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A dry and wet bulb thermometer is also known as

The psychrometer consists of a dry-bulb thermometer and a wet-bulb thermometer. The dry-bulb thermometer shows the temperature of the air, and the wet-bulb thermometer, whose bulb is wrapped with wet cambric, shows a temperature that is dependent on the amount of evaporation from the surface of its bulb The temperature of the air measured by the ordinary thermometer is called as the dry bulb temperature of air, commonly referred as DBT. When ordinary thermometer is exposed to the atmosphere, it indicates the dry bulb temperature, which is nothing but the atmospheric temperature. Wet Bulb Temperature of Air (WBT)

The Wet Bulb temperature is the adiabatic saturation temperature. Wet Bulb temperature can be measured by using a thermometer with the bulb wrapped in wet muslin. The adiabatic evaporation of water from the thermometer bulb and the cooling effect is indicated by a wet bulb temperature lower than the dry bulb temperature in the air The wet-bulb temperature (WBT) is the temperature read by a thermometer covered in water-soaked cloth (wet-bulb thermometer) over which air is passed. At 100% relative humidity, the wet-bulb temperature is equal to the air temperature (dry-bulb temperature); at lower humidity the wet-bulb temperature is lower than dry-bulb temperature because of evaporative cooling Wet-bulb thermometers allow researchers to work out whether humans can sweat. If the water evaporates, the thermometer cools down, so that the wet-bulb temperature will be lower than the dry bulb temperature. In high humidity, the water will not evaporate, and the wet-bulb temperature will be the same as the dry-bulb temperature Sling psychrometers are devices used to determine the relative humidity in the air. They look like this: A sling psychrometer has two thermometers: a dry bulb thermometer (on the left) and a wet bulb thermometer (on the right). The bulb of the wet..

The wet-bulb temperature (WBT) is the temperature read by a thermometer covered in water-soaked cloth (wet-bulb thermometer) over which air is passed. At 100% relative humidity, the wet-bulb temperature is equal to the air temperature (dry-bulb temperature) and it is lower at lower humidity One of the most useful is wet bulb temperature — the temperature that a wet thermometer in the shade measures as water evaporates freely off it. This temperature will be lower than the temperature..

Relative Humidity is measured using a device called a sling psychrometer.This consists of 2 side by side conventional thermometers, one of which (the wet bulb thermometer) has a wetted wick placed at the bottom, the other (the dry bulb thermometer) has no wetted wick. When the psychrometer is swung around by its attached chain or handle, the air causes the water on the wick to evaporate which. Dry Bulb Temperature - Tdb - can be measured with a simple thermometer as shown above. Wet Bulb Temperature - Twb - can be measured with a standard thermometer with some wet clothing, cotton or similar, around the bulb The dry-bulb temperature is also known simply as air temperature. The natural wet-bulb temperature , is best described as an old-fashioned thermometer, wrapped in a wet cloth. As water evaporates from that wet cloth, evaporation cools the thermometer, which is identical to how the human body cools itself with sweat Also Know, how does a dry and wet bulb thermometer work? A dry thermometer has the bulb exposed to air. A wet thermometer has the bulb covered with a muslin cloth which is dipped in water. It is used to measure the relative humidity of temperature. When air is saturated, evaporation stops and the two bulbs show the same reading This thermometer is part of a device called a psychrometer. It includes a dry-bulb thermometer, a wet-bulb thermometer and a psychrometric chart - a graph that plots the relationships between the dry and wet-bulb temperature, relative humidity, and dew point at constant pressure

Wet-and-dry-bulb thermometer Article about wet-and-dry

  1. This temperature will be lower than the temperature on a dry thermometer in the same place (which is known as dry bulb temperature), and the difference between the two is a measure of humidity. So to get wet bulb temperature we can either measure it directly with a wet thermometer, or calculate it from dry bulb temperature and humidity
  2. One way is to use an instrument called a psychrometer (also known as a wet- and dry-bulb thermometer). It uses a pair of thermometers standing side by side. One has a bulb open to the air; the other has a bulb covered in a wet cloth. You measure the humidity by comparing the readings from the two thermometers
  3. e the relative humidity. This procedure is explained in details below in the Dry and Wet Bulb Method. The thermometers should be placed horizontally on the same level
  4. ed through the use of the table and calculate

What is Dry Bulb Temperature, Wet Bulb Temperature, Dew

The dry-bulb temperature is also known simply as air temperature. The natural wet-bulb temperature, is best described as an old-fashioned thermometer, wrapped in a wet cloth. As water evaporates from that wet cloth, evaporation cools the thermometer, which is identical to how the human body cools itself with sweat It is also known as the dry bulb temperature, as it is made with the bulb of the thermometer in the air (and out of the sun). However, when you want to measure the humidity of the air, you also use what is called a wet bulb thermometer. This is a thermometer which has its bulb covered completely with a wet cloth The numerical difference between the dry- and wet-bulb temperatures is known as the wet-bulb depression. Since the rate of moisture evaporation depends on the speed of the air over the wet-bulb, the wet-bulb temperature will also depend on the air speed. However, the wet-bulb becomes independent of the air velocity above 2 m/s A wet bulb temperature taken with air moving at about 1-2 m/s is referred to as a screen temperature, whereas a temperature taken with air moving about 3.5 m/s or more is referred to as sling temperature. A psychrometer is a device that includes both a dry-bulb and a wet-bulb thermometer T w = Natural wet-bulb temperature (combined with dry-bulb temperature indicates humidity) T g = Globe thermometer temperature (measured with a globe thermometer, also known as a black globe thermometer) T d = Dry-bulb temperature (actual air temperature) Equation: Heat Index = -42.379 + 2.04901523T + 10.14333127R.

Dry Bulb, Wet Bulb and Dew Point Temperature

PSYCHROMETRIC CHART CARRIER A dry bulb air temperature thermometer reads degrees Fahrenheit and a wet bulb thermometer lsychrometric 68 degrees Fahrenheit. Also known as air temperature, the reading of psychrimetric unwetted bulb in a thermometer Wet-bulb temperature accounts for both heat and humidity, unlike the standard temperature measurement you see on your weather app. It reflects what that combination means for the human body's. Whirling Hygrometer also known as Sling Psychrometer Wet and Dry Bulb Thermometers R1,650.00 Whirling Hygrometer (also known as Sling Psychrometer) - wet and dry bulb dry-bulb temperature (DBT) (1) temperature of air indicated by an ordinary thermometer shielded from solar and long wave radiation. (2) in general, any thermometer that indicates the temperature of air (or other fluids); distinguished from a wet-bulb thermometer

boggy thicket: Psychrometer

Why is the difference between the wet bulb temperature and the dry bulb temperature is always 0 OC when the relative humidity is 100%? The thermometers are whirled until the wet bulb is dry. When the air is saturated with water vapor, then the water on the wet bulb cannot evaporate This temperature will be lower than the temperature on a dry thermometer in the same place (which is known as dry bulb temperature), and the difference between the two is a measure of humidity is called the wet bulb depression This quantity along with the dry bulb from ESSE 1011 at York Universit Explanation: . Dry Bulb Temperature (DBT): It is a normal temperature measured by an ordinary thermometer.; Wet Bulb Temperature (WBT): It is a temperature measured by thermometer when its bulb is covered with a wet cloth.; Dew point temperature (DPT): It is a temperature at which moisture present in the atmosphere starts condensing or it is the temperature at which the first droplet of. The difference in the value of the wet bulb temperature compared with the air's dry bulb temperature, (θ-θ')(K), is known as the wet bulb depression, (wet bulb is always less than or equal to dry bulb temperature). Dry bulb temperature and wet bulb depression tables (or calculations) can be used to determine the air moisture content

Wet-bulb temperature - Wikipedi

the amount of water vapor, by mass, in each cubic unit of air, can be measured using several different types of mass ratios, is also known as the vapor density For every ________ increase in temperature, twice as much water vapor can enter the atmosphere through evaporation dry bulb. Wet bulb depression is the difference between wet bulb and ___ temperature readings. psychrometric chart. A (n) ___ is a chart that defines the condition of air at various properties. Standard conditions. ___ are values used for comparing properties of air at different elevations and pressures The coolest possible temperature that can be reached through evaporation of water in any given air condition is called Wet Bulb Temperature. At 100% humidity the wet bulb temperature equals the air temperature, because no more water can evaporate and thus no cooling is possible. If the combination of temperature and relative humidity.

T g = Globe thermometer temperature (measured with a globe thermometer, also known as a black globe thermometer) T d = Dry-bulb temperature (actual air temperature) Temperatures may be in either Celsius or Fahrenheit; Indoors, or when solar radiation is negligible, the following formula is often used: W B G T = 0.7 T w + 0.3 T g {\displaystyle. Clarification: The psychrometric chart has DBT on the x-axis and specific humidity on the y-axis. The obliquely inclined lines from the saturation curve and on the dry-bulb temperature lines denote Specific volume. 7. Specific humidity lines are also known as_____ a) moisture content lines b) relative humidity c) specific volume d) moist line So the wet bulb temperature depends on the moisture in the air. When the atmospheric air is saturated with water (that is, it has 100% relative humidity), no water can evaporate from the wet bulb. Hence the wet bulb temperature will be same as the dry bulb temperature. This temperature is therefore also referred to as the saturation temperature.

One way is to use an instrument called a psychrometer (also known as a wet- and dry-bulb thermometer). It uses a pair of thermometers standing side by side. One has a bulb open to the air; the other has a bulb covered in a wet cloth. The water on the cloth causes evaporation and loss of heat from the bulb, making its reading lower than that on. One is a standard dry-bulb thermometer to measure the air temperature. The other is a wet-bulb thermometer, also known as a psychrometer or hygrometer, which has a material wick around the thermometer bulb that is continuously wet because it dips into a reservoir of water. Evaporation cools the wet-bulb thermometer You can also take the percentage of relative humidity with a wet bulb thermometer. For this, you'll need a dry bulb thermometer as well. The dry bulb thermometer is simply a temperature gauge that is not used in connection with a wet bulb sock. It will take the temperature of the air within the space, as opposed to the wet bulb temperature - Dry bulb temperature, wet bulb temperature, humidity, and vapor process, but also to minimize the operational surface of the plant leaf), this is known as a vapor pressure differential or deficit. This is important for two reasons: first, we know tha At the point where the wet-bulb temperature and the dry-bulb temperature are equal (at the adiabatic saturation temperature), there is no opportunity for a net movement of water molecules from a wetted surface into the air and so no further evaporative cooling is possible. (air) and is the ratio of momentum diffusivity (also known as.

What are 'wet-bulb temperatures' - and why are they so

Instead, we present Delta T, also known as wet bulb depression. Delta T is an atmospheric moisture parameter whose use in spraying has made its way to North America from Australian operations. It is defined as the dry bulb temperature minus the wet bulb temperature, and provides a better indication of water evaporation rate than RH The dry-bulb temperature (air temperature) decreases from the entering to the exiting side during most of the schedule. This is known as temperature drop across the load, or TDAL. The wet-bulb temperature (temperature of a wetted thermometer) does not change from the entering to the exiting side after the kiln is warmed What are the wet bulb and dry bulb temperatures? Taking a reading of the wet bulb temperature is a way of measuring humidity. It is the temperature of a volume of air that has been cooled adiabatically until the humidity is at 100 percent and then compressed to the original pressure of the system prior to cooling

A dry-bulb thermometer is just a standard thermometer. On the other hand, a wet-bulb thermometer is a standard thermometer that uses a wet or moist piece of cloth that is wrapped around the bottom, or the bulb, of the thermometer. Thus, the dry-bulb temperature is the standard air temperature. The wet-bulb temperature is known as the adiabatic. A well-known measure called wet-bulb temperature has exceeded the temperature at which humans can no longer regulate body heat. | ydylg/Flickr Heat and humidity beyond human tolerance is occurring in some parts of the world faster than expected under global climate change, scientists report in the May 8 issue of Science Advances

What is the difference between the dry bulb and wet bulb

After this interval time, the period temperature must be noted for both bulbs. The difference between the temperature of both bulbs is recorded. Let's suppose the temperature of dry bulb = 38°C and wet bulb = 28°C. A graph is drawn where the y-axis shows the dry-bulb temperature and the x-axis shows the difference between both temperatures The dry bulb temperature is just the temperature measured by an ordinary thermometer that is dry. The wet bulb thermometer has a small, wet sock over the bulb, It is cooled to a temperature where heat gain from heat conducted down the stem of the. For this experiment, the dry-bulb and wet-bulb air temperature in the room was calculated using two forms of hygrometer-the sling psychrometer and the thermo-hygrometer capacitive humidity sensor. In addition, using the dry-bulb, wet-bulb temperature and psychrometric diagram seen in Figure 3 in the appendix 2, the basic humidity, enthalpy, dew. This is the dew point temperature. At saturation, the dew point temperature equals the wet bulb temperature, which also equals the dry bulb temperature, and the RH is 100%. This temperature is shown as horizontal lines on the chart. 5. Moisture content. This is also known as the humidity ratio and is usually designated as W

What does a wet bulb thermometer measure

  1. The term dry-bulb is customarily added to temperature to distinguish it from wet-bulb and dew point temperature. 10. WET BULB TEMPERATURE Wet bulb temperature is the temperature recorded by thermometer when the bulb is enveloped by cotton wick saturated with water. The accuracy of a simple wet-bulb thermometer depends on how fast air passes.
  2. evaporates, latent heat is removed and the temperature drops. You can also read the web-bulb temperature from a Psychrometric chart. From the current point, draw a line parallel to the lines of constant wet-bulb temperature, until you reach the 100% relative humidity line, and then read the temperature
  3. WB = Wet-bulb; the temperature of the air with the evaporative effect of a wet bulb taken into account. Quite literally, wet-bulb temperature is the temperature a thermometer bulb will be when covered in a wet fabric and whirled in the air or placed in an air stream. If the RH is below 100%, the WB will always be lower than the DB
  4. Removes heat from a low temperature body and delivers it to a high temperature body. Very wet vapour. High pressure saturated liquid. Dry vapour The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressur
  5. T w = Natural wet-bulb temperature (combined with dry-bulb temperature indicates humidity) T g = Globe thermometer temperature (measured with a globe thermometer, also known as a black globe thermometer) T d = Dry-bulb temperature (actual air temperature) Temperatures may be in either Celsius or Fahrenhei

Wet bulb temperature: The crucial weather concept that

Dew point temperature: From the state, the point follows the horizontal line of constant humidity ratio to the intercept of 100% RH, also known as the saturation curve. The dew point temperature is equal to the fully saturated dry bulb or wet bulb temperatures For centuries, freshly cut lumber has been allowed to dry in response to the temperature and humidity of the surrounding air, also known as the ambient conditions. The result was air-dried or air-seasoned lumber, which in Missouri typically has a moisture content (MC) between 12 and 14 percent.Moisture content is defined as:MC percent =Green weight - ovendry weightOvendry weightx 100The green. Wet-bulb temperature is the temperature of the air (in the dehydrator) as measured by a sensor that is wrapped with a cloth that is kept continuously wet with water by wicking action. Because of the evaporative cooling on the wet-bulb sensor, it is impossible for the wet-bulb temperature to exceed the dry-bulb temperature Hygrometers are instruments used for measuring humidity. A simple form of a hygrometer is specifically known as a psychrometer and consists of two thermometers, one of which includes a dry bulb and the other of which includes a bulb that is kept wet to measure wet-bulb temperature. Evaporation from the wet bulb lowers the temperature, so that the wet-bulb thermometer usually shows a lower. 10. Wet Bulb Depression: This is the difference between the dry bulb temperature and wet bulb temperature at any point. The wet bulb depression indicates relative humidity of the air. 11. Dew Point Temperature: It is the temperature of air recorded by the thermometer when the moisture (Water vapor) present in it begins to condense. In other words

Relative Humidity Calculator - 1728

Wet-bulb globe temperature

Air Humidity measured by Dry and Wet Bulb Temperatur

  1. Dry bulb temperature in Psychrometric chart. Measurement: You take a thermometer and hold it in the room and note the temperature. It's basically the ambient temperature that you see, is known as 'Dry Bulb Temperature'. Wet Bulb Temperature. The Wet Bulb Temperature is simply the temperature of the air which is associated with moisture
  2. Wet-bulb temperature. The wet-bulb temperature in an oven is measured by fitting a wet, moisture-wicking cloth over an ordinary dry-bulb sensor and placing it in the oven air stream. If the air is not saturated with moisture (i.e. the relative humidity is less than 100%), evaporation of moisture from the sock will cool the sensor to
  3. Except at relative humidity equal to 1, all the time the quantity of the dry bulb temperature is more than temperature of wet bulb (Zhao et al. 2008; Mohanraj et al. 2012). According to guidelines, the difference between the wet bulb and dry bulb temperatures is known as the wet-bulb depression (Zhao et al. 2008). The wet-bulb depression is an.

Dew Point Temperature Relative Humidity Humidity Ratio Dry Bulb Temperature Wet Bulb Temperature Humidity - Specific humidity - Absolute humidity Psychometric Ratio. Dew Point. The temperature at which moisture starts to condense out of the air is known as dew point. Dew point is also known as saturation temperature Wet And Dry Bulb Temperature Test One of the easiest and most efficient ways to make a homemade hygrometer is known as the wet and dry bulb test. The method is named after the use of a wet-bulb and dry-bulb thermometer and the temperatures they produce. A dry-bulb thermometer is just a standard thermometer. Also, Do I need a hygrometer

The oldest and the most common is to use a dry bulb and a wet bulb thermometer, this is what is known as a psychrometer. In order to determine the relative humidity and dew point with a psychrometer you need to have a dry bulb thermometer and a wet bulb thermometer so that you can compare the difference The wet-bulb temperature is a widely used moist thermodynamic variable. The relationship between the wet-bulb temperature, the dry-bulb temperature, and the dewpoint temperature is nonlinear. Most atmospheric thermodynamics textbooks indicate or imply that no simple and accurate approximation relating these three meteorological variables exists Relative humidity is computed from the ambient temperature as shown by the dry-bulb thermometer and the difference in temperatures as shown by the wet-bulb and dry-bulb thermometers. Relative humidity can also be determined by locating the intersection of the wet- and dry-bulb temperatures on a psychrometric chart (see below) The dry bulb temperature is the present temperature of air measured by a just putting a bare thermometer in air. It is called dry-bulb since the sensing tip of the thermometer is dry (see wet bulb temperature for comparison). When the dry bulb temperature line reaches the saturation line the following conditions exist air at a given dry bulb temperature, T, and absolute humidity, H, can bring air to saturation adiabatically at the same tempera-ture, Tad, while the pressure PT, is maintained constant. The adia-batic saturation temperature is also known as the thermodyna-mic wet bulb temperature. For a given G-V system, it may be defined as the temperature To T

What is Wet Bulb Temperature? (with pictures)

dry bulb temperature and 57°C wet bulb temperature) experiences a temperature drop of 3°C as it passes through the 1.2-m wide stack of lumber. Determine the properties of the air at state point 2 and compare them with those at state point 1. If the air is flowing at a rate of 2 meters per second, determine the dryin This thermometer is known as wet bulb thermometer. The second thermometer is not covered by any cloth and is left open. This is known as dry bulb thermometer. Both the thermometers record different temperature & because temperature of wet bulb is lesser than that of dry bulb because of coolness created by moisture & evaporation The term wet bulb comes from a way the measurement can be taken, by wrapping a piece of wet cloth around the end of a thermometer to see how much evaporation can decrease the temperature This is also known as Whirling hygrometer. This is an instrument made up of two thermometers properly mounted on a metal frame attached to a handle. One of these thermometers is known as the dry bulb thermometer and records the dry bulb temperature. The second thermometer has its bulb covered with a wick which can be wet before use temperature. Measure the wet-bulb temperature by placing a wet cotton wick over a conventional thermometer. Water evaporating from the cotton wick cools the thermometer. The wet-bulb temperature will always be lower than the dry-bulb temperature. The difference between these readings is called wet-bulb depression. It is a measure o

The wet bulb temperature is normally lower than the dry bulb temperature, as the evaporation of water exerts a cooling effect. The exact relative humidity is measured by working out the difference between the wet and dry thermometer and then using a table that looks at the difference between the wet bulb and the dry bulb temperatures Find the intersection of the two known properties, dry-bulb and wet-bulb temperatures, on the psychrometric chart, Figure 1. The dry-bulb temperature is located along the bottom horizontal axis. Find the line for 78°F, which runs vertically through the chart Of course, 120 and up in a dry heat means potential death from hyperthermia for people in at-risk groups. What is more dangerous is humid air, where the body's sweat can no longer evaporate, therefore causing the body to overheat, just like the 'wet' thermometer bulb In other words, a set of dry and wet bulb thermometers is known as psychrometer. Using the hygrometric table and dew point temperature, humidity can be obtained. 2. Assman Psychrometer: In Assman psychrometer (Fig. 2.15), the dry and wet bulb thermometers with cylindrical bulbs are fixed vertically

Carmel Software Blog — The Art and Science of Psychrometrics

Wet Bulb Globe Temperature (WBGT) Tool - Convergence of

  1. Humid heat is the heat required to raise unit mass of dry air and associated vapour through 1 degree K at constant pressure or 1.00 +1.88H kJ/kg K. Dew point is the temperature at which condensation will first occur when air is cooled. Wet bulb temperature. If a stream of air is passed rapidly over a water surface, vapor
  2. WBGT = 0.7T w + 0.2T g + 0.1T d. Where T w = Natural wet-bulb temperature (humidity indicator) ; T g =Globe thermometer temperature (measured with a globe thermometer, also known as a black globe thermometer, to measure solar radiation) ; T d =Dry-bulb temperature (normal air temperature) ; Temperatures may be in either Celsius or Fahrenheit; Indoors, or when solar radiation is negligible, the.
  3. 2.Define dry bulb temperature (DBT)? The temperature which is measured by an ordinary thermometer is known as dry bulb temperature. It is generally denoted by . 3.Define wet bulb temperature (WBT)? It is the temperature of air measured by a thermometer when its bulb is covered with wet cloth and exposed to a current rapidly moving air
  4. The Wet Bulb Globe Temperature (WBGT) is an indicator of heat related stress on the human body at work (or play) in direct sunlight. It takes into account multiple atmospheric variables, including: temperature, humidity, wind speed, sun angle, and cloud cover. Current WBGT / Calculate. Forecast Maps. WBGT vs Heat Index

Video: What are wet bulb and dry bulb temperatures

Dry-bulb temperature definition: A dry-bulb temperature is the temperature of a dry surface in a vapor-gas environment . | Meaning, pronunciation, translations and example known. The properties can be found by intersection point of dry-bulb and wet-bulb temperature.Relative humidity is a curve line while the absolute humidity (also called as humidity ratio) was the horizontal line on the psychrometric chart. Enthalpy is a diagonal line same as the wet-bulb temperature but have a slight difference in slope. Specific volume is another diagonal line but have is.

PSYCHROMETRY

Wet Bulb Calculato

  1. Natural wet-bulb temperature (combined with dry-bulb temperature indicates humidity) T. g = Globe thermometer temperature (measured with a globe thermometer, also known as a . black globe thermometer) T. d = Dry-bulb temperature (actual air temperature) Temperatures may be in eithe
  2. ed through the use of psychic graphics if both the temperature of the dry bulb (T) and the temperature of the wet bulb (Tw) of the mixture are known. These quantities are easily estimated using a sleigh psiccromator. There are several empirical formulas that can be used to estimate water vapor balance pressure as a temperature function
  3. ed by an ordinary glass thermometer. It is called dry-bulb since the sensing tip of the thermometer is dry (see wet bulb temperature for comparison)
  4. The process in which the moisture or water vapor or humidity is added to the air without changing its dry bulb (DB) temperature is called as humidification process. This process is represented by a straight vertical line on the psychrometric chart starting from the initial value of relative humidity, extending upwards and ending at the final value of the relative humidity
  5. e appropriate exposure levels to high temperatures. It is derived from the following formula
  6. will feel. The difference between the dry bulb and wet bulb temperatures, known as the wet bulb depression because typically the wet bulb temperature is lower for the reason I've just explained, is then used to calculate the relative humidity. To prepare the wet bulb thermometer, distilled water is added to the reservoir of the hygrometer
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Wet Bulb Globe Temperature (WBGT) is similar to the Heat Index in that it is an indicator of the stress on the body from the heat. While it is not as well-known as the Heat Index, it's not a new term. WBGT was developed in the 1950s after heat related illnesses affected the US armed services during the 1940s A psychrometer also called a sling psychrometer has two thermometers attached. One is dry (often called the dry bulb thermometer) and measures the actual air temperature. The other called the wet bulb thermometer has a has a wet cloth at the tip The wet-bulb temperature given in psychrometric charts is really the adiabatic saturation temperature. enthalpy (also known as heat content), thermodynamic quantity equal to the sum of the internal energy of a system plus the product of the pressure volume work done on the system 1. Introduction. First principles dictate that for any given ambient air mass, the difference between aspirated (well coupled) air temperature that includes ambient water vapor (dry-bulb temperature T a) and the temperature of the same air mass (wet-bulb temperature T w) at saturation provides a direct measurement of the amount of water vapor that air mass contains Find the intersection of the two known properties, dry-bulb and wet-bulb temperatures, on the psychrometric chart, Figure 1. The dry-bulb temperature is located along the bottom horizontal axis. Find the line for 78 o F, which runs vertically through the chart. Wet-bulb temperature is located along diagonal dotted lines leading to scale.