JNTU B.Tech II THERMAL SCIENCE Previous Question Paper (November/December - 2017 - R16)

A nozzle is a device for increasing the velocity of a steadily flowing stream. At the inlet to a certain nozzle, the enthalpy of the fluid passing is 3000 kJ/kg and a velocity is 60 m/s. At the discharge end, the enthalpy is 2762 kJ/kg. The nozzle is horizontal and there is negligible heat loss from it. (a) Find the velocity at exit from the nozzle. (b) If the inlet area is 0.1 m² and the specific volume at the inlet is 0.187 m³/kg, find the mass flow rate. (c) if the specific volume at the nozzle exit is 0.498 m³/kg, find the exit area of the nozzle.

A gas flows steadily through a rotary compressor. The gas enters the compressor at a temperature of 160°C, a pressure of 100 kPa, and an enthalpy of 391.2 kJ/kg. The gas leaves the compressor at a temperature of 2450°C, a pressure of 0.6 MPa, and an enthalpy of 534.5 kJ/kg. There is no heat transfer to or from the gas as it flows through the compressor. (a) Evaluate the external work done per unit mass of gas assuming the gas velocities at entry and exit to be negligible. (b) Evaluate the external work done per unit mass of gas when the gas velocity at entry is 80 m/s and that at exit is 160 m/s.

A heat engine operating between the two reservoirs at 1000 K and 300 K is used to drive a heat pump which extracts heat from the reservoir at 300K at a rate twice that at which the engine rejects heat to it. If the efficiency of the engine is 40% of the maximum possible and the COP of the heat pump is 50% of the maximum possible, what is the temperature of the reservoir to which the heat pump rejects heat? What is the rate of heat rejection from the heat pump if the rate of heat supply to the engine is 50 kW?

An air standard Otto cycle operates with a compression ratio 8. At the beginning of the compression the air is at 1.01 bar and 30°C, and during the heat addition process the pressure is tripled. Calculate (a) the thermal efficiency of the cycle and (b) the efficiency of the Carnot engine operating between the same overall temperature limits.

An air standard dual cycle has a compression ratio of 16, and compression begins at 1 bar, 45°C. The maximum pressure is 65 bar. The heat transferred to air at constant pressure is equal to that at constant volume. Estimate (a) The pressures and temperatures at the cardinal points of the cycle, (b) the cycle efficiency and (c) the m.e.p of the cycle, C_v = 0.718 kJ/kg K, C_p = 1.005 kJ/kg K.