China
Africa
Explore chapters and articles related to this topic
Thermal Comfort
Published in Neha Gupta, Gopal Nath Tiwari, Photovoltaic Thermal Passive House System, 2022
Relative humidity is defined as the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water for a given air temperature. Relative humidity depends on temperature as well as pressure. Thus, humidity is associated with the moist air which is the mixture of dry air (fixed part) and water vapor (variable part). Relative humidity is always less than one (1). Saturated air is known as when the absorption of water reaches its maximum value for a given volume of dry air.
Dew Point Temperature
Published in Yeqiao Wang, Atmosphere and Climate, 2020
the partial pressure of the water vapor remains constant (constant moisture content in the air) and the equilibrium vapor pressure of water decreases as the temperature decreases. Eventually, the air temperature would have decreased such that the equilibrium vapor pressure equals the partial vapor pressure. Thus, as the air cools, the numerator remains constant while the denominator decreases until unity is reached in Equation 10.7. In the case where pressure remains constant, the relative humidity would be a function of both temperature and humidity ratio. As the dew point temperature is solely a function of the humidity ratio (at constant pressure), the dew point temperature is a better indicator of the amount of moisture in the air than relative humidity.[1,5,6-
Gas Dehydration
Published in Arthur J. Kidnay, William R. Parrish, Daniel G. McCartney, Fundamentals of Natural Gas Processing, 2019
Arthur J. Kidnay, William R. Parrish, Daniel G. McCartney
Both Equation 11.2 and Figure 11.1 show that at a given temperature the water content decreases with increasing pressure. Also, at a given pressure, water content increases with increasing temperature because the vapor pressure of water increases with temperature. These trends are valid as long as CO2 and H2S (acid gases) concentrations are low. The pressure effect on water content becomes complex if acid gas concentrations are higher. (Engineering Data Book, 2016b). Water content of gases containing high concentrations of H2S and/or CO2 such as the acid gas from an amine regenerator is discussed in Chapter 16.
Climate change and extreme weather: A review focusing on the continental United States
Published in Journal of the Air & Waste Management Association, 2021
Turning from statistics to physics, higher temperatures amplify the rate of evaporation from Earth’s surface and increase the amount of water available for rain in storms. Both effects stem from the Clausius-Clapeyron relation, familiar to students of thermodynamics (cf. Petty 2008). Over the range of temperatures typical of Earth’s surface, the equilibrium (or saturation) vapor pressure of water increases approximately exponentially with increasing temperature, rising nearly 7% for each 1°C of warming. The implication is that for a fixed relative humidity (the ratio of the actual vapor pressure of water to its saturation value) the amount of water vapor in the atmosphere available for conversion into rain increases strongly with the temperature. At the same time, in drying conditions over land, the loss of water from the surface by evapotranspiration, at a given relative humidity and with a given amount of soil moisture, also increases strongly with temperature. The practical consequences are that as Earth warms the heaviest rains can become heavier and soils and surface vegetation can dry out more rapidly (the latter effect is captured in “bulk formulae” for surface evaporation: cf. Hartmann 2016).
Drying and Atterberg limits of Cochin marine clay
Published in International Journal of Geotechnical Engineering, 2020
Amal Azad Sahib, Retnamony G. Robinson
To verify the role of shrinkage stresses upon drying, suction values were measured in Cochin marine clay specimens using Dew point Potentiameter (WP4) that employs the chilled mirror hygrometer. The device is used as a rapid means of determining the total suction of unsaturated soils (Leong, Tripathy, and Rahardjo 2003; Vikas and Singh 2005). The specimens were filled in slurry state (about 1.5 times liquid limit) in a mould of 35 mm diameter and 7 mm height. The soil sample was placed in a sealed chamber containing a mirror with a detector of condensation. The dew-point is the temperature to which the air must be cooled so that the water vapour in the air condenses to liquid water. At the dew-point, the water vapour present in the air is just sufficient to saturate it. When equilibrium prevails, the relative humidity of the air in the chamber is equal to the relative humidity of the soil sample. Relative humidity is calculated as the ratio of the saturated vapour pressure of water at the dew-point to the saturated vapour pressure of water at the air temperature. This ratio can be substituted in the following thermodynamic equation to calculate the total suction pressure.
Red pepper (Capsicum annuum L.) drying: Effects of different drying methods on drying kinetics, physicochemical properties, antioxidant capacity, and microstructure
Published in Drying Technology, 2018
Li-Zhen Deng, Xu-Hai Yang, A. S. Mujumdar, Jin-Hong Zhao, Dong Wang, Qian Zhang, Jun Wang, Zhen-Jiang Gao, Hong-Wei Xiao
The drying rate versus moisture content curves of red pepper are shown in Fig. 4. It is apparent that drying rate decreased continuously as the moisture content decreased. The entire drying process for red pepper occurs in the falling-rate period, which indicates that the internal moisture diffusion phenomenon controlled the drying process. The drying rates increased with the increasing drying temperature. This phenomenon can be attributed to the vapor pressure of water inside the product was enhanced by increasing the drying temperature. As indicated in Fig. 4, the sample dried under IR-HAD had higher drying rate than the samples dried by HAD or PVD at the same given drying temperature. This can be attributed to the fact that, during IR-HAD drying, the absorption of radiation generates heat rapidly at the surface and in the inner layers of the sample, which increased the rate of water removal. However, Fig. 4 also indicates that PVD gives a lower drying rate of materials. It partly due to the fact that, during the atmosphere pressure operation of PVD, the pressure release valve remains open and allows cold air to ingest into drying chamber, and during vacuum holding period, much heat is pumped out to the surrounding by vacuum pump, both of which decrease the temperature of the drying chamber and sample and thus decrease the drying rate of sample.[26]