Psychrometrics

Summary

Psychrometrics (or psychrometry, ; also called hygrometry) is the field of engineering concerned with the physical and thermodynamic properties of gas-vapor mixtures. Common applications Although the principles of psychrometry apply to any physical system consisting of gas-vapor mixtures, the most common system of interest is the mixture of water vapor and air, because of its application in heating, ventilation, and air-conditioning and meteorology. In human terms, our thermal comfort is in large part a consequence of not just the temperature of the surrounding air, but (because we cool ourselves via perspiration) the extent to which that air is saturated with water vapor. Many substances are hygroscopic, meaning they attract water, usually in proportion to the relative humidity or above a critical relative humidity. Such substances include cotton, paper, cellulose, other wood products, sugar, calcium oxide (burned lime) and many chemicals and fertilizers. Industries that

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https://en.wikipedia.org/wiki/Psychrometrics

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Toward Assessing the Sensitivity of Buildings to Changes in Climate

Sönke Frederik Horn

A building is designed for one set of typical climatic conditions. In the context of expected climate change, substantial numbers of existing and new buildings are expected to survive long enough to experience perceptible shifts in climate ‘normals’ (averages). This is problematic for predicting building performance, largely because the exact nature of climate change is hard to predict with certainty. Thus an optimal design is not only tuned to the original design conditions, but is also robust to changes in climatic conditions in the sense of a low sensitivity of its performance. To predict a building’s response to changes in typical weather, two inputs are required: weather data representing this change, and suitable metrics to compare building performance across different climate normals. This report presents initial work on a proposed method for assessing the sensitivity of new or existing buildings to climate change. This method begins with a selection of weather files to represent climate change, then quantifies a building’s passive performance in those climates using an enthalpy-based metric, and ends with a graphical analysis of the performance of the building in different climates to assess its robustness. In this report, we propose an objective performance metric based on the extent to which a building creates indoor conditions passively, i.e. without auxiliary systems. Initial work suggests that the performance assessment carried out here is reproducible and applicable for indoor environment design and evaluation in different ranges of climate change. This approach enables a comparison of building performance without the bias introduced by inherent differences in climatic conditions.

2013

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Timber building industry is facing a major transformation with digitalization and automation being more broadly adopted. Prefabricated timber frame structures can be mass-produced on large robotic assembly lines, increasing the productivity and competitiveness of wood over standard inorganic materials such as steel or concrete. While standardization is likely to limit creativity, new digital tools, on the contrary, give the possibility to design and build complex and unique geometries. Recent research in bespoke digital prefabrication notably led to the development of Integrally Attached Timber Plate Structures (IATPS). This system consists in assembling wooden panels connected only with timber joints inspired by traditional Japanese carpentry. The elements are digitally prefabricated and inserted into one-another to form bespoke architectural structures. In order to propose a fully automated process for IATPS, from design to construction, this paper investigates a method for assembling the panels with a 6-axis robotic arm. Preliminary studies have shown that significant discrepancies can occur between virtual models and physical prototypes due to joint tolerances, hygrometric variations, and self-weight deformations. To address this challenge and to adapt the robot position to the actual location of the elements, a visual feedback loop was developed using fiducial markers. Several tests were performed with structural wood panels to assess the accuracy of the method for different configurations and adapt the geometry of the joints in consequence. Finally, the insertion of a panel with two through-tenon joints was achieved by taking pictures of the target with a camera mounted on the end-effector of the robot.

2020