In order for a high temperature boiler or steam engine to produce superheated water, or steam?
steam quality increase
If by dry steam you mean superheated steam then dry steam because it has a higher calorific value
The heat transfer coefficient of superheated steam is poor. Saturated steam has a better heat transfer coefficient, and also most of the heat transferred from steam occurs because of the condensation phase change.
If you heat steam under pressure you get "superheated steam" under higher than original pressure
In order for a high temperature boiler or steam engine to produce superheated water, or steam?
Superheated steam.
steam quality increase
That would depend on if the steam is superheated dry steam or not and if superheated dry steam its temperature. It should be possible to google "boiler equations" or "boiler design" to get details.
If by dry steam you mean superheated steam then dry steam because it has a higher calorific value
No, superheated steam gives off little energy. Most of the heat given off by steam is the latent heat of condensation as it undergoes a phase change from vapor to liquid. Superheated steam could first be "desuperheated" by adding water until it reaches the saturation point, then used for heat transfer processes.
The heat transfer coefficient of superheated steam is poor. Saturated steam has a better heat transfer coefficient, and also most of the heat transferred from steam occurs because of the condensation phase change.
because if the steam is not superheated the remaining water droplets reduce efficiency and can cause corrosion and pitting. +++ Nearly! Saturated steam, as non-superheated steam is called, is really only steam at the pressure and temperature in the boiler. Once it starts to expand as a gas in doing its work, the pressure and temperature fall and condensation will set in, leaving less and less useful water-vapour to act as a gas. Hence, as you say, the efficiency falls.
If you heat steam under pressure you get "superheated steam" under higher than original pressure
Superheated steam is steam at a temperature higher than water's boiling point
Saturated steam occurs when steam and water are in equilibrium. If you have a closed container of water and heat it, above 100 celsius the steam pressure will start to rise, and as the temperature continues to rise, the pressure will go on rising. What is happening is that steam is being evolved to match the temperature (steam tables will give this relation) and the steam conditions are said to be saturated because if the pressure is raised by external means, some of the steam will start to condense back to water.If the steam pressure is held at a lower level than that achieved at saturation, by taking steam off to feed a turbine or other steam usage, there is effectively an excess temperature for that pressure, and the steam is said to be superheated. It in fact then becomes dry, and behaves as a gas. The amount of superheat can be quantified as so many degrees of superheat (celsius or fahrenheit).Turbine designers want steam to be superheated before reaching the turbine, to avoid condensation causing blade erosion, and steam producing boilers in power plants are designed to produce superheated steam. In plants where no turbines are used, only satured steam is normally generated.In heating applications, saturated steam is preferable, because it has a better energy exchange capacity. Superheated steam must cool down, and become saturated steam, before condensing in a heat exchanger. Also, superheated steam is a thermal insulator, like air.That is why it is necessary to direct superheated steam through a desuperheater before using the steam in heating applications.
Expansion of steam in either the saturated or superheated state is generally not isothermal. When steam expands from a high pressure to a lower pressure the temperature will be reduced, unless energy is added during the process. When steam expands in an engine such as a steam turbine, the temperature reduction is greater than during free expansion