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Objective

Lumped Burrito Using Lumped Capacitance to Cook a Frozen Burrito Chad Pharo & Chris Howald ME EN 340 Heat Transfer Project. Objective.

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Objective

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  1. Lumped BurritoUsing Lumped Capacitance to Cook a Frozen BurritoChad Pharo & Chris Howald ME EN 340Heat Transfer Project

  2. Objective • In ME EN 340, we have to make many assumptions for our homework problems. Lumped capacitance is no exception – several assumptions are made during a typical problem. • For our project, we wanted to see how accurate the lumped capacitance method would be for predicting the cooking time of a frozen burrito. Lumped Burrito

  3. Description of Experiment • We cooked 3 frozen burritos at different temperatures – 300°F, 350°F, and 400°F • The burritos were cooked for the time specified by the lumped capacitance calculations using Tfinal = 165°F • At the end of the time period, we measured the interior temperature of the burrito and compared it to the interior temperature of a burrito cooked with the recommended time and oven temperature. Lumped Burrito

  4. Assumptions • Burrito assumed to be a cylinder • Tsur = T∞ for radiation calculations • Only modes of heat transfer considered are free convection, radiation, and conduction through the burrito (ignore conduction through the cooking rack) • Thermophysical properties of burrito were estimated as those of water (Table A-6)… like the quizzes in class • Emissivity value of plaster board was assumed (ε = 0.92) since the outer tortillas are hard • Final temperature of Tfinal = 165°F was chosen based on average food quality standards Lumped Burrito

  5. CalculationsVariables Defined L = 0.143 m • Properties of water @ 273 K: ρ = 1000 kg/ m3 ; k = 0.569 W/m*K ;  cp = 4217 J/kg*K ; α = 1.3493e-7 m2 / s • Ti = 0°F = 255.37 K • T∞,1 = 300°F = 422.04 K • T∞,2 = 350°F = 449.82 K • T∞,3 = 400°F = 477.59 K • Tfilm,1 = 338.71 K • Tfilm,2 = 352.60 K • Tfilm,3 = 366.48 K D = 0.0381 m Lumped Burrito

  6. CalculationsEquations Used • Free Convection: • Radiation: Lumped Burrito

  7. CalculationsEquations Continued • Biot Number: • Lumped Capacitance: Lumped Burrito

  8. Carrying Out the Experiment… Internal temperature was measured with food thermometer Lumped Capacitance Burrito @ 400°F was crispy on the outside Burrito @ recommended settings burst in the oven (too hot for too long) Lumped Burrito

  9. Results Lumped Burrito

  10. Conclusions • We did not reach the desired Tfinal = 165°F using the lumped capacitance model; however, the burritos were still an acceptable temperature for consumption. • The lumped capacitance results (in our opinion) were better than the recommended package directions because the package directions caused the burrito to burst open inside the oven. • Overall, the lumped capacitance method is an acceptable way to cook a frozen burrito. Lumped Burrito

  11. FYI… Lumped Burrito

  12. Appendices(Hand Calculations) Lumped Burrito

  13. Appendices Lumped Burrito

  14. Iteration 1 Iteration 2 Iteration 3 Lumped Burrito

  15. Lumped Capacitance times Actual temperatures Lumped Burrito

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