| Author | Tao, Qihua |
| Call Number | AIT Thesis no. AE-92-13 |
| Subject(s) | Food industry and trade--Electric equipment
|
| Note | A thesis submitted in partial fulfillment of the
requirements for the degree of Master of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | In this study an experimental ohmic heating unit was
designed and fabricated for the continuous flow thermal
processing of liquid foods. The unit was supported by a
specifically developed data acquisition system for sensing the
liquid temperature distribution, system voltage and current with
time. A separate small ohmic heating unit was also used for batch
heating tests.
The developed ohmic heating system was thoroughly tested for
evaluating its performance based on both static and steady-state
continuous flow experiments. The data acquisition system
performed well and enabled the recording of temperatures, voltage
and current at an interval of every two second s. It was found
that the ohmic heating was fast and homogenous. The current flow
in the system increased with the temperature rise showing a n
increase in the electrical conductivity of the product whereas
the voltage remained almost constant. After calibrating the
system with NaCl solution, the electrical conductivity of the
fresh orange juice was determined as a function of temperature.
In continuous flow heating experiments , the . steady-state
temperature of liquid was automatically decided by the flow rate,
applied voltage gradient, physical properties and dimensions of
the heating unit . The horizontal heating configuration showed
better performance than the vertical configuration both in the
static and continuous heating operations .
. Using the heat loss characteristics of the ohmic heating
unit and electrical conductivity of the product, it was possible
to model the heating operation both in static and steady-state
continuous flow conditions. For any given voltage gradient,
electrical conductivity and dimensions of heating unit, the
relationship of temperature rise with heating time was estimated
reasonably well in case of the static model, and steady-state
temperatures and current for the continuous flow mod e l. The
developed models may be effectively used for scaling- up of the
similar proto-types. Finally, the physical quality of the orange
juice was not adversely affected by the ohmic heating.
|
| Year | 1992 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Jindal, Vinod Kumar |
| Examination Committee(s) | Illangantileke, Sarath G. ;Athapol Noornhorm ;Maohua, Wang
|
| Scholarship Donor(s) | Japan; |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 1992 |