Flow boiling data and prediction method for enhanced boiling tubes and tube bundles with R-134a and R-236fa including a comparison with falling film evaporation

New enhanced boiling tubes from Wolverine Tube Inc. (Turbo-B5) and Wieland-Werke AG (Gewa-B5) were investigated using R-134a and R-236fa as test fluids. The tests were done at saturation temperatures of 5 and 15 °C, mass flow rates from 4 to 35 kg m⁻² s⁻¹ and heat fluxes from 15 to 70 kW m⁻². A new prediction method based on a theoretical analysis of thin film evaporation was used to propose a new correlating parameter. A large new database of local heat transfer coefficients was obtained and utilized to generate an improved prediction method for bundle boiling and the onset of dryout. Onset of dryout and the simultaneous reduction in heat transfer performance occurred at very high vapour quality on these enhanced tubes in convective bundle boiling. Furthermore, a direct comparison was made between the tubes operating in falling film and convective bundle boiling modes.     

Chilling and freezing fishery products: changes in views and usages

Some of the main criteria used in the assessment of quality of fish and fish products are discussed. Objective and subjective tests are contrasted. Various methods of shipboard preservation are reviewed, including chilling and deep chilling and freezing. The significance of TTT and PPP studies are stressed.     

Crack growth predictions using a strip‐yield model for variable‐amplitude and spectrum loading

Fatigue‐crack‐growth tests were conducted on compact, C(T), specimens made of D16Cz aluminum alloy. Constant‐amplitude tests were conducted over a range of stress ratios (R = P_min/P_max = 0.1 to 0.75). Comparisons were made between test data from middle‐crack tension, M(T), specimens from the literature and C(T) specimens. A crack‐closure analysis was used to collapse the rate data from both specimen types into a fairly narrow band over many orders of magnitude in rates using proper constraint factors. Constraint factors were established from single‐spike overload and constant‐amplitude tests. The life‐prediction code, FASTRAN, which is based on the strip‐yield‐model concept, was used to calculate the crack‐length‐against‐cycles under constant‐amplitude (CA) loading and the single‐spike overload (OL) tests; and to predict crack growth under variable‐amplitude (VA) loading on M(T) specimens and simulated aircraft loading spectrum tests on both specimen types. The calculated crack‐growth lives under CA and the OL tests were generally within ±20 % of the test results, the predicted crack‐growth lives for the VA and Mini‐Falstaff tests on the M(T) specimens were short by 30 to 45 %, while the Mini‐Falstaff+ results on the C(T) specimens were within 10 %. Issues on the crack‐starter notch effects under spectrum loading are discussed, and recommendations are suggested on avoiding these notch effects.     

A generalized analysis for cascading single fluid vapor compression refrigeration cycles using an entropy generation minimization method

This paper focuses on cascading an ideal vapor compression cycle and determining the optimal intermediate temperatures based on the entropy generation minimization method. Only superheating and throttle losses of the cycle are considered since they are inherent to the ideal vapor compression refrigeration cycle. The second law equations have been developed in terms of specific heats and temperature ratios with the intent of reducing involved property modeling. Also the entropy generation was expressed in terms of a single independent variable and minimized to develop an advanced rule for selecting optimum intermediate temperatures. Results for a cascade system operating between reduced temperatures of 0.684 and 0.981 with R-134a as the working fluid are presented. The approximate method presented here predicted the optimum intermediate reduced temperature for a two-stage system to be 0.88, a difference of 2% from the optimum. The method presented was a much better predictor of the optimum temperature than the geometric mean method which was 0.82, a difference of 5% from the optimum. The entropy generation distribution of the optimum solution was investigated. For a two-stage system, the lower stage and higher stage entropy generation was 44% and 56%, respectively. In comparison to the single stage, the two-stage reduced losses by 78%.     

Acceptability of frozen stored consumer fish products

Wide range testing is reported of customer acceptability of various fish products after varying periods of frozen storage at −18°C. Four products of cod, breaded fillets, glazed fillets, fillet fingers and minced fingers, were tested by trained assessors and by groups of students in Colleges of Home Economics after storage periods of up to one year. Some trends were apparent, but in general the acceptability to the consumers remained essentially unchanged even after 1 year at −18°C.     

平遥县尹回水库工程存在问题及处理措施

文中根据尹回水库工程存在问题，分析了水库工程除险加固改造的必要性，提出了水库除险加固工程措施。     

Refrigeration and the world's food supply — especially in developing countries

The reason for starvation today is poverty. Refrigeration can help the developing countries to export high value products. This helps to improve the economical situation and their buying power. Refrigeration can also help to reduce waste. Primitive distribution systems using refrigeration can be used at an early stage but the infrastructure is the limiting factor for introduction of modern transport equipment. Appropriate refrigeration technology is required, and the IIR should promote this by, for example, introducing an award for good proposals.     

Heritage values and functions of wetlands in Southern Mexico

There is a wealth of heritage values and contemporary functions of freshwater and estuarine wetlands along the coast of the Yucatan Peninsula in Mexico and northern Belize. These vary from ancient Maya use for multicropping and aquaculture to current use for fishing, hunting, freshwater supplies, salt extraction and nature tourism. Potential conflicts and collaborations will be discussed with reference to proposed restoration of ancient Maya water management systems combined with modern technologies. Particular attention will be paid to wetland use, which combines both traditional and “new” uses including partial restoration, agro-ecology and ecotourism.