Heat & Mass Transfer Final Project

Emma Coleman and Benjamin Rawls

Introduction

Sous Vide● Modernist cooking technique ● Uses water bath at exact temperatures ● Usually done with immersion circulator

and vacuum sealer ● Precise repeatable results ● Can create formerly impossible flavors

and textures

Objective

To determine the effect of object geometry on convection coefficients

in a hydroheater.

Materials ● 1 beet● 1 zuchinni● 2 hot plates● 1 stir bar● 1 HOBO● 3 TMC6-HC

temp sensor● 1 tank● 1 temp

controller

Methods

Energy Balance Procedure1. System/Control Volume Boundary: Beet

or Zucchini2. Direction of Heat Transfer: Radial3. Approximate Geometry: Sphere or Cylinder4. Energy Flows & Modes of Heat Transfer:

a. no mass flowb. convection at surfacec. Conduction

5. Boundary Conditions: a. Convection at surfaceb. Symmetrical temp profile

6. Reactions Occurring: none

T∞

T∞

T∞

Beet

Zucchini

Energy Balance Procedure7. Constant k?: Yes

8. Steady State?: No, transient

9. Heat Diffusion Equation:

a) Cylinder: b) Sphere:

10. Solving Approach: Heisler

T∞

T∞

T∞

Beet

Zucchini

Results & Discussion

HOBO Data

Data Analysis

Analytical Solution- Heisler● Fo = αt/r2

○ α=thermal diffusivity○ t=time○ r=radius

● θ=(T0-T∞)/(Ti-T∞)○ T0=final temperature at center of object○ T∞=temperature of fluid ○ Ti= initial temperature of object

● Bi=(hr/k)○ h= convection coefficient○ r=radius○ k=thermal conductivity

Knowns- Fo, θ:

● T∞, Ti, T0, α, t, r, k

Unknowns- Bi, h

Results:

● Zucchini: h=24.71 W/mK● Beet: h=59.41 W/mK

Numerical Solution- COMSOLZucchini:

Experimental T0 : 42.94 °C

Theoretical T0 : 42.79 °C

Experimental T0 : 42.94 °C

Theoretical T0 : 38.74 °C

Beet:

Conclusion

-Factors affecting convection coefficient (h):● Surface geometry● Fluid properties (conductivity, viscosity, density)● Fluid velocity-Only surface geometry varied in this experiment● Convection coefficient for beet, 59.41 W/mK, (sphere)

was greater than that of the zucchini, 24.71 W/mK, (cylinder)

● Beet heated at faster rate initially than the zucchini

Appendix

References1. Ramaswamy, H. S., G. B. Awuah, and S. D. Ali. "Thermophysical Properties of Selected Vegetables as Influenced by

Temperature and Moisture Content." Journal of Food Process Engıneerıng 25.5 (2007): 417-33. Web. 17 Apr. 2016.

2. Tabil, Lope G., Marshall V. Eliason, and Hong Qi. "Thermal Properties of Sugar Beet Roots." Journal of Sugar Beet Research

40.4 (2003): 221-25. Web. 17 Apr. 2016.

3. "What Is Sous Vide." ChefSteps. N.p., n.d. Web. 17 Apr. 2016.<https://www.chefsteps.com/activities/what-is-sous-vide>.