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A boiler produces 9000 kg of steam while I tonne of coal is burnt. The steam is produced at 10 bar from water at 15^ prime prime c The dryness fraction of steam is 0.9. Determine the efficiency of the boiler when the calorific value of the coal is 32 000 kJ/kg [Ans. 70.65%]

Unit mass of a certain fluid is contained in a cylinder at an initial pressure of 25 bar. The fluid is p * V ^ 2 = allowed to expand reversibly behind a piston according to a law constant until the volume is doubled. The fluid is then cooled reversibly at constant pressure until the piston regains its original position; heat is then supplied reversibly with the piston firmly locked in position until the pressure rises to the original value of 25 bar. Calculate the net work done by the fluid, for an initial volume of 0.05 m^ 3 .

1.   A turbine is supplied with steam at 40 bar, 400oC, which expands through the turbine in steady flow to an exit pressure of 0.2 bar, and dryness fraction of

0.93. The inlet velocity is negligible, but the steam leaves at high velocity through a duct of 0.14m2 cross-sectional area. If the mass flow is 3 kg/s, and the mechanical efficiency is 90%, calculate the power output of the turbine. Show the process is irreversible and calculate the change of entropy. Heat losses from the turbine are negligible. Sketch TS diagram.

A certain fluid of 10 bar is contained in a cylinder behind a piston, the initial volume being 0.05m³. Calculate the work done by the fluid when it expands reversibly according to the linear law to a final volume of 0.2m³ and a final pressure of 2 bars.

The shaft of a steam turbine produces 600 Nm torque at 50rev/s. Calculate the work transfer rate from the steam

A compressed spring above the piston exerts a force of 60 N on the position. If the atmospheric pressure is 95kpa, determine the pressure inside the cylinder

. A wet steam at a pressure of 1.0 𝑀𝑃𝑎 has a quality of 85%.

i. Use thermodynamic steam tables to determine its entropy and specific volume.

ii. Use the Mollier chart to determine its enthalpy.

iii. For each of the results above, calculate the internal energy of the steam.

Determine the enthalpy of a saturated steam at 30𝑜 𝐶 using the non-flow energy equation

and the tabulated properties of pressure, specific volume and internal energy. Compare

the result with the tabulated value of ℎ𝑔.

Find out about the wall construction (number and type of layers) of a sauna (treatment and/or relaxation room as illustrated in Figure 6), thereby determining the heat transfer mode, the range of ambient conditions under which they operate, typical heat transfer coefficients on the inner and outer surfaces of the wall, and the heat generation rates inside. Determine the size and methodology of the heating and air-conditioning system that will be able to maintain the typical sauna conditions, for when 10 persons are inside the sauna at the same time.

Two large parallel planes having emissivities of 0.4 and 0.6 are maintained at temperatures of 846 K and 288 K, respectively. A radiation shield having an emissivity of 0.2 on both sides is placed between the two planes. Calculate (a) the heat-transfer rate per unit area if the shield were not present, (b) the heat-transfer rate per unit area with the shield present. If the emissivity of the shield is increased by 50%, how many shields are needed for the heat transfer rate per unit area as compared with the obtained results from (b)?

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