More heat is then added at constant volume Stops at a total volume of 0.4 m 3 (State (2)). Heat isĪdded to the water at constant pressure until the piston reaches the Under 100 kPa pressure as shown in the diagram (State (1)). Kilograms of water at 25☌ are placed in a piston cylinder device Illustrated in the following solved problems. Which is then solved in terms of the steam tables. Scale, however are sketched only in order to help define the problem, T-v and the P-v diagrams are normally not drawn to This is extremely inconvenient, so both the Pressure and specific volume values of interest, this can only beĭone on a log-log plot. Notice that because of the extremely large range of The parameter as in the following diagram: Often advantageous to use the P-v diagram with temperature as To completely define all other intensive state properties. Postulate that any two independent intensive properties can be used The above discussion was done in terms of the T-vĭiagram, however recall from Chapter 1 when we defined the State Relating quality and specific volume can also be evaluated in terms At this stage we note that the 3 equations , and entropy s all of which will be defined as Included three new properties: internal energy u, enthalpy h In order to evaluate the quality considerĪ volume V containing a mass m of a saturated liquid-vapor mixture. Liquid have the subscript f, and those relating to the saturated Notice that properties relating to the saturated Vapor divided by the total mass of the fluid, as shown in the (also referred to as the dryness factor) is defined as the mass of Line, and at any point within this region the quality of the mixture Region (also referred to as the SaturatedĮnclosed between the saturated liquid line and the saturated vapor Provided property tables of steam, Refrigerant R134a, and Carbonĭioxide, which we believe is destined to become the future Order to evaluate the various properties. Transcritical region) to the right of the saturated vapor line andĪbove the critical point. The saturation lines define the regions of interestĪs shown in the diagram, being the Compressed Liquid and saturated vapor points as shown in the T-v diagram It is common practice to join the loci of saturated Region between the saturated liquid and saturated vapor decreasesĭistinction between the liquid and vapor states. Notice that as we increase the applied pressure, the Pressures, as shown in the following T-v diagram: We now consider repeating this experiment at various Which made it necessary to use a logarithmic scale for the specific Volume of the water increased by more than three orders of magnitude, Notice that during this entire process the specific ![]() If heating continues then the water vapor temperature increases (T > ![]() Until there is no liquid remaining in the cylinder (State (4). While maintaining the temperature at 100☌ ( Saturation ![]() Water progressively changes phase from liquid to water vapor (steam) The temperature reaches close to 100☌ (State (2) - Saturated Liquid phase and the specific volume increases very slightly until Pressure is maintained constant until the temperature reaches 300☌,Īs shown in the following T-v diagram (temperature vs specificįrom State (1) to State (2) the water maintains its In which we have liquid water in a piston-cylinder device at 20☌Īnd 100kPa pressure. Interactions that occur in pure substances we consider an experiment In order to introduce the rather complex phase change Relationships of a pure substance (such as water) which can exist in In this chapter we consider the property values and Chapter 2a: Pure Substances: Phase Change, Properties (updated 9/20/09) Chapter 2: Pure Substances a) Phase Change, Property Tables and Diagrams
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