lab # - rheology
TRANSCRIPT
Student’s Name:
Determination of the rheological characteristic of mayonnaise
BAEN /CHEN-422-622 page 1 of 6
UNIT OPERATION IN FOOD PROCESSING
Department of Biological and Agricultural Engineering
Texas A&M University
Lab # - Rheology
The product The rheometer The spindles
Model
Number
Torque Range
[dynes-cm]
Shear Stress Range
[Pa]
LV 673.7 10-90
RV 7,187 5-100
HA 14,374 1-200
HB 57,493 4-800
1) Describe the system used to measure the rheological properties of mayonnaise
Rhreometer model:
Spindle type and number:
2) Define if the method is empirical or fundamental, why?
Fundamental: concentric cylinder - Searle or Couette flow - measures shear stress and shear rate
Empirical: any spindle (disk) in a beaker - measures torque and rpm
3) Is mayonnaise thixotropic? Explain your answer.
Thixotropy - is the property of some non-newtonian fluids to show a time-dependent change in viscosity; the longer the fluid undergoes shear, the lower its viscosity.
(a) (b)
4) Calculate the shear stress and shear rate data and determine the rheological properties of this product using only the upper curve results.
BAEN /CHEN-422-622 page 2 of 6
UNIT OPERATION IN FOOD PROCESSING
Department of Biological and Agricultural Engineering
Texas A&M University
Lab 1 - Rheology
Brookfield spindle kσ [Pa]
1 0.035
2 0.119
3 0.279
4 0.539
5 1.05
6 2.35
7 8.40
Brookfield Model M [dyne.cm] C
1/2 RV 3,584 0.5
RV 7,187 1.0
HA 14,374 2.0
HB 57,496 8.0
Determination of the rheological characteristic of soybean oil
Table 1 : Information on the sensor available for couette flow configuration
BAEN /CHEN-422-622 page 3 of 6
UNIT OPERATION IN FOOD PROCESSING
Department of Biological and Agricultural Engineering
Texas A&M University
Lab 1 - Rheology
The product
The sensor
SC4-18 SC4-21 SC4-28
Rotor (BOB)diameter (cm)equivalent length (cm)
1.73.3
1.63.3
0.83.3
Stator (CUP)diameter (cm)height (cm)
2.056.3
2.056.3
2.056.3
HBDV-III is equipped with a head which gives a torque reading of
574.96 dyn m/scale grad. Full scale is 0 to 57,496 dyn- cm for 0 to 100
scale range.
1) Describe the system used to measure the rheological properties of soybean oil
2) Define if the method is empirical or fundamental, why?
3) Is soybean oil Newtonian or non-Newtonian, Thixotropic? Explain
4) Calculate the Shear stress and shear rate for a specific torque value
Method σ [Pa]
γ[1/s]
Newtonian approximation
Viscometer value
Torque ___________ [Nm] angular velocity ___________ [rad/s]
Cup dimensions: d = 27.62 [mm]
BOB dimensions: h = 92.39 [mm] d = 25.15 [mm]
α = Rc/Rb = __________
Discuss your results:
BAEN /CHEN-422-622 page 4 of 6
UNIT OPERATION IN FOOD PROCESSING
Department of Biological and Agricultural Engineering
Texas A&M University
Lab 1 - Rheology
Shear stress calculation - concentric cylinder
Shear rate calculation - approximations
Newtonian Power-Law
BAEN /CHEN-422-622 page 5 of 6
UNIT OPERATION IN FOOD PROCESSING
Department of Biological and Agricultural Engineering
Texas A&M University
Lab 1 - Rheology
M = torque
h = bob hight
Rb = bob radius
Rc = cup radius
Ω = angular velocity = 2πN/60
Determination of the yield stress of ketchup
1) Describe the system used to measure the yield of ketchup
2) Describe the procedure to measure the yield stress
BAEN /CHEN-422-622 page 6 of 6
UNIT OPERATION IN FOOD PROCESSING
Department of Biological and Agricultural Engineering
Texas A&M University
Lab 1 - Rheology
The product The rheometer
The vanes
The results