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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第2期12卷 139-145页

作者： Qin WANG Kang CUI Teng-fei SUN guang-ming chen Institute of Refrigeration and Cryogenics State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

This paper proposes a new approach to the performance optimization of an auto-cascade refrigerator(ACR) operating with a rectifying column and six types of binary refrigerants(R23/R134a,R23/R227ea,R23/R236fa,R170/R290,R170/R600a,and R170/R600) at a temperature level of -60 °C. Half of the six binary refrigerants are nonflammable,of which the 0.5 and the 0.6 mole fractions of R23 for the R23/R236fa possess the most prospective composition for the medium and low suction pressure compressors,respectively. The remaining three binary refrigerants are flammable but with low global warming potentials,of which the 0.6 mole fraction of R170 for the R170/R600 is the most prospective one. The results show that the overall matching as well as local matching of heat capacity rates of hot and cold refrigerants in the recuperators are important for the improvement of coefficient of performance of the cycle,which can be adjusted through the simultaneous optimization of the pressure level and composition. The new approach proposed also offers a wider range of applications to the optimization in performance of the cycle using multi-component refrigerants.

关键词： Auto-cascade Binary refrigerant Refrigerator Optimization

Performance of a single-stage Linde-Hampson refrigerator operating with binary refrigerants at the temperature level of-60°C

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第2期11卷 115-127页

作者： Qin WANG Kang CUI Teng-fei SUN Fu-sheng chen guang-ming chen State Key Laboratory of Clean Energy Utilization Institute of Refrigeration and Cryogenics Zhejiang University Hangzhou 310027 China

The optimization of the performance of a single-stage Linde-Hampson refrigerator （LHR） operating with six different binary refrigerants （R23/R134a, R23/R227ea, R23/R236ea, R170/R290, R170/R600a and R170/R600） with ozone depletion potentials （ODPs） of zero was conducted using a new approach at the temperature level of-60℃. Among these binary refrig- erants, the 0.55 and the 0.6 mole fractions of R23 for R23/R236ea are the most prospective nonflammable ones for the medium and low suction pressure compressors, respectively. For these two kinds of compressors, the 0.6 and the 0.65 mole fractions of R170 for R 170/R600, respectively, are the most prospective binary refrigerants with low global warming potentials （GWPs）. The results of optimization of pressure levels indicate that the optimum low pressure value for coefficients of performance （COP） is achieved when the minimum temperature differences occur at both the hot and the cold ends of the recuperator at a specified composition and pressure ratio. Two useful new parameters, the entropy production per unit heat recuperated and the ratio of heat recuperating capacity to the power consumption of the compression, were introduced to analyze the exergy loss ratio in the recuperator. The new approach employed in this paper also suggests a promising application even to the optimization of the performance with multi-component refrigerants.

关键词： Linde-Hampson Binary refrigerant Refrigerator Performance Optimization

Experimental evaluation of the effect of an internal heat exchanger on a transcritical CO_2 ejector system

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第2期12卷 146-153页

作者： Xiao-xiao XU guang-ming chen Li-ming TANG Zhi-jiang ZHU Shuang LIU Institute of Refrigeration and Cryogenics State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

This study presents experimental results focused on a performance comparison of a transcritical CO2 ejector system without an internal heat exchanger(IHX) (EJE-S) to a transcritical CO2 ejector system with an IHX(EJE-IHX-S) . The comparison includes the effects of changes in operating conditions such as cooling water flow rate and inlet temperature. Experiments are conducted to assess the influence of the IHX on the heating coefficient of performance(COPr) ,heating capacity,entrainment ratio,pressure lift,and other parameters. The primary flow rate of the EJE-IHX-S is higher than that of the EJE-S. The pressure lift and actual ejector work recovery are reduced when the IHX is added to the transcritical CO2 ejector system. Using a more practical performance calculation,the compression ratio in the EJE-S is reduced by 10.0%-12.1%,while that of EJE-IHX-S is reduced only by 5.6%-6.7% compared to that of a conventional transcritical CO2 system. Experimental results are used to validate the findings that the IHX weakens the contribution of the ejector to the system performance.

关键词： CO2 ejector system Transcritical cycle Heating coefficient of performance (COPr)

Permeation of dimethyl sulfoxide into articular cartilage at subzero temperatures

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2012年第3期13卷 213-220页

作者： Shao-zhi ZHANG Xiao-yi YU guang-ming chen Institute of Refrigeration and Cryogenics Zhejiang University Hangzhou 310027 China

Osteochondral allografting has been proved to be a useful method to treat diseased or damaged areas of joint surfaces. Operational long-term stocks of grafts which supply a buffer between procurement and utilization would contribute to the commercialization or industrialization of this technology. Vitrification has been thought to be a promising method for successful preservation of articular cartilage （AC）, but high concentration cryoprotectants （CPAs） are used which may cause high cellular toxicity. An effective way to reduce CPA toxioity is to increase CPA concen- tration gradually while the temperature is lowered. Understanding the mechanism of （31~A permeation at subzero temperatures is important for designing the cryopreservation protocol. In this research, the permeation of dimethyl sulfoxide （MezSO） in ovine AC at subzero temperatures was studied experimentally. Pretreated AC discs were ex- posed in Me2SO solutions for different time （0, 5, 15, 30, 50, 80, and 120 min） at three temperature levels （-10, -20, and -30℃）. The Me2SO concentration within the tissue was determined by ultraviolet （UV） spectrophotometry. The diffusion coefficients were estimated to be 0.85×10-6, 0.48×10-8, and 0.27×10-6 cm2/s at -10, -20, and -,30℃, respectively, and the corresponding activation energy was 29.23 kJ/mol. Numerical simulation was performed to com- pare two Me2SO addition protocols, and the results demonstrated that the total loading duration could be effectively reduced with the knowledge of permeation kinetics.

关键词： Articular cartilage Vitrification Dimethyl sulfoxide Permeation Diffusion coefficient Subzero temperature

Experimental investigation of an adjustable ejector for CO_2 heat pump water heaters

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第11期10卷 1678-1682页

作者： guang-ming chen Li-xia LIANG Li-ming TANG Xiao-xiao XU Zhi-jiang ZHU Qi chen State Key Laboratory of Clean Energy Utilization Institute of Refrigeration and Cryogenics Zhejiang University Hangzhou 310027 China

An adjustable ejector expansion device for a CO2 heat pump water heater (HPWP) is proposed to improve the system performance. It has been designed to investigate experimentally the effects of the motive nozzle throat area of the ejector, entrained flow pressure, back pressure and primary flow pressure on the entrainment ratio. Experiments based on different motive nozzle throat areas were conducted and the results of the prototype ejector using CO2 as working fluid are presented. The results show that an adjustable ejector can achieve high performance and work well in a wide range of working conditions.

关键词： Adjustable elector System nerformance CO2 heat oumo water heater (HPWH) Entrainment ratio

Direct decarbonation of micrometer-scale layered double hydroxides without morphology damage

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Chinese Chemical Letters 2012年第7期23卷 805-808页

作者： Kong Li Xu guang ming chen Jian Quan Shen Beijing National Laboratory for Molecular Sciences(BNLMS) Institute of ChemistryChinese Academy of SciencesBeijing 100190China Graduate University of Chinese Academy of Sciences Beijing 100049China

A direct decarbonation route without obvious morphology damage was developed for large micrometer-scale layered double hydroxides（LDHs）.First,we synthesized pure,hexagonal-shaped LDHs with lateral dimension of micrometer-size by the recently reported urea hydrolysis ***,using HNO_3-NaNO_3 mixed solution,the obtained LDH with carbonate anions in the interlayer（LDH_CO_3） was directly decarbonated to its nitrate form,LDH_NO_3,its morphology and particle size were still *** with the recently published two-step decarbonation method,the direct decarbonation reported herein is very convenient.

关键词： Direct decarbonation Layered double hydroxides Micrometer-scale

Random projection method for ultra wideband signal acquisition

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The Journal of China Universities of Posts and Telecommunications 2011年第6期18卷 14-21页

作者： LIN Jie SHI guang-ming chen Xu-yang ZHANG Li School of Electronic Engineering Xidian University Xi＇an 710071 China

High-speed high-resolution analog-to-digital （A/D） conversion demanded by ultra wideband （UWB） signal processing is a very challenging problem. This paper proposes a parallel random projection method for UWB signal acquisition. The proposed method can achieve high sampling rate, high resolution and technical feasibility of hardware implementation. In the proposed method, an analog UWB signal is projected over a set of random sign functions. Then the low-rate high-resolution analog-to-digital convertors （ADCs） are used to sample the projection coefficients. The signal can be reconstructed by simple linear calculation with the sampling matrix, without complying with optimization algorithm and prior knowledge. In other aspects, unlike other approaches that need to utilize an accurate time-shift at extremely high frequency, or design a hybrid filter bank, or generate specific basis functions or work for signals with prior knowledge, the proposed method is a universal sampling approach and easy to apply. The simulation results of signal to noise ratio （SNR） and spurious-free dynamic range （SFDR） validate the efficiency of the proposed method for UWB signal acquisition.

关键词： random projection high speed high resolution data acquisition UWB signal

Experimental study on a cryosurgery apparatus

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第2期11卷 128-131页

作者： Shao-zhi ZHANG Dong-bo WU Ge YANG guang-ming chen Institute of Refrigeration and Cryogenics Zhejiang University Hangzhou 310027 China

Cryosurgery is an effective way of curing many diseases including tumors and cancers. It can be applied using a variety of systems and cryogens. Cheap, convenient, reliable equipment still needs to be developed so that cryotherapy may be accepted by surgeons and hospitals. This paper presents a cryosurgery apparatus that utilizes an auto-cascade refrigeration system. Refrigerant mixture R50/R23/R600a was selected as the working fluid. The mixture composition was altered to achieve lower temperatures and higher capacity. The lowest temperature at the cryoprobe could be as low as -100℃, and 8 W refrigeration capacity could be obtained at -80 ℃. An ice ball of 11.6 mm diameter could be formed when the cryoprobe was immersed in a water bath at 37 ℃.

关键词： Cryosurgery Cryoprobe Auto-cascade refrigeration system Refrigerant mixture

Experimental study on rehydration conditions of freeze-dried platelets

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第5期10卷 697-703页

作者： Ju-li FAN Xian-guo XU Shao-zhi ZHANG Fa-ming ZHU guang-ming chen Li-xing YAN Institute of Refrigeration and Cryogenics Zhejiang Universit Hangzhou 310027 China Key Laboratory of Blood Safety Research Ministry of Health Blood Center of Zhejiang Province Hangzhou 310006 China

A rehydration process for freeze-dried human platelets was studied on 1 ml of samples. The effects of prehydration duration, prehydration temperature, an rehydration solution on the recovery rate, mean platelet volume （MPV）, and platelet distribution width （PDW） were investigated. The mass changes during the prehydration process were also studied. Three prehydration durations： 0, 1.5, and 3.5 h, and two rehydration solutions： platelet-poor plasma and phosphate-buffered saline （PBS）, were tested. It was found that：（1） the prehydration was of significance; （2） 1.5 h of prehydration had better effects than 3.5 h of prehydration; （3） as a rehydration solution, the platelet-poor plasma behaved better than the PBS. The impacts of prehydration duration and temperature on the results were studied. There was almost no difference between 35 and 37 ℃. Among all the prehydration durations tested, 15, 30, 60, 90, and 120 min, the best result was achieved with the time duration of 15 min. The weights of prehydrated platelets at the end of each test were measured and the water contents were calculated. After 15 min ofprehydration, the water contents in the samples were about （4.8±0.01）% and （5.27±0.29）% （w/w） corresponding to the conditions of 35 and 37 ℃, respectively. These results will be helpful for further studies on the freeze-drying of mammalian cells.

关键词： Freeze-drying Platelets Rehydration Prehydration Rehydration solution

Cycle performance studies on a new HFC-161/125/143a mixture as an alternative refrigerant to R404

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第2期13卷 132-139页

作者： Xiao-hong HAN Yu QIU Ying-jie XU Men-yuan ZHAO Qin WANG guang-ming chen State Key Laboratory of Clean Energy Utilization Institute of Refrigeration and CryogenicsZhejiang UniversityHangzhou 310027China

In this paper, a new ternary non-azeotropic mixture of HFC-161/125/143a （0.15/0.45/0.40 in mass fraction）, as a promising mixed refrigerant to R404A, is presented. The ozone depletion potential （ODP） of the new refrigerant is zero and its basic thermodynamic properties are similar to those of R404A, but its global warming potential （GWP） is much smaller than those of R507A and R404A. Meanwhile, theoretical calculations show that, under the working condition 1 （the average evaporation temperature： -23℃, the average condensing temperature： 43℃, the superheat temperature： 28℃, the subcooling temperature： 5 ℃）, the volumetric refrigerating effect and specific refrigerating effect of the new mixture are 2.33% and 15.48% higher, re- spectively, than those of R404A. The coefficient of performance （COP） of the new mixture is 5.19% higher than that of R404A and the pressure ratio of the new mixture is 0.82% lower than that of R404A. Equally, under the working condition II （the average evaporation temperature： -40℃, the average condensing temperature： 35℃, the superheating temperature： 30 ~C, the subcooling temperature： 5℃）, the volumetric refrigerating effect and specific refrigerating effect of the new mixture are 2.24% and 20.58% higher, respectively, than those of R404A. The COP of the new mixture is 4.60% higher than that of R404A and the pressure ratio of the new mixture is similar to that of R404A. The performances of the new mixture and R404A are compared in a vapor compressor refrigeration apparatus originally designed for R404A under several working conditions （condensing temperatures： 35-45℃, evaporation temperatures： -40--20℃）. Experimental results show that the new mixture can obtain a higher COP, by 6.3% to 12.1%, and a lower pressure ratio, by 1.8% to 6.6%, compared to R404A; although the discharge temperature of the new mixture is slightly higher than that of R404A. The advantages of the new mixture will be further verified in the actual system.

关键词： Alternative refrigerant Mixture Cycle nerformance. R404A HFC-161