1. Team P08404: Solar Pasteurizer Concept / Detailed Design Review
Review Date: 2/18/2008
Team Members:
Ben Johns (ME)
Adam Yeager (ME)
Brian T Moses (ME)
Seby Kottackal (ME)
Greg Tauer (ISE)
Faculty Guide:
Dr. Stevens

2. P08404 Detailed Design Review
Discussion Content
Team Roles/Responsibilities
Project definition
General overview
Customer Needs
Engineering specs
Functional Diagram
Modeling
Path to Pasteurization
Input Bucket
Heat Exchanger
Convective Loop/Collector Plate
Valve System
Plenum
Output Bucket
Fault Tree Diagram
Bill of Materials
P08404 Detailed Design Review

3. Team Roles and Responsibilities
P08404 Detailed Design Review

4. P08404 Detailed Design Review
Project Background
Daily 5000 children are dying from diahorreal diseases directly related to lack of poor drinking water quality (Who Water for Life).
It is this team’s goal to design a working prototype that can safely pasteurized water in a developing country.
P08404 Detailed Design Review

5. Project Background Continued
P08404 Detailed Design Review

6. P08404 Detailed Design Review
Customer Needs
End User Oriented Needs:
Safely pasteurize enough H20 for one typical family in a tropical climate.
Cheap
To maintain: Must be affordable to upkeep for typical family of interest.
To produce: Unit must be cheap enough to get into hands of customer.
To use: Should have no consumables – no direct cost to run.
Easy to
Use: Customer will likely have limited educational background, may be illiterate, and probably won’t know English.
Assemble: If possible, end customer should be able to set up unit themselves.
Maintain: Again, should be serviceable by end customer.
Safe: Device must not pose direct health risk to end user (no sharp edges, hot surfaces, excessive glare, etc.)
Durability: Device should last a significant amount of time
EPA Oriented Needs:
Environmentally Friendly: Should be made of materials and employ processes that will not be harmful to the environment.
Distributable: Should be easy to get into end user’s hands.
Tamper Resistant: Should resist undesired repurposing.
Solar: Must be powered by solar energy, per project guidelines.
Need
Importance
Safely Pasteurize Enough Water 9
Cheap
Easy to Use 3
Easy to Assemble
Easy to Maintain
Safe
Environmentally Friendly
Distributable
Resistant to Unintended Uses 1
Solar Powered
P08404 Detailed Design Review

7. P08404 Detailed Design Review
Engineering Specs
P08404 Detailed Design Review

8. P08404 Detailed Design Review
Functional Diagram
P08404 Detailed Design Review

9. System Model
Heat Exhanger
THXexit = Tamb + єHX(m) * (Tpast-Tamb)

10. Calculation
The system was modeled in two simultaneous pieces
-Solar contribution to collector & losses from collector
-Heat Removal from collector plate by water
This formed two open-ended equations containing plate temperature and mass flow rate. Solved simultaneously, steady-state output can be found as a function of solar conditions and ambient temperature by assuming that the output water has reached a specified temperature

11. Solar Contributions, Losses
qabsorbed = (Acoat)(1-Aglass)(qincident – qreflected) qemitted = (Kb)(є)(Tplate^4 – Tglass^4)
Estimated Flow Coefficients ReExt Air =6.5x10^5 RaInt Air =1.1x10^6
Utop = (1/hplate + 1/hglass + 1/hsurf)-1
Ubottom = (1/hplate + t/kwood + 1/hsurf)-1
Losses through side assumed same as bottom

12. Thermal Transfer to Water
1: Conductance of tube-plate bond =kputtyDo/(Do*.5)
2: Conductance of Plate = kplate / (width/2)
3: Convection from water to tube = hconv*Pi*Di
Thermal Bond:
Goldsmith Trans-aTherm
K = 45 W / m2K
q’ = (Tplate – Tfluid)
(1 / C1 + 1/C2 + 1/C3)
(Heat gain, per meter of tubing)

13. Transients Valve Opening Valve Closing Startup
Pressure at top of loop drops, check valve closes, New unpurified water starts closing valve
Valve response: 15K Temperature Change
35g wax, Cp = .55 J/gK, Etotal = 385 J
Estimated 30 seconds max for close
Valve Closing
Flow slows, then stops. After a time lapse, a thermal loop will start, as avg. density will be lower in the collector than in the loop.
Startup
-System volume of 1.2 L must be pasteurized before any usable output. Using lumped capacitance and accounting for losses to atmosphere:
[(Ewater + Eplate)(Tpast-Tamb) + Losses(Time)] = 1
Eabsorbed(Time)
Estimated startup time is < 1 hr for Summer, and < 2 hr for Winter
(In tropical regions)

14. Path to Pasteurization

15. Path to Pasteurization-Input Bucket-Bucket Holder
Our team Choose to use these (5) gallon buckets from USPlastics.com because of their Size shape and lid configuration.
By mounting a mesh screen across the hole, large particulates will be filtered out.
The inputs and output buckets are the same make and model.
P08404 Detailed Design Review

16. Path to Pasteurization-Heat Exchanger
Our Team is using a tube in a tube counter flow heat exchanger. The inside tube 5/16” OD Aluminum tubing, which carries the hot water. The outside tube is made of FDA approved Santoprene 3/8” ID.
By having the cooler water wrapped around the hot water we will minimize the losses and maximize the efficiency.
A counter flow heat exchanger was chosen for a higher temperature change.
P08404 Detailed Design Review

17. Path to Pasteurization-Convective Loop/Solar Collector
The collector consists of a piece of glass, aluminum tubing, and an aluminum plate. The tubing is routed across the plate and is where the water flows through the system. The system is isolated from the surroundings by Cocoon insulation. It is a product which is made of 85% recyclable material.
P08404 Detailed Design Review

18. Path to Pasteurization-Valve System1 5 4 2 3
Water from the collector will flow from point one to point two. This flow over the valve will help the valve react more quickly to temperature changes. Water flows in a loop from 2 through a gas purge system and back into 3. If the Valve is open because pasteurization temperature has been reached then water can flow out through 5. If temperature has not been reached then water flows back through the system from 4 to 1.
The complexity of the system is due to the lag in reaction time in the valve. The valve operates by having calibrated wax go through a phase change, expanding and pushing out a plunger, which then opens our valve. Since the valve takes 30 seconds for a 2/3 stroke, a loop has been built in which gives the valve time to react to cooler water before that water reaches the output.
P08404 Detailed Design Review

19. Path to Pasteurization-Hot Water Reservoir
Pasteurization is a function of temperature and time. Since temperature at which the valve opens can be controlled, a system was designed to hold the water at this pasteurization temperature for a given time. This is accomplished through a reservoir where high temperature water is held for the necessary amount of time.
Taken from Dr. Steven’s Thesis
P08404 Detailed Design Review

20. Bill of Materials Total Cost $217.98
Subsystem Cost of Materials
Collector
$86.52 HX
$31.00
Valve
$30.88
Buckets
$27.11
Box
$14.42
Misc
$9.53
Loop
$6.87
Plenum
$6.69
Vent
$4.96
Total
$217.98
The bill of materials results in the raw materials costing roughly twice the marginal value. This is our first draft of the bill of materials and we hope through using ingenuity and different suppliers we may be able to find cheaper alternatives and drive down costs. Our team was committed to making a device that would be safe and have the desired output. The only way to do this was to harness more of the sun's energy and to make a more efficient heat exchanger, unfortunately both drove the cost of the raw materials up.
P08404 System Review

21. P08404 Detailed Design Review
Fault Tree Diagram
P08404 Detailed Design Review

22. Current State of Design
SD I
SD II 1 2 3 4
Prototype Complete
Current point of project
Phase Zero: Planning
Phase One: Concept Development
Phase Two: System Level Design
Phase Three: Detailed Design
Phase Four: Testing and Refinement
P08404 System Review

23. Plan to Meet Engineering Specs and Customer Needs
Our team plans to meet all of the engineering specs and customer needs except manufactured cost, and fitting a standard pallet*.
*We plan on using a 6' post to hold the buckets which may have to be shipped separately from the rest of the device if it is to be placed on a 48in x 40in pallet
P08404 System Review