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Summary This paper deals with the modeling, thermodynamic analysis and comparison of irreversibility in two configurations of the double generator absorption chiller. First a computer simulation model is developed for each configuration on the basis of mass and energy balances. Simulation results were then used to analyse the entropy generation and irreversibility (or exergy destruction) of each component. It is found that the parallel flow configuration is more powerful than the serie flow configuration. Exergy losses in the parallel flow configuration are lower than that of the serie flow. The results indicate that the absorber and the solution heat exchangers have the most potential to improve the chiller energy efficiency. Also they indicate that focusing on irreversibility is more direct way of analysing the potential for improving the efficiency of ammonia-water absorption chiller.

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Abstract  

A new method is presented to analyze the irreversible melting kinetics of polymer crystals with a temperature modulated differential scanning calorimetry (TMDSC). The method is based on an expression of the apparent heat capacity,
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\Delta \tilde C{e}^{---{i\alpha }} = mc_p + i(1/{\omega }F'_{T}$$ \end{document}
, with the true heat capacity, mcp, and the response of the kinetics,
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$F'_{\text{T}}$$ \end{document}
. The present paper experimentally examines the irreversible melting of nylon 6 crystals on heating. The real and imaginary parts of the apparent heat capacity showed a strong dependence on frequency and heating rate during the melting process. The dependence and the Cole-Cole plot could be fitted by the frequency response function of Debye's type with a characteristic time depending on heating rate. The characteristic time represents the time required for the melting of small crystallites which form the aggregates of polymer crystals. The heating rate dependence of the characteristic time differentiates the superheating dependence of the melting rate. Taking account of the relatively insensitive nature of crystallization to temperature modulation, it is argued that the ‘reversing’ heat flow extrapolated to ω → 0 is related to the endothermic heat flow of melting and the corresponding ‘non-reversing’ heat flow represents the exothermic heat flow of re-crystallization and re-organization. The extrapolated ‘reversing’ and ‘non-reversing’ heat flow indicates the melting and re-crystallization and/or re-organization of nylon 6 crystals at much lower temperature than the melting peak seen in the total heat flow.
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Abstract  

Reversible and irreversible crystallization and melting of high-density polyethylene at low temperature has been re-evaluated and is discussed in terms of the concept of the specific reversibility of a crystal. The concept of the specific reversibility links reversible and irreversible melting of a specific crystal such that reversible melting occurs only at slightly lower temperature than irreversible melting. In this study evidence for irreversible crystallization at low temperature in high-density polyethylene is provided, non-avoidable by primary crystallization and extended annealing at high temperature. The simultaneously observed reversible crystallization and melting at low temperature can be attributed to lateral-crystal-surface activity in addition to the well-established reversible fold-surface melting, dominant at high temperature, and evidenced by small-angle X-ray data available in the literature.

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242 158 171 Cannon R, Ellis S, Hayes D, Narayanan G, Martin RCG: Safety and early efficacy of irreversible electroporation for hepatic tumors in

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Abstract  

New approaches to the analysis of differential scanning calorimetry (DSC) data relating to proteins undergoing irreversible thermal denaturation have been demonstrated. The experimental approaches include obtaining a set of DSC curves at various scanning rates and protein concentrations, and also reheating experiments. The mathematical methods of analysis include construction of a linear anamorphosis and simultaneous fitting of a theoretical expression for the dependence of the excess heat capacity on temperature to a set of experimental DSC curves. Different kinetic models are discussed: the one-step irreversible model, the model including two consecutive irreversible steps, the Lumry and Eyring model with a fast equilibrating first step, and the whole kinetic Lumry and Eyring model.

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Summary We assessed the applicability of the extrapolation procedure at infinite scanning rate to differential scanning calorimetry (DSC) data related to irreversible protein unfolding. To this aim, an array of DSC curves have been simulated on the basis of the Lumry-Eyring model N↔U→F. The results obtained confirmed that when the apparent equilibrium constant K app (T=T1/2) is lower than 3, the application of the extrapolation procedure provides accurate thermodynamic parameters. Although this procedure applies only to monomeric proteins for which the Lumry-Eyring model is a reasonable approximation, it will hopefully contribute to increase the potential of DSC in obtaining reliable thermodynamic information regarding the folding/unfolding equilibrium.

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Journal of Thermal Analysis and Calorimetry
Authors: Zhongliang Zhang, Fuming Liu, Manhong Liu, Zhenzhen Wang, Faping Zhong, and Feng Wu

Abstract  

Calorimetric measurements were carried out on the electrorefining of copper using different current densities with a Calvet type microcalorimeter at room temperature. The ratio (R) of the measured heat (Q m orW m) to the input electric energy (Q in orW in) and the excess heat (Q ex orW ex), i.e. the difference betweenQ m (orW m) andQ in (orW in) during the electrorefining process were discussed in terms of general thermodynamics. It was found thatR andQ ex were related to the current density employed in the experiment and varied as a logarithmic function. The results obtained here indicate that the heat generation under different conditions, such as different currents or voltages, may be caused partially by the irreversibility of the process or by some unknown processes.

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Abstract  

In this work some calorimetric measurements were also carried out on the electrorefining silver by using different current densities with a Calvet type microcalorimeter at room temperature. The ratio (R) of the measured heat (

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m) to the input electric energy (
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in) and the excess heat (
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ex), i.e., difference between
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m and
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in during the electrorefining process, were discussed in terms of general thermodynamics. It was found that the R and
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ex for silver were related with the current density or cell voltage employed in the experiment. The results obtained here also indicate that the heat generation under different conditions, such as different currents or voltages may be caused partially by the irreversibility of the process or by some unknown processes.

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41 113 131 Pennings, E. (2004): Optimal Pricing and Quality Choice when Investment in Quality is Irreversible. Journal of Industrial Economics , 52

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rates. A maximum limiting value of the flow was thus established, above which further increase in the flow rate has no effect. Under these conditions the reaction 2 can be assumed as irreversible. Conversion of phthalic anhydride was calculated

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