![]() PDP already has a higher dew point than that of atmospheric dew point (a PDP of 2 degrees Celsius is equal to -23 degrees Celsius at atmospheric pressure). The more a dew point needs to be lowered, the greater the investment (and operational cost) it takes to get it there. Selecting a primary type of drying equipment should be determined by the PDP, not the atmospheric dew point (the dew point in the air, not within the compressed air system, which the PDP measures). Low PDP means there are small amounts of water vapor in the compressed air higher PDP values mean higher amounts of water vapor in the compressed air. This is the temperature at which water vapor (a gas) condenses into water (liquid state) at the current working pressure. The water content in compressed air is measured in PDP, or Pressure Dew Point. That’s why, to avoid disturbances and disruptions due to water and humidity in the pipes, compressed air must be dried with after-coolers and drying equipment. This is true in compressed air systems as well, and if our bodies are any indication of the ways excess water and humidity can impact performance, imagine how this impacts a compressed air system (which can’t step into the shade with a cold glass of lemonade for some brief respite). Why does this matter, and what is the relevance? All atmospheric air contains varying amounts of moisture based upon the temperature – higher air temperatures can hold more water, while air at lower temperatures is not capable of holding as much. Therefore, a dryer heat, despite possibly reaching a warmer environment temperature-wise, keeps you feeling cooler. And since sweating is the way our bodies cool themselves, more humidity equals feeling warmer. What is dry heat, and why do people favor it over wet heat (also known as humidity)? Essentially, greater humidity retains sweat on the skin. It’s an idiom that is repeated everywhere from sitcoms to T-shirts, an optimistic outlook on an otherwise oppressive atmospheric condition. Therefore, when indicating a dew-point, the related pressure must always be stated as well, in order to avoid a mix-up and thus mistakes when selecting and sizing a dryer.ĭew-points of compressed air dryers are usually stated as pressure dew-points, but it is always worth to double-check! In case it should be necessary, atmospheric dew-points and pressure dew-points can be converted into each other.Dry compressed air is more effective and efficient compressed air, and determining the water content in a system is critical to its performance and durability. As a consequence, the dew-point of a gas, measured at atmospheric conditions, is much lower than the pressure dew-point of the same gas, measured in compressed conditions. The moisture, solute in the gas, is dispensed to a bigger volume – the gas gets drier. When expanding a compressed gas to atmospheric pressure, its volume expands. compressed air) at a specific operating pressure Is related to non-pressurized, atmospheric air (atmospheric dew-point) Identical gas and dew-point temperatures mean a relative humidity of 100% and thus a gas saturated with moisture.įurthermore, it is important to distinguish between dew-point and pressure dew-point: However, there is a direct relationship between the dew-point and the relative humidity (rh). Thus, the dew-point itself is not suitable for a mass balance indication, but can be converted by means of formulas or tables (see water vapor content table). stated as g/m³), the dew-point describes the "behavior" of moisture within a gas depending on the gas temperature. Therefore, it is easy to understand and directly related to many process parameters, which is why the dew-point is a favored expression when measuring or indicating the moisture content in a gas.Ĭompared to indications of a concentration, which describe the ratio of amounts of water and gas (e.g. ![]() The dew-point is a temperature measured in ☌. ![]()
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