Reciprocating Compressors & Steam Power Plants

The report presents an outline on the performance of the reciprocating compressors and steam power plants. The report begins by showing some of the main factors that influence the efficiency of the operation of the reciprocating compressors. The report also presents the factors that involve safe operation of the compressors while identifying where faults and hazards mainly occur and how to avoid the faults. The report presents the steam power plant operation details through the Rankine cycle among other factors that determine the efficiency of operating the steam power plants.

Clearance volume is presented as the volume difference as well as the swept volume, where the piston and cylinder head difference presents the gap to show the volume difference. The clearance volume is maintained to ensure the head of the piston does not collide with the head of the cylinder. The distance contained at the circular area presents the clearance volume. The clearance volume can also be given through induced volume when compared to the swept volume to determine the volumetric efficiency.

Volumetric efficiency is the useable piston displacement used for the delivery of gas at the suction stroke end, which also contains the total mass of displacement. Therefore, the volumetric efficiency is identified as the efficiency used to operate an engine to move the fuel and air in the cylinders. The volumetric efficiency is important since it presents the thermal capacity of the cylinder.

The isothermal efficiency refers to the ratio of the work input compared to the pumping work. It ensures that the pressure increased for the air compressor is efficient using the minimum work input through the isothermal compression. Thus, the isothermal efficiency is important since it shows the ideal minimum work input required.

The pressure ratio affects the volumetric and isothermal efficiency through minimizing the total work input to the compression ratio in different stages mainly as a decrease in pressure occurs, which is identified as the ratio of compressor. Thus, the pressure ratio leads to an increase in the isothermal efficiency whereas the pressure increases, the clearance volume increases reducing volumetric efficiency. The pressure ratio has positive results for the isothermal efficiency and negative results for the volumetric efficiency.

Cooling during the process of compression helps in maintaining the consistency of the pressure to ensure the volumetric efficiency is increased. The intercooler helps in ensuring the cooling process occurs effectively while removing unwanted heat within the compressors.

Safety Risks

The operation of the reciprocating air compressors may face numerous issues linked to safety. Thus some of the safety issues to consider include the probability of air entering the orifices such as the mouth or ears leading to fatal injuries. The operation of the compressors at high pressures also depicts a challenge since the pressure can penetrate the skin and cause harm to the individual operating the compressor. Thus, health safety issues need to be considered since other particles or oils can damage the eyes of the individuals (Nag, 2013).

Additionally, safety risks may also include areas where a possible blocked outlet may restrict the flow, which impacts the general performance of the compressor. The failure of controls also, as well as low air consumption affects the compressors since over-pressurization may occur leading to the negative performance of the compressors. The compressors may also encounter other problems such as overheating that may lead to major explosions and fires, which may cause major damages (Nag, 2013).

Another major safety risk that has been related to reciprocating air compressors is the possible application of dirty or wet air, which causes possible fine particles to agglomerate leading to blocking of the valves that ensure safety. Consequently, over-pressurization is experienced leading to other major fatalities such as fires. Safety risks also involve the application of safety valves effectively to ensure that the valves are fitted on medium and large multi-stages to ensure positive displacement of the compressors is attained as the air enters the cooler circuit. Isolation valves should also be installed effectively to ensure the piping for discharge that occurs between the receiver and the compressor. Thus, the safety risk should consider also ensuring the safety valves are designed to withstand high pressures.

Safety risk should also be attained through thermal protection to minimize the possible risks of overheating. The thermal protectors should be given near to the last stage of the compressor of the discharge valve. This protects by eliminating the possible issue of automatically shutting the compressors. Thus, since automatic shutoff of the compressor may negatively affect the dependent safety pressures.

Other safety risks to be considered include the issue on the coolant protection, which ensures the temperature of the water does not exceed the maximum limit recommended. The lubricant protection, explosion protection by determining the compressors working pressure limits, the design outlet temperature remit and outlet bore of the compressors. Safety risks have to be considered on the receivers, the coolers, the air dryers and other issues involved in the processes of installing compressors (Patil, et al., 2015).

The Safe Operation of Reciprocating Air Compressors

The information below presents the safe operation of the reciprocating in the air compressors. The standard operation of the compressors is determined through the following procedures.

  • The compressors hoses, pipes and wires should be inspected prior to usage since if they are worn out or damaged, they may lead to challenging injuries and fatalities through the operation of the compressors.

  • One must also inspect the air tank since it may have holes that influence the operation or efficiency of the outcomes.

  • The reciprocating compressor should only be operated by following the manual, which is provided by the instructor.

  • The safety valves are important to the compressor since they ensure the compressor does not become over-pressurized. Each valve should be inspected through the valve ring.

  • The compressors should be operated using gloves and caution to avoid been harmed by the hot areas of the compressor. The fan and other motor pulleys should be protected from causing any injuries.

  • The compressed air nozzle should be protected, since if the compressed air is released it can damage major parts of the body.

  • When shutting the compressor, one needs to follow the right procedure, which includes first shutting off the compressor, and then unplugging it later. The valve regulator should also be closed to balance the pressure, and draining the air tank. Thus, de-pressurizing the tank, gauges, hoses and pipes to ensure the cooling process is attained.

The Principle Causes of Faults in Reciprocating Air Compressors

  • Faults in the reciprocating compressor occur if outlets are blocked, which may lead to problems of overheating due to over-pressurization that cause major fatalities such as fire explosions.

  • Faults occur from any pressure device in the compressor, which include the valves, gauges and air tanks among others. For instance, if the air compressors safety valves are not well installed between the stop valves, major complications occur that either damage the compressor or end product.

  • The blow-off valves should also be installed well to avoid the faults that cause injuries to personnel and may damage other equipment’s.

  • The valves are the main causes of faults where, if the temperatures freeze the valves collect water, which damages the safety valves causing blockages that may damage the compressors.

  • The air hoses should also be checked and maintained well to avoid faults such as tripping hazards. The air hoses need to be connected to the outlet of the pipes while inspecting other defects that damage the equipment or may cause injury to the personnel operating the compressors.

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Circuit Diagram of a Steam Power plant

B: Operation of the Rankine Cycle of the Steam Power Plant

The Rankine cycle presents the operation cycles of the steam power plants. The diagram above presents the Rankine cycles processes of operating the steam power plant, which include the boiler, turbine, condenser and pump. The Rankine cycle presents that the first process involves the water from the condenser, which is at the lowest pressure gets pumped into the boiler using the highest pressures. The process is adiabatic reversible, which leads to the second process. The second process is where water gets transformed into steam at a continuous balanced pressure level when passing through the boiler. The third process then follows the reversible process leading to the expansion of the steam through the steam turbine, leading to the constant pressure where the condensed steam is changed into water (Wang, et al., 2011).

The Rankine Cycle, therefore, as presented above gives an outline of the steam heating engine. The processes given above gives the expansion and compression reactions, which are not isentropic through the turbine and the feed pump respectively. The liquid (water), passes through the boiler and is transported to the feed pump and then heated on the temperature required. The Rankine cycle processes are identified as the steady flow devices identified in the figure above.

In the cycle above, the Rankine Cycle is used other than the carrot cycle because when using the Rankine Cycle, Vapor can be heated at a balanced pressure level without any challenges. However, if the Carnot cycle was to be used, heating the vapor, the pressure level varies. Thus, one cannot gain the correct end product when using the Carnot cycle since the steam in the process experiences both the expansion and compression during the cycle, affecting the end product. Thus, the consistency anticipated and achieved in using the Rankine cycle brands it effective for the steam power plants operations. The Carnot cycle has 4 reversible processes. The Carnot cycle is therefore, not the best for the steam power plants. The Rankine Cycle is ideal since it eliminates all impracticalities that are highly linked to the Carnot cycle through superheating linked to the steam attained in the boiler, which is then condensed in the condenser. However, this Rankine cycle does not have any internal irreversibility’s. It is ideal as it consists of the isentropic compression perceived in the pump, while the pressure in the boiler is constant. The turbine should experience isentropic process of expansion and heat rejection perceived in the condenser through ensuring constant pressure (Boyce, 2010).

The Rankine Cycle presents that a reciprocating condenser has four main components which include the boiler, the turbine, the condenser and the water pump. The following assumptions are given:

Pressure of the boiler = 100 Bar

Pressure of the condenser is given as = 0.07 bar

Steam temperature that leaves the boiler = 400 oc

Rate of the Mass flow =55 kg/s

Steam data values of the Enthalpy are given as = (Reciprocating Compressors & Steam Power Plants – 2   16

The fraction of dryness Reciprocating Compressors & Steam Power Plants – 2   17

The Rankine cycle has four main processes, which include the four main components as presented in the figure above. They include the boiler, turbine, condenser and the pump. The first process is perceived as the water goes into the pump, it is then compressed through the isentropic process to the pressure of operating the boiler. At this level, the temperature of the water increases (Sotirios & Andreas, 2008).

The second process of the Rankine cycle involves water been compressed from liquid to vapor in the boiler. At the boiler, heat exchange takes place where heat from the gases of combustion are transferred to water at the constant pressures (Patil, et al., 2015).

The third process involves where the vapor from the boiler enters the turbine and is expanded through the process of isentropic. At this level, the temperature and pressure levels decrease, leading the vapor into the condenser. The fourth state is where the water and the vapor mix. The steam has to be condensed at a pressure that is considered constant where heat is rejected to the process of cooling. The steam will then enter into the pump as liquid.

Based on the information provided above, the steam will leave the boiler at a pressure of 100 bar and it is compressed to the turbine. Consequently, the liquid is expanded at a pressure of 400 oC, then enters the condenser at a pressure of 0.7 bar. The steam gets heated again and the process repeats itself.

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Temparature-entropy Chart (T-S)

Based on the chart above, Rankine cycle efficiency is attained when the regeneration process occurs continously. The process of regeneration increases the temparature levels at which the heat gets transported to the boiler as steam.

Cycle Efficiency of the Rankine Cycle based on the figures given above

h2 = 3097 kJ/kg at 100 bar and 400 oC

hf = 163 kJ/kg

h fg = 2409 kJ/ kg

The isentropically process of expansion is given as

S2 = 6.213 kJ/ kg

K = S3 = 0.559 + 8.13x

h3 = hf + x hfg = 163 + 0.733 (2409) = 1928.8 kJ/Kg


h4 = hf at 0.7 bar = 163kJ/kg

Steam out = m (h3 – h4) = 55 (1928 -163) = 97. 1MW

The pump power of the input is attained and displaced through the following values:

h4 = h1 = 163kJ/kg

ɵ in = h2 – h1 = 3102 kJ/ kg

3097kJ/kg – 163 kJ/kg = 2924kJ/kg

The final input of power is given through the process of energy flow variations that are given in (mv (Δp)

Power in = 55 (0.001) (100 bar – 0.7 bar) * 105 = 550Kw

Therefore, the power in = m (h1 – h4)

55 (h1 – 163 kJ/kg)

H1 = 173 kJ/kg


P (Output) = h2 –h3 = 1189.4 kJ/kg

P (output) = 3097 -1928 = 1169kJ/kg

n = p / ɵ in = — %

n = 1169 kJ/kg / 2924 kJ/kg = 0.4%

The Net Power Output

Power output occurs in the second process of the turbine, where expansion occurs. The process is reversible in the turbine given through:

Turbine Power Output

Pout = m (h2 – h3)

Pout = 55 (3097 – 1928)

Net Power output of the turbine is therefore:


Condenser Heat Output

ɸout = m (h3 – h4)

ɸout = 55 (1928 -163)

= 97.075MW

General Efficiency is given through

Power output – Input power

64.29 – 0.55

In percentage form the efficiency is given as

64.3/ Boiler power input

Boiler power input =

m (h2 – h1)

55 (3097 – 173) = 161

Efficiency = 63. / 161 = 0.396

Steam Consumption

Steam consumption is given through:

The net power output divided by the rate of the mass flow given

Thus; 63.7 / 55 = 1.158 MW/ kg/s

The specific steam consumption is therefore, 1,158 MW of a kg/ s


The efficiency of the steam power plant is related to clearance volume that determines the volumetric efficiency and isotheral efficiency as well as the pressure ratio. However, to improve the efficiency of the steam power plants, the efficiency of the turbine should be attained. The turbine of the compressor can be designed through a design that allows the exhausting of the steam at a constant pressure rather than the condenser to increase the general power output efficiency. The design would allow the steam to the process through the expansion stage of the compressor.

The compressor used the energy from the different stages of the turbine that involve the reciprocating processes. The design should ensure that the steam mass flow rate used by the pump should be optimized to ensure the efficiency of the power output process despite low power inputs mainly through the Rankine cycle since the Carnot cycle is not the best process of operating the vapor/ steam power plants (Sotirios & Andreas, 2008).

Gantt chart

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Start Date (2016)

Duration (date)

Task 1: Single and Multi-Stage Reciprocating Compressor cycles

Task 2: Safety risks and faults related to reciprocating air compressors

Task 3: Single Stage Reciprocating Compressors in Air at atmospheric pressure

Task 5: Power Point Presentation on Impulse and reaction Turbines

Task 6: Steam Power Plants and Rankine Cycle

Task 7: Rankine Cycle details for operation steam power plants

Task 8: Reflection and time plan for achieving the results given in the report and logbook

Task 9: Submission of Assignment

Date and month 2017


Period Completed

Competency and Research conducted

Supervisor/ expert

16th of June

Single and Multi-Stage Reciprocating Compressor cycles

Reciprocating air compressors

17th of June

Safety risks and faults related to reciprocating air compressors

Reciprocating Air Compressors

18th June

Single Stage Reciprocating Compressors in Air at atmospheric pressure

Calculations on Reciprocating air compressors

20th June

Power Point Presentation on Impulse and reaction Turbines

Turbines analysis research

20th June

Steam Power Plants and Rankine Cycle

Rankine Cycle and steam power plants

20th June

Rankine Cycle details for operation steam power plants

Rankine Cycle and Steam plant operations

21st June

Reflection and time plan for achieving the results given in the report and logbook

Summary of the report and research

21st June

Submission of Assignment


Boyce, M. P., 2010. Performance and Mechanical Equipment Standards. New York: ASME Press.

Nag, P. K., 2013. Engineering thermodynamics. New York: Tata McGraw Hill Education.

Patil, P. V., Jadhav, S. S. & Dhas, D. N., 2015. Performance and Analysis of Single Stage Reciprocating Air Compressor Test Rig. International Journal of Mechanical Engineeing, 2(5), pp. 56 — 64.

Sotirios, K. & Andreas, S., 2008. Supercritical Fluid Parameters in Organic Rankine Cycle Applications. International Journal of Thermodynamics , 11(3), pp. 101 — 108.

Wang, H. et al., 2011. Performance of a combined organic Rankine cycle and vapor compression cycle for heat activated cooling. Energy, 36(1), pp. 447 — 458.