtain wall could almost be avoided; when the outlet angle of the supply air is 16°, the larger the distance between the air vent and curtain wall is, the less the condensation on envelope structure will be; while the outlet angle of the supply air is more than 45°, the less the distance between the air vent and exterior wall is, the less condensation will appear .关键词：environment with high temperature and humidity;moisture condensation;air distribution;field measurement;numerical simulation2877|3431|0发布时间：2024-07-18
- 摘要：In order to solve the problem that the hydrate grows slowly with a long induction time and randomness, the technology of promoting HCFC-141b（R141b）hydrate formation is studied in quiescent systems. The effect of surfactant SDS and copper wire on HCFC-141b hydrate formation is investigated experimentally. The induction time of R141b hydrate is reduced greatly, and hydrate could form rapidly by adding SDS or (and) copper wire in quiescent systems. The effect of SDS mass concentration on hydrate formation is also studied with copper wire. Experimental results show that the best mass concentration of SDS is about 0.1 %, and the average induction time is about 1.3 h. The repeatability of R141b hydrate formation is good, and hydrate forms compactly.关键词：refrigerant;hydrate;cold storage;Induction time;growth in quiescent systems2537|2731|7发布时间：2024-07-18
- 摘要：In order to precisely represent the output performance of multi-stage thermoelectric generators, three kinds of connection modes for thermoelectric modules were proposed. Based on thermodynamics theory, semiconductor thermoelectric theory and law of energy conservation, the model was built with an elemental approach. Newton-Raphson method was introduced to simulate the model and return the results of the output performance. In addition, the load resistance, the contact effect of thermoelectric module and thermal resistance on both hot and cold ends of the module were discussed. The results showed that the proposed model is easy and robust to be solved with less computing time. And the model can be used to predict the important parameters such as the inner temperature, the output performance and the load resistance of multi-stage thermoelectric generator, which are of great significance to the design and optimization of thermoelectric generator.关键词：TEG;multi-stage structure;connection type;output performance2914|4004|1发布时间：2024-07-18
- 摘要：Cooling rate is the key factor that determines the cryopreserving effect of cells, which has much to do with the forms and the usages of freezing carrier. In this study, digital oscilloscopes and type T thermocouple of 80 μm diameter were employed to establish a high speed temperature measurement system. The cooling rates of cells were measured by using a new type of enclosed oocyte freezing carrier in different ways of being inserted from air to liquid nitrogen. The results showed that the cooling of freezing carrier is mainly fulfilled via heat convection; When the carriers were horizontally placed, the cooling rate of carrier when the air hole was perpendicular to liquid nitrogen is higher than that when the air hole was tangent to liquid nitrogen; when the freezing carrier was directly inserted into liquid nitrogen, the cooling rate of carrier was higher than that when the freezing carrier was inserted into liquid nitrogen and then swayed; when the freezing carrier was placed downwards, the cooling rate of carrier was higher than that vertically or horizontally placed. Based on the results mentioned above, when the carrier was directly inserted into liquid nitrogen downwards, the cooling rate could reach as high as 54572 ± 1338 K/min, which is the highest and favorable to verification of oocytes.关键词：freezing carrier;cooling rate;liquid nitrogen;Leidenfrost effect2729|3128|2发布时间：2024-07-18
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