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Abstract: In air-conditioning field, a dehumidification has become increasingly important for human health and comfort especially in hot and humid climates. However, a conventional mechanical dehumidification with a vapor compression refrigerator has some problems. Therefore, much attention has been paid recently to a desiccant air-conditioning system as an alternative to the conventional system. In this paper, we focus on a rotary desiccant wheel which is the main component of the desiccant air-conditioning system and develop and validate the mathematical model by comparison with experimental results. The validation is conducted under various operating conditions. The mathematical model discussed in this paper includes, for example, the entrance region effect in air channel, detailed diffusion phenomenon in porous solid. In experiments, effects of the regeneration air temperature, air superficial velocity, wheel thickness and wheel rotational speed on the desiccant wheel performance are investigated. In addition, the temperature and humidity distribution at the outlet of the desiccant wheel are measured. As a result, an average relative error between the predicted and the measured humidity ratio difference distribution is 3.3% and temperature difference distribution 10.8%. Moreover, the effect of the regeneration air inlet temperature, the air superficial velocity, wheel thickness and wheel rotational speed on the desiccant wheel performance are clarified and the predicted results are totally in good agreement with the measured results. [Copyright &y& Elsevier]

Abstract: Gas diffusivity in snow and firn is a basic transport parameter that is important for snow-air exchange processes and for ice core interpretation of past atmospheric composition. Firn is snow that is more than one year old, and it exists over many thousands of kilometers of the polar ice sheets, comprising approximately the upper 60–120m of the ice sheet. Because use of firn air for climate and environmental investigations is a relatively new science, and because of the difficulties in working with firn as a temperature-dependent porous material, few direct measurements of the gas diffusivity through the firn column have been made. This paper describes the development, testing, validation, and initial use of a diffusion chamber specifically designed to measure inert gas diffusivity on firn cores. A brief review of previous methods for determining gas diffusivity for various porous media is discussed. The new technique and apparatus are described. Results of validation of the technique on multiple sizes of glass beads are presented, including comparison to experimental and theoretical results from the literature. After this verification, initial results obtained from using the technique to measure the SF6 gas diffusivity of firn samples from Summit, Greenland are presented; results ranged from 0.005cm2/s to 0.033cm2/s. This set of measurements is compared to the diffusivity of other natural porous media and also to the few previous measurements of gas diffusivity of firn. The improved technique offers a more direct measurement of the transport parameter than other techniques previously used, and offers good potential for future investigations aimed at understanding processes of firnification and gas trapping for ice core climate change research. [Copyright &y& Elsevier]

Abstract: Most building materials are porous, composed of solid matrix and pores. The time varying indoor and outdoor climatic conditions result heat, air and moisture (HAM) transfer across building enclosures. In this paper, a transient model that solves the coupled heat, air and moisture transfer through multilayered porous media is developed and benchmarked using internationally published analytical, numerical and experimental test cases. The good agreements obtained with the respective test cases suggest that the model can be used to assess the hygrothermal performance of building envelope components as well as to simulate the dynamic moisture absorption and release of moisture buffering materials. [Copyright &y& Elsevier]