China
Africa
Explore chapters and articles related to this topic
IoT-Based Smart Irrigation and Monitoring System for Agriculture
Published in S. S. Nandhini, M. Karthiga, S. B. Goyal, Computational Intelligence in Robotics and Automation, 2023
K. P. Sampoornam, S. Saranya, Hyder Ali Segu Mohamed
Humidity is the amount of air vapor from water. Moisture sensors detect the relative humidity of the environment surrounding them. DHT11 evaluates humidity and atmospheric temperature. By calculating the electrical resistance between the two electrodes, the DHT11 calculates relative humidity. It expresses relative humidity as a percentage of the air humidity ratio to the maximum amount that can be held at the current temperature in the air. Moisture sensors use capacitive methods to find out how much moisture is present in the air. Measurement of temperature is done using the thermistor principle. This sensor provides stability and high reliability over the long term. It also offers the benefits of high-cost performance, quick results, and quality satisfaction. This sensor can also monitor moisture, as it highlights a precise calibration of the calibration chamber for humidity. Figure 9.12 shows DHT11-temperature and humidity sensor.
Design for the Climate
Published in Dorothy Gerring, Renewable Energy Systems for Building Designers, 2023
Figure 6.1 is a simplified psychrometric chart. The horizontal line across the bottom is the dry bulb temperature. This is what you think of as air temperature: it is what your thermometer reads. It is called dry bulb because it doesn’t tell you anything about the humidity in the air. The temperature of 20°F (−6.7°C) is on the left and the chart ends at 130°F (54.4°C). The dry bulb temperature is read vertically up the chart. Hot air can hold a lot more water molecules than cold air. The lines on the chart for humidity are curving lines. The horizontal line that is shared with the dry bulb temperature is 0% relative humidity (RH). The top curved line is 100% RH. The air can’t hold more than 100% humidity. If the air continues to cool down, the “extra” humidity falls out of the air: we call this dew. That means that the 100% RH line is also labeled the saturation or dewpoint line. Relative humidity is measured with a hygrometer. The simplest hygrometer is a sling psychrometer which has both a dry bulb and a wet bulb (a wet wick on the tip) thermometer. It is then spun (slung) around the handle which causes evaporative cooling on the wet bulb. The temperature on the wet bulb starts with the numbers along the 100% RH line and then is read diagonally downwards and to the right. Comparing the two temperatures gives the relative humidity.
Climatic factors affecting plants
Published in Stephen R. Gliessman, V. Ernesto Méndez, Victor M. Izzo, Eric W. Engles, Andrew Gerlicz, Agroecology, 2023
Stephen R. Gliessman, V. Ernesto Méndez, Victor M. Izzo, Eric W. Engles, Andrew Gerlicz
Water can exist in the atmosphere in a gaseous form (as water vapor) or in a liquid form (as droplets). At constant pressure, the amount of water vapor that air can hold before it becomes saturated and its water vapor begins to condense and form droplets is dependent on temperature. As the temperature of the air goes down, the amount of water that can be held in vapor form goes down as well. Because of this dependence on temperature, humidity—the amount of moisture in the air—is usually measured in relative terms rather than according to the absolute amount of moisture in the air. Relative humidity is the ratio of the water-vapor content of the air to the amount of water vapor the air can hold at that temperature. At a relative humidity of 50%, for example, the air is holding 50% of the water vapor it could hold at that temperature. When the relative humidity is 100%, the air is saturated with water vapor, and water vapor begins to condense to form mist, fog, and clouds.
Thermal management of an unloaded hybrid dryer by generalized predictive control
Published in Drying Technology, 2022
Abdenouri Naji, Zoukit Ahmed, Salhi Issam, Doubabi Said
During the whole duration of our experiments, the dryer was placed in an unshaded and clear area. A fan was fixed in the chimney of the dryer to ensure an even distribution of air and also to exhaust the humidity of the product to the surrounding air. In the solar drying process, the drying air temperature changes with the magnitude of solar radiation. Thus, the auxiliary electric heater was used to adjust the drying air temperature. The preliminary heated drying air by solar radiation arrived in the inlet of the cabinet dryer will be heated by electrical resistance. The power of the electrical resistance was varied using an analog power controller (037N0057, Danfoss). Temperature, humidity, and solar radiation were recorded every 10 min. The temperature was measured and recorded at different locations inside the drying chamber (bottom, middle, and the top) using temperature sensors type (TM-110 pt100, 0.5 °C accuracy). Hygrometer sensors (HM-110, 0.5% accuracy) were employed for measuring the ambient relative humidity. Incident global solar radiation was measured during the experiments by a Keep and Zonnen pyranometer with a sensitivity of 14.69 10−3. The velocity of drying air was measured using an anemometer (Kimo model CTV-210-BOS, 0.03 m/s accuracy) at the exit of the exhaust fan. The experimental rig of the hybrid dryer is presented in Figure 2.
Performance of pole mounted flat photovoltaic panel under varying ambient parameters
Published in International Journal of Ambient Energy, 2021
M. Chandrasekar, T. Senthilkumar
The variation in the experimentally recorded values of relative humidity, solar irradiation and wind velocity during the months of January – December 2016 was presented in Figure 3. The current location, Tiruchirappalli, India experiences a tropical savanna climate and designated as ‘Aw’ under the Koppen climate classification. The summer months exist generally from April to June while the rainy seasons exist between October and December. During the months from December to February, the climate is cool and moist (Indian Meteorological Department (IMD) accessed on http://www.imd.gov.in). The water vapour content in the atmospheric air is represented by the value of relative humidity. Higher values of relative humidity indicate higher level of water vapour or moisture and vice versa. The solar radiation meets the water vapour particles in the atmosphere before reaching the earth's surface and a complex phenomenon occurs involving the combination of reflection, refraction and diffraction of solar radiation which affects the amount of solar radiation received. Therefore, maximum solar radiation will be received only when the moisture content is low as there will be a minimum reflection, refraction and diffraction. This is because of this reason, maximum solar radiation was observed at minimum relative humidity conditions during the summer months of May–June 2016 as shown in Figure 3.
Probabilistic assessment of the potential indoor air impacts of vent-free gas heating appliances in energy-efficient homes in the United States
Published in Journal of the Air & Waste Management Association, 2018
Gary K. Whitmyre, Muhilan D. Pandian
The relationship of indoor relative humidity to indoor sources of water vapor, outdoor relative humidity, and building factors (e.g., air exchange rates, heat exchange) is complex. Relative humidity is defined as the percent saturation of air with water vapor at a given temperature. The warmer the air, the greater is the mass of water per cubic meter required to achieve a given relative humidity level (Dunn 1951). The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has recommended an indoor relative humidity range of 40–60% as being desirable based on comfort; the U.S. Environmental Protection Agency (EPA) has recommended a range of 30–60% for indoor relative humidity based on comfort. During the heating season, cold “dry” air is often brought into the home via normal infiltration/air exchange (Liebmann 1965). Cold air entering the home in winter through infiltration is then heated, which results in a higher capacity to contain water vapor. A relative humidity level greater than 70% can result in active growth of mold and mildew on indoor surfaces (Kalliokoski et al. 1993; Morey et al. 1984). Indoor environments commonly contain a variety of mold and mildew species, including Penicillium, Aspergillus, Cladosporium, and Fusarium species (DeKoster and Thorne 1995; Lipkowitz and Novarra 2001; Pasanen, Niininen, and Kalliokoski 1992).