Question 2 A single-effect solar vapour absorption refrigeration system is shown in Figure. Q2a. It uses water (H20) as

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Question 2 A Single Effect Solar Vapour Absorption Refrigeration System Is Shown In Figure Q2a It Uses Water H20 As 1 (201.84 KiB) Viewed 32 times

Question 2 A single-effect solar vapour absorption refrigeration system is shown in Figure. Q2a. It uses water (H20) as the refrigerant and lithium-bromide (LiBr) as the absorbent, operating with the following temperatures: • Evaporator Temperature = 10°C Condenser Temperature = 42°C • Absorber Temperature = 35°C Generator Temperature = 100°C The flow rate of the solution delivered by the pump is 0.8 kg/s. The weak and strong solution concentrations are 45% and 65%, respectively. (a) Using the table and the graphs, work out the enthalpies and show the state points 1, 2, 3, 4, 5, 6 and 7 of Figure Q2a & b on graphs attached. (10%) (b) Determine the mass flow rate of the refrigerant and the mass flow rate of the solution returning from the generator to the absorber. (10%) (c) Determine the heat transfer rates in / from; Generator, Absorber, Condenser, Evaporator along with ideal and actual coefficient of performance. (50%) (d) The above system is modified by installing a heat exchanger between the generator and the absorber. During the process, the condensing temperature drops causing concentration to increase to 69%. The parameters surrounding the heat exchanger are shown in Figure Q2b below. (1) Determine the enthalpy and the temperature of strong solution at the inlet to the absorber (at point b in Figure Q2b). (10%) (ii) Is there a danger of crystallisation? Show point b on the enthalpy LiBr-H20 solution graph. Discuss the risk of crystallisation as result on installing the heat exchanger. (10%) (e) Give five advantages of a single effect Water/LiBr absorption cooling in comparison with a conventional vapour compression cooling system of an equivalent cooling output. (10%)
3 + Condenser Generator -1 4 21 65% 45% 7+ 67 Evaporator Absorber 5 Figure Q2a Schematic diagram of a single effect LiBr-H20 absorption refrigeration cycle. T = 95 °C X = 69% T = 52°C a dl X = 45% Solution heat exchanger b C 0.8 kg/s Figure Q2b Solution heat exchanger.