The effect of home storage conditions and packaging materials on the quality of frozen green beans

Home storage is the final step of the frozen foods distribution chain, and little is known on how it affects the products quality. The present research describes frozen green beans (Phaseolus vulgaris, L.) quality retention profile during the recommended ‘star marking’ system dates, at the storage temperatures of +5, −6, −12 and −18 °C (along 1, 4, 14 and 60 days, respectively).

The quality profile was assessed by a simulation system. Simulations were set by a response surface methodology to access the effect of different packaging materials (thermal conductivities and thickness), surface heat transfer coefficient, and refrigerator dynamics (effect of refrigeration cycles at the different storage temperatures) on the average retentions of Ascorbic Acid, total vitamin C, colour and flavour.

Green beans quality losses along frozen storage are significantly influenced by temperature, refrigerator dynamics and kinetic properties. Quality is also highly dependent on packaging materials thermal insulation (e.g. at temperatures above the melting point). Temperature cycles inside frozen chambers have a long term effect, and at the higher storage temperatures (e.g. T>−6 °C) are detrimental to frozen green beans quality after shorter periods.     

Numerical analysis of two-dimensional steady-state and transient heat transfer in a parallel duct filled with pressurized He II

Analysis on steady-state and transient heat transfer on a flat plate at the middle of a parallel duct immersed in He II was performed for bath temperatures from 1.8 to 2.1 K at 101.3 kPa. Two-dimensional computer code named SUPER-2D developed by the authors based on the two-fluid model and the theory of mutual friction was used. Steady-state critical heat flux (CHF) and the time lag from the application of a step heat input to λ transition, that is called a lifetime, were obtained numerically for various step heat fluxes and for the channel gaps from 2 to 20 mm. Effect of the gap restriction on the CHF and the lifetime were clarified. The solutions were compared with the experimental data for the ducts with the same structures and the corresponding conditions. They agreed well with the experimental data. The heat transport mechanism in the parallel duct was clarified.     

Critical heat flux on a flat plate heater located at the middle of a duct in forced flow of pressurized He II

Critical heat fluxes (CHFs) were measured for two types of rectangular ducts containing horizontal flat plate heaters. One has the flat plate heater of 6 mm wide and 20 mm long located on the inner lower wall at 50 mm from the inlet. The other duct has two horizontal flat plates of 6 mm wide and 20 mm long on inner upper and lower walls at 50 mm from the inlet. The equation of CHF for the forced convection containing a new nondimensional-parameter m introduced in order to calculate cross-sectionally averaged liquid temperature at the center of the duct was derived based on two fluid model, ordinary convection theorem and experimental results. It was confirmed that this correlation can describe not only the author's data on the duct but also other worker's data for channels with different shapes and sizes.     

The Difference in Turbulent Diffusion between the Active and Passive Scalars in a Thermally Stably Stratified Medium

The difference in the turbulent diffusion between the active (heat) and passive (mass) scalars in a thermally stably stratified medium is investigated. The axisymmetric problem is treated on the formation of a turbulent circulation flow above a heated disk and on the turbulent diffusion of a passive scalar (impurity) from a continuous surface source in a stably stratified medium. The results indicate that the thermal stratification causes appreciable differences in the coefficients of turbulent transfer between the active (heat) and passive (mass) scalars. This means that the assumption of the identity of the coefficient of turbulent diffusion of heat and mass, employed in conventional models of turbulence, produces significant errors in estimating the heat and mass transfer in a thermally stably stratified medium.     

Transfer formalisms

We discuss some different ideas about the sort of formalism appropriate for translation (more specifically, transfer) that have been explored within Eurotra. The intention is not to evaluate these different ideas, but to outline the issues of general interest and relevance that they raise. Section 1 describes some common assumptions, section 2 describes the different ways they have been interpreted, and section 3 considers some further implications.     

Development of a Ceramic Micro Heat Exchanger – Design,Construction, and Testing

This article presents the development of a ceramic micro heat exchanger. Starting from its geometrical design, results obtained from a simplified simulation of the heat exchanger efficiency will be given. The alumina microcomponents were manufactured by a rapid prototyping process chain. Here, stereolithography was combined with a low‐pressure injection molding process for the rapid and precise manufacturing of ceramic components down to the micrometer range. A micro heat exchanger, joined from sintered components using a glass solder, was applied as a prototype and checked for its performance at a system pressure of 8 bar.     

Context-gated knowledge partitioning in categorization.

According to the knowledge partitioning framework, people sometimes master complex tasks by creating multiple independent parcels of partial knowledge. Research has shown that knowledge parcels may contain mutually contradictory information, and that each parcel may be used without regard to knowledge that is demonstrably present in other parcels. This article reports 4 experiments that investigated knowledge partitioning in categorization. When component boundaries of a complex categorization were identified by a context cue, a significant proportion of participants learned partial and independent categorization strategies that were chosen on the basis of context. For those participants, a strategy used in one context was unaffected by knowledge demonstrably present in other contexts, suggesting that knowledge partitioning in categorization can be complete. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Linear predictive transform of monochrome images

Digital monochromatic images are encoded using a novel minimum mean square error (MSE) linear predictive transform (LPT) coding formulation. The new formulation is appealing for two important reasons. First, it leads to simple coder implementation with a satisfactory signal-to-noise ratio (SNR). Second, it provides a general theoretical framework from which minimum MSE predictive coding and minimum MSE transform coding arise as special cases. Some specific results of this paper that illustrate the previous ideas are: a simple and generally suboptimum two-dimensional LPT coder operating at 2 bit pixer⁻¹ has approximately one third the complexity of a 4 × 4 Hadamard coder while yielding a better SNR; an optimum 2D LPT coder operating at 2 bit pixer⁻¹ has approximately one sixth the complexity of a 4 × 4 Karhunen-Loeve transform (KLT) coder while yielding a better SNR.     

Performance of unitary heat pumps: review of ASHRAE Symposium session

1. 1. System design optimization and validation for single-speed heat pump by S.K. Fischer and C.K. Rice, Oak Ridge National Laboratories.

2. 2. Analysis of on/off cycling for an air-to-air heat pump operating in the heating mode by W.A. Miller, Oak Ridge National Laboratories.

3. 3. Field measured cycling, frosting and defrosting losses for a high efficiency air source heat pump by V.D. Baxter and J.C. Moyers, Oak Ridge National Laboratories.

4. 4. Design and available energy analysis of a heating-only residential heat pump for the Western Pacific Northwest by D.E. Elger, C.M. Reistad and S. Lang, Oregon State University.

5. 5. A study of heat pump service life by Nance C. Lovvorn, Alabama Power Company and Carl C. Hiller, Electric Power Research.

垂直管吸收器内泡式吸收过程的数值研究

建立垂直管吸收器管内泡式吸收过程中传热传质的数学物理模型，对其泡式吸收过程进行数值研究，获得泡式吸收方式的一些传热传质特性，为吸收器的优化设计提供一定理论指导。