![]() ![]() As a result, a large number of superheated steam tables use representative pressure-temperature values to form a summary table. In fact, the number of possible temperature-pressure combinations is so great that it would be virtually impossible to gather them all in a single table. This is because the temperature of superheated steam, unlike saturated steam, can vary considerably for a same pressure. Values related to superheated steam cannot be obtained through a regular saturated steam table, but rather require the use of a Superheated Steam Table. *Atmospheric pressure is 101.3 kPa (14.7 psi) Zero-referenced against Absolute Pressure.Zero-referenced against Atmospheric Pressure*.Important note: Problems can easily occur when absolute pressure is mistaken for gauge pressure (or vice versa), so it is always extremely important to pay close attention to the pressure units used in the table. Steam Pressure = Steam Pressure + 14.7 psi Steam Pressure = Steam Pressure + 101.3 kPa For Imperial Units Also, to distinguish gauge pressure from absolute pressure, a "g" is typically added to the end of the pressure unit, for example kPaG or psig. Steam tables based on gauge pressure indicate atmospheric pressure as 0, while steam tables based on absolute pressure indicate it as 101.3 kPa (14.7 psi). Gauge pressure was created because it is often easier to reference measured pressure against the pressure we normally experience. As saturated steam pressure rises, the latent heat of evaporation gradually decreases until it reaches 0 at supercritical pressure, i.e. As seen in the table, this latent heat of evaporation is greatest at lower pressures. Heating processes using steam generally use the latent heat of evaporation (Hfg) to heat the product. hg = Specific enthalpy of saturated steam (total energy required to generate steam from water at 0☌ (32☏)).hfg = Latent heat of evaporation (energy required to transform saturated water into dry saturated steam).hf = Specific enthalpy of saturated water (energy required to heat water from 0☌ (32☏) to the boiling point).vg = Specific volume of saturated steam (gas).vf = Specific volume of saturated water (liquid).T = Saturation point of steam/water (boiling point).Because H2O can be either liquid or gas at its saturation point, two sets of data are required: data for saturated water (liquid), which is typically marked with an "f" in subscript, and data for saturated steam (gas), which is typically marked using a "g" in subscript. This is the point where water (liquid) and steam (gas) can coexist at the same temperature and pressure. The data found in a saturated steam table always refers to steam at a particular saturation point, also known as the boiling point. In addition to pressure and temperature, these tables usually include other related values such as specific enthalpy (h) and specific volume (v). It's typically used to determine saturated steam temperature from steam pressure, or the opposite: pressure from saturated steam temperature. A saturated steam table is an indispensable tool for any engineer working with steam.
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