Section A
Q1.
(a) Calculate the decrease in available energy when 25 kg of water at 95 °C mixed
(b) with 35 kg of water at 35 °C, the pressure being taken as constant and the temperature of the surroundings being 15 °C. (Specific heat of water = 4.2 kJ/kg K) Draw a typical boiling curve for pool boiling of water at saturation temperature
(c) and atmospheric pressure, and mark each boiling regime. A diesel engine is working with a compression ratio of 18 : 1 and expansion
(d) ratio of 12 : 1. Calculate the air-standard cycle efficiency. Assume γ = 1.4. If the relative efficiency of the engine is 50% and calorific value of diesel fuel is 45000 kJ/kg, find out the specific fuel consumption of the engine in kg/kWh. If this engine has its application for DG set purpose of 500 kW rating at full-load condition and is expected to operate for two hours every day, work out the inventory requirement of diesel for next days. Also work out fuel cost of diesel for days period if cost of fuel per litre is ₹60. Make suitable assumptions if required. Consider diesel density as 0.83 kg/litre. A natural draught cooling tower used in a large cold storage plant receives
(e) water from the condenser outlet at a flow rate of 35000 kg/s and 40 °C temperature. The ratio of flow rate of water to air is 1.2:1 in the cooling tower. Inlet condition of the air entering the cooling tower is dry-bulb temperature (DBT) of 20 °C and wet-bulb temperature (WBT) of 10 °C. Air leaves the cooling tower at DBT of 35 °C with relative humidity of 90%. For this cooling tower- draw the inlet and exit conditions of air in psychrometric chart and name u) the process; determine the rate of evaporation of water in kg/s; (ii) determine the heat carried away by the air; (iii) determine the maximum possible temperature drop of water realizable. (iv) 12 [Psychrometric Chart is placed at the end] Glycerine is pumped at a constant rate of litres/s through a straight,
(a) 2. 100 mm diameter pipe, 45 m long, inclined at 15° to the horizontal. The gauge pressure at the lower inlet end of the pipe is 590 kPa. Verify that the flow is laminar and calculate the pressure at the outlet end of the pipe and the average shear stress at the wall. (Relative density of glycerine = 1.26 and dynamic viscosity of glycerine = 0.9 Pa s) 20 2 ISO-7-MCHE | 56
