Question

6-108 An air-conditioner with refrigerant-134a as the working fluid is used to keep a room at 23C by rojece ing the waste heat to the outdoor air at 34'C. The room gains heat through the walls and the windows at a rate of 250 J/min while the heat generated by the computer, TV, and lights amounts to 900 W. The reſngcrant enters the com- pressor at 400 kPa as a saluralod vapor at a rate of 80 L/min and leaves at 1200 kPa and 704 Determine (a) the actual COP. (b) the maximum COP, and (c) the minimum volume flow rate of the refrigerant at the compressor inlet for the sum compresor inlet and exit audivine Air (4.33 26.9. c) 129 1 min M4

Answer 1

Problem solo an the enthalpy, entropy & specific volume at state 1 determined from the given from the given pressure using the saturated wabor values from A-12 h = 255.55 kJ /kg 1, = 0.92691 kolleg di = 0.051201 m?! Kg k K

the enthally at state 2 (at P = 1.2MPa & Toc from h₂ = 300.61 kolky Q = 250K3 Table A-13 250 Y 1000 900 60 Goow + min Q = 5.067 kols 80x10] mia vi L, 0.026 kile 60 0:0 51201 s:Won (5,-2) 5:067 0.026% (300-61-255 55) د لمان: م Copa ♡ W COP 4.33 Ane Ane 23 + 273 (b) the maximum COP = Tr-TL 34 - 23 COP= 26.9 the

(( the minimum volume flow rate can be determined from the cop for the reversible cycle Wmin QL a 1 Copruv Colmas Vi min Cha-hil L QL Colmax - Vi min = 5:067 X 0.051 201 0.005 7576 m (300161 - 255,55) x 269 26.9 Vimia - 0.0057576 x 1000 x 60 L/min 26.9 = 12.85 L/min Vimin = 12.9L/min Ang