Air conditioning

Summary

Air conditioning, often abbreviated as A/C (US), AC (US), or air con (UK), is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as "comfort cooling") and in some cases also strictly controlling the humidity of internal air. Air conditioning can be achieved using a mechanical air conditioner or alternatively a variety of other methods, including passive cooling or ventilative cooling. Air conditioning is a member of a family of systems and techniques that provide heating, ventilation, and air conditioning (HVAC). Heat pumps are similar in many ways to air conditioners, but use a reversing valve to allow them to heat and also cool an enclosed space. Air conditioners, which typically use vapor-compression refrigeration, range in size from small units used within vehicles or single rooms to massive units that can cool large buildings. Air source heat pumps, which can be used for heating as well as cooling, are

Official source

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

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Dynamic CO2 sorption on MgO-based sorbent in the presence of CO and H2O at elevated pressures

Seongmin Jin

The presence of gas species other than the target adsorbate in practical conditions causes complications in implementing a sorption-based process because of synergistic or detrimental effects on the sorption mechanism. MgO-based sorbents have attracted massive attention for the pre-combustion CO2 capture, where H2O and CO coexist in emission gas. Although H2O has been reported to greatly enhance CO2 sorption kinetics, CO2 sorption behavior and mechanism under a large quantity of H2O as in the practical condition remain unclear. Furthermore, CO2 sorption behavior in the presence of CO has not been adequately examined. Here, the dynamic CO2 sorption behavior of MgO-based sorbent was understood by coupling the breakthrough experiment under practically relevant conditions with in situ DRIFTS results. At elevated pressures, the sorption performance was considerably enhanced, whereas the influence by temperatures was insignificant. In addition, H2O enhanced CO2 sorption kinetics and initial CO2 sorption on MgO-based sorbent, whereas CO hindered them. In situ DRIFTS analyses for the mechanism study revealed that OH groups generated from H2O dissociation created highly basic sites that promoted the formation of monodentate carbonate, thereby enhancing the initial CO2 sorption. In contrast, CO hampered CO2 sorption through two mechanisms: (1) competitive sorption between CO2 generated from the water-gas shift reaction and CO2 in the feed; (2) interference of the promoted sorption by the molten nitrate salts. This study demonstrated that the practical condition of the pre-combustion CO2 capture significantly alters the CO2 sorption behavior of MgO, thereby providing insights for the ultimate implementation of MgO-based sorbents.

ELSEVIER SCIENCE SA2022

This paper proposes a novel ventilation strategy for capturing CO2 with scheduled occupancy diversity, and changes in recirculating ratio and infiltration rate. While many publications have described filters and a lamp that can efficiently capture and remove most pollutants (such as VOCs, dust, odors and viruses) to levels equivalent to those of conventional air dilution systems, no such system exists for CO2. This paper evaluates a strategy to recirculate air in the breathing zone through simulations with occupancy diversity factors from ASHRAE 90.1 2004 and Duarte et al.'s results for weekdays from 6 AM to 9 PM to evaluate a possibility of implementing a CO2 capture device. Using a lower indoor air recirculation ratio in spaces with high CO2 concentration is more effective at reducing CO2 concentration in the breathing zone. The results indicate that maximizing the air recirculation ratio by using the CO2 capturing unit could replace conventional air ventilation systems by sufficiently reducing the concentration of CO2 and supplying enough oxygen for occupational safety and health. Such a system could save air cooling or heating energy in buildings in hot or cold days or seasons, or when there are high outdoor pollution levels for a limited period of time. (C) 2015 Elsevier Ltd. All rights reserved.

Pergamon-Elsevier Science Ltd2015

Analysis of Free Vibration Characteristics of Tapered Friction Piles in Non-homogeneous Soil Layers

Kwangwoo Lee

This paper presents a new analytical model for estimating the free vibration of tapered friction piles. The governing differential equation for the free vibration of statically axially-loaded piles embedded in non-homogeneous soil is derived. The equation is numerically integrated by the Runge-Kutta method, and then the eigenvalue of natural frequency is determined by the Regula-Falsi scheme. For a cylindrical non-tapered pile, the computed natural frequencies compare well with the available data from literature. Numerical examples are presented to investigate the effects of the tapering, the skin friction resistance, the end condition of the pile, the vertical compressive loading, and the soil non-homogeneity on the natural frequency and mode shape of tapered friction piles.

2019