Question

ycles 1. A refrigeration system operates with a superheated cycle using R134a. The required refrigerating capacity is 30 TR. The evaporator works at -10 Cand the condenser pressure is 1 MPa. The refrigerant is superheated by 10°C before entering to the compressor. Assume isentropic compression in the compressor and isenthalpic expansion in the expansion valve. Answering the following questions using the ph diagram. and the c Sion in the ring to a) Sketch the process in the p-h diagram and write down the required enthalpy values. b) Determine the refrigeration effect. kJ/kg c) Determine the mass flow rate of refrigerant. kg/s a) What is the volumetric flow rate under the discharge conditions? kg/s d) Calculate the theoretical power of the compressor. ann e) Calculate the Coefficient of Performance of the system. COPA 1) What would be the additional cooling load achieved (gained) due to the superheating of the refrigerant? Aq2 = _kJ/kg

Answer 1

Pressure(Bar) 100 100 100 100 0.1 44 3. 02- 09- - 1 .1 --50 °C R134a .1.11 -0.60 kJ/kg.K- -0.65 -0.70 +0.75 +0.80 -0.85 +0.90 -0.95 +1.00 +1.05 3. Ot- -30 °C- =-20 °C -020000 - Saturated Liquid 3.01- 200 | Subcooled Liquid 200 102 H 0 °C 10 °C = 20 °C +1.15 A Constant Quality 3.0 A Constant Temperature -60°C +1.25 + 5 1.30 - -40 °C 0.00080 -50 °C 0.512 8 1.35-03 -60 °C +1.40-+ +1.45 300 300 70 °C 2 °C HIT 300 1 6 , 6 -30 CHHHHH +20°6' HHHHH / 6 +1.504 +1.55- +1.60- +1.65+ 80 °C TTTTT + 0.8 TAH56601/ Enthalpy(kJ/Kg) ου Ο y Liquid - Vapour Mixture 26.0016_ 270 +1.75 1.802 + -30 °C -20 °C -10 °C 14.40.0011: 4X80 CHF Saturated Vapdur 400 _/:/ : 400 A3.0A 1.90 Enthalpy(kJ/Kg) 10 °CH 20 °C X Critical Point HVITVAHT 1.95 / 52.00 2.05 22.10 80 °C 3.06 -2.154 500 2.20 500 141414 100 °C 110 °C 120 °C 130 °C 140 °C 150 °C 160 °C Superheated Vapour A THTnn 40.0018- at Specific Volume >2.304 22.354 2.404 600 t 600 0.0022 m3/kg 0.0040 0.0030 +2.45 kJ/kg.K 5 230 °C + -240 °C | -Constant Entropy 0.0080 0.0060 4.0 0.010 2.0 1.5 0.015 0.80 1.0 0.60 0.50 0.40 0.30 0.20 0.15 0.020 0.10 0.080 0.060 0.050 0.040 0.030 + 700 + HHHHHH 700 0.01 0.1 10 Pressure(Bar)

salu, Refregerant R134a RC = m(RE) Refrigeration capacity (RE) = 30 TR = 105 kitap RC = ™ x Refrigeration Effeet, P 1 @ 72 rath 1 T4= -10°C TL = 10 °C Po = P2 = Looohpa Py = P₂ = 200 174 kia (from table) Bocess (1-2) = Process (2-3) = Procers (3-4) = bocess (4-2) = Igentropic. (S=() Isobaric (P=C) → Igenthalpic Ch=c) Isobaric (P=6) compression heat rejection Expansion Heat addition, from R 1349 chart O ht=450kJ/ing h2= 428 kJ/kg, h3= huz 230 kJ/org. RE= ht-hv = 410- 230 z 18063 Arq. ITR z 3.5 hola RE= 300315 And = m (hy-hu) m = 30x3,5 410 - 20 1 kg/sec t 0.58 33 kg 1sec - © mi z

* Power of compressor (Pc = ll) Pc = ń Cha-ha) = 0.5833 ( 428 -410) u = 100 499 kn B HLO-230 RE COP © COPR = RET = 400-1010 hz-hi 428 -410 = 10 (1) DqL = ht-hm hal = 390 67/mg; 3, from chart. I 410 – 390 = 20m3/ng. # What is the voleumetric flow rate ander discharged conolition? Discharged condition meas point ® be discharge . form compressor. at point @ form Rf34a chant. 1. Sp. volm = 0,025 m3/ng. & ma o 5833 kg/s.. ý z 015833 x 0.025 m/s 0.0145 mm/sec.