Psychrometric Charts . .. . ASHRAE Fundamentals Handbook (SI) Mass of water added per unit mass of dry air is (W.* – W), which. AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR- CONDITIONING ENGINEERS, INC. T. SENSIBLE HEAT. 0. 5. DRY BULB TEMPERATURE – °C. 5.

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Home Technical Resources Bookstore. The user then enters a desired Dry Psychroketric temperature and one of three humiditymetrics: Specific humidity is defined as the proportion of the mass of water vapor and mass cgart the moist air sample including both dry air and the water vapor ; it is closely related to humidity ratio and always lower in value.

Molds and fungi can be controlled by keeping relative humidity low. Load Calculation Applications Manual, 2nd ed. These intersect the saturation curve at DBT point.

Analogous to the specific volume of a pure substance. Purchase Understanding Psychrometrics, 3rd ed. There appears to be error in the calculations when converting from one unit system to another.

Psychrometric Chart + Duct Calculator

Instructions for the Psychrometric Calculator This on-line program calculates typical psychrometric state point properties. The horizontal component of the condition line is the change in sensible heat while the vertical component is the change dhart latent heat. The psychrometric ratio of air-water vapor mixtures is approximately unity, which implies that the chrt between the adiabatic saturation temperature and wet bulb temperature of air-water vapor mixtures is small.

The inner scale represents sensible-total heat ratio SHF. Analogous to the specific enthalpy of a pure substance. The ratio of the vapor pressure of moisture in the sample to the saturation pressure at the dry bulb temperature of the sample.

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Pressure Liquid water Avogadro’s law Nucleation Thermodynamic equilibrium. In meteorology and psycnrometric the word temperature by itself without a prefix usually means dry-bulb temperature. 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 psychrometric ratio is the ratio of the heat transfer coefficient to the product of mass transfer coefficient and humid heat at a wetted surface.


The mass of water vapor per unit volume ashtae air containing the water vapor. Common atmospheric pressure values are:. The value indicated by a wet-bulb thermometer often provides an adequate approximation of the thermodynamic wet-bulb temperature.

Archived from the original on A chart is valid for a given air pressure or elevation above sea level. What is the difference between the six different humidity metrics shown? These are oblique lines drawn diagonally ashrad from left to right across the chart that are parallel to each other.

This is the t —axis, the abscissa horizontal axis. This program is provided for your use without charge. This page was last edited on 10 Mayat Retrieved 18 September Technically, the temperature registered by the dry-bulb thermometer of a psychrometer.

Psychrometrics Humidity and hygrometry Heating, ventilating, and air conditioning. Email a list of all the points and their properties for a completed chart, along with a PDF of the chart itself.

However, in psychrometrics, the term quantifies the total volume of both the dry air and water vapour per unit mass of dry air. Although the principles of psychrometry apply to any physical system consisting of gas-vapor mixtures, the most common system of interest is the mixture of water vapor and air, because of its application in heating, ventilating, and air-conditioning and meteorology. Views Read Edit View history. This second edition, available in both I-P and SI units, provides clear understanding of the state of the art in heating and cooling load calculation methods.

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. The dew point temperature is equal to the fully saturated dry bulb or wet bulb temperatures. So the temperature value that allows this process condensation to take place is psychromrtric the ‘dew point temperature’.


In other projects Wikimedia Commons. Not to be confused with Psychometricsa discipline of psychology and education.


You show a ‘Virtual’ Temperature under Thermodynamic properties. 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. Display a fully customizable psychrometric chart in both landscape and portrait modes. It will also provide a number uits other thermodynamic properties not found on a typical psychrometric chart.

They are identically straight but are not exactly parallel to each other. Archived copy as title Webarchive template wayback links. At the end of the calculation, the user has the option to convert from the English to the SI or vice versa unit system. Industries that use these materials are concerned with relative humidity control in production and storage of such materials. To calculate properties, the user must enter either a site elevation from which an average barometric pressure is calculated or an actual barometric pressure.

This is used to establish the slope of a condition line between two processes.

The range is from 0 for dry air up to 0. The outer scale gives the ratio of enthalpy difference to humidity difference. As you move your finger around the graph, the psychrometric properties at the top of the screen dynamically update. These are the horizontal lines on the chart. Why psychgometric this program show two different values of specific volume?