Background · Web viewProject Page | 9 Page | 9 Section: ……………… Student name ID Signature Date Submitted Mark Background Cogeneration or combined heat and power (CHP

Abu Dhabi Men’s College

EMC-4923 Desalination & PowerProject

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Section: ………………

Student name ID Signature

Date Submitted Mark

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Background Cogeneration or combined heat and power (CHP) is the use of a power station to generate

electricity and useful heat at the same time from the combustion of a fuel or an alternate thermal energy source.

In separate production of electricity, some energy must be discarded as waste heat, but in cogeneration this thermal energy is put to use. All thermal power plants emit heat during electricity generation, which can be released into the surroundings through cooling towers, flue gas, or by other means. In contrast, CHP captures some or all of the by-product for heating, either very close to the plant, or — especially in cold climates — as hot water for district heating with temperatures ranging from approximately 80 to 130 C. This is also called combined heat and power district heating (CHPDH). Small CHP plants are an example of decentralized energy. The process heat at moderate temperatures (100–180 C) can also be used in absorption refrigerators for cooling. [ref: Wikipedia].

With respect to desalination, cogeneration is the process of using excess heat from electricity generation, or useful process heat, for another task: in this case the production of potable water from seawater or brackish groundwater in an integrated, or "dual-purpose", facility where a power plant provides the energy for desalination.

Cogeneration takes various forms, and theoretically any form of energy production could be used. However, the majority of current cogeneration desalination plants use fossil fuels and nuclear power as their source of energy. Most desalination plants located in the Middle East or North Africa use their petroleum resources to offset limited water resources. The advantage of dual-purpose facilities is they can be more efficient in energy utilization, thus making desalination a more viable option for drinking water. [ref: Wikipedia].

Project Problem Statement This mini-project is to be completed in partial fulfillment of the course “Desalination & Power, EMC-

4923”; Student will work individually and submit a MS word report documenting the solution and results, and a PPT presentation of the results highlights – Parts k, l.

In this mini-project, you will consider the study of a hypothetical cogeneration-desalination problem in order to gain some insight into the process, the calculations involved, and the behavior of the various outputs. This should bring together the different fragments of the process covered in the [Desalination and Power, EMC-4923] course at ADMC.

The purpose of the report is to document the solution to the given cogeneration-desalination problem using what you learned in class. A discussion of the results is to be documented and presented.

In the project problem description statement given below, the process heat generated is used as the heating load to a single-effect evaporator (SEE) to generate a distillate product. The SEE process hardware is described by figure 1a. Figure 1b shows a general profile of the temperature variation

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across the hardware. Detailed description of the SEE process and the mathematical model can be found in the class notes [EMC-4923] for learning outcome 4.

Help for the treatment of a cogeneration problem can be found in the class notes for learning outcome 5.

a. SEE Schematic Diagram [EMC 4923]

b. Apparent temperature variationFigure 1. Single Stage Evaporation Process [EMC 4923]

The above SEE desalination configuration is common to all the projects. The following set of

specifications is to be used in the solution of the SEE process:

The seawater temperature, Tcw, varies over a range of 5°C to 30°C.

The feed water temperature, Tf, is less than the brine boiling temperature by 4 to 15 °C.

The steam temperature, Ts , is higher than the brine boiling temperature by 4 to 15°C.

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The seawater salinity, Xf, range is 32,000 to 42,000 ppm.

The salinity of the rejected brine, Xb, is 70000 ppm.

The boiling temperature, Tb, varies over a range of 55 to 100 °C.

The heat capacity of seawater, distillate, and reject brine are assumed constant and equal to

4.2 kJ/kg °C.

You must first solve the cogeneration problem, and use the results to continue the solution of

the SEE process. The connection between the two processes (power generation and

desalination) is through the process heater block (left to students), where you will use your

understanding of the individual processes that make up the overall problem.

While the cogeneration process is well defined and fixed, the desalination of seawater via

SEE can be analyzed by varying some key operating parameters (the cooling water

temperature, seawater and brine salinity, and feedwater temperature) in order to investigate

the behavior of the SEE process based on the mathematical model formulated in class. This

means that you will rely on the same formula sheets provided for SEE (LO4) and CHP (LO5)

in order to develop your solution. The analysis should shed light at the behavior of key

output and control parameters (such as the cooling water mass flow rate, the performance

ratio, and the evaporator and condenser heat transfer areas.)

You may use MS Excel, Matlab, EES, or similar tools to help you do the calculations… But I would

encourage everyone to first do the work on scratch paper, and then type your report when done. If

you need help, do not hesitate to see me immediately…

You will need to use the steam tables A4 – A7 (Y. Cengel’ s Thermodynamics textbook)

Your report should include the material presented above to begin with. Add sections under

the headings: Calculations (for parts a, b, c, d, e, f, g, h, i, j, k, l); Discussions (for parts a,

b, c, d, e, f, g, h, i, j, k, l);

Marking: See Rubric for Report and Presentation…

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Cogeneration Plant & Single Effect Evaporation (SEE) Desalination A desalination SEE plant requires 4 kg/s of saturated steam at 2 MPa, which is extracted from

the turbine of a cogeneration plant. A schematic of the hardware and a T-s diagram are shown in

figure 2 for the cogeneration plant. Steam enters the turbine at 8 MPa and 500°C at a rate of 11

kg/s and leaves at 20 kPa. The extracted steam leaves the process heater as a saturated liquid and

mixes with the feedwater at constant pressure. The mixture is pumped to the boiler pressure.

Assuming an isentropic efficiency of 88%for both the turbine and the pumps, determine

a. temperature of the process heater steam.

b. the rate of process heat supply.

c. the net power output.

d. the utilization factor of the plant.

a. Cogeneration plant hardwareb. T-s Diagram

Figure 2. Cogeneration plantBased on the results of the cogeneration system, choose proper SEE operating parameters

according to general specifications given earlier, and produce plots of the following output and

control parameters against variations of key input parameters (here we consider only the cooling

temperature, Tcw, and salinity, Xf as inputs) in the proper range suggested at the beginning of

this problem statement. In each case, interpret and discuss your plots… Explain in simple terms

the meaning of the variables you are plotting, and then explain the behavior based on the plot and

the physics of the process..

e. The distillate product mass flow rate.

f. The performance ratio.

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g. the specific heat transfer area sAe of the evaporator.

h. the specific heat transfer areas sAc of the condenser.

i. the specific cooling seawater mass flow rate, sM cw.

IMPORTANT: In each case above, show the formulation, and a sample calculation. But

for plots, you must use the Excel workbook provided.

Effect of seawater temperatureConsider a range of Tcw = 5 oC to 30 oC. Calculate and tabulate as follows, then plot.

Tcw (oC) Md (kg/s) PR Ae/Md Ac/Md Mcw/Md51015202530

1. Calculation and Plot of the product mass flow rate vs seawater temperature: Md vs Tcw.

2. Calculation and Plot of performance ratio vs seawater temperature: PR vs Tcw.

3. Calculation and Plot of specific heat transfer area vs seawater temperature: Ae/Md vs Tcw

4. Calculation and Plot of specific heat transfer area vs seawater temperature: Ac/Md vs Tcw.

5. Calculation and Plot of specific cooling water flow rate vs seawater temperature: Mcw/Md vs

Tcw.

Effect of seawater salinityConsider a range of Xf = 32000 ppm to 42000 ppm. Calculate and tabulate as follows, then plot.

Xf (%) Md (kg/s) PR Ae/Md Ac/Md Mcw/Md3.23.43.63.84.04.2

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6. Calculation and Plot of the product mass flow rate vs seawater salinity: Md vs Xf.

7. Calculation and Plot of performance ratio vs seawater salinity: PR vs Xf.

8. Calculation and Plot of specific heat transfer area vs seawater salinity: Ae/Md vs Xf

9. Calculation and Plot of specific heat transfer area vs seawater salinity: Ac/Md vs Xf.

10. Calculation and Plot of specific cooling water flow rate vs seawater salinity: Mcw/Md vs Xf.

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Report Rubric Name: ……………………………………… Section ………….Scale A B C D F

Cover page 5 5 4 3 2 1

Background 10 10 8 6 4 2

Problem Statement 10 10 8 6 4 2

Calculations&

Discussions100 A B C D F

1.Assumptions

2. Formulas,

3. Solutions,

4. Plugins,

5. Results,

6. Discussions

A 10 8 6 4 2

B 10 8 6 4 2

C 10 8 6 4 2

D 10 8 6 4 2

E 10 8 6 4 2

F 10 8 6 4 2

G 10 8 6 4 2

H 10 8 6 4 2

I 10 8 6 4 2

J 10 8 6 4 2Excel Plots

& Discussions

30 A B C D F

1. Excel sheet

2. Tables

3. Plots

4. Discussions

30 24 18 12 6

Report Quality 15 A B C D F

Organization, Proper format 5 4 3 2 1

Neatness, Relevancy 5 4 3 2 1Clear discussions &

conclusions 5 4 3 2 1

Report Total 170

Report mark

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Total from above ………………… . Percent: ……………

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Presentation Rubric Name: ……………………………………… Section ………….Excel Plots A B C D F

Assumptions 5 4 3 2 1

Plot 1Data / Plot 5 4 3 2 1

Discussion 5 4 3 2 1

2Data / Plot 5 4 3 2 1


3Data / Plot 5 4 3 2 1


4Data / Plot 5 4 3 2 1


5Data / Plot 5 4 3 2 1


6Data / Plot 5 4 3 2 1


7Data / Plot 5 4 3 2 1


8Data / Plot 5 4 3 2 1


9Data / Plot 5 4 3 2 1


10Data / Plot 5 4 3 2 1


Total 105Presentation mark

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Total from above ………………… . Percent: ……………

Summary: Report + Presentation mark (255 max)

Report (10%) Presentation (5%) Total Mark %

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Documents

Background · Web viewProject Page | 9 Page | 9 Section: ……………… Student name ID Signature Date Submitted Mark Background Cogeneration or combined heat and power (CHP