乙炔吸收系统倒开车实现装置产品快速合格

中国石油吉林石化公司聚乙烯厂700kt/a乙烯装置老区采用溶剂吸收技术脱出乙炔精制乙烯工艺。多年来,乙炔吸收塔塔顶回流泵开车初期不上量问题一直制约着装置开车进度。经过摸索,技术人员尝试对开车流程进行调整,攻克了难题。文中对该装置具体的调整措施进行了阐述。     

蒸发式冷凝器结构特点及工程应用

本文对蒸发式冷凝器的结构、工作原理及安装、使用过程中应注意的问题作一下介绍.并结合工程实例,对蒸发式冷凝器和水冷式冷凝器作综合比较.     

Determination of heat transfer coefficients for cylindrical products exposed to forced-air cooling

An analytical model for estimation of transient heat transfer coefficients in forced-air precooling experiments of cylindrically shaped grapes, using a lumped capacitance approach were addressed and investigated. In order to determine transient heat transfer coefficients, the centre transient temperature measurements during forced-air precooling were used. Experiments involved cooling individual grapes in air flow without water losses. The individual grapes were instrumented with several interior thermocouples for measuring the centre transient temperature response during cooling. The transient values of the heat transfer coefficient history for five different air velocities were found to be about 21–40 W/m² K. These values were in good agreement with the values predicted using well-known Nusselt-Reynolds empirical correlation for forced convection. The present technique has the capability of determining transient heat transfer coefficients in a single transient experiment.     

启动时液氧泵损坏原因分析及预防

介绍液氧泵在试运行期间发生的损坏情况,分析后认为损坏原因是液氧泵预冷不彻底和发生汽蚀现象,总结了液氧泵的启动步骤和故障预防措施。     

预冷机组蒸发器堵塞的原因分析及处理

分析了预冷机组蒸发器堵塞的原因,介绍了处理措施。     

Hydrofluoroolefin-based mixed refrigerant for enhanced performance of hydrogen liquefaction process

Hydrogen has the highest gravimetric energy density of all fuels; however, it has a low volumetric energy density, unfavorable for storage and transportation. Hydrogen is usually liquefied to meet the bulk transportation needs. The exothermic interconversion of its spin isomers is an additional activity to an already energy-intensive process. The most significant temperature drop occurs in the precooling cycle (between ?150 °C and up to ?180 °C) and consumes more than 50% of the required energy. To reduce the energy consumption and improve the exergy efficiency of the hydrogen liquefaction process, a new high-boiling component, Hydrofluoroolefin (HFO-1234yf), is added to the precooled mixed refrigerant. As a result, the specific energy consumption of precooling cycle reduces by 41.8%, from 10.15 kWh/kg_LH2 to 5.90 kWh/kg_LH2, for the overall process. The exergy efficiency of the proposed case increases by 43.7%; however, the total equipment cost is also the highest. The inflated cost is primarily due to the added ortho-to-para hydrogen conversion reactor, boosting the para-hydrogen concentration. From the perspective of bulk storage and transportation of liquid hydrogen, the simplicity of design and low energy consumption build a convincing case for considering the commercialization of the process.     

移动式预冷设备在果蔬保鲜中的应用

本文讨论了发展移动式预冷设备的必要性,具体介绍了冰水预冷、注冰预冷、小型机械制冷冷库预冷、差压预冷、蓄冷板预冷、真空预冷、蒸发冷却预冷等实用的移动式预冷设备,指出移动式预冷设备在果蔬保鲜中具有广阔的应用前景。     

An exact heat transfer analysis of spherical products subjected to forced-air cooling

The thermal analysis of forced-air cooling processes being of primary concern, an experimental and analytical study program was undertaken to investigate the heat transfer during the cooling of figs as spherical food products. The process conditions were analysed according to a mathematical model to gain a better understanding of the product's behaviour. The heat transfer between the product and air was influenced by conduction inside the product, convection outside the product, radiation, respiratory heat rate (internal heat generation), and moisture evaporation at the surface of the product. These situations were considered as three cases, such as h = h_c, h = h_c + h_c, and h = h_c, + h_r + h_e. The four various air velocities of 1.1, 1.5, 1.75, and 2.5 m/s were applied in the experimental study. The results obtained by the mathematical model in the estimation of the heat transfer rates from the products were compared with the experimental data, and the best agreement was found for the third case (h = h_c + h_r + h_e). The fastest cooling was accomplished with the highest airflow velocity.     

The effect of hydrocooling on ripening related quality attributes and cell wall physicochemical properties of sweet cherry fruit (Prunus avium L.)

The aim of this study was to evaluate the effect of hydrocooling, as a precooling treatment, on ripening related parameters of two sweet cherry cultivars (Prunus avium L. cvs. ‘Tragana Edessis’, ‘Mpakirtzeika’) after 1-week cold storage (0 °C, 95% R.H.). Results indicated that hydrocooling delayed the deterioration and senescence of cherry fruit, maintaining a higher quality, as indicated by reduced stem browning and surface shrivelling. In particular, hydrocooled ‘Tragana Edessis’ fruit showed considerably less stem browning (14.6–29.6%), while the benefits of hydrocooling were less pronounced in ‘Mpakirtzeika’ fruit. Other quality attributes, such as cracking, decay, external color and soluble solids content were not affected by hydrocooling. Furthermore cell wall properties, as indicated by uronic acid and neutral sugars content in cell wall material extracted from the cherry fruits, were slightly or not affected by the hydrocooling process. Overall, the present study showed that cherry fruit subjected to hydrocooling followed by 1 week's storage at 0 °C and 95% R.H. retained their quality for a further 3 days at room temperature, but after 5 days at room temperature many of the fruit were of unacceptable quality.     

金属矿山深井高温巷道通风预冷降温技术

依据金属矿山井下巷道热交换的能量方程,分析了井下巷道的热交换基本规律,以及矿井通风风流预冷降温的理论依据,并通过冬瓜山铜矿实践证明,对巷道入风风温控制可提高井巷热交换效率,达到降温目的。