- 1 (80.21 KiB) Viewed 35 times
- 2 (66.85 KiB) Viewed 35 times
- 3 (45.04 KiB) Viewed 35 times
- 4 (81.3 KiB) Viewed 35 times
• To locate the point 1 (before going into the compressor) find the intersection of a horizontal line at p1 = P4 and the T=T1 curve (red lines are isotherms). That intersection will be on the part of the T = T1 curve that is outside the vapor dome and rapidly decreasing with increasing enthalpy. • To get the line between point 1 and point 2 (coming out of the compressor) you will note that point 1 is about halfway between two isentropes (green lines). Make the line between point 1 and point 2 run between the sold line isentrope and the dashed line isentrope and take that line up until you reach the height of p3 = P2. This establishes point 2. • The horizontal between point 2 and point 3 goes from point 2 to somewhere close to the vapor dome boundary (about to go liquid). This establishes point 3. • Drop straight down from point 3 to point 4 at the height of p4 = p1. This establishes point 4. • Close the sketch of the cycle by joining points 4 and 1.
Ta = 10°C Pu= P4 T2= 62°C + 8 P2 = P3 P2 = P3 A T3 = 44.9°C P₂ = 10 bar Tyž -5.20 Pu= 1.55 bar Py
8.2 Mollier diagram An ideal cycle can be represented by a Mollier diagram by measuring pressures p(3) and p(4) before and after the expansion valve and the tem- perature (1) before the compressor: T(1) and p(4) determine point 1 of the Mollier di- agram (see Fig. 5). The intersection of the corre- sponding isentropes with the horizontal line p(3) = constant defines point 2. The intersection of the horizontal with the line representing the boiling point gives point 3, then a perpendicular down to the horizontal p(4) = const provides point 4. Additionally, measuring temperatures T(2), T(3) and T(4) provides an extra insight into the pro- cesses taking place inside the heat pump: The temperature T(4) measured externally is in agreement with the overall temperature read from the temperature scales of the corresponding ma- nometer to within the precision of the equipment. This temperature scale is based on the curve rep- resenting work done by the refrigerant. The meas- urement therefore shows that the refrigerant be- yond the expansion valve is in a mixture of liquid and gaseous states. The externally measured temperature T(3), how- ever, differs from the temperature read from the manometer on the high-pressure side. The refrig- erant at this point contains no gas content. It is entirely liquid. The following equipment is recommended for tak- ing external measurements (see section 4. ac- cessories): Temperature sensor NTC with measurement terminal 1021797 VinciLab 1021477