Effect of precooling temperature on physiological quality of cold stored Agaricus bisporus

Effect of precooling temperatures(2℃,6℃,10℃and 14℃)on the physiological quality of postharvest Agaricus bisporus during cold storage was investigated.After six hours’precooling,Agaricus bisporus was stored at 3℃and sampled on day 3,6 and 9,respectively,for physiological quality analysis.Results showed that physiological quality of the Agaricus bisporus increased with the decrease of precooling temperature in the range of 2-14℃.Precooling at 2℃before cold storage had a positive impact on the storage quality of Agaricus bisporus.The decrease of hardness,whiteness and pH value was delayed,while the increase of cell membrane permeability and PPO and POD activities was restrained.Whiteness value of the Agaricus bisporus precooled at 2℃was above 80 on day 9,which means it was still acceptable,but the Agaricus bisporus precooled at 6℃and 10℃lost their commercial values.

Temperature Fluctuation of a Closed-Cycle Helium Joule-Thomson Cryocooler with Two-Stage Precooling

For quantum communications,single-photon detection,millimeter wave detection and other space projects,all of them need to work at liquid helium temperatures to achieve excellent performance.The closed-cycle helium Joule-Thomson cryocooler(JTC)is currently one of the mainstream solutions to realize the liquid helium temperature.While realizing the liquid helium temperature,the detector has strict requirements on the temperature fluctuation of the JTC,because the thermal noise caused by the JTC temperature fluctuation will have a critical impact on the detection performance.The typical closed-cycle helium JTC is precooling by a two-stage precooler.When the operating parameters of the JTC compressor remain unchanged,the change of the precooler is the main factor that affects the temperature fluctuation of the JTC.To explore the influence mechanism of JTC temperature fluctuations,experimental and theoretical studies are carried out.Based on the real gas equation of state,the influence of various parameters on the evaporator temperature fluctuations is explained.Research results show that the increase in temperature of each stage will cause the temperature of the JTC to increase.Especially,the change of the secondary precooling temperature(T_(pre2))has the most obvious influence on JTC temperature.Furthermore,the influence of the JT compressor’s buffer tank volume Vb on temperature fluctuation is studied.By increasing the Vb,the JTC temperature fluctuation caused by the temperature change of the precooler can be effectively reduced.

Thermodynamic Analysis and Optimization of the C3/MRC Liquefaction Process

In the natural gas liquefaction process,the mixed refrigerant natural gas liquefaction process is widely used in LNG liquefaction plants because of its advantages of low energy consumption.This paper focuses on the influences of important parameters in the C3/MRC liquefaction process,that is,the comparison between propane precooling temperature and the number of moles of methane in mixed refrigerant,power consumption and loss.In addition,the total process was optimized with the optimizer and manual adjustment in HYSYS software to minimize the total power consumption.The results show that with increasing propane precooling temperature,the propane flow rate is almost unchanged,while the mixed refrigerant flow rate decreases significantly,and the loss of the heat exchanger increases significantly.The power consumption of the propane precooling cycle and hybrid refrigeration cycle increases with increasing methane content in the refrigerant,so the power consumption of the whole process increases accordingly.The effect of the methane content in the mixed refrigerant on the process evaluation index is more significant than that of the propane precooling temperature.