Powerplant.docx

(a) Drawing schematic diagram for supplying saturated vapour at desired condition.

(b) Drawing T-S,P-V and H-S diagram.

(c)Write the equation for ideal power of pump. Power of pump = uDP �m3 � Power of pump = ( 1/1000 ) � � ( 5000 - 1000 ) kPa �kg � Power of pump=4.9 kJ/kg As mass flow rate is 2 kg/sec multiply by 2 kg/sec in the equation to get power in kw Power= 9.8 kw Efficiency of pump is given as 80% Actual power required for pump is 9.8 kw / 0.8

Therefore actual power required is 12.25 kw (d) Assuming in first case the isentropic efficiency of turbine as 100% The pressure at the exit of turbine is 200 kpa (given),the saturation temperature at this C (since we are considering saturation vapour at exit) and entropy pressure is 120� �kJ � 7.127 � � �kgK � corresponding to these condition is

Entropy at the inlet of turbine will be same as that of exit of turbine because the process in turbine is isentropic �kJ � 7.127 � � �kgK �which is the upper limit of turbine.and So the entropy at inlet of turbine is C which is the maximum value of the temperature corresponding to this entropy is 560� temperature. The figure below shows the condition for max temperature at the inlet of turbine.

K and the temperature corresponding to The value for minimum entropy is 6.9781 kJ/kg � C (from steam table). this entropy value and 5 MPa is 500� (e) Calculate the isentropic efficiency of turbine. actutal power output hturbine = idealpoweroutput =

( 500�C - 120�C ) ( 560�C - 120�C )

= 0.8636 = 86.36% Inlet Temperature 520 530 540

( �C )

hturbine % 90.90 93.18 95.45

The figure below represents the graph between inlet temperature and hturbine .

Comment: The efficiency of the turbine increases with the increase in the inlet temperature of turbine, which is true from thermodynamic point of view. Efficiency of turbine is the function of inlet temperature of turbine. (f) Rate of work output by the turbine = ( 3574.1 - 2201.9 ) kJ/kg = ( 1372.2 kJ/kg ) �2 kg/sec =2744.4 kw the rate of heat input = ( 3574.1 - 256 ) kJ/kg =3318.2kJ/kg �2kg/sec =6636.2 kw

(g) By heat balance Equation. 6636.2 kw = 2(1000)(Tsource - 560) Tsource = 563.31� C (h)

DQ Rate of entropy generation= T S&= 7.93kW/K No, it does not violet the 2nd law of thermodynamics since entropy increases during heat addition (i) Yes, we are going to sell this idea to the CEO of EKG and Associates as we have seen that the efficiencies and the power output of the plant is really in a good and satisfactory stage after we are going to use a pump to supply the saturated steam in comparison to the normal flow of the steam. As the calculations made in above steps are really impressing and briefs a really good idea that what are the advantages and disadvantages of using a pump instead of allowing the steam to flow freely. As on using the pump in the cycle the time required by the steam to reach the destination is reduced and due to which there is no vapor formation in the steam and the steam is dry and has a greater temperature than that of flowing freely. As the steam is passing by the pump the pressure of the steam is also high and the steam must have a greater impact on the turbine or the palce to which it is destinated. On comparison it is found that the efficiency of the plant is more than the efficiency of the plant which is before using the pump. Also the work done by the turbine also increases after using the pump for transporting the saturated steam and the turbine blades last more longer than they are lasting in the free flow of the steam as the steam takes more time to

reach the turbine blades so the temperature of the steam decreases and the formation of water droplets takes place which lead to the corrosion of the turbine blades takes place. There are also other factors why using a pump is more beneficial to the CEO and the plant as the overall efficiency is increased and therefore the overall production is is also increased and the profit to plant also increases excluding the cost and input required by the pump. As the calculations made above are clearly telling us that a small investment will lead to the greater profit of the firm. The implementation of the pump for transferring the steam also lead to the high temperature steam to reach the turbine at higher pressure with the help of which we can also drive an another turbine to increase the production without adding any other reheater or any other pressure increasing device. Therefore, with all the above mentioned points and facts we are going to sell this idea to the CEO of EKG and Associates.