Thermal Power Engineering Answers

100 kg/min of steam at 34 bars, 340°C (h=3082.0kJ/kg) expands through a turbine isentropically until the pressure becomes 0.25 bars (h= 2540.37kJ/kg). Find the work in hp.

Hot combustion gases of a furnace are flowing through a square chimney made of concrete (k = 1.4 W/m-K). The flow section of the chimney is 20 cm x 20 cm, and the thickness of the wall is 20 cm. The average temperature of the hot gases in the chimney is T, = 300°C, and the average convection heat transfer coefficient inside the chimney is h; = 70 W/m-K. The chimney is los ing heat from its outer surface to the ambient air at T = 20°C by convection with a heat transfer coefficient of h,= 21 W/m2K and to the sky by radiation. The emissivity of the outer surface of the wall is e=0.9, and the effective sky temperature is estimated to be 260 K. Using the finite difference method with Ax = Ay = 10 cm and taking full advantage of symmetry, determine the tem pressure at the nodal points of a cross section and the rate of heat loss for a 1-m-long section of the chimney.

A train starts from rest at a station and accelerates at a rate of 2 m/s2
for 10 sec. It then runs at constant speed for 30 sec, decelerates at 4 m/s2
until it stops at the next station. Find the total distance covered.

A car's speed changes from 15m/s to 25m/s in 5.0s along a straight road. Find the
acceleration of the car during this period.

A turbine operating under steady-flow conditions receives steam at the following state: pressure 13.8 bar, specific volume 0.143 m3/kg, specific internal energy 2590 kJ/kg, velocity 30 m/s. The state of the steam leaving the turbine is as follows: pressure 0.35bar,specific volume 4.37 m3/kg, specific internal energy 2360 kJ/kg, velocity 90 m/s Heat is rejected to the surroundings at the rate of 0.25 kW and the rate of steam flow through the turbine is 0.38 kg/s. Calculate the power developed by the turbine.

Air at 1 atm absolute pressure, 38oC and 80% relative humidity is to be cooled to 18oC

and fed into a plant area at a rate of 510 m3

/min (STP). Calculate the rate (kg/min) at which

water condenses

restaurant food storage air conditioning working on air refrigeration cycle of 10

tonnes capacity works between 4 bar and 16 bar. The air leaves the cold chamber at

0

oC and discharges air at 25oC to the expansion cylinder after air cooler. The

expansion and compression cylinders are double acting. The mechanical efficiency of

compressor and expander are 85% and 80% respectively. The compressor speed is

250 r.p.m and has a stroke of 250mm Determine:

1. C.O.P

2. Power required

3. Bore of compression and expansion cylinder

(Assume isentropic compression and expansion as polytropic with n = 1.25)

An aircraft air conditioner works between the pressure limits of 1 bar and 5 bar. The

temperature of the air entering the compressor from the cabin and expansion

cylinder are 10o

c and 25oC respectively. The expansion and compression follow the

pv1.3=constant. Find the following:

1. The theoretical C.O.P of the refrigeration cycle:

2. If the load on the system assuming the actual C.O.P is 50% of the theoretical

C.O.P

3. The stroke length and the piston diameter of single acting compressor

running at 300 r.p.m and the volumetric efficiency is 85%.

(Take L/d = 1.5 : cp = 1.005 kJ/kgK ; cv = 0.71 kJ/kgK

Refrigerant-134a enters the condenser of a heat pump at 180 psia and 140 ºF at a rate of 8.3 lbm/min and leaves as a saturated liquid. If the compressor consumes 103.25 Btu/min of power, determine the coefficient of performance of the heat pump unit.

2 boilers r connected with parallel to chimney.each boiler is 250 kg/s steam flow with enthalpy 3450 KJ/KG n efficiency is 88.05%,fuel used is 34.3MJ/kg n 8% sulphur.Calculate the chimney height.