1. Solar Pasteurizer Team P08404 Project Review Team Members:
Ben Johns (ME)
Adam Yeager (ME)
Brian T Moses (ME)
Seby Kottackal (ME)
Greg Tauer (ISE)

2. Discussion Content Project Overview Customer Needs
Key Engineering Metrics
Design Overview
Mathematical Model
Risk Assessment

3. Project Background

4. Discussion Content Project Overview Customer Needs
Key Engineering Metrics
Design Overview
Mathematical Model
Risk Assessment

5. Customer Needs 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

6. Engineering Specs

7. Discussion Content Project Overview Customer Needs
Key Engineering Metrics
Design Overview
Mathematical Model
Risk Assessment

8. Key Engineering Metrics
Amount of water necessary for family of five

9. Key Engineering Metrics
Defining water as “Pasteurized”
Feachem, Richard G - Sanitation and disease: Health aspects of Excreta and Wastewater Management
Conservative water pasteurization curve for a group of particularly resilient pathogens, enteroviruses.
Other sources propose that this curve is conservative: ex: 65C for 6 minutes. (Stevens, 98)
Team meeting with Dr. Jeffrey Lodge (Microbiologist, RIT) suggested above graph is conservative

10. Key Engineering Metrics
Quantifying Pasteurization
A “Multiple-Tube Fermentation Technique” will be used to verify pasteurization has occurred. This is the same test used by the U.S. EPA when analyzing drinking water.
This technique will involve attempting to culture Coliform organisms in various dilutions of treated water. Results are measured by a Most Probable Number (MPN) Index of organisms per 100 ml.
Coliforms organisms themselves are not dangerous but indicate the presence of other, more dangerous, micro organisms.
Ideal value: Zero Coliform organisms per 100ml given input water with an initial concentration of > 200 MPN per 100ml.

11. Discussion Content Project Overview Customer Needs
Key Engineering Metrics
Design Overview
Mathematical Model
Risk Assessment

12. Functional Diagram

13. Overview of Concepts ExaminedB A C E D

14. Path to Pasteurization
System Components of Chosen Design
Input bucket stores incoming water at elevation for pressure
Water is pre-heated in Tube-in-Tube counter-flow Heat Exchanger
Water enters solar collector and convective loop subsystem
As water comes to temperature, air is released through air vent
Thermostat valve opens at chosen pasteurization temperature
Water is held at temperature in Hot Reservoir
Pasteurized water flows through heat exchanger, putting heat back into incoming water
Pasteurized water collected in output bucket

15. Path to Pasteurization: Water Storage
5 gallon buckets chosen for water storage
By mounting a mesh screen across the fill hole, large particulates will be filtered out.
UV resistant tubing for water delivery
Design Review Feedback / Risk Assessment:
Stand design and bucket size chosen to minimize cost
Life cycle failure of cantilevered supports / bucket handle mount analysis planned for SDII

16. Path to Pasteurization-Heat Exchanger
Tube in a tube counter flow heat exchanger. Inside tube 5/16” OD Aluminum tubing, which carries the hot water. The outside tube is made of FDA approved Santoprene 3/8” ID. Approx. 0.03” thick flow annulus.
Wrapping the cooler incoming water around the hot water minimizes the losses and maximizes the efficiency.
A counter flow heat exchanger was chosen for higher temperature change.
Risk Assessment:
Stagnation Temperature: Temperature inside flat plate solar collectors can reach 400 F. Materials outside of collector area must withstand boiling temperatures.
Tube in Tube Apex: Flow annulus will not be uniform due to Al tubing apexing the arcs in the santoprene tubing.

17. Path to Pasteurization-Convective Loop/Solar Collector
Upstream Temperature Regulation (UTR)
Automotive Thermostat Valves can react slowly to temp change. Sensing temperature upstream from where valve opens prevents leaking of unpasteurized water past valve.
SENSE TEMP
Convective Loop Flow
Water outside of collector is not being heated. This temp differential will drive a change in density between the cooler and hotter areas of the loop. This, combined with the vertical displacement of the angled collector will drive flow through the collector.
This flow can reduce the warm up time of the system.
Check Valve prevents backflow through valve
CHECK VALVE

18. Path to Pasteurization-Venting of Excess Air
Heating water results in the release of previously dissolved air. A method was devised for releasing this excess air through a vent tube coming from a T-fitting at the highest point of the collector.
Design Review Feedback / Risk Assessment:
This method will result in a tall column of coldwater that may flow back into, and contaminate, the system.
Other methods of venting air, such as a floating ball valve, being examined.

19. Path to Pasteurization-Valve System
Water from upper convective loop
Water to upper collector
Design Review Feedback / Risk Assessment:
Seal at thermostat and O-ring angled seal difficult
Extensive testing necessary
Spring clearance value
New concepts for sealing being finalized as of Design Review on 2/18/07
Water from lower collector
Water to hot reservoir
Inside Collector
Outside
Collector

20. Path to Pasteurization-Hot Water Reservoir
Reservoir Design:
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 71C for 6 minutes
This is accomplished through a well insulated reservoir where high temperature water is held for the necessary amount of time.
Design Review Feedback / Risk Assessment:
Thermal losses can reduce efficiency of heat exchanger

21. Cost Calculation
Total Cost $217.98
Marginal Value $100.00
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
Shown: the raw material cost necessary to build a prototype. More complete high volume manufacturing costs will be calculated in SDII

22. Discussion Content Project Overview Customer Needs
Key Engineering Metrics
Design Overview
Mathematical Model
Risk Assessment

23. Mathematical Model Purpose of the Cost Model:
Model assumes a worst case scenario for incident solar radiation and calculates heat transfer to the water, modeled as finned tubes. It also calculates the efficiency of the heat exchanger.
The model approximates the dimensions of the system: the plate size and tubing length for both HX and collection area.
The model also optimizes dimensions based on cost inputs for the tubing, glazing, and plating materials
Design Review Feedback / Risk Assessment:
Verify output by modeling hourly weather data for a range of environments, calculating total daily output.

24. Discussion Content Project Overview Customer Needs
Key Engineering Metrics
Design Overview
Mathematical Model
Risk Assessment

25. Fault Tree Diagram