MTX221. Dr. Jaco Dirker. These slides also appear on Click-UP. 8 th edition / 8e uitgawe Hierdie skyfies verskyn ook op Click-UP. Ses.

Transcription

1 Ses MTX221 Sessie 26 Session 26 DIE EERSTE WET VAN THE FIRST LAW OF TERMODINAMIKA THERMODYNAMICS Dr. Jaco Dirker These slides also appear on Click-UP Hierdie skyfies verskyn ook op Click-UP 8 th edition / 8e uitgawe

2 Ses Compressor Example Derived from EX4.5 Ed 8. The temperature probe at the inlet of an adiabatic compressor in a plant is faulty. The compressor received N 2 at 100 kpa with a low velocity. At the discharge the N 2 exits at 1500 kpa, 400 K, with a velocity of 20 m/s. This outlet has a diameter of Ф 100 mm. After the compressor the N 2 is cooled to 300 K in a cooling section. Afr. Op volgende skyfie If 60 kw of power is supplied to the compressor calculate the following: a) Inlet temperature to the compressor b) Heat transfer in the cooling section.

3 Ses Examples of Steady State Processes Kompressor Voorbeeld Gebasseer op V4.5 Wge8. Die temperatuur sensor by die inlaat van n adiabatiese kompressor in n aanleg is foutief. Die kompressor ontvang N 2 teen 100 kpa teen n lae snelheid. By die uitaat is die N 2 teen 1500 kpa, 400 K, met n snelheid van 20 m/s. Hierdie uitlaat het n diameter van Ф 100 mm. Na die kompressor word die N 2 verkoel tot 300 K in n verkoeller. Engish on previous slide Indien 60 kw drywing aan die kompressor gelewer word, bepaal die volgende: a) Inlaat temperatuur van die kompressor b) Hitte-oordrag in die verkoeler.

4 Ses Do Example Example 4.6 (8 th Ed) yourself. Doen Voorbeeld 4.6 (8 e Wge) self.

5 Ses Power Plant and Refrigerator Kragstasie en Yskas-stelsel Now we will incorporate several devices into Complete Thermodynamic Systems

6 Ses Power Plant and Refrigerator Kragstasie en Yskas-stelsel Ketel Pype Turbine Pomp Power Plant system consisting of Boiler (Heat Exchanger which evaporated water into steam) Pipes (Which may act as a heat exchanger if the steam loses heat) Turbine (Steam Turbine) Condenser (Heat Exchanger which condenses steam into liq. water) Pump Do EX4.7 (8 th Ed) yourself. Ketel Doen VB4.7 (8 th Wge) self. Turbine Pomp

7 Ses Power Plant and Refrigerator Verkoeler (hitte-pomp) Refrigerator system (heat pump) consisting of: Kompressor Compressor (increases pressure of vapour refrigerant) Condenser (heat exchanger which condenses refrigerant vapour to liquid, and thus expels heat to environment) Uitsettingsklep / kapilêre buis Expansion Valve / capillary tube (Throttle liquid to lower pressure) Verdamper Evaporator (heat exchanger which evaporates refrigerant liquid to vapour, and thus extracts heat from refrigerated space) Kragstasie en Yskas-stelsel Warm damp Warm vloeistof Uitsettingsklep Kompressor Verdamper Kapilêre buis Koue damp Koue vloeistof + damp

8 Ses Refrigeration Example EX4.8 (Ed. 8) The refrigerator shown in the figure uses R134-a as the working fluid. The mass flow rate through each component is 0.1 kg/s and the power input to the compressor is 5 kw. The following state data are known (by measurement): Afr. Op volgende skyfie State/ Toestand P [kpa] T [ºC] x 0.0 Determine the following: Quality at evaporator inlet (x 4 ) Rate of heat transfer at the evaporator Rate of heat transfer at the compressor Warm damp Kompressor Verdamper Warm vloeistof Uitsettingsklep Kapilêre buis Koue damp Koue vloeistof + damp

9 Ses Yskas Voorbeeld VB 4.7 (Wge. 8) Die yskas getoon in die figuur gebruik R134-a as die werkvloeier. Die massavloei tempo deur elke komponent is 0.1 kg/s en die drywingsinset aan die kompressor is 5 kw. Die volgende toestand-data is bekend (dmv meting): English on Previous slide State/ Toestand P [kpa] T [ºC] x 0.0 Bepaal die volgende: Kwaliteit by die verdamper-inlaat (x 4 ) Tempo van hitte-oordrag by die verdamper Tempo van hitte-oordrag by die kompressor Warm damp Kompressor Verdamper Warm vloeistof Uitsettingsklep Kapilêre buis Koue damp Koue vloeistof + damp

10 Ses Multiple Flow Devices = Do examples yourself Meervoudige Vloei toestelle = Doen self voorbeelde