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• When the heating temperature is increased from 65.0 °C to 85.0 °C, the complete melting time is reduced by 56.0%. • When the cooling temperature is reduced from 30.0 °C to 10.0 °C, the full solidification time is shortened by 40.0%. • Increasing the temperature difference between the PCM and the heating/cooling fluid can enhance the temperature response rate but weaken the temperature uniformity in the PCM region. Solar energy has addressed the significant issue of energy conservation and emission reduction through providing an alternative solution to the building energy utilization. To solve the inherent intermittency problem, latent heat phase change module is designed to even the fluctuation of energy supply. This paper designs a phase change heat storage/release unit and builds a visual test system for phase change heat storage/release. To study the influence of different heating and cooling temperatures upon thermal cycle of melting and solidification, a series of experiments are carried out. Melting front evolution, temperature field and response, and uniformity analysis are assessed. Experimental results demonstrate that the phase interface changes from top to bottom in the melting process. However, solidified covers appear evenly up and down during solidification process. Reasonably increasing the heating temperature effectively shortens the complete melting time. 56.0% reduction in full melting time is achieved if increasing the heating temperature from 65 °C to 85 °C. However, this is done at the expense of decreasing the temperature uniformity of the PCM. The results proved guidance for the design strategy on passive building energy utilization. [ABSTRACT FROM AUTHOR]

Heat loss from the shell of a rotary kiln accounts for a certain proportion of total energy consumption. In order to reduce heat loss, a practical heat recovery system with nine heat exchangers is proposed to preheat water in this paper. We first propose a mathematic model to analyze the shell temperatures and heat loss rates of several regions on rotary kilns. Integration of theoretical analyses and experimental measurements yields the temperatures and heat transfer rates of heat exchangers, i.e. the design requirements of the nine heat exchangers in the practical system. Secondly, an optimization model is formed to describe the relation between design parameters, i.e. heat transfer area and mass flow rate of each heat exchanger, and system requirements without introducing any intermediate temperatures. With the aid of the Lagrange multiplier method, the optimal design parameters are obtained. Finally, an optimization case of the practical system is studied. The results show that the heat recovery system should meet the requirements of chemical reactions in rotary kilns and mechanical characteristic of shell. The required total heat transfer area of the system after optimization is reduced by 15.6% compared to the value before optimization. As the total mass flow rate increase and inlet temperature decreases, the required heat transfer area decreases while the mass flow distribution ratios remains unchanged. [ABSTRACT FROM AUTHOR]

Abstract: The rapidly growing of data center energy consumption rates are contributing to concern about energy conservation. Reasonable airflow organization is an effective way to reduce the cooling system energy consumption and to upgrade the energy utilization efficiency. Comprehensive and accurate analyses are important for airflow organization optimization. This paper presents the entransy dissipation analysis method to analyze the influences of hot and cold air mixing and cooling air distributions on data center heat transfer process. The thermal resistance based on entransy dissipation is used to define three indexes to evaluate hot and cold air mixing, cooling air distributions and the integrated heat transfer performance. A sample data center is studied with the analytical results showing that the smaller the entransy-dissipation-based thermal resistance is, the lower the average heat source temperature will be. Thus, the minimum thermal resistance principle is applicable to the analysis and optimization of data center heat transfer process. The three indexes can be used to guide the improvement and optimization of airflow organization. [Copyright &y& Elsevier]