Chapter 7, Problem 7.106P

The blade tip angles of a reaction turbine are 32° and 25º for fixed and móving blades respectively. The mean ring diameter of a pair of blades is 1.5 m and the blade height is 0.15 m. The steam which passes through the pair at a rate of 20 kg/s is dry saturated at 24 bar. Find, (a) Axial velocity (b) Blade speed (c) Power developed at that speed.

A certain SSSF turbine (irreversible and adiabatic) operates on air with the following conditions, Inflow: Ti=1000 K, Pi = 13223.07354 kPa Outflow (actual): Te = 402.3904382 K Find the actual specific work output of the turbine, wt in KJ/kg. (Assume single inflow/outflow, neglect change in KE and PE. Assume constant specific heats in this problem, with Cp0 =1.004 kJ/(K*kg) and k= 1.4. Next if the hypothetical ideal, reversible adiabatic (isentropic) specific work output of the turbine is wt= +800 Kj/kg: Find the isentropic efficiency of the turbine, outflow pressure Pe in kPa and finally what is the ratio of the outflow pressure of the actual turbine to the same pressure for the ideal turbine.

Subject : Thermofluid

The first stage of a turbine is a two-row velocity compounded wheel. Steam at 40 bar and 400 °C is expanded in the nozzles to 15 bar, and has a velocity at discharge of 700 m/s. The inlet velocity to the stage is negligible. The relevant exit angles are: nozzle 18°; first row blades 21°; fixed blades 26.5°; second row blades 35°. Take the blade velocity cocfficient for all blades as 0.9. The mean diameter of the blading is 750 mm and the turbine shaft speed is 3000 rev/min. Draw the velocity diagram for this wheel and calculate: 11.5 (i) the diagram efficiency; (ii) the stage efficiency. (70.8%: 67.4%)

Problem 4.01. A carnot refrigerator (carnot cycle heat pump in reverse) operating between Th and Te is used to cool and freeze a bottle of water, volume V, at a temperature To < Th to freezing temperature T (known density Pw, heat capacity cw). (a) Find the work required to cool and freeze the water. (b) Find the change in entropy in the heat baths, and use it to place a limit on the change in entropy of the water (without calculating the entropy change in the water). The C.O.P. of a carnot refrigerator: KR= Qc = W Te Th-Te

2.A steam throttling valve with inlet conditions of 3MPA and 500C is connected to the inlet of the turbine. The turbine has 800kW power output and heat absorbed of 500kw. If the mass flow rate is 1kg/s and the exit temperature of steam is 400C, find the exit turbine pressure. (

5.29 From a constant temperature reser- voir (in the surroundings) at 3000°F, there are transferred 2000 Btu of heat to a Carnot engine. The engine receives the heat at 440°F and discharges at the sink temperature of 80°F. (s) Are the heat transfers reversible? Compute the change of entropy of the engine system accompanying the heat added process and the heat rejection process. (b) What is the net change of entropy of the universe in one cycle? of the engine in one cycle? (c) When all the Carnot work produced has been used, what is AS, for the universe? (d) If the input to the engine is 2000 Btu of paddle work (other events remaining as first des- cribed), what is AS, for the universe? Ans. (a) 2.222, -2.222 Btu/°R, (b) 1.644 Btu/°R, 0, (c) 3.124, (d) 2.222 Btu/°R.

Q4// The nozzles of the impulse stage of turbine receive steam at 15 bar, 300 °C and discharge it at 10 bar. The nozzle efficiency is 95 % and the nozzle angle is 20°. The blade speed is that required for maximum power and the inlet angle of the blades is that required for entry of steam without shock .the blade exit angle is 5° less than the inlet angle. The blade velocity coefficient is 0.9. Calculate for steam flow rate 1350 kg/hr: 1. The diagram power. Answer (30.3 kW , 86.3 % ) 2. The diagram efficiency.

20. If 10 kg/min of air are compressed isothermally from P1 = 96 kPa and Vi 7.65 m³/min to P2 = 620 kPa, find the work, change in entropy %3D for a non-flow process and a steady flow process with vị = 15 m/s and v2 = 60 m/s.