Heat Transfer Device For Off-Grid Medical Sterilization William Dunk David Luker Samuel MajorDaniel Rist Mechanical Engineering The Problem: Unsterile Medical Equipment in Off-Grid Developing Countries 1/5 of humanity lacks access to electricity (International Energy Agency 2009) Off-grid medical clinics unable to sterilize tools Infectious diseases spread rapidly throughout communities Rural Pakistani clinic: 94% observed injections involved unsterile syringe…44% of these patients tested positive for Hepatitis C (World Health Organization 2000) We have designed a thermally powered heat transfer device that will be able to operate an autoclave to sterilize medical tools in off- grid locations Our Solution Production of Thermal Power Steam generated by pre-designed Capteur Soleil Steam flows through our heat transfer device Heat transfer device heats autoclave Water inside autoclave boils becoming steam Temperature and pressure inside autoclave reach desired level, sterilizing medical tools Curved mirrors reflect sunlight on to water filled pipe to produce steam at up to 165°C and 6 bar Proven deployable system: currently utilized in Haiti for cooking Can be expanded to increase capacity (greater steam output) Acknowledgements Our Design Testing and Results Design 1Design 2 *Design Inverted to Show Details Heat Transfer Device Design Criteria Heat transfer device must be able to power an unmodified, commercially available autoclave o All-American 1915x autoclave Heat transfer device must be powerful enough to meet Centers for Disease Control steam sterilization standards o Autoclave must maintain an internal temperature of 121°C for 30 minutes System (power source + heat transfer device) must be completely self-sustainable o Thermal power requires only the sun Heat transfer device must be economical and practical for deployment to developing countries o Total cost of device must be less than $200 Design 1 Maintains 121°C for 30 minutes Biological test results: negative o Biological spores neutralized o Effective steam sterilization Conclusions Our heat transfer device is able to sterilize medical instruments with an unmodified autoclave per CDC requirements Our system is completely self-sustainable requiring only the sun and water Our heat transfer device is economical with a total cost of $175 Our system is a promising solution to the medical sterilization problem currently affecting the 1/5 of humanity who currently live in off-grid locations Steam from Capteur Soleil enters aluminum plate at “steam inlet” Steam travels through grooves, heating aluminum plate by convection Autoclave rests on top aluminum plate, heated by conduction Autoclave and plate are insulated by combination of aerogel, foam and wood with total R-value = 3.45 m 2  K/W = R-20 Front view of Capteur Soleil, designed by Jean Boubour Aramid fiber gasket with SBR rubber binder for steam (0.4/1.6 mm) Bottom aluminum plate (9.5 mm) Top aluminum plate (9.5 mm) Power Results Power testing was conducted using an electric steam generator to maintain a constant pressure Plate designs 1 and 2 were tested with gaskets of 0.4 mm and 1.6 mm thickness Global F Test conducted at significance level of 0.05 F statistic: 11.64;.0001 < critical-value <.001 Data provides sufficient evidence to conclude there is a difference among plate design and gasket thickness with respect to mean power output t test conducted at significance level of 0.05 between gasket thicknesses o t statistic: 6.05; critical value <.001 o Data provides sufficient evidence at the.05 level of significance to conclude that the.4 mm and 1.6 mm gaskets differ in their mean power output o 1.6 mm gasket yields 95% greater power output ANOVA Table for Power Output SourcedfSSMS Between plates and gaskets Within plates and gaskets Total t test conducted at significance level of 0.05 between plate designs o t statistic:.305; critical value <.40 o Data does not provide sufficient evidence at the.05 level of significance to conclude that design 1 and design 2 differ in their mean power output o Plate designs 1 and 2 have equal mean power outputs Sterilization Results Groove dimensions: 6 mm deep x 4.75 mm wideGroove dimensions: 4 mm deep x 3 mm wide GETINGE 24 hour biological test pack Medical tools not properly sterilized All-American 1915x autoclave Insulation container (43 cm x 43 cm) Dr. Douglas Schuler Joe Gesenhues Jean Boubour Attempt at sterilization: sunlight exposure Photo courtesy: Dr. Fischer-Hoch, UTH, Brownsville