Humidity | types of Humidity| measurement of humidity
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The document discusses the definition and significance of humidity, its effects on animal and plant life, human comfort, and various industries, including electronics and building construction. It provides detailed information on measurement techniques, such as sling psychrometers, and the use of satellites for global humidity monitoring. The conclusion highlights the environmental conditions of a studied house, indicating generally favorable temperature and humidity levels but suggesting the need for further long-term studies.
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equipment. Such short circuits may cause substantial permanent damage if the equipment is
powered on before the condensation has evaporated. A similar condensation effect can often
be observed when a person wearing glasses comes in from the cold (i.e. the glasses become
foggy). It is advisable to allow electronic equipment to acclimatise for several hours, after
being brought in from the cold, before powering on. Some electronic devices can detect such
a change and indicate, when plugged in and usually with a small droplet symbol, that they
cannot be used until the risk from condensation has passed. In situations where time is
critical, increasing air flow through the device's internals, such as removing the side panel
from a PC case and directing a fan to blow into the case, will reduce significantly the time
needed to acclimatise to the new environment.
In contrast, a very low humidity level favors the build-up of static electricity, which may
result in spontaneous shutdown of computers when discharges occur. Apart from spurious
erratic function, electrostatic discharges can cause dielectric breakdown in solid state devices,
resulting in irreversible damage. Data centersoften monitor relative humidity levels for these
reasons.
Building construction:
Common construction methods often produce building enclosures with a poor thermal
boundary, requiring an insulation and air barrier system designed to retain indoor
environmental conditions while resisting external environmental conditions.[35] The energy-
efficient, heavily sealed architecture introduced in the 20th century also sealed off the
movement of moisture, and this has resulted in a secondary problem of condensation forming
in and around walls, which encourages the development of mold and mildew. Additionally,
buildings with foundations not properly sealed will allow water to flow through the walls due
to capillary actionof pores found in masonry products. Solutions for energy-efficient
buildings that avoid condensation are a current topic of architecture.
Industry:
High humidity can often have a negative effect on the capacity of chemical plants and
refineries that use furnaces as part of a certain processes (e.g., steam reforming, wet sulfuric
acid processes). For example, because humidity reduces ambient oxygen concentrations (dry
air is typically 20.9% oxygen, but at 100% relative humidity the air is 20.4% oxygen), flue
gas fans must intake air at a higher rate than would otherwise be required to maintain the
same firing rate .
Baking:
High humidity in the oven, represented by an elevated wet-bulb temperature,
increases the thermal conductivity of the air around the baked item, leading to a quicker
baking process or even burning. Conversely, low humidity slows the baking process down.
Contained within in a parcel of air can vary significantly. For example, a parcel of air near
saturation may contain 28 grams of water per cubic meter of air at 30 °C, but only 8 grams of
water per cubic meter of air at 8 °C.](https://image.slidesharecdn.com/humidity-190215190704/85/Humidity-types-of-Humidity-measurement-of-humidity-4-320.jpg)
Humidity | types of Humidity| measurement of humidity
- 1. 1 Table of Contents Humidity:.....................................................................................................................................2 Effects:.........................................................................................................................................2 Animal and plant life:.............................................................................................................. 2 Human comfort:.................................................................................................................. 3 Electronics:......................................................................................................................... 3 Building construction:..........................................................................................................4 Industry: .............................................................................................................................. 4 Baking: ................................................................................................................................ 4 Measurement:............................................................................................................................ 5 Description of Sling Psychrometer:............................................................................................. 5 Operation of SlingPsychrometer: .............................................................................................. 6 Application of SlingPsychrometer:............................................................................................. 6 Limitation of Sling Pschrometer:................................................................................................ 6 Satellites:.....................................................................................................................................7 Conclusion:..................................................................................................................................8 References:..................................................................................................................................9
- 2. 2 Humidity: Humidity is a term used to describe the amount of water vapor present in air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. The amount of water vapor needed to achieve saturation increases as the temperature increases. As the temperature of a parcel of air decreases it will eventually reach the saturation point without adding or losing water mass. Effects: Animal and plant life: Humidity is one of the fundamental abiotic factors that defines any habitat, and is a determinant of which animals and plants can thrive in a given environment. The human body dissipates heat through perspiration and its evaporation. Heat convection, to the surrounding air, and thermal radiation are the primary modes of heat transport from the body. Under conditions of high humidity, the rate of evaporation of sweat from the skin decreases. Also, if the atmosphere is as warm as or warmer than the skin during times of high humidity, blood brought to the body surface cannot dissipate heat by conduction to the air. With so much blood going to the external surface of the body, less goes to the active muscles, the brain, and other internal organs. Physical strength declines, and fatigue occurs sooner than it would otherwise. Alertness and mental capacity also may be affected, resulting in heat stroke or hyperthermia. Fig: 1Effects on Plants
- 3. 3 Fig: 2 Effects on Animals Human comfort: Humans are sensitive to humid air because the human body uses evaporative cooling as the primary mechanism to regulate temperature. Under humid conditions, the rate at which perspiration evaporates on the skin is lower than it would be under arid conditions. Because humans perceive the rate of heat transfer from the body rather than temperature itself, we feel warmer when the relative humidity is high than when it is low. Some people experience difficulty breathing in humid environments. Some cases may possibly be related to respiratory conditions such as asthma, while others may be the product of anxiety. Sufferers will often hyperventilate in response, causing sensations of numbness, faintness, and loss of concentration, among others. Air conditioning reduces discomfort by reducing not just temperature but humidity as well. Heating cold outdoor air can decrease relative humidity levels indoors to below 30%, leading to ailments such as dry skin, cracked lips, dry eyes and excessive thirst. Electronics: Electronic devices are often rated to operate only under specific humidity conditions (e.g., 5% to 45%). At the top end of the range, moisture may increase the conductivity of permeable insulators leading to malfunction. Too low humidity may make materials brittle. A particular danger to electronic items, regardless of the stated operating humidity range, is condensation. When an electronic item is moved from a cold place (e.g. garage, car, shed, an air conditioned space in the tropics) to a warm humid place (house, outside tropics), condensation may coat circuit boards and other insulators, leading to short circuit inside the
- 4. 4 equipment. Such short circuits may cause substantial permanent damage if the equipment is powered on before the condensation has evaporated. A similar condensation effect can often be observed when a person wearing glasses comes in from the cold (i.e. the glasses become foggy). It is advisable to allow electronic equipment to acclimatise for several hours, after being brought in from the cold, before powering on. Some electronic devices can detect such a change and indicate, when plugged in and usually with a small droplet symbol, that they cannot be used until the risk from condensation has passed. In situations where time is critical, increasing air flow through the device's internals, such as removing the side panel from a PC case and directing a fan to blow into the case, will reduce significantly the time needed to acclimatise to the new environment. In contrast, a very low humidity level favors the build-up of static electricity, which may result in spontaneous shutdown of computers when discharges occur. Apart from spurious erratic function, electrostatic discharges can cause dielectric breakdown in solid state devices, resulting in irreversible damage. Data centersoften monitor relative humidity levels for these reasons. Building construction: Common construction methods often produce building enclosures with a poor thermal boundary, requiring an insulation and air barrier system designed to retain indoor environmental conditions while resisting external environmental conditions.[35] The energy- efficient, heavily sealed architecture introduced in the 20th century also sealed off the movement of moisture, and this has resulted in a secondary problem of condensation forming in and around walls, which encourages the development of mold and mildew. Additionally, buildings with foundations not properly sealed will allow water to flow through the walls due to capillary actionof pores found in masonry products. Solutions for energy-efficient buildings that avoid condensation are a current topic of architecture. Industry: High humidity can often have a negative effect on the capacity of chemical plants and refineries that use furnaces as part of a certain processes (e.g., steam reforming, wet sulfuric acid processes). For example, because humidity reduces ambient oxygen concentrations (dry air is typically 20.9% oxygen, but at 100% relative humidity the air is 20.4% oxygen), flue gas fans must intake air at a higher rate than would otherwise be required to maintain the same firing rate . Baking: High humidity in the oven, represented by an elevated wet-bulb temperature, increases the thermal conductivity of the air around the baked item, leading to a quicker baking process or even burning. Conversely, low humidity slows the baking process down. Contained within in a parcel of air can vary significantly. For example, a parcel of air near saturation may contain 28 grams of water per cubic meter of air at 30 °C, but only 8 grams of water per cubic meter of air at 8 °C.
- 5. 5 Measurement: A device used to measure humidity is called a psychrometer or hygrometer. A humidistat is a humidity-triggered switch, often used to control a dehumidifier. There are various devices used to measure and regulate humidity. Calibration standards for the most accurate measurement include the gravimetric hygrometer, chilled mirror hygrometer, and electrolytic hygrometer. The gravimetric method, while the most accurate, is very cumbersome. For fast and very accurate measurement the chilled mirror method is effective. For process on-line measurements, the most commonly used sensors nowadays are based on capacitance measurements to measure relative humidity, frequently with internal conversions to display absolute humidity as well. These are cheap, simple, generally accurate and relatively robust. All humidity sensors face problems in measuring dust-laden gas, such as exhaust streams from dryers. FIG: 3 Hygrometer Sling Psychrometer: Sling Psychrometer is used to measure both the dry bulb and wet bulb temperatures at time. These temperatures are a measure of humidity content in air. Descriptionof Sling Psychrometer: The main parts of the instrument are The instrument frame which holds the thermometers. One mercury in glass thermometer whose sensing bulb is bare to directly contact the air and to measure the temperature which is called as the dry-bulb temperature. Fig : 4 Sling Psychrometre
- 6. 6 One mercury in glass thermometer whose sensing bulb is covered with a cotton or muslin wick made wet with pure water. This sensing bulb covered with the cotton wick moistened is made to contact the air and the temperature indicated by this thermometer is called as the wet bulb-thermometer. The instrument frame carrying the thermometer is covered by a glass casing. A swivel handle is attached to frame-glass casing – thermometer arrangement to ensure that the air at the wet bulb always in immediate contact with the wet wick. When a thermometer bulb is directly exposed to an air-water vapour mixture, the temperature indicated by the thermometer is the dry-bulb temperature. When a thermometer bulb is covered by a constantly wet wick and if the bulb covered by the wet wick is exposed to air water vapour mixture, the temperature indicated by the thermometer is the wet bulb temperature. Operation of Sling Psychrometer: In order to measure the dry bulb and wet bulb temperature, the Psychrometer frame – glass covering – thermometer arrangement is rotated at 5 m/s to 10 m/s to get the necessary air motion. Note: An important condition is that correct/accurate measurement of wet bulb temperature is obtained only if air moves with velocity around the wet wick. In order to get this air velocity, the Psychrometer is being rotated. The thermometer whose bulb is bare contacts the air indicates the dry bulb temperature. At the same time, the thermometer whose bulb is covered with the wet wick comes in contact with the air and when this pass on the wet wick present on the bulb of the thermometer, the moisture present in the wick starts evaporating and a cooling effect is produced at bulb. Now the temperature indicated by the thermometer is the wet bulb thermometer which will naturally be lesser than the dry bulb temperature. If the Psychrometer is rotated for a short period, then the wet bulb temperature recorded will not be proper. Application of Sling Psychrometer: It is used for checking humidity level in air-conditioned rooms and installations. It is used to set and check hair hygrometer. It is used in the measurement range of 0 to 100% RH. It is used for measuring wet bulb temperature between 0’C to 180’C. Limitation of Sling Pschrometer: The measured medium is disturbed due to the act of measurement. The evaporation process at the wet bulb will add moisture to the air. It cannot be used in automation requirement situations. It cannot be used for continuous recording purpose. If the wick is covered with dirt, the wick will become stiff and its water absorbing capacity will reduce, however, a stiff/dirty wick will resume normalcy when boiled in hot water.
- 7. 7 Satellites: Humidity is also measured on a global scale using remotely placed satellites. These satellites are able to detect the concentrationof water in the troposphere at altitudes between 4 and 12 kilometers. Satellites that can measure water vapor have sensors that are sensitive to infrared radiation. Water vapor specifically absorbs and re-radiates radiation in this spectral band. Satellite water vapor imagery plays an important role in monitoring climate conditions (like the formation of thunderstorms) and in the development of weather forecasts. Fig:5 Map Planet`s soil moisture content Fig: 6 how to Weather Radar work
- 8. 8 Conclusion: Overall, the environmental conditions with respect to temperature and relative humidity were not as bad as would be expected; particularly given the age of the house and the way it is insulated (which is to say, barely at all). Generally speaking, the temperature levels were within or below the stated guidelines, with temperatures slightly below guideline-level being considered less damaging than temperatures above the guideline. The office proved to be the most temperate room in the house, although it may not be an ideal artifact storage space due to the more profound temperature fluctuations encountered there (see Appendix A for individual room charts). Regarding relative humidity, the rooms generally stayed within the guidelines for a majority of the time. The only room to have relative humidity levels in excess of the guidelines was the attic, which also demonstrated temperature levels consistently lower than the other rooms under study. This indicates, not surprisingly perhaps, that the attic is one of the least controlled environments in the house, and that further environmental controls for the attic need to be implemented before it is suitable for long-term artifact storage. Overall, the conditions measured in the house were favorable, with temperature and relative humidity levels at or below the operating guidelines. Note, however, that the time period that the house was under study was only a few weeks in the autumn, which can hardly be said to be representative of year-round conditions. As the environment within the house seemed to be largely driven by the ambient conditions, it may very well be that the higher temperature and relative humidity levels that are exhibited in Eugene during the spring and summer months may very well result in conditions in the SMJ House that are unacceptable for storage of historic artifacts. It is recommended that a further long-term study be implemented to fully test the hypothesis.