Instructions

For the following questions answer them individually

Question 71

A two stage centrifugal compressor operating at 3000 rpm is to compress refrigerant R134a from an evaporator temperature of $$O^\circ C (h_i = 398.6 kJ/kg)$$ to a condensing temperature of $$32^\circ C (h_e = 419.8 kJ/kg)$$. If the impeller diameter of both the stages have to be same, what is the diameter of the impeller?

Assume suction condition to be dry saturated, compression process isentropic, impeller blades radial and refrigerant enters impeller radially

Question 72

Water with specific heat $$(c_p = 4 kJ/kgK)$$ is fed to a boiler at $$30^\circ C$$, the enthalpy of vaporization at atmospheric pressure in the boiler is 2400 kJ/kg, the steam coming from the boiler is 0.9 dry. The net heat supplied (in kJ/kg) in the boiler is

Question 74

The isentropic heat drop in the nozzle of an impulse steam turbine with nozzle efficiency 0.9, blade velocity ratio 0.5 and mean blade velocity 150 m/s in kJ/kg is

Question 75

Consider a simple gas turbine (Brayton cycle) and a gas turbine with perfect regeneration. In both the cycles, the pressure ratio is 8 and the ratio of specific heats of working medium is 1.5. The ratio of minimum to maximum temperatureis 0.2 (with temperature in K) in the regenerative cycle. The ratio of the thermal efficiency of the simple cycle to that of tpseneralive cycle is

Question 76

A simply supported beam PQ is loaded by a moment of 1 kN-m at the mid span of the beam of length 1 m. The reaction forces $$R_p and R_q$$ at supports P and Q respectively are

Question 77

Two solid shafts โAโ and โBโ are made of the same material. The shaft โAโ is 50 mm diameter and shaft โBโis 100 mm diameter.The ratio of strength of shaft โBโ compared to shaft โAโis

Question 78

Two simply supported beams โAโ and โBโ of same breadth and depth and same material carries constant central load W at the centre. The span of beam B is double that of beam A. The deflection of beam B compared to beam A will be

Question 80

The rectangular beam โAโ has length l, width b and depth d. Another beam โB of same material has the same length and width but depth is double that of โAโ. The elastic strength of beam B compared to that of A will be