Temperature drop issues in saturated steam and superheated steam
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Different calculation methods should be used to determine the temperature drop of saturated steam and superheated steam. For superheated steam, the final enthalpy drop can be calculated by accounting for heat losses along the path, and then the final temperature can be found using a table, from which the temperature drop can be determined. But how should one calculate the temperature at the end of a pipe for saturated steam? Is it the same as determining the heat loss along the way to obtain the enthalpy drop? In this case, this enthalpy drop isn’t entirely reflected in a temperature decrease, right? Should the heat released during phase change also be taken into consideration? Therefore, I would like to ask how to calculate the temperature at the end of a pipe for saturated steam.
It seems to be a condition related to the pipes transferring part of the heat away; let’s see what factors are involved. Such as thermal conductivity, heat exchange area, atmospheric temperature, and steam temperature. Heat transfer coefficient of the pipe material, heat transfer coefficient of the insulation layer. . . . . It is recommended to get a copy of \"Principles of Chemical Engineering\" to read; it seems that no theory of entropy or enthalpy is needed for these calculations. For reference.
All those parameters are available; I just want to find a direction for considering the temperature drop during the transport of saturated steam.
With these conditions as a basis, finding a heat formula is straightforward.
I’m not sure which formula to use. For example, if I know the initial temperature, pressure, and other parameters of a mass of saturated steam, as well as the heat losses along its path, how can I determine the temperature at the end? The temperature of superheated steam can be determined based on the enthalpy drop, but how do I calculate it for saturated steam?
There should be no need for calculation; if it is saturated steam, pipe losses will occur as it moves along the pipeline； Knowing the final pipeline pressure allows one to use a table to determine directly what the final temperature will be...
But when calculating pressure loss, can saturated steam be treated in the same way as ordinary gases? For ordinary gases, we consider adiabatic conditions when making calculations; using this method, I found that for steam pipelines over 100 meters long, the pressure loss is actually very small. However, when calculating pressure loss, the formulas do not take into account factors such as insulation and the surrounding environment, which seems to be a problem as well. After all, there must be a difference between steam pipes that are insulated and those that are not.
Is the saturated steam temperature related only to pressure?
Under normal conditions, there is a relationship between the temperature and pressure of saturated steam; this can be found using tables or graphs. If nothing else is available, the simplest way is to multiply the saturated vapor pressure by 10 after doubling it, and that will give the corresponding temperature
Superheated steam uses sensible heat to overcome heat losses, while saturated steam relies on latent heat (i.e., partial condensation) to overcome heat losses. Generally, the main pipes within a plant are saturated; this is why it is necessary to install steam traps
If it is saturated steam, the steam temperature remains unchanged; the heat loss arises mainly from the latent heat released during the condensation of the steam. The value of enthalpy reduction you calculated can be equated to the latent heat of vaporization of the steam at that pressure, which corresponds to the amount of steam that condenses along the way