Thermo-hygrometric indoor conditions, as well known in literature, depend on the indices directly measurable in the place (Tba, Tbu, φa, va) and analytical solutions (Tmr, Top) and also on subjective assessments, metabolic activity carried out, and thermal resistance of clothing. They are tied to the subject occupied position within the work environment, substantially. In air conditioned rooms designed by systems with average parameters, it may happen that an individual, in some places or times, may feel sensations of thermal discomfort.These phenomena can be exacerbated by heat exchanges occurring in the presence of sources of radiation, such as radiant floors or ceilings or large glass surfaces sunny; these surfaces accentuate the radiative heat exchange with the body surfaces of the exposed individual. This paper proposes a "local mean radiant temperature" valid for the regular calculation of comfort in environments characterized by the presence of radiating surfaces. The present study compares the values of the parameters representing the hygrothermal comfort punctual, PMV, in environments characterized by radiating surfaces located in specific positions (ceiling, floor or walls), calculated with the local radiant temperature suggested in this study, with the corresponding values obtained with the mean radiant temperature proposed by the literature.
The process of urbanization in this new millennium is characterized by the fact that more than three quarters of Europe's population is concentrated in urban areas, thus it becomes essential the issue of how to reconcile the development of our cities with the respect and protection of the environment. Polluting vehicle emissions constitute a major contribution to the deterioration of urban air quality and represent a potential risk to public health of citizens. The qualitative improvement of processes of production it is to be considered in the near future, a priority for urban pollution reduction and for improving the quality of life of our cities. This paper shows the air pollution analysis of the urban center of four Sicilian city, and the concentrations of the critical pollutants (PM10, NO2, SO, O3, CO, C6H6, NH3, NMVOC). Linear regressions were performed to represent the relationships between the main pollutants; they were analyzed also the differences between the concentrations of pollutants, and their progress over the years.
There are many parameters belonging to environmental or subjective kind and influencing thermohygrometric well -being conditions in both living and working places : thermo-hygrometric indexes measurable in the environment directly (Tba, Tbu, φa, va) or analytical ones (Tmr, Top) both give only a superficial and partial assessment of the environmental conditions because they do not take into account subjective evaluation parameters. The heat exchange -in case of sources of radiation marked by a surface temperature such different from the mean value of the remaining surfaces (for example a large glass surface in winter and / or summer conditions) -enhances the feeling of radiative heat exchange with the body surfaces of the exposed subject. The ISO7726 standard "Thermal Environments-Instruments and Methods for Measuring Physical Quantities" has been developed to give guidance on the correct methods to be adopted in the measurement of environmental parameters; this paper presents a study on the influence of radiative exchange on the thermo hygrometric comfort in living and working environments. Two cases will be examined: case "A" with the radiant wall only formed by single wall named "1" from the wall, and case "B" with two radiating walls named "1" and "2".
Abstract:Heat exchangers (HXs) constitute key components of thermoacoustic devices and play an important role in determining the overall engine performance. In oscillatory flow conditions, however, standard heat transfer correlations for steady flows cannot be directly applied to thermoacoustic HXs, for which reliable and univocal design criteria are still lacking. This work is concerned with the initial stage of a research aimed at studying the thermal performance of thermoacoustic HXs. The paper reports a detailed discussion of the design and fabrication of the experimental set-up, measurement methodology and test-HXs characterized by two different pore geometries, namely a circular pore geometry and a rectangular (i.e., straight fins) pore geometry. The test rig is constituted by a standing wave engine where the test HXs play the role of ambient HXs. The experiment is conceived to allow the variation of a range of testing conditions such as drive ratio, operation frequency, acoustic particle velocity, etc. The procedure for estimating the gas side heat transfer coefficient for the two involved geometries is described. Some preliminary experimental results concerning the HX with straight fins are also shown. The present research could help in achieving a deeper understanding of the heat transfer processes affecting HXs under oscillating flow regime and in developing design optimization procedures.
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