使用步进马达制冷控制阀费用的直接和间接节约

在空调和制冷行业追求更高效率和使用不同制冷剂时,各类电子控制器和电动阀正前所未有地大量使用.电动阀几乎可以在制冷系统中任何一个地方使用,而并不局限于膨胀阀.直接费用的节约,通常是由于电动阀根据冷凝压力和回气压力变化作出调整来实现的.间接费用的节约,通常是通过冷柜空间内温度的稳定,增加食品的寿命来获得的.     

USE OF ABLATION TO DETERMINE THE CONVECTIVE HEAT TRANSFER COEFFICIENT IN TWO-PHASE FLOW

The fluid to particle convective heat transfer coefficient (h_fp) is an essential design parameter in the development of an aseptic processing system. The convective heat transfer coefficient was determined using a new method based on ablation heat transfer. The amount of solid lost (ablated) was shown to be directly proportional to the energy flux across the fluid‐solid interface with the constant of proportionality being h_fp. Change in mass of an ice sphere was used as an ablation probe to study h_fp in straight, round conduit. Values of h_fp ranged from 1,369 to 2,749 W/m²K over a Reynolds number range of 2,766 to 17,081.     

Electron spin resonance spectra of γ-irradiated citrus fruit skins, skin components and stalks

The ESR spectra of the stalks and skins of a number of non-irradiated and γ-irradiated citrus fruits suggest that ESR spectroscopy could be used to establish the irradiation history. Two major spectral changes occur up on irradiation. Two additional features appear and are only observed in irradiated specimens (Features B and D, the latter separated by c. 5.9mT) and these are accompanied by an increase in the intensity of the main central signal (Feature A). Observations on the stability of Features A and D indicate that they arise from different radicals. Experiments on the meso- and exo-carps indicate that Features B and D are located mainly in the former and Feature A mainly in the latter.     

Microorganisms Isolated from Surimi Processing Operations

Heterotrophic bacteria isolated from two shore-based surimi processing plants in Alaska were identified to the genus level. In one plant, the major bacterial constituents were Flavobacterium and Pseudomonas, followed by Moraxella, Aeromonas, Lactobacillus, Serratia, and Acinetobacter. In the other plant, major bacterial groups were Flavobacterium and Arthrobacter/Corynebacterium, followed by Pseudomonas and Acinetobacter. Pseudomonas, Aeromonas, and Serratia were capable of rapid growth as low as 8°C, with respective generation times 3.0, 3.1, and 3.6 hours. Freezing and thawing of surimi reduced microbial counts to 45–67% of the pre-frozen load; however, the composition of the microbial flora was maintained. The plant environment was a potential source of microbial contamination.     

PINK SALMON (ONCORHYNCHUS GORBUSCHA) QUALITY DURING ICE AND CHILLED SEAWATER STORAGE

Pink salmon were stored up to ten days in ice, chilled seawater (CSW), transferred from ice to CSW and from CSW to ice, and evaluated by chemical, physical, microbiological, and sensory methods. The sensory quality of CSW-held fish declined at a faster rate than for iced fish. CSW-held fish had higher weight gain, higher salt and hypoxanthine levels and had softer texture than iced fish. Microbial counts were highest for iced fish and a two-log increase occurred during storage. Moraxella species were predominant in the microbial flora of iced fish whereas Pseudomonas species were predominant in the microbial flora of CSW-held fish. Ice was superior to CSW for maintaining salmon quality.     

Effects of Cooking in Solutions of Varying pH on the Dietary Fiber Components of Vegetables

To study the effect of pH on dietary fiber components of vegetables, beans, cauliflower, potatoes, peas and corn were cooked in buffers of pH 2, 4, 6, and 10. Water-soluble pectin and hemicellulose, water-insoluble pectin and hemicellulose, cellulose and lignin were quantitated in raw, cooked vegetables and cooking medium. Tenderness and pH of raw and cooked vegetables were determined. Texture varied with cooking medium. Cooked vegetables were most firm at pH 4 and softest at pH 10. Dietary components found in cooking medium reflected these textural changes. Vegetables which showed greater pH effects exhibited greater changes in fiber components.     

Microorganisms on Commercially Processed Alaskan Finfish

Whole and processed Alaskan fish were examined for aerobic plate counts, total coliforms, and Escherichia coli. Washing whole salmon and halibut reduced skin microbial counts from 10³/cm² to 10²/cm². Whole and dressed fish had coliform counts less than 13/cm² and E. coli counts less than 0.3/cm². Alaska pollock and Pacific cod fillets had microbial counts between 10³/g and 10⁶/g, coliform counts less than 70/g, and E. coli counts less than 4/g. Whole fish contained microbial flora predominated by Moraxella species whereas dressed fish and fillets had microbial flora consisting of Arthrobacter/Corynebacterium, Flavobacterium, and Pseudomonas species. Microorganisms on conveyor belts and other contact surfaces may have contributed contaminants to fillets.     

Effects of pH on Calcium, Zinc, and Phytate Solubilities and Complexes Following In Vitro Digestions of Soy Protein Isolate

High intraluminal gastric pH values in young infants could affect the bioavailability of zinc in soy protein isolate formula. This investigation examined the effects of pH on the solubilities and complexes of calcium, zinc and phytate following in vitro pepsin and pepsin-pan-creatin digestions of soy protein isolate. The results of these in vitro studies suggested that (1) high intraluminal gastric pH values could lead to the formation of insoluble calcium-zinc-phytate complexes in the stomach following ingestion of soy protein isolate and (2) high intraluminal gastric pH values would only affect resultant soy zinc solubility in the small intestine in the absence of exogenous calcium or zinc but not in the presence of same.     

Theory of Fatigue for Brittle Flaws Originating from Residual Stress Concentrations

A theory is formulated for the general fatigue response of brittle flaws which experience residual stress concentrations. The indentation crack is taken as a model flaw system for the purpose of setting up the basic fracture mechanics equations, but the essential results are expected to have a wider range of applicability in the strength characterization of ceramics. A starting fatigue differential equation is first set up by combining an appropriate stress intensity factor for point- or line-contact flaws with a power-law crack velocity function. Analytical solutions are then obtained for the case of static fatigue. The resulting relation between lifetime and failure stress is shown to have exactly the same power-law form as the conventional solution for Griffith (residual-stress-free) flaws. This "equivalence" is used as a basis for extending the results to dynamic fatigue. A comparison of these analytical solutions with numerical counterparts defines the limits of accuracy of the theoretical procedure. However, while the form of the lifetime relation remains invariant, the values of the exponent and coefficient differ significantly for flaws with and without residual stress. Accordingly, the application of conventional fatigue theory to evaluate crack velocity parameters, without due regard for the nature of the critical flaw, can lead to serious errors. Explicit conversion formulas are given for transforming "apparent" velocity parameters for indentation flaws directly into "true" parameters. The implications of these results concerning the use of the indentation method for materials evaluation are discussed.