Utilización del diagrama psicrométrico. Carrier. Ed. Marcombo. Barcelona, • Sistemas de control para calefacción, ventilación y aire. Psychrometrics, psychrometry, and hygrometry are names for the field of engineering . psychrometric chart, shown here, was pioneered by Willis Carrier in It depicts . The Mollier diagram coordinates are enthalpy and humidity ratio. Gramom 3 m 3 kg pfernandezdiezes tablas diagrama DIAGRAMA PSICROMÉTRICO DEL AIRE, (Carrier) Tablas Image of page.

A sling psychrometer requires manual operation to create the airflow over the bulbs, but a powered psychrometer includes a fan for this function. The psychrometric chart allows all the parameters of some moist air to be determined from any three independent parameters, one of which must be the pressure.

Psychrometric chart. This guide is an easy 8 step framework designed to demystify the psychrometric chart: Step 1. Locate the dry bulb tem - perature along the bottom axis and the associated vertical line for each temperature. This scale will be in degrees F or degrees C. Locate the ‘humidity ratio’ along the right vertical axis. Psychrometrics is the study of the air and water vapor mixture. Proficiency in the use of the psychrometric chart is an important tool for designers of air conditioning systems. Psychrometrics is required to properly calculate heating and cooling loads, select equipment, and design air. PSYCHROMETRIC CHART BAROMETRIC PRESSURE 29.921 inches of Mercury Linric Company Psychrometric Chart, www.linric.com.1.2.3.4.5.6.7.8.9 1 1.1 1.2 1.3 VAPOR PRESSURE - INCHES OF MERCURY-20 0 10 20 25 30 35 40 45 50 55 60 65 70 75 80 85 DEW POINT - °F. Title: ASHRAE Psychrometric Chart #1 (SI) Created Date: 9/29/2011 3:30:29 PM. Psychrometric chart. This guide is an easy 8 step framework designed to demystify the psychrometric chart: Step 1. Locate the dry bulb tem - perature along the bottom axis and the associated vertical line for each temperature. This scale will be in degrees F or degrees C. Locate the ‘humidity ratio’ along the right vertical axis.

Occupants control their environment by means of clothing, operable windows, fans, personal heaters. Other formulations of thermodynamics psicromftrico in the following decades, statistical thermodynamics, or statistical mechanics, concerned itself with statistical predictions of carroer collective motion of particles from their microscopic behavior.

El diagrama de Mollier: Pressure Liquid water Avogadro’s law Nucleation Thermodynamic equilibrium. Psychrometrics, psychrometry, and hygrometry are names for the field of engineering concerned with the physical and thermodynamic properties of gas-vapor mixtures. The mass of water vapor per unit volume of air containing the water vapor.

The carta psicrometrica carrier chart is a visual representation of 3 components: This is the t —axis, the abscissa horizontal axis. Caarrier that use these materials are concerned with relative humidity control in production and storage of such materials.

Many substances are hygroscopicmeaning they attract water, usually in proportion to the relative humidity or above a critical relative humidity.

Psychrometrics – Wikipedia

Analogous to the specific enthalpy of a pure substance. In many industrial applications it is important to avoid condensation that would ruin product or cause corrosion. Molds and fungi can be controlled by keeping relative humidity low. This property of air-water vapor systems simplifies drying and cooling calculations often performed using psychrometic relationships.

Click “Download Now” above-right to download this program to your PC. These lines are drawn straight, not always parallel to each other, and slightly inclined from the vertical position. The inner scale represents sensible-total heat ratio SHF. Humid heat is the constant-pressure specific heat of moist air, per unit mass of the dry air.

In psychrometrics, the term quantifies the total energy of both the dry air and water psixrometrico per kilogram doagrama dry air.

CARTA PSICROMETRICA CARRIER EPUB

Temperature is important in all fields of science carta psicrometrica carrier carta psicrometrica carrier, geology, chemistry, atmospheric sciences, medicine. These lines are oblique lines that differ slightly from the enthalpy lines.

In industrial drying applications, such as drying paper, manufacturers usually try to achieve an optimum between low relative humidity, which increases the drying rate, and energy usage, which decreases as exhaust relative humidity increases. The “Mollier i – x ” Enthalpy – Humidity Mixing Ratio diagram, developed by Richard Mollier in[12] is an alternative psychrometric chart, preferred by many users in Scandinavia, Eastern Europe, and Russia. Chapter 2, Measurement of Temperature. The psychrometric chart quality is simply exquisite, combined with advanced psychrometric methodologies providing unmatched accuracy.

Archived from the original on System Design Load General.

Psychrometrics

The psychrometric chart quality is simply exquisite, combined with carta psicrometrica carrier psychrometric methodologies providing unmatched accuracy. These charts focus on the carrirr of temperatures most suitable for comfort-cooling HVAC applications, and include the Trane coil curves, which depict the condition of the air leaving a cooling coil.

Operation of the psicrometrco is simple point and click, providing an easy-to-use program performing high level detailed process energy and psychrometric analysis. The psychrometric chart is also known as the Carta psicrometrica carrier diagram or enthalpy pressure psicdometrica. The dew point temperature is equal to the fully saturated dry bulb or wet bulb temperatures.

CARTA PSICROMETRICA CARRIER EPUB

A chart is valid for a given air pressure or elevation above sea level. The thermodynamic wet-bulb temperature is a thermodynamic property of a mixture of air and water vapor.

The outer scale gives the ratio of enthalpy difference to humidity difference. Nobody Does it Better! They are also available in low and high temperature ranges and for different pressures. Knowing both the dry-bulb temperature DBT and wet-bulb temperature WBTone can determine the relative humidity RH from the psychrometric chart appropriate to the air pressure.

The term dry-bulb is customarily added to temperature to distinguish it from wet-bulb and dewpoint temperature. The accuracy of a simple wet-bulb thermometer depends on how fast air passes over the bulb and how well the thermometer is shielded from the radiant temperature of its surroundings.

To this point, we’ve taken a look at what exactly psychrometrics is and defined the top nine psychrometric quantities. Now we’re going to delve into how we can combine those quantities and create the psychrometric chart. As you might expect, taking nine variables and putting them into one chart puts a lot of information at your fingertips. It also can take a while to figure it all out. On top of all that, having nine different variables means you’ve got a lot of options for how to show them in a chart.

To this point, we’ve taken a look at what exactly psychrometrics is and defined the top nine psychrometric quantities. Now we’re going to delve into how we can combine those quantities and create the psychrometric chart. As you might expect, taking nine variables and putting them into one chart puts a lot of information at your fingertips. It also can take a while to figure it all out. On top of all that, having nine different variables means you’ve got a lot of options for how to show them in a chart.

A lot of folks have been involved in the development of the psychrometric chart over the past century. Willis Carrier was the first, with what he called the hygrometric chart in 1904. Richard Mollier from Germany made an important contribution in 1923, as you’ll see in the next section. Aside from that, the other versions of the psychrometric chart out there are mostly specialty charts and curiosities. (For more on the history and variety of psychrometric charts, see Don Gatley’s book, Understanding Psychrometrics. Have I mentioned that one before?)

In fact, the chart itself has shifted from being a great calculation tool to being more of an educational or illustrative tool. With all the computing power at our fingertips these days, we can get accurate results from smartphone apps and don’t need to try to pull precise numbers off of psych charts.

OK, let’s jump in and place those eight psychrometric quantities on the chart and take a visual look this week. In case you’re wondering why I said eight instead of nine, recall that barometric pressure is one of the nine I defined in part 2 of this series, and that variable determines the scale of the chart. When you change barometric pressure (or equivalently, altitude), you need to redraw the chart. Notice that the chart shown in this article says “SEA LEVEL” in big letters.

Dry bulb temperature

That was Mollier’s big contribution to this chart. Carrier originally used dry bulb temperature and humidity ratio as rectangular coordinates and used the various psychrometric relationships to place the rest of the quantities on the chart.

One of the problems with this choice is that it makes finding specific enthalpies a bit difficult because the lines of constant enthalpy apply to saturation only, so then you have to put enthalpy deviation curves on the chart to make the adjustment for non-saturated conditions. If that sounds like Greek to you, don’t worry about it. You can still understand the chart just fine without knowing about this detail.

There are still plenty of the old-style charts out there, but ASHRAE has settled on the Mollier version with humidity ratio on the vertical axis and specific enthalpy as the other coordinate. If you want to see the dry bulb isolines as vertical and parallel, that’s fine. They nearly are. Take a look at a larger version of the ASHRAE psychrometric chart zoom in, you should be able to see the difference, especially if you look down at the bottom left.

Wet bulb temperature

Wet bulb temperature tells you how easy it is for water to evaporate. The New York Times had a really nice article relating wet bulb temperatures to climate change recently, and they defined wet bulb temperature as, “a measure of how well you can cool your skin by sweating.” When it’s hot outside, as it was in India this summer, that’s one of the primary ways we keep our bodies from overheating.

The wet bulb isolines are diagonal across the chart, as you see here, and there’s one place where the wet bulb and dry bulb temperatures are equal: at the saturation point. Evaporation doesn’t happen there under normal conditions, at least not without an equal amount of water vapor condensing.

From the saturation point, what happens to the wet bulb temperature as we heat a volume of air? Well, that depends on what happens to the amount of water vapor in the air. If you don’t humidify or dehumidify, you move horizontally to the right, increasing the dry bulb temperature. As you do so, you start crossing different wet bulb isolines with higher and higher values of wet bulb temperature.

For example, if you have air at 100° F and 40% relative humidity, the wet bulb temperature is 79° F. That’s going to be quite uncomfortable. The closer that wet bulb temperature gets to our body temperature, the harder it is for our bodies to lose enough heat to maintain a stable temperature. According to the New York Times article, a physically active person is in danger of overheating when the wet bulb temperature is 80° F.

The psychrometric chart can show us how wet bulb temperature changes as other conditions change.

Specific enthalpy

On theASHRAE chart, the specificenthalpy lines are one of the two main coordinates used to lay out the chart. As you can see here, they’re diagonal and oh, so close to being parallel to the wet bulbisolines. That’s because those two quantities are closely related.

Specific enthalpy tells you about the work and energy in changing air conditions and is given in BTU per pound of dry air in the imperial system of units. It’s only changes that matter here, so if you have any two statepoints on the chart, you can find the enthalpy difference. That tells something about how much energy you’ll have to put into the system or how much you’ll get out when you make the change.

Humidity ratio

Humidity ratio is the other defining coordinate for theASHRAE version of thepsychrometric chart. As you can see, theisolines are horizontal. In this case, the scale given on the chart is in pounds of water vapor per pound of dry air. Some charts show grains of water vapor per pound of dry air, which is often shortened to grains. (It takes 7000 grains to make one pound.)

Humidity ratio isolines are horizontal and evenly spaced on the chart.

Water vapor pressure

Vapor pressure is rarely shown on the psych chart, and thisASHRAE chart is no exception. I’ve drawn the lines here, and for temperatures below ~120° F, the scale (with units given in inches of mercury in this case) is simply the product:

p_WV = 48.11 x W

When you’re doing calculations for vapor diffusion or trying to figure out which way water vapor will travel through materials, you’ll need the vapor pressures for the various locations.

Dew point temperature

Dew point temperature is yet a third quantity that has horizontal isolines on the psych chart. What this means is that these three quantities are not independent of each other so if they’re all you have, you still don’t know your state point.

Another interesting thing here is that when wet bulb and dry bulb temperatures are equal, so is the dew point temperature. All three have the same value at the saturation point, shown on the curve that bounds the left side of the chart.

Relative humidity

And speaking of curves, the saturation curve is the 100% relative humidityisocurve. When the volume isn’t saturated with water vapor, the vapor pressure will be lower than the saturation vapor pressure and the relative humidity is less than 100%.

Unlike the three preceding quantities with horizontal isolines, relative humidity isn’t related to the other psychrometric quantities under discussion here. If you know RH and any of the other quantities, you’ve got your statepoint.

Specific volume

Specific volume shows up as a diagonal line on thepsychrometric chart, but it has a significantly different slope than specificenthalpy and wet bulb temperature. It’s also not quite as simple as I made it out to be last time. I wrote that it’s just the reciprocal of the density, but I glossed over a detail that may or may not be important in what you do.

As with the other psychrometric ratios here (specific enthalpy and humidity ratio), the denominator is not mass of the moist air. It includes only the dry air component. So its units (in the imperial system) are cubic feet per pound of dry air. Since the water vapor component is usually small, however, the specific volume defined this way isn’t greatly different from the volume per pound of moist air.

Understanding the chart

Free Psychrometric Chart

OK, so there are the quantities in the chart. By studying those individual charts, you can see how the different quantities change. For example, changing dry bulb temperature without humidifying or dehumidifying the air has no effect on dew point temperature, humidity ratio, or vapor pressure. And what happens to the relative humidity of air as it passes across an evaporator coil in your air conditioner?

So now we’re ready to start doing the fun stuff with the psychrometric chart. Next time we’ll take a look at some different processes like air conditioning or dehumidification. Stay tuned!

Carrier Psychrometric Chart software, free download

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Photo of psycho grafitti by Mark Mozart from flickr.com, used under a Creative Commons license.

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