3 The Strenuis Ardua Will Be Powered By A Diesel Electric Propulsion System Each Marine Diesel Engine Will Take In Air 1 (167.59 KiB) Viewed 24 times
3 The Strenuis Ardua Will Be Powered By A Diesel Electric Propulsion System Each Marine Diesel Engine Will Take In Air 2 (72.89 KiB) Viewed 24 times
3. The Strenuis Ardua will be powered by a diesel-electric propulsion system. Each marine diesel engine will take in air (at state 1) at 1 bar and 293 K. The compression ratio will be 20 and the heat supplied due to combustion between states 2 and 3 will be 2200 kJ kg ¹. If needed take the acceleration due to gravity to be g = 9.81 m s¯¹ and the properties of air to be R = 287 J kg-¹ K-¹, Cp = 1004 J kg-¹ K-¹, C₂ = 718 J kg-¹ K-¹ and y = 1.4. (i) Predict the exhaust temperature in Kelvin at state 4. (ii) Predict the efficiency of the engine. To reduce vessel energy losses an engineer proposes that the exhaust of each diesel engine should enter a closed-loop heat exchanger, where it would transfer energy to a water-based heating system for the cabins. The volumetric flow of the exhaust gasses would be 50 m³ s-1. They would enter the heat exchanger at temp T4 and P4 and exit to the atmosphere at 100 °C, and at the same pressure P4. The water from the heating system would leave the heat exchanger at 80 °C and return at 40 °C. If needed its density can be taken as p = 1000 kg m-³ and its heat capacity as C = 4180 J kg-¹ K-¹. (iii) Assuming perfect heat transfer, with no losses of useful energy in the heat exchanger, predict the mass flow-rate of the water. [6 marks] [10 marks] [3 marks]
A diagram of an early proposal for the hull of the Strenuis Ardua is shown in Fig. Q3. 10m 5m 33m 5m Figure Q3: Cross-section of an early proposal for the hull. (iv) Assuming it sails in a winter sea, with density 1025 kg m-³, determine what the draft (depth in the water) of the vessel would be if it had a length of 360 m and the cross-section shown was constant over that length. (v) If it sailed to warmer waters would the draft increase, decrease or stay the same? Explain why. [4 marks] [2 marks] [Total 25 marks]
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