一种适于低温冷气内冷却的CBN砂轮的研制

本文介绍了一种适于低温冷气内冷却的电镀CBN砂轮。实验结果表明 ,此CBN砂轮的结构不仅能够满足低温冷气内冷却的要求 ,而且与传统磨削相比能够使磨削温度降低 30～ 4 0 %。此外 ,本文对冷气压力对磨削温度的影响也进行了实验分析。本文研究表明 ,在磨削过程中 ,使用冷气代替磨削液冷却是降低磨削温度、减少由于磨削液排放造成的环境污染的一种有效的方法。

Integration of Low-level Waste Heat Recovery and Liquefied Nature Gas Cold Energy Utilization

Two novel thermal cycles based on Brayton cycle and Rankine cycle are proposed, respectively, which integrate the recovery of low-level waste heat and Liquefied Nature Gas （LNG） cold energy utilization for power generation. Cascade utilization of energy is realized in the two thermal cycles, where low-level waste heat,low-temperature exergy and pressure exergy of LNG are utilized efficiently through the system synthesis. The simulations are carried out using the commercial Aspen Plus 10.2, and the results are analyzed. Compared with the conventional Brayton cycle and Rankine cycle, the two novel cycles bring 60.94% and 60% in exergy efficiency, respectively and 53.08% and 52.31% in thermal efficiency, respectively.

Bubble counter based on photoelectric technique for leakage detection of cryogenic valves

In order to overcome the inconvenience of manual bubble counting, a bubble counter based on photoelectric technique aiming for automatically detecting and measuring minute gas leakage of cryogenic valves is proposed. Experiments have been conducted on a self-built apparatus, testing the performance with different gas inlet strategies (bottom gas-inlet strategy and side gas-inlet strategy) and the influence of gas pipe length (0, 1, 2, 4, 6, 8, 10 m) and leakage rate (around 10, 20, 30, 40 bubbles/min) on first bubble time and bubble rate. A buffer of 110 cm3 is inserted between leakage source and gas pipe to simulate the down- stream cavum adjacent to the valve clack. Based on analyzing the experimental data, experiential parameters have also been summarized to guide leakage detection and measurement for engineering applications. A practical system has already been suc- cessfully applied in a cryogenic testing apparatus for cryogenic valves.

PH_3 monitoring in Arctic and Dalian bay areas

In this paper, we use pre-column 2 times low-temperature cryo-trap enrichment--gas chromatography（GC） /nitrogen and phosphorus detector（NPD）to detect and analyze phosphine in Arctic pole area for the first time. The results show phosphine exists in all of the samples in Arctic pole biosphere and phosphine concentration in Arctic atmosphere is between 18.54- 132.18 ng/m^3, almost the same as that in Antarctic atmosphere; phosphine concentration in Dalian bay sea surface sediments is between 116. 8- 554.3 ng/kg, almost the same as that reported in Jiao-zhou bay. Our research of phosphine will shed new light on the mechanisms showing how the phosphorus supplement influences the biogeochemical cycle and global warming.

Thermodynamic Analysis and Comparison on Low Temperature CO_2-NH_3 Cascade Refrigeration Cycle

This paper is focused on the cascade refrigeration cycle using natural refrigerant CO 2-NH 3. The properties of refrigerants CO 2 and NH 3 are introduced and analyzed.CO 2 has the advantage in low stage of cascade refrigeration cycle due to its good characteristics and properties. The thermodynamic analysis results of the CO 2-NH 3 cascade refrigeration cycle demonstrates that the cycle has an optimum condensation temperature of low stage and also has an optimum flow rate ratio.By comparing with the R13-R22 and NH 3-NH 3 cascade refrigeration cycles, the mass flow rate ratio of CO 2-NH 3 is larger than those of R13-R22 and NH 3-NH 3, the theoretical COP of CO 2-NH 3 cascade refrigeration cycle is larger than that of the R13-R22 cascade cycle and smaller than that of the NH 3-NH 3 cascade cycle. But the real COP of CO 2-NH 3 cascade cycle will be higher than those of R13-R22 and NH 3-NH 3 because the specific volume of CO 2 at low temperature does not change much and its dynamic viscosity is also small.

Spatio-temporal Analysis of Changes in Winter Wheat Cold Damage with Meteorological Elements in Huang-Huai-Hai Plain from 2011 to 2020

The Huang-Huai-Hai Plain is one of the typical agri-ecosystems in China,which suffers from cold damage frequently resulting in substantial economic losses.In order to monitor the changes in the occurrence of cold damage in an effective and large-scale manner,and to determine their meteorological causes,this paper collected low temperature data from the agricultural meteorological stations and remote sensing data of MODIS from 2005 to 2015,and constructed a monitoring model of cold damage to winter wheat in Huang-Huai-Hai Plain based on the Logistic regression model.This model was used to analyze the spatio-temporal changes of cold damage of winter wheat in Huang-Huai-Hai Plain from 2011 to 2020,and correlation analysis was performed with the spatio-temporal changes of meteorological factors to ascertain how they affect cold damage.The results show that the harm from cold damage in winter wheat has been gradually decreasing from 2011 to 2020,and the cold damage areas with high probability and high frequency are moving from north to south.The meteorological elements with the greatest impacts on the degree of cold damage from stronger to weaker are heat,precipitation and sunshine duration,whose influence has spatial variability.

Experimental study on a cryosurgery apparatus

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 ℃.