Question

PLEASE PROVIDE STEP-BY-STEP SOLUTION WITH EXPLANATION:

Question 1 (40 marks) An initial design calculation is to be undertaken for a large refrigeration plant that will service a frozen goods warehouse. The warehouse is to be kept at a temperature of -20.0°C and the total refrigeration heat load is 1.50 MW. The refrigeration system is to reject heat to the ambient air at 30.0°C and operate with a discharge pressure of 1.60 MPa and a suction pressure of 60.0 kPa Model the refrigeration system as an ideal vapour compression cycle (i) Draw an equipment diagram, labelling all heat transfer and work interactions. (2 marks) Draw the refrigeration cycle on T-s (temperature-entropy) and P-h (pressure-enthalpy) diagrams On the diagrams show the cycle with respect to the saturation lines, indicate the direction of the cycle progress and label all heat transfer and work interactions. (6 marks) (ii) (iii) Determine the mass flow rate of the refrigerant flowing through the cycle (in kg/s). (4 marks) (iv) Determine the power required to drive the compressor (in kW). (6 marks) Determine the coefficient of performance of the refrigeration system. (1 marks) (v) (vi) If the refrigeration system were modified by replacing the throttling valve with an isentropic turbine, what would the required net power input into the modified refrigeration cycle be (in kW)? (10 marks) (vii) Show the modified refrigeration cycle in part vi) on a T-s (temperature-entropy) with respect to the saturation lines, indicating the direction of the cycle progress and labelling all heat transfer and work interactions. (3 marks) (vii) If an ideal reversed Carnot cycle refrigeration system were used to cool the warehouse, what would the net input power requirement be (in kW)? (5 marks) (ix) Show the reversed Carnot refrigeration cycle in part viii on a T-s (temperature-entropy) with respect to the saturation lines, indicating the direction of the cycle progress and labelling all heat transfer and work interactions. (3 marks)

ANSWERS

Answer 1

TH- 30C waam environment 3 Condensor T Expansion Valve Eporαi Compaessr wase hoe Ts-Diagram GMPA 3 WW 6OКра Soluriatad Liuid lne Sata ated Vaypolut uie

Ph diagsam РА 3 '0kfa 4 state! P- 60kPa, Satutated Vapouy hi = hg@ 60kfa = 227-79 KJ/kg s Sa Go KPa - 0.964 KJIkg k. S S2= Or64-41 KJ Ikgk h2 27-04- KJIkg State 3 P3-6MPa, Saturated uyd h3- hf@ 1HPa h3= 135.43 KJlkg P=6okPa State L Throffeng proas h4 h3 13543 KJ/kg

mass fHow Tate of refogerant -5x1 KJec= m'p (227.79- 13s-9) KJ|kg -16-329 kg Isec Gv Pouve eguved dve the Campaesst P = RCh-hi) -46.329 kgls) (217-04-227-79) KJIk = 1130. 8 kw Heat nemoved uj evapusalos CoP= hi-h4 h2-h CoP = (227-79-135 93) KJ/kg 297-04-227-79) kJlkg I3265 COP