最新刊期
卷 35 ， 期 4 ， 2014
- 摘要：In order to determining the relevance between thermal comfort and key energy design elements during energy-saving design process, the method of extracting energy design factors of air conditioning and calculating its weight is proposed. The house of quality based on thermal comfort is built with the energy-saving design frame. The thermal comfort requirements are converted to function and weight of air conditioning. The energy characteristic of the function is analyzed, and the extract means of energy design factors is provided based on the relation of functions with energy. The method of calculating influence degree of energy design factors on thermal comfort and energy consumption is also put forward. Taking the household air conditioning as a case study, the energy design factors based on thermal comfort are extracted. Two coupled factors, volume efficiency and heat transfer coefficient, are decoupled, and the influence coefficient of energy design factors on thermal comfort and energy consumption in overall layer are calculated. The comprehensive influence coefficient in descending order is compressor power, system control mode, ventilation quality and heat exchange amount.关键词：household air conditioning;energy design factors;thermal comfort;energy-saving design1863|2027|0发布时间：2024-07-18
- 摘要：The separation mechanism of reverse osmosis membrane was described. Flux formulas, applications and limitations of various theoretical separation models were summarized here. The effects that operating pressure, feed temperature, feed concentration and feed flow rate have on performance of the reverse osmosis membrane separation were analyzed systematically. Finally, the applications using reverse osmosis membrane separation technology in refrigeration and air conditioning industry were demonstrated, which provides a reference for the applications of reverse osmosis membrane separation technology in refrigeration and air conditioning industry.关键词：air-conditioning;reverse osmosis;review;separation model;application1907|2212|0发布时间：2024-07-18
- 摘要：The two-phase ejector refrigeration cycle (TPERC) system with a dual-serial-throat nozzle ejector was investigated experimentally, and the entrainment ratio of the ejector and the COP of the system were compared with those of the ejector with Laval nozzle and the TPERC system respectively. The experimental results indicate that the entrainment ratios of the dual-serial-throat nozzle ejectors with different geometric size are greater than those of the Laval nozzle ejectors under the working condition of the evaporating/condensing temperatures 1 ℃/45 ℃, the maximum increment of the entrainment ratio is about 18%; and the COP of the TPERC system with dual-serial-throat nozzle ejector is greater than that of the TPERC system with Laval nozzle ejector, the maximum increment of the COP is about 12%. Under the condition of the fixed evaporating temperature 1 ℃, the entrainment ratios of both the dual-serial-throat nozzle ejector and the Laval nozzle ejector achieve the maximum values as the condensing temperature is about 45 ℃. Under the condition of the fixed condensing temperature 50 ℃, the entrainment ratios of the two types of ejectors achieve the maximum values as the evaporating temperature is about 3 ℃.关键词：ejector;two-phase flow;dual-serial-throat nozzle;entrainment ratio2000|2365|0发布时间：2024-07-18
- 摘要：Offshore platforms will shake and tilt because of marine motion, which will influence flow distribution in the header of plate-fin heat exchanger. The distribution of pure water/air and air-water two-phase flow in horizontal and tilt state were conducted in the air-water two-phase flow distribution experimental apparatus. The effect of gas-liquid ratio and tilt angle on flow distribution in the header of plate-fin heat exchanger in tilt state were studied. The results show that flow distribution in static state is subject to the influence of the inertial force, and the flow distribution unevenness increases with the increase of the inlet flow and gas-liquid ratio. In tilt state, flow distribution is subject to the influence of both inertial force and gravity, and flow distribution evenness is much lower than the static state. Flow distribution unevenness increases with the increase of tilt angle, and is more sensitive to tilt when gas-liquid ratio increases. It is suggested that the header and heat exchanger should be fixed and installed strictly at horizontal/vertical state. Meanwhile the influence of tilt can be eliminated through the improvement of liquefaction process and heat exchanger design.关键词：plate fin heat exchanger;header structure;tilt;two-phase;flow distribution1866|2272|0发布时间：2024-07-18
- 摘要：In order to investigate the distribution of temperature and relative humidity of the fruit and vegetable open display cabinet with single-band air curtain, an experimental platform of the vertical open display cabinet was used for refrigeration test. The distribution characteristics of temperature and relative humidity of the testing display cabinet under the cooling and temperature raising conditions was analyzed. The effect of night covers was also explored. The experimental results showed that the temperature and humidity are well-distributed under temperature raising condition, and the coefficient variation (CV) of temperature and the relative humidity distribution is 0.25 and 0.08 respectively. The temperature and relative humidity of the right of the display cabinet are higher than those of the left horizontally. The distribution of temperature and relative humidity in four shelves differs significantly (P<0.05) in the orthogonal direction. During the steady-state operation the temperature and relative humidity distribution in four shelves is periodic oscillation and the period is about 17min. To study the overall temperature and relative humidity of the display cabinet, the linear regression method was used to predict the effect of the relative humidity on the temperature. The regression model showed that temperature is linear with the relative humidity. Night covers can keep the relative humidity and the amplitude of temperature with minor changes, shorten the cooling time and prolong the temperature raising time. Compared with no night covers, the average relative humidity is higher by 5.74%RH and average temperature is lower by 0.43℃. The results will provide references to optimize the performance design of the fruit and vegetable open display cabinet.关键词：display cabinet;temperature;relative humidity;distribution1819|2040|0发布时间：2024-07-18
- 摘要：The experimental system of a cooling device using Fe3O4-R600a as magnetic nano-refrigerant was built up. And the influences of magnetic field distribution, magnetic field intensity, heat load, cooling temperature were discussed. The results show that the effect of the device was improved obviously by external magnetic field, and the heat was transferred by the circulating fluid without a pump. On the meantime, synergic function between the external magnetic field and the thermal field has impact on the velocity of the working fluid and the cooling performance of the device. Using external magnetic field, the cooling performance of the device also can be effectively controlled.关键词：refrigerant;cooling;magnetic field;thermomagnetic convection1912|2492|0发布时间：2024-07-18
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A General Modeling Approach for Complex Evaporative Cooling Heat Exchanger Based on Spatial Scanning
摘要：In order to overcome the disadvantages of existing modeling methods of the complex evaporative cooling heat exchangers, a general modeling approach based on spatial scanning theory is proposed. In this approach, the 3-D heat exchanger is divided into calculation nodes according to its spatial location. Each node is regarded as a micro heat exchanger, and connected with each other through air, water/solution, and/or refrigerant. An iterative algorithm is developed based on conservation of energy and mass of nodes in steady flow and steady-state heat transfer. Finally, the model is verified by comparing the simulated results and the experimental results of two closed-type wet cooling towers. Results show that the proposed model is highly accurate and reliable. This model can be used to simulate the performance of the evaporative cooling heat exchanger with complicated configurations and flow under different modes.1845|1971|0发布时间：2024-07-18 - 摘要：The wet performance of microchannel heat exchanger (Fin Pitch=1.1mm) with hydrophobic, hydrophilic and without surface coating were studied under different conditions experimentally. The results indicated that hydrophobic surface coating had bad effects on air side performance: the capacity decreased by 14% under low air velocity and the decrease became less with the increase of air velocity; the pressure drop increased at least by 130% under different conditions except the condition of high air velocity & humidity. The capacity of hydrophilic heat exchanger decreased by 2%-8% under different conditions; the pressure drop decreased up to 50% under high air velocity & humidity and got improved under most conditions except for the 17% decrease under the condition of low air velocity & high humidity. Air side performance of microchannel heat exchanger with hydrophilic and without surface coating were studied after 260h salt spray corrosion. The capacity of hydrophilic coating heat exchanger increased by 4%-6% compared to the one without surface coating, and pressure drop decreased by 14%-16%. The result indicated that hydrophilic coating was good for anti-corrosion.关键词：microchannel heat exchanger;surface coating;heat transfer performance;pressure drop;salt spray corrosion1934|2566|0发布时间：2024-07-18
- 摘要：The condensation heat transfer coefficients of R1234ze in a single circular minitube of 2mm inner diameter were investigated experimentally. The experiment are conducted at saturation temperature of 35 ℃ and 40 ℃, mass flux of 100~400 kg/(m2?s) and heat flux of 4~22 kW/m. The test results showed that the range of heat transfer coefficients is 1.5~8 kW/(m2?K). Both the heat transfer coefficients and frictional pressure drop of R1234ze increase with the rise of mass flux, and decrease with the rise of saturation temperature. Compared with R134a and R32, the heat transfer coefficient of R1234ze is relatively low (22% lower than R134a and 31% lower than R32), and the frictional pressure drop of R32 is higher than R1234ze. After comparing the results with several typical predicted correlations, it is shown that Baird model can predict the experimental heat transfer coefficients well and Müller- Heck model can predict the experimental frictional pressure drop with best accuracy.关键词：refrigerant;R1234ze;condensation heat transfer coefficients;frictional pressure drop;horizontal small tube1873|2128|0发布时间：2024-07-18
- 摘要：The domestic and international investigations on CO2 gas cooler with different forms were summarized. The performance of three kinds of tube-in-tube gas coolers, plain tube, rectangular spiral tube and circular spiral tube were simulated. The heat transfer amount of unit pressure drop was put forward to evaluate the gas cooler performance in the supercritical condition. According to the simulated result, a set of tube-in-tube gas cooler with rectangular spiral tube was designed and the influences of CO2 inlet pressure, inlet water flowrate and temperature on heat transfer coefficient, heat transfer amount, COP and heat exchanger efficiency were studied experimentally. The results show that the system COP can reach 2.85 when CO2 inlet pressure is 8 MPa, inlet water flowrate is 1.56 kg/min and inlet water temperature is 9 ℃. The results can provide reference for the practical application of the CO2 heat pump water heater.关键词：heat transfer performance;experimental study;CO2 heat pump water heater;tube-in-tube gas cooler1949|2720|0发布时间：2024-07-18
- 摘要：Heat transfer performance of a flat pulsating heat pipe with single-sided wave plate was experimentally investigated. Influence factors of heat transfer performance were analyzed under the effect of forced air convection cooling conditions, including liquid filling ratio, heating power and inclination angle. The results show that the best liquid filling ratio of pulsating heat pipe is 20%~30% except laid at 0° angle. The effect of inclination angle on the heat transfer performance of pulsating heat pipe is very small, but 90° is relatively the best. Heat transfer performance of heat pipe is poor when it is laid at 0° angle, even loses pulsating effect when liquid filling ratio is low. The main reason is that the backflow of working fluid is in difficulty in this case, which has a lot to do with the design of groove of plate pulsating heat pipe. In addition, heat transfer performance of heat pipe may be undulated when heating power is low, sometimes heat pipe even can't start.关键词：pulsating heat pipe;heat transfer performance;trapezoidal channel;influence factors1908|2074|0发布时间：2024-07-18
- 摘要：In order to grasp the influence parameters of bubble pump performance more accurately and improve the performance of Einstein refrigeration, the theoretical model and experiment on bubble pump were carried out with water as the working fluid at atmospheric pressure by using different lift height under the same immersion ratio. According to the theoretical and experimental results, it is found that under the condition of the other factors unchanged, the theoretical and experimental results have the same trend; the amount of the lifted liquid is inversely proportional to the lift height, the lifting capacity difference can reach to 0.82g/s; the lift height is proportional to the lifting efficiency, and the maximum lifting efficiency difference can reach to 10.16%, which has a important effect on the whole refrigeration system.关键词：refrigeration;bubble pump;two phase flow;vertical lift tube;Einstein cycle1871|2027|0发布时间：2024-07-18
- 摘要：In terms of direct-contact heat transfer process between cold air bubbles and immiscible liquid, the convection heat transfer equation was established and solved numerically. A correlation between Nu and Re as well as Pr was obtained, and the validation of the model was verified by comparing the theoretical value and the experimental data. Entropy generation during the heat transfer process was studied. The variation of entropy generation rate was presented regarding Re. An optimal Re would lead to a minimum entropy generation during the heat transfer process. The research provides a theoretical basis of optimizing the direct-contact heat transfer process.关键词：direct-contact heat transfer;cold air bubbles;entropy generation1963|2483|0发布时间：2024-07-18
- 摘要：In a mainframe computer system, CPU cooling problem has always been the focus of industry experts. Some novel heat sinks were presented to enhance the heat transfer effect during heat transfer process. A mathematic model of the CPU heat sink in the experiment duct was developed and compared with experiments. Based on the experiment research of the CPU heat sink, the velocity field and the velocity gradient field of the heat sink in the duct were acquired by PIV and fluid-solid coupling numerical calculation. It is showed that the synergy of the velocity field and the velocity gradient field in an entire flow domain would affect the heat convection of CPU heat sink. The results of the study are possible to improve the performance and the design of CPU cooling system.关键词：heat sink;PIV;field synergy;numerical calculation1941|2398|0发布时间：2024-07-18
- 摘要：The influence of some structural factors, i.e. the nozzle style, relative gas charge time on the flow in and the performance of pressure wave refrigerator are studied theoretically and experimentally in this paper. The results show that the strength of incident shock wave is the strongest when using the contraction nozzle, follows by using the laval nozzle, and is the weakest when using the uniform nozzle when the ratio of the expansion ε is from 2.0 to 12.0. Thus the cooling effect of pressure wave refrigerator is the strongest when using the contraction nozzle. The maximun refrigerating efficiency ηmax is increased first and then decreased when the relative gas charge time τ is increased. The optimum relative gas charge time τ is about 0.06 when the ratio of the expansion ε is 4, the ratio of length to diameter L/d is 400 and the relative depth of the jet hole in gas distribution is 0.55. When τ>0.075, the optimum pulsing frequency (fopt) is on the second peak of the refrigerating efficiency , while fopt is on the third peak of the refrigerating efficiency when τ>0.075.关键词：pressure wave refrigerator;validation;gas distribution;nozzle;refrigerating efficiency1887|2099|0发布时间：2024-07-18
- 摘要：In order to replace the traditional heat exchanger of room air conditioner, a new non-contact thermal resistance aluminum heat exchanger was designed. Enthalpy method is then used to compare the cooling performance between new heat exchanger and tube-fin heat exchanger of household air conditioner. The capillary size and refrigerant charge capacity of air conditioner are tested and optimized for better cooling performance. The results show that the heat transfer area of the new non-contact thermal resistance aluminum heat exchanger is decreased 37.53%, the rated cooling capacity is just reduced by 2.7%, EER increased by 7% instead. The new heat exchanger has a stronger heat capacity and is the ideal alternative product for heat exchangers of room air conditioners.1916|2179|0发布时间：2024-07-18
- 摘要：In order to reduce the effect of defrosting heat on the cold storage temperature change during defrosting process, a heat insulation defrosting device is additionally provided to the air cooler in the storage, and the experimental study on the defrosting process was carried out. The results showed that in the defrosting processes with and without heat insulation, the temperature of the upper area in the storage changed greatly. The temperature changes relatively small during the defrosting process with heat insulation, and the overall fluctuating temperature is 3.2 ℃ lower than that without heat insulation. In the meantime, the defrosting time with heat insulation is shortened by nearly 300s, which proves that the insulation defrosting device can stabilize the storage temperature and shorten the defrosting time in the defrosting process.关键词：hot gas defrosting;heat insulation defrosting device;temperature distribution1866|2208|0发布时间：2024-07-18
- 摘要：A new type of refrigerator cabinet with composite phase change materials was designed in this paper. In order to assess the refrigerator heat preservation function. First of all, the three dimensional unsteady phase change heat transfer process with variable heat source was simulated and calculated by ANSYS software. Then the simulation results were verified experimentally with cold storage and transportation of Shanghaiqing（Brassicachinensis L.）, the Chinese vegetable. The results showed that the temperature rise of Shanghaiqing inside the cabinet was delayed when the composite phase change materials was applied. So that adding composite phase change materials can effectively improve the effect of the cold in refrigerated vehicle.1970|2090|0发布时间：2024-07-18
- 摘要：Low-temperature fracture is often observed during the low-temperature preservation of articular cartilage. However，the biomechanical damaging mechanism of cryopreservation is still unclear. During freezing from 0 ℃ to -60 ℃，Thermol Mechanical Analysis (TMA) was used to investigate the effects of 4 kinds of cryoprotecants with different concentrations. The results indicate that: (1) the cartilage produced a great thermal stress due to the extracellular thermal expansion during the cooling process；(2) when adding a higher concentration of ethanol and glycol，the faster the cooling rate，the greater thermal stress the articular cartilage will produce，and thus，slower cooling rate is more suitable for the cryopreservation of articular cartilage；(3) while adding 1, 2 - propylene and glycerin，there is an optimal cooling rate (30C/min) and it produces cartilage a minimal thermal stress. Moreover，cryoprotectants of higher methylation will contribute better protective effect to the thermal expansion among the 4 kinds of alcohols.关键词：cryopreservation;thermal strain;thermal mechanical analyzer;articular cartilage;slow cooling rate1722|2389|0发布时间：2024-07-18
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