Monday, March 1, 2010

2009 winning posters at grand challenge summit

i was just looking up some winning posters at the 2009 summit.

heres 2nd place winner in security: HOMES: Highway operation monitoring and evaluation system.
article link: http://www.ncr.vt.edu/Highlights/Dai.html
POSTER LINK: http://www.ncr.vt.edu/Highlights/VA_HOMES_DEMO_POSTER.pdf

And 3rde place winner in Energy and Environment: Experimental Investigation of Non-Wetting Phase Entrapment in Counter-Current Subsurface Flows
Heres the whole list of 2009 winners on grand challenges website: http://summit-grand-challenges.pratt.duke.edu/poster_contest
-justin

Thursday, January 21, 2010

Meeting: Jan. 19th Highlights

meeting time: Tuesday, Jan. 19th
team present: Kevin Hawkins, Skyler Olsen

topics discussed:

- Design Package Document: there are only a few more pieces of our design that need to be figured out before we are ready to order parts. Some of these include: evaporator/condenser sizing, MPPT system (which we can buy if need be), the manufacturing technique for the stainless cap (Kevin suggested we use a different material which may turn out to be a better idea), the final design of the presentation, and the programming.
- Job Assignments:
-Evap/Condenser sizing: skyler
-MPPT system: Justin
-Manufacturing technique for stainless cap: Kevin and Skyler
-design of presentation layout: Kevin and Skyler
-programming: Matt/Skyler/Kevin/Justin

I will be submitting the Design Package document for revisions late tonight and will hopefully see everyone tomorrow at 12:30 in DUKE.

Friday, December 4, 2009

Program flowchart draft/attempt 1


Here is my first attempt at the program flowchart. Let me know if you guys think of anything I've left out.

Wednesday, December 2, 2009

Charge controller circuit

here are 2 circuit schematics. The schematic below drops the voltage level down to 14.4V for fast charge of the battery.

This next schmatic is drop the input voltage down to 13.5V. Its for the float charge.

(for some reason the blog can't upload it)

I have uploaded these images to my public server. http://www.coe.uncc.edu/~jkhan/

I'm going to work on putting these 2 schematics together to make 1 circuit that can accomplish both tasks of Vout at 13.5 and 14.4

Monday, November 30, 2009

Pin In/Out tables

This is the table I have come up with for Pin In/Out.
I know I forgot a few things cause I did this off the top of my head at the beach.


























completed refrigeration design

Below is a diagram of the basic refrigeration design. Upon some HVAC engineer's advice, a switching junction was placed upstream from the TEC to allow refrigerant to flow through only one evaporator at a time while a one-way junction valve was placed downstream to allow suction to evacuate oil from both evaporators and prevent oil starvation.


This design allows us to use one compressor to cool two different areas at different times.

Sunday, November 29, 2009

meeting monday @ 6:30 and comments

Hey everyone,

I wanted to remind everyone of a couple things:

1. Monday @ 6:30 PM in Duke lobby we will have our weekly meeting.
2. I want to try and meet everyday this week in order to get wrapped up for this semester.
3. Please post any progress you have made to the blog.

I finalized work on the heat exchanger and decided to go with a counter-flow design.  This design should give us better heat transfer and allow for a cooler batch of milk entering the refrigerator.

On my web site you can see all of the mathcad files for the project.

Saturday, November 28, 2009

power system

heres some of the stuff of what i have for the solar/power system.

A typical off grid solar panel generator requires solar panels, DC disconnect, charge controller, battery bank & system meter.

Panels: kyocera KC 130TM $450
Disconnect: Outback PV array 20A-125V DC breaker $16
Charger Controller: MPPT-20 $89
Battery: Trojan 24 TMX 12V 85Ah group 24 flooded deep cycle battery $135
(i hope 85Ah will be enough)
System meter: Trimetric TM-2025 12-48 Volt battery monitor system $150

The total of these are right now is $840 which is alot. Right now i'm trying to figure out is how to make some of these things our selves. With the charge controller i'm trying to find out how to charge a battery safely and using MPPT(maximum power point tracking) to store the most power. If we incorporate MPPT, it will allow us to use excess voltage from the pv to charge the battery with more efficienty instead of wasting that extra power.

-Justin

Wednesday, November 25, 2009

roles: Skyler: project management and math models/design

Skyler will continue to mathematically model the rest of the system and will begin to focus on actual components of the refrigeration system including the sizing of the condenser, evaporator and the immersion chiller system. Most of the design is out of the way and the next week will be used to iron out details.

- the immersion chiller needs to be sized
- the condenser and evaporator need to be sized

Skyler will also manage the use of time in the next few weeks so that the project is competed on time.

roles: Kevin: CAD models

An important part of this project will be conveying our ideas to the engineering community by way of CAD models. Kevin will be modeling all of the components of the system in various methods convey our design. Some methods he will use includes:

- Microsoft Visio: this program will be used to create a detailed drawing of our overall design setup and will include power flowcharts, models of complete refrigeration system etc.

- ProE: this program will be used to design the mounting base for all of the components and to make engineering drawings of the components.

- Multisim: this modeling program makes electrical circuit diagrams and will be used to convey our electrical system (SKYLER WILL BE USING MULTISIM TO CONVEY ELECTRICAL SYSTEM)

Many models will have to be made and some outlines will be posted soon for reference.

roles: Justin and Matt: electrical system

Electrical system overview:

the main focus of the electrical system is to run the refrigerator efficiently as possible while making it simple to diagnose problems with the system. the system can be reduced to a series of inputs and outputs that will be listed below.

inputs: 1. power coming from solar panel
2. charge of battery
3. pressures in high and low side of refrigeration system
4. temperature inside chiller system
5. temperature inside refrigerator
6. on/off switch
7. refrigeration cycle switch

outputs: 1. chiller water pump
2. compressor speed
3. solenoid to control refrigeration cycle (immersion chiller or refrigerator)
4. charge to battery or secondary power sink
5. LED display safety system
6. mixing fan

More may be in the works than listed but this should be a basic outline of what needs to be included into the algorithms. Feel free to make amendments by posting comments.

Meeting: Nov. 23 Highlights

meeting time: Monday, Nov. 23
team present: Justin Khan, Kevin Hawkins, Matt White, Skyler Olsen

topics discussed:

- The project design is nearing completion and an abundance of work will need to be accomplished in the next few weeks. Team members discussed each others role and everyone seems to have direction. Here are everyone's roles:

- Justin and Matt: completing the design for the charge controller and CPU for the entire system. This includes a '
voltage controller, charge controller (to distinguish between charging main battery and alternate
source), a CPU to control motor speed, inputs and output signals and a display
- Kevin: creating appealing and detailed CAD models for the entire system
- Skyler: project management and completing the mathematical calculations for the system.

- A detailed post will follow outlining all of these tasks in greater detail. The team is working towards a completion date on Dec. 4th.

Wednesday, November 18, 2009

Meeting: Nov. 16th Highlights

meeting time: Monday, Nov. 16th
team present: Kevin Hawkins, Justin Khan, Skyler Olsen

topics discussed:

- there are three weeks left in the senior design time frame and much is left to be completed. some of the most important aspects left to finish include:

- circuit design for charge controller and compressor speed control
- finalizing refrigeration design including figuring out exact high and low side pressures
tube lengths, a way of cooling the condenser, a way to cool the thermal mass (water-glycol
mix)
- completing the budget

- justin and i discussed what is needed from an electrical standpoint. this included the charge controller, the compressor controller, and safety monitors (under/over charge, leaks, ice over requiring manual defrosting, etc).
- kevin and i discussed solid models and methods of graphic interpretation
- i stated that i would continue to work on a complete model for the refrigerator and proving different systems mathematically. i am going to submit a requirement change/add document that states the maximum allowable milk added to the fridge daily (currently it is theoretically 40L but after the change it will be fixed to 15-17L).

Below is a brief sketch of our design thus far:


Our time is dwindling but everything should be fine if we put our heads together and invest some time into the project. I look forward to working with everyone.

Wednesday, November 11, 2009

its been a while...

So...

Sorry it has been a while since the last post. I have done quite a bit of calculations trying to get the power requirements and different scenarios in sync with each other. As you all are aware we have a power and money problem...as in we don't have very much to work with. Some new design ideas include:

- a heat exchanger used to cool the milk down to a certain temperature using nothing more than a radiator and a human powered fan. By human powered I mean bicycle pedals hooked to a small generator capable of making roughly 150 watts. If the farmer is willing and able to use the bike for a small amount of time to run the fan, it would be quite helpful in cooling the milk and reducing the load on refrigerator. The bicycle setup would also be used in an emergency to charge the battery. The picture below shows a common plate heat exchanger. These heat exchangers are expensive on my first look and therefore we may think about using a cheaper, albeit less effective, heat exchanger using a fan and radiator setup or maybe having a separate small insulated container that contains water/glycol mix with the compressor and running the milk through the chilled mixture via stainless tubes/copper tubes.

Sunday, October 25, 2009

Meeting: Oct. 25 highlights

meeting time: Sunday, Oct. 25
team present: Kevin Hawkins, Justin Khan, Skyler Olsen

topics discussed:

- Our conceptual design presentation is this Friday (Oct. 30). The design of the refrigerator was further discussed and refined. We started a PowerPoint presentation and plan to develop it further on Monday. Significant time was put into trying to develop flow within the presentation. We are meeting with Dr. Kelly on Tuesday (2:00pm, Duke) to practice our presentation.

- From my calculations, thermoelectric modules are too costly, too large (with required heat sinks), and require to much power to use efficiently. I contacted Melcor, a company that specializes in thermoelectric modules and asked if they could confirm my calculations. They sent me a program which calculates the type, quantity and power needed to cool a certain load. The numbers were surprising as they far surpassed the power calculations that I had calculated previously and at last settled the debate of whether thermoelectric modules are a feasible option.

- Insulation was further discussed and no major decisions were made. We will need decide what and how we plan to implement our insulation.

- We decided upon the vapor-compression refrigeration because of its efficiency and reliability. We looked at the Danfoss BD35 model compressor and decided it would be a great fit for our project because it is designed to be used with solar power systems.

- The control system is a point of ambiguity and accounted for a large part of the discussion. The Danfoss compressor can be fitted with a controller that takes care of the entire control circuit requred for our project. The only downfall is that it costs just as much as the compressor at a whopping $220! I would like to try and develop a control system for an 1/8th of the cost.

Wednesday, October 21, 2009

risk assessment doc due this friday...

The risk assessment document is due this Friday. This document anticipates problems that may arise during the project design and build. Problems range from parts ordering, back-ordered products, shipping failures, electrical malfunction, compressor overheating, etc. Any ideas about certain risks would be greatly appreciated.

Monday, October 19, 2009

Meeting: Oct. 19 highlights

meeting time: Monday, Oct. 19
team present: Kevin Hawkins, Skyler Olsen

topics discussed:

- The risk assessment document is due Friday, Oct. 23. The details of the document can be found on the Senior Design website. I will be working on it throughout the week and will be in the Duke building at various times that he will make everyone aware of. If anyone would like to meet anywhere else at anytime let me know and I will be more than happy to accommodate.

- Some discussion about ideas including using polyurethane, paper and wood to build the insulating portion of the fridge. After some brief calculations, this set up should work nicely if we can mimic the steady state environment...which isn't too likely. I will continue to think about new ideas for cheap and effective insulation and welcome any thoughts, criticism, etc.

- There was further discussion about how the milk will be stored inside the refrigerator. We must assume that the milk can be poured directly into the refrigerator as well as being stored in containers and then placed into the refrigerator. The former will require some thought into making the inside of the fridge easily cleanable, safe to be in contact with milk and allow for efficient and sanitary bottling. This seems to be an interesting problem and again I welcome some ideas. The latter will be less problematic as the fridge can be "copied" from other designs.

- Kevin will be doing some research into cutting techniques for the polyurethane as well as finding some information about milk storage.

- I will be working on various parts of the project this week with the majority of my time being taken up with the red tape of the documents due Friday. Some elements I will be exploring include further analysis of refrigeration systems (insulation techniques, materials, compressors, control systems, etc), a breakdown of the circuit required to operate a variable speed compressor, energy usage and methods of storage to reduce energy usage.

- I would like to see some development in a control system (read microprocessor and program code) that can control a variable speed compressor using thermocouples as temperature sensing devices. I would really like to have a prototype built for next weeks conceptual design review.

Let me know if there is anything that I can do to help.

paper...not dirt...

Hey everyone,

I was doing some basic 1-D steady state conduction with a fridge design and came up with some pretty nice numbers...

Using polyurethane as the outside and inside "skeletons" my original idea called for adobe due to its high thermal mass (i.e. it takes a relatively long time for adobe, of the correct thickness, to change its temperature). After running into some difficulty finding any information (and at Dr. Wilson's website it appears that the thermal conductivity has never been found???), I decided to go with another cheap and readily available material...paper. Paper has a thermal conductivity of 0.05 (W/mK), which when compared to other materials and factoring in price...its pretty good. For a frame of reference, fiberglass has a thermal conductivity of 0.04 (W/mK) but is not as cheap as paper.
Another option to reduce cost is to build the outside "skeleton" with wood and then fill the inside gap with paper. If we kept the polyurethane (which by the way has a low thermal conductivity of 0.02 (W/mK)) for the inside box to retain easy cleaning and an inert surface for the milk, we could reduce the cost even more.
Anyway, here are the numbers (all polyurethane w/ paper fill): q= 4.62 Watts

This is the heat that escapes through the fridge walls and doesn't include heat losses due to gaps in the fridge.

Wednesday, October 14, 2009

adobe refrigerator idea...

The rural Mexicans build a lot of structural components from adobe because of its thermal properties. I was thinking we make a polyurethane 'skeleton,' and fill all the areas with adobe (including the lid). If we cut flat sheets of polyurethane with dovetail joints so that the construction would be easy and the joints would be strong, we could ship the entire refrigerator in a relatively small box.

I will post detailed pictures shortly.

Thursday, October 8, 2009

Meeting: Oct. 5 highlights

meeting time: Monday Oct. 5
team present: Kevin Hawkins, Justin Khan, Skyler Olsen

topics discussed:

- New documents were released Friday, October 2nd. These documents outline a clear picture of what is required of the team. Points of interest include the size of the refrigerator (40L/1.45 cu.ft.), the place of installation (permanent, but I believe there is ample design room to make the refrigerator transportable), and that the refrigerator will not be refrigerating anything else.

- We further discussed the possibilities of thermoelectric cooling. Through my brief research, thermoelectric cooling seems very inefficient to cool 1.45 cu.ft. of liquid at 100 degrees F. The thermoelectric problem is one that needs further research and a more defined mathematical model

NOTE: I had said earlier in the week that we would meet up with Dr. Kelly. I will try to complete the necessary work to present to Dr. Kelly and keep everyone involved.

Monday, October 5, 2009

Work Breakdown Structure

Here is the makeshift WBS as promised...



Let me know what you think so we can make changes.

Friday, October 2, 2009

New Requirements Document

Peter just sent some detailed requirements, supplied by Dr. West.

Some interesting comments include:

-refrigerator must store 40L of milk (they would like to see a model for 80L)
-roads are rough and rocky
-refrigerator will be stored inside (possibly in the ground) and be insulated by adobe and concrete
-the milk is goat milk and is the main concern because the cheese is salted
-families work together to transport milk so availability of transportation is not an issue
-refrigerator will need to be a bulk liquid refrigerator
-assume the refrigerator will not need to keep anything other than milk

Very cool that we got some parameters to work within and I am excited to get this thing underway.

I placed a link to the requriments file as well as another link (brush up on your Spanish), in the tool bar.

Thursday, October 1, 2009

my thought from the meeting

i've read what you guys discussed and as for the electrics, we should stay away from using programming as the control system. Programming seems like it would require alot more electronic components. I think we shoud use analog feedback as the control system. As for the accuracy of the temperature control, i dont think it needs to be very accurate. As long as the temperature gets below our required temperature, we've done our job, it should also keep the overall cost less. We need to build a refridgerator for a rural Mexican family, not the 21th century American family. So price should be a bigger concern to us than efficiency.

i've come up with a simple mock up circuit for the refridgeration portion if its using thermoelectric cooling. i can show it tomorrow.

-justin

Wednesday, September 30, 2009

Meeting: Sept. 28 highlights

meeting date: Monday, September 28
team present: Kevin Hawkins, Skyler Olsen, Matthew White

topics discussed:

- A lack of requirements and what exactly to do about the problem dominated the meeting. We discussed possible avenues to take. A mathematical model depicting the feasibility of thermoelectric units versus vapor-compression systems will be created. This model will evaluate three basic sizes of refrigerator: small (1-3 cu.ft.), medium (3-8 cu.ft.) and large (8-14 cu.ft.). These three basic sizes will give the team three different options to investigate while we wait for further requirements from Dr. Jason West.

- Insulation was the next topic discussed. Through Kevin's and Skyler's preliminary research, we have some basic ideas about how refrigerators are insulated. Polyurethane seems to be popular in high-efficiency refrigerators and freezers. Reflective "blankets" could also prove to be effective. More information needs to be retrieved before any solutions can be reached.

- Matthew's experience in electronic control systems was next on the list. He has much experience with control systems and he is fluent in programming language and FPGA's. This comes as a welcome surprise and is exactly what the team needs! We discussed possible methods of control including temperature monitoring devices (infrared, thermistor) and methods to use the data. Sensitivity was a topic discussed and it was agreed upon that a sensitive and accurate controller is needed to maximize efficiency.

- The requirements document (Due Friday Oct. 2) as well as the timesheets were discussed and those requirements will be created and turned in by Skyler.

NOTE: We discussed in the meeting that Skyler needed the timesheets by Friday. This is incorrect. You need to send the timesheets by 7 PM Thursday to allow ample time for Dr. Kelly to sign off on them. Thanks.

Monday, September 28, 2009

some more TE's...

Here is a good link describing the application of thermoelectrics. There seems to be some ambiguity as to what a good application of TE's are other than the known "this thing is way too small to be cooled by vapor-compression." i guess we have a lot of calculations to go through to get a good cost/benefit analysis of what is our best option.

I also just added a collection of links about Thermoelectrics to the sidebar. A lot of good resources.

Thursday, September 24, 2009

Refrigeration 101...

Below is a couple of pictures and links for anyone who needs to brush up on basic refrigeration theory...




Wednesday, September 23, 2009

Solar/cost potential...

Here is a link to solar power potential in Mexico. One of the potential areas, Matehuala, Mexico, appears to have at least 4-5 hours of sun each day during the year. The city has a temperate climate with an average year round temperature of 64 F.

Here is a design for a solar fridge I found at SunDanzer's website. These refrigerators alone cost from $699-1249 and the cost of the batteries, solar panels and control systems could match those prices.

Using the weather information (with safety factor of 1.5 for temperature, 96 F) a 5.8 cu. ft. refrigerator would require 320 Watts of power and need a 133 W (PV rated) solar panel (at 5 hours of sun per day) and a battery rated at 259 Amp-hrs. Gathered the information from this table. The total cost of this set-up would approach $1800 for the fridge ($1149), battery ($250) and solar panel ($400). It would of course cost more because control system, packaging of components and shipping have not been included.

Check out the new link that details Dr. West's contributions to families in Mexico.

Tuesday, September 22, 2009

catching up...

While we wait for guidance from our sponsor lets take it upon ourselves to investigate areas of refrigeration, refrigeration control systems, insulation, solar energy and then post onto this blog about our ideas. This will help us all get up to speed and make sure that we are not trying to solve problems previously dealt with by other researchers. Let me know what you think.

Monday, September 21, 2009

Evaporation Fridge...


Check this out...

I guess it cools to 6 C (43 F). What if we used a hybrid between this and a conventional refrigerator? We could design a refrigeration system to cool the contents an additional 9 degrees and be way better off in terms of power requirements and size. Photo from inhabitat.com

Saturday, September 19, 2009

thermoelectrics

this is justin, i think dr. west want us to look into thermoelectrics as the cooling system.
heres a website that talks about thermoelectrics: http://www.tellurex.com/12most.html

the basic idea of thermoelectrics is the Peltier effect, when an electric current flows through a conductor, 1 side of the conductor will absorb heat while the other side releases heat.

-justin

Thursday, September 17, 2009

Requirements...

Some requirements that I have come up with:

- unit needs to be able to withstand sustained temperatures of 120 degrees F
- the refrigerator unit needs to be able to be lifted by 2 people
- unit must be big enough to store milk and cheese...indefinitely?
- unit must be able to be transported by a vehicle
- refrigerator must keep food under 40 degrees without charge for at least 3 hours
- unit must be comparable in cost to leading solar refrigerators...and hopefully better

Please feel free to post any other requirements.
Here is the statement of work on the senior design website for reference.