Cook Stove for Haiti Project Date: February 11, 2011 Location: 78:2150 Time: 10:15am – 12:15pm Detailed Design Review

Team Members Project Leader Rob Reid (ME) Lead Engineer Jordan Hunter(ME) Team Engineers Alex Seidel (ME) Brian Knight (ME) Mike Lagos (IE)

Presentation Overview Project Background Project Overview Customer Needs Assessment Engineering Specifications System Architecture System Integration Risk Assessment Test Plan Flow of Analysis Design Analysis BOM Plan for MSD 2 Traditional Cook Stove

Project Background Image from feaststl.com shows a basic lump charcoal cooking stove The World Health Organization estimates 3 billion people use biomass cooking regularly. Approx. 1.5 million people die each year from stove emissions Our main focus is the people of Haiti who’s main method of cooking is open flame stoves, utilizing charcoal and wood. We are partnering with the H.O.P.E. Organization, which works with the Haitian people to help improve their living conditions and save lives. H.O.P.E. is working with RIT to create an improved cook stove design which is more efficient and less hazardous to its users.

Project Overview Mission Statement Design and construct all mechanical and structural aspects of a thermoelectric biomass cook stove. The stove will utilize a blower/fan powered by thermo-electrics to significantly increase efficiency and reduce fuel consumption and emissions. In comparison with current Haitian stoves, the project stove will have a reduction in emissions and required fuel of 50% Deliverables An improved RIT stove design that has been tested and validated using a working prototype. The improved stove is to reduce fuel use and emissions by more than 50% from traditional Haitian stoves. Build at least two prototype stoves to be sent to Haiti for field testing. Detailed project report. Detailed presentation for Imagine RIT.

Customer Needs

Engineering Specifications

System Architecture

Risk Assessment

Testing Plan Testing Groups Non-Operational Testing Group Operational Testing Group Non Testing Group Destructive Testing Group Untestable Testing Group

Testing Plan Non Testing ES6 – Cost to Produce ES7 – Cost to Operate Destructive Testing ES5 – Pot Weight Range Test ES11 – Stove Drop Test Untestable Testing ES9 – Stove Life Test ES10 – Cycles without Cleaning Test ES12 – Corrosion Test Non-Operational Testing NES –Thermoelectrics Connection Test ES4 – Pot Diameter Range Test ES13 – Time to Replace Parts Test ES14 – Stove Volume Test ES15 – Stove Weight Test ES16 – Lifting Index Text ES21 – Assembly Time Test Operational Testing ES1 – Time to Combustion Test ES2 – Time to Boil Water Test ES3 – Range of Heat Output Test ES8 – Tasks to Maintain Combustion Test ES17 – CO Emissions Test ES18 – Hazardous Emissions Test ES19 – Required Fuel to Boil Water Test ES20 – Maximum Temperature Test

Stove Design Important Dimensions: Stove base Height: 8.5” Radius: 6” Combustion Chamber Height: 6” Radius: 7.25”

Stove Assembly Made up of 5 Components Base Outside combustion chamber shell Combustion chamber Top cover Pot supports

Structural Analysis

Combustion - 2 reactions occur in the combustion of charcoal -- First, a very rapid reaction between Air (Oxygen) and Charcoal (Carbon) to produce CO2 and an extreme amount of heat. -- Second, a much slower reaction that consumes the charcoal and converts the CO2 into CO while consuming heat. - Emissions should be reduced if full combustion is achieved - The larger the lump charcoal size, the deeper a vertical stove would have to be to ensure complete combustion (If not enough vertical space exists in the heated zone for both reactions to fully occur the charcoal will not be fully burned) - Air Flow should be very close to the base and come in from the side -- Air flow holes should be circular unless the stove has a very wide inner diameter or has a rectangular base in which cases rectangular holes with the longest side being the horizontal should be used -- If air holes are used they need to be kept as clean and unblocked as possible - Slower air flows velocities are preferred to ensure full combustion occurs inside of the stove without making it extremely tall/long (There is a certain point where the air flow velocity is too low) - Preheating the air before it first enters will decrease the fuel consumption - All data point to the fact that additional air holes at the top of the stove will not be beneficial in any way. Data from: The mastery and uses of fire in antiquity By J. E. Rehder

Combustion

Analysis Process : Combustion Chamber Heat require to meet specs is calculated Heat gain to sustain boiling is estimated from heat lost Combustion chamber spectrum analyzed with various possible efficiencies and charcoal energy contents Stoichiometric Ratio of the varying charcoals is calculated Calculated : - Heat Output Range - Fuel Consumption - Air Flow Combustion chamber dimensions calculated from estimated density of charcoal

Charcoal Specs

Fuel Consumption vs Time to Complete Boil

Stoichiometric Air Flow vs Time to Complete Boil

Air Flow Analysis Pressure drops due to – Rapid Expansion when air enters outer stove chamber – Orifice – Charcoal Bed – Annulus Pressure Rises due to – Head supplied by fan – Heating of air in combustion chamber Pressure drops through the system are determined to ensure the fan is not supplying more than 1W of power to the air entering the system.

Flow Schematic Annulus Fan Pot & Water Packed Bed of Charcoal Orifices Combustion Air Flow

Major Equations

Assumptions Rapid Expansion coefficient – K=0.85 Determine from Area ratio=A1/A2 – Used Figure 8.15 in Introduction to Fluid Mechanics by Fox, Pritchard, McDonald – Velocity is determined from fan volumetric flow rate Orifice has a square edged inlet – K=0.5 from Area Ratio=A2/A1 – a=0.5 Pressure drop across packed bed of charcoal – Assumed particle size is approximately 1.5”-2.0” – ε (Void Ratio)=Void Volume/Total Volume Power supplied by fan cannot exceed 1W

Parameters

Spreadsheet Layout

Effects of Varying Orifice Size

Effects of Varying Particle Diameters

Thermal Analysis A Thermal analysis of the stove system was then completed in order to help understand the affects of different forms of heat transfer. The key pieces of information needed from this analysis are: Heat Loss Through stove walls Surface Temperatures of the various chambers. (Shown to Right) Affects of different insulations and barriers. This data would then help us to optimize the stove in terms of heat transfer and minimize thermal loses throughout the stove.

Thermal Analysis Equations Used to Calculate Losses due to Conduction, Convection, and Radiation. Radiation Within Combustion Chamber & To Atmosphere q rad = Ac* ε * σ* (T1^4 – T2^4) [Large Cavity] Radiation Within Annulus q rad = (Ac* σ *(T1^4 – T2^4)) [Annulus] ((1/ ε1)+((1- ε2)/ ε2)*(r1/r2)) Conduction Within Insulation Layer q cond =(2*Pi*L*K*(T1-T2)) / ln(r2/r1) Convection Within Combustion Chamber, Annulus, & To Atmosphere q conv = h*A*(T1-T2) Energy Lost in Air q forced = mdot*Cp*(T1-T2) Thermal Circuit Diagram T fire T s1 T s2 T s3 Combustion Chamber Air Annulus 1” Ceramic Insulation Blanket

Thermal Analysis Energy Balances Were used to optimize the system using Excel Solver. Energy Balance Surface 1 q conv-fire + q rad-fire – q conv-annulus1– q rad-12 = 0 Energy Balance Surface 2 q rad-12 + q conv-annulus2 – q cond-ins = 0 Energy Balance Surface 3 q cond-ins + q rad-amb – q conv-amb = 0 Energy Balance Air q conv-annulus1 + q conv-annulus2 – q forced = 0 The energy balances were used in conjunction with the heat transfer equations to solve for the air and surface temperatures in and around the stove.

Thermal Analysis Using the constants to the left, I was able to calculate the approximate surface temperatures. According to these results we exceed our target spec of having a 50 C outside stove wall (TS3). These values were found using 1” thick layer of ceramic insulation (L=1”, K=0.29 W/m KL), From Thermal Ceramics Corp. The inner stove wall is also made of a polished steel, which acts as a radiant barrier.

Thermal Analysis Convection Insert 1” thick ceramic insulation blanket between combustion chamber and outside wall. Secondary wall of polished steel to promote fluid flow and act as a radiant barrier. Radiation Conduction This combination yields a theoretical total heat loss through the stove walls of ~ 120 W.

BOM

Project Plan

Questions?