Compressed Liquid

Compressed liquid, saturated liquid

Consider a piston-cylinder device containing liquid water to

20 ° C and 1 atm pressure. Under these conditions, water exists in liquid phase and liquid is called compressed or liquid sub ​​cooling. Heat is transferred to water to increase its temperature. for example. 40 ° C. With increasing temperature, liquid water expands slightly and thus increases its specific volume. So due to this expansion the piston rises slightly. The cylinder pressure remains constant at 1 atm during this process because it depends on the external barometric pressure and the weight of the piston, which are constant. EI water is still a compressed liquid in this state since it has not started to evaporate.

As more heat is transferred, the temperature increases to

100 ° C, at which point the water still remains liquid. but any addition of heat causes them to vaporize some water: ie. It is about to have a process of phase change from liquid to vapor. A liquid is called saturated liquid: thus, state 2 corresponds to a liquid salitrado.

Saturated steam and superheated steam

Once b starts boiling temperature rise is stopped until all the liquid is evaporated. That is, if the pressure remains constant during the phase change process so does the temperature. It is easy to check this by placing a thermometer in pure water boiling on a stove. At sea level (P 1 atm), the thermometer will always indicate the b 100 ° C pan is covered or not with a light cover. During a process of boiling, the only observable change is a large increase in volume and a steady decrease in the level of the liquid as a result of a greater amount of it become steam. Almost half of b ab evaporation line, the cylinder containing equal amounts of liquid and vapor. As heat transfer continues b, the process of evaporation to evaporate b continue fluid ounce. At that point the cylinder is full of steam which is at the edge of liquid phase b. Any amount of heat lost to the steam (vapor phase change to liquid) to condense. A steam is called saturated steam: therefore, the state 4 is a saturated vapor state, and a substance between states 2 and 4 is known as wet vapor or saturated vapor-liquid mixture, because in these states in equilibrium. .

Once completed, the process of change and end stage is reached

a region of a single phase (this time vapor). At this point. More heat transfer results in an increase in temperature and specific volume. In state 5 b is steam temperature. For example. 300 ° C: if some heat is transferred from the steam. The temperature would drop a bit but not as b would condensation temperature remains above 100 ° C (P = atm).

A steam (ie, saturated steam is not) is called superheated steam: therefore. water in the state 5 is a superheated steam. The described example of a phase-change process at constant pressure from a diagram Tv.

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