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31.
Chilled foods are stored for periods of between a few hours and many days in domestic refrigerators. However, there are little published data on the temperature performance of domestic refrigerators within the home. A survey has been taken in 252 households in the UK and some of the results are presented in this paper. The refrigerators investigated in the survey were found to have an overall mean temperature of approximately 6°C, which ranged from 11.4 to −0.9°C. Temperature ranges over the whole refrigerator varied from 4.5 to 30.5°C with 3.7% of the total being warmer than 20°C. On average 29.9% of refrigerators operated below 5°C and 66.7% operated below 7°C. Few refrigerators (7.3%) ran, on average, above 9°C. No refrigerator characteristic (apart from type) could be related to temperatures or temperature distribution in the refrigerators investigated. 相似文献
32.
The probability of contamination of domestic refrigerators seems to be greater for Salmonella, than other, distinctly psychrotolerant bacteria. This survey investigated Salmonella spp. contamination of domestic refrigerators in households (n = 100). The presence of Salmonella species was found in 13.95% of households that kept eggs in designated egg storage in refrigerators (n = 86). We identified 12 serotypes of Salmonella spp. with antimicrobial resistance, of which 50% were identified as S. Typhimurium. The results obtained confirm the need to strongly advise consumers how to properly arrange different foodstuffs inside household refrigerators. 相似文献
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34.
单级半导体制冷器设计中常用公式的推导 总被引:1,自引:0,他引:1
利用数学方法分析了半导体制冷器的最大制冷量、最大制冷温差和最大制冷系数,讨论了半导体制冷器工作电流和使用参数的关系,并归纳总结出一组公式,如最大制冷量工况I=αTc/R,U=αTb;最佳制冷效率工况I0=αΔT/R(M-1),U=αΔTM/M-1其中M=√1 0.5z(Th Tc)等.用该组公式对某制冷件进行计算,计算值与实测结果非常接近,说明公式的推导合理,可信度较高. 相似文献
35.
为研究气调冰箱(氧分压为18.0%~18.5%)对冷藏肉类的保鲜效果,选取雪花牛肉、三文鱼和金枪鱼3种高价值肉类,置于气调冰箱中冷藏。以普通冰箱作为对照,对贮藏期间肉类表层细胞形态、汁液流失率、挥发性盐基氮(total volatile basic nitrogen,TVB-N)含量、硫代巴比妥酸反应物(thiobarbituric acid reactive substances,TBARs)值和菌落总数等指标进行定期监测。结果表明:相较于普通冰箱,气调冰箱显著降低了雪花牛肉、三文鱼和金枪鱼贮藏过程中的汁液流失率、TVB-N含量、TBARs值和菌落总数,延缓了3 种肉类贮藏过程中品质的降低,表明相较于普通冰箱,气调冰箱对冷藏雪花牛肉、三文鱼和金枪鱼具有更好的保鲜效果。综合分析各项评价指标发现,在使用气调冰箱冷藏肉类过程中,雪花牛肉应选用TVB-N含量作为判断保质期的指标,而三文鱼和金枪鱼应选用菌落总数作为判断保质期的指标。 相似文献
36.
We present switching methods that make thermoelectric refrigerators efficient and optimal for all cold storage applications.
These temporal methods double the coefficient of performance (COPs) of the refrigerators during cooling transients and allow
highly energy-efficient operation in the steady state by turning off the thermoelectric devices both electrically and thermally
so as to avoid back-conduction of heat through the devices. We describe thermoelectric refrigerator cooling engines that attain
these enhancements without using any unreliable mechanically moving switching components such as pumps. These switching techniques
can provide a fivefold reduction in energy consumption of cold storage refrigerators. 相似文献
37.
H. Gurudath Nayak 《低温学》2009,49(7):350-359
There is a worldwide interest in the development of auto refrigerant cascade (ARC) refrigerators operating with refrigerant mixtures. Both flammable and non-flammable refrigerant mixtures can be used in these systems. The performance of an ARC system with optimum nitrogen-hydrocarbon and argon-hydrocarbon mixtures between 90 and 160 K is presented in this paper. 相似文献
38.
This paper presents the comparative performance analysis of the low GWP refrigerants HFO1234yf, HFO1234ze(E) and HC600a inside a commercial roll-bond evaporator for household refrigerators. The vaporisation performances were evaluated at two evaporation temperatures, −15 and −20 °C, and different refrigerant mass flow rates and compared with those of the traditional refrigerant for domestic refrigeration HFC134a. The performance analysis was carried out using both thermocouples installed on the rear side of the roll-bond evaporator and an IR thermo-camera. Each of the low GWP refrigerants tested can be considered a good substitute for HFC134a, provided that the compressor displacement is adjusted to deliver the proper refrigerant mass flow rate. Only HFO1234yf exhibits performance similar to HFC134a at the same mass flow rate, therefore it can be considered a direct drop-in substitute for HFC134a. 相似文献
39.
《低温学》2018
Nitrogen-hydrocarbon mixtures are widely used as refrigerants in J-T refrigerators operating with mixtures, as well as in natural gas liquefiers. The Peng-Robinson equation of state has traditionally been used to simulate the above cryogenic process. Multi parameter Helmholtz energy equations are now preferred for determining the properties of natural gas. They have, however, been used only to predict vapour-liquid equilibria, and not vapour-liquid-liquid equilibria that can occur in mixtures used in cryogenic mixed refrigerant processes. In this paper the vapour-liquid equilibrium of binary mixtures of nitrogen-methane, nitrogen-ethane, nitrogen-propane, nitrogen-isobutane and three component mixtures of nitrogen-methane-ethane and nitrogen-methane-propane have been studied with the Peng-Robinson and the Helmholtz energy equations of state of NIST REFPROP and compared with experimental data available in the literature. 相似文献
40.