3/22/2021 0 Comments Online Psychrometric Chart
This tool is intented to support all professionals and students involved in air conditioning, knowing the properties of the air that we process.The table on the left will show main results for both points, and its difference.Results for both points and its difference are shown on the table at the left.To change the position of the red point, modify the values above, at the beginning of this page.
Click on Center to move the ( red ) point to the same position than the green. If we try to cool down a solid object with an air flow of, lets say, 20C, the minimum temperature that theoretically we can reach for this solid object. In the case of the drop of water, in addition to conduction, some of the water. This process absorbs energy and produce a further reduction of the water temperature. If the relative humidity of the air is 100 (in other words it is saturated with moisture), evaporation will not happen. Wet bulb temperature can be measured by using a thermometer with the bulb wrapped in a water soaked cloth over which enough air is passed. The psychrometric chart is built upon two simple concepts. 1. Indoor air is a mixture of dry air and water vapor. 2. There is a specific amount of energy in the mixture at a specific temperature and pressure. This template allows a designer or operator to work backwards from a desired room relative humidity to the desired condition of the air as it enters the supply duct. Control of humidity is not required by most codes in all areas, but is for some in most geographic areas. The Uniform Mechanical Code (Uniform Mechanical Code, 2003) calls for OR relative humidities of 50-60. In a warm and humid climate, supply air can be drawn into a system and then exposed to cooling coils that drop the air temperature to 55F. Then, if the air is heated to 70F without the addition of water, the humidity will change to about 60, according to the chart. In climates of low humidity, it is necessary to inject water vapor into the supply air to increase the humidity to the target level. Steam can be provided by steam boilers or electric steam generators that boil water directly. Online Psychrometric Chart Full Chapter URLView chapter Purchase book Read full chapter URL: Properties of Humid Air Roger Legg, in Air Conditioning System Design, 2017 The Psychrometric Chart The psychrometric chart is a most useful design tool for air conditioning engineers. A typical chart is shown in Fig. The air properties on the chart are: Fig. Psychrometric chart. Reproduced from Section C1 of the CIBSE Guide, with the permission from the Chartered Institute of Building Services Engineers.) dry-bulb temperature, sling wet-bulb temperature, moisture content, specific enthalpy, specific volume, percentage saturation. When working with the chart, the following points should be noted: Sling wet-bulb is used in preference to screen wet-bulb temperature as it is considered to be the more consistent of the two measurements. This property is rarely required by the air conditioning engineer. Dew-point temperature can be obtained for a given air condition as previously described. The lines of constant dry-bulb temperature are not at right angles to the lines of constant moisture content. This is because the chart is based on enthalpy and moisture content and dry-bulb temperature is added subsequently, determined from the enthalpy equation. See Example 2.1 in the following chapter.) View chapter Purchase book Read full chapter URL: Sensors and Auxiliary Devices The reading text for this course was originally written by. Robert McDowall P. Eng., in Fundamentals of HVAC Control Systems, 2008 4.3 Humidity and the Psychrometric Chart Humidity is the moisture content in air. Before we consider humidity sensors, it is important that you understand what is being measured and how the various measurements relating to moisture content and temperature interact. Since moisture and temperature relate to the energy, or enthalpy, of the moist air we will also introduce that issue. The relationships between temperature, moisture content, and energy are most easily understood using a visual aid called the psychrometric chart. The psychrometric chart is an industry-standard tool that is used to visualize the interrelationships between dry air, moisture, and energy. If you are responsible for the design or maintenance of any aspect of air-conditioning in buildings, a clear and comfortable understanding of the chart will make your job easier. Initially, the chart can be intimidating, but as you work with it you will discover that the relationships that it illustrates are relatively easy to understand. Once you are comfortable with it, you will discover that it is a tool that can make it easier to troubleshoot air-conditioning problems in buildings. In this course, we will only introduce the psychrometric chart and provide a very brief overview of its structure. The psychrometric chart is built upon two simple concepts. Indoor air is a mixture of dry air and water vapor. There is a specific amount of energy in the mixture at a specific temperature and pressure.
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