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排序方式: 共有75条查询结果,搜索用时 15 毫秒
1.
分析了几种超市制冷系统的特点,得出超市制冷系统应向着占地小,耗能少,对环境污染小的方向发展,采用自然制冷工质,不仅节约能源而且保护环境,是未来的发展方向。 相似文献
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The paper presents a model-based analysis on the energy saving potential of supermarket HVAC (heating, ventilating, and air-conditioning) and refrigeration systems using multiple subcoolers among the high-temperature HVAC system, the medium-temperature refrigeration system, and the low-temperature refrigeration system. The principle of energy reduction is to have the higher COP (coefficient of performance) system generate more cooling capacity to increase the cooling capacity or reduce the power consumption of the lower COP system. The subcooler could be placed between the medium-temperature and low-temperature systems, between the high-temperature and medium-temperature systems, and between the high-temperature and low-temperature systems. All integration scenarios of adding one, two and three subcoolers have been investigated. The energy saving potential varies with the load ratio between high-, medium- and low-temperature systems, COP of three systems, and the “on-off” duty time of HVAC system. The optimal sequence of adding subcoolers is also proposed. 相似文献
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Temperature ranges of the application of air-to-air heat recovery ventilator in supermarkets in winter, China 总被引:5,自引:0,他引:5
Energy consumption is an important issue in China. In heating, ventilation and air conditioning (HVAC) systems, more and more commercial buildings use air-to-air heat recovery ventilators as energy saving units for recovering heat from the exhaust air in ventilation systems in current years. In the present paper, critical temperatures of air-to-air heat recovery systems for supermarkets in winter are recommended and discussed for the four cities in different climate zones of China. The analysis shows that the temperature of fresh air in winter can be categorized into three regions, i.e., recovery region, transition region and impermissible recovery region. The results also indicate that the latent heat recovery is not suitable for ventilation energy savings in supermarkets in winter. Meanwhile, the applicability of sensible heat recovery in supermarkets depends on outdoor climate and fresh air flow rate. If a variable rotational speed fan is used to introduce fresh air into the building, heat recovery does always function as planned in winter for all the selected cities except Guangzhou, and most values of the COP are much higher than 2.5. Otherwise, there is the risk of negative impact on building energy savings in all cities except Harbin. 相似文献
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Schwaiger K Helmke K Hölzel CS Bauer J 《International journal of food microbiology》2011,148(3):191-196
The aim of this study was to elucidate whether and to what extent fresh produce from Germany plays a role as a carrier and reservoir of antibiotic resistant bacteria. For this purpose, 1001 vegetables (fruit, root, bulbous vegetables, salads and cereals) were collected from 13 farms and 11 supermarkets in Germany and examined bacteriologically. Phenotypic resistance of Enterobacter cloacae (n = 172); Enterobacter gergoviae (n = 92); Pantoea agglomerans (n = 96); Pseudomonas aeruginosa (n = 295); Pseudomonas putida (n = 106) and Enterococcus faecalis (n = 100) against up to 30 antibiotics was determined by using the microdilution method. Resistance to ß-lactams was most frequently expressed by P. agglomerans and E. gergoviae against cefaclor (41% and 29%). Relatively high resistance rates were also observed for doxycycline (23%), erythromycin (21%) and rifampicin (65%) in E. faecalis, for spectinomycin (28%) and mezlocillin (12%) in E. cloacae, as well as for streptomycin (19%) in P. putida. In P. aeruginosa, relatively low resistance rates were observed for the aminoglycosides amikacin, apramicin, gentamicin, neomycin, netilmicin and tobramycin (< 4%); 11% was resistant to streptomycin. No glycopeptide-resistant enterococci were observed. Resistance rates of bacteria isolated from farm samples were higher than those of the retail markets whenever significant differences were observed. This suggests that expressing resistance is at the expense of bacterial viability, since vegetables purchased directly at the farm are probably fresher than at the supermarket, and they have not been exposed to stress factors. However, this should not keep the customer from buying directly at the farm, since the overall resistance rates were not higher than observed in bacteria from human or animal origin. Instead, peeling or washing vegetables before eating them raw is highly recommended, since it reduces not only the risk of contact with pathogens, but also that of ingesting and spreading antibiotic resistant bacteria. 相似文献
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Trogoderma granarium Everts, khapra beetle, and Trogoderma inclusum LeConte, larger cabinet beetle, are highly destructive insect species that can infest a variety of food sources. Methoprene is an insect growth regulator, IGR, and recently has been incorporated into packaging materials as a treatment option for packaged grain, food, birdseed, and feed products, and labeled for this use by the US Environmental Protection Agency. The objective of this research was to investigate the effect of continual exposure to this novel packaging technology on the development of T. inclusum and T. granarium larvae, and its potential use as a packaging treatment to prevent the penetration or invasion of T. inclusum and T. granarium into food packages. The methoprene-treated packaging incorporated into Kraft paper, woven bag material, polyethylene-polyethylene (PE-PE) material, and a polyethylene terephthalate-polyethylene (PET-PE) material, reduced normal adult emergence of exposed larvae. No normal adult emergence was observed on the inside surface of the PET-PE material. The polymer-based materials were the most effective at preventing penetration or invasion by Trogoderma spp. Only 2% of packages were invaded among all packaging treatment combinations compared to 16.7% invasion of untreated packages. The materials were ranked in effectiveness as Kraft < woven < PET-PE < PE-PE, however, all materials demonstrated significant positive results on Trogoderma spp. This novel packaging could easily be adopted as a packaging control strategy against these and other stored product insects in packaged products destined for commercial, international, and smallholder farm storage of cereal grains, feed, and other food products. 相似文献
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Improvement of air distribution in refrigerated vertical open front remote supermarket display cases
I. Gray P. Luscombe L. McLean C.S.P. Sarathy P. Sheahen K. Srinivasan 《International Journal of Refrigeration》2008,31(5):902-910
This paper presents some of the results derived from extensive experimentation on display cases for supermarkets and derives some possible improvements to augment temperature uniformity and energy performance. The effect of the perforation pattern of the rear duct on the distribution of airflow between these and the front curtain is brought out. The critical component is air infiltration across the curtain, which is governed by internal air distribution and curtain characteristics. It is observed that a 70–30 distribution of flow between the curtain and the rear duct perforations yields a performance that satisfies the standards. Further, a judicious distribution of perforations on the rear duct at various levels and across is necessary. Correlations available in the literature are useful in making a qualitative assessment of the results. 相似文献