Assignment Instructions: 

• Provide descriptive/ step-by-step / detailed solution to all questions, to demonstrate your approach for assessment (see Marking Guides).
• Use drawings where possible/ relevant.
• Use symbols and approaches consistent with learnings in this course.
• The assignment must be done by students individually and any source of information used outside of course material must be referenced properly (see Academic Integrity in course description for details).

Q1 (30marks): The Stokes’ Law is defined by the equation:

1. Describe all of the terms involved, and, state their units in SI.
2. Provide three applications for its use in food processing.
3. Using dimensional analysis, show that it is correct from a dimensional perspective.

Tip: The dimension of Dr is the same as r.

Q2 (30marks):  A fruit juice manufacturer produces a juice concentrate at 65% solids and a fresh juice product at 12% solids content. They want to market a new semi concentrated juice at 20% solids by mixing the two existing products. How much of each stream should they mix to achieve the new product target? Solve the problem using mass balance method.

Tip: Solve the problem for 100kg final product.

Q3 (40marks):  A double jacketed heat exchanger is used to produce tomato paste at 32% solids content from 2 tonnes of tomato juice at 93% moisture content.  Using mass and energy balances calculate:

a) how much water needs to be removed (evaporated) from the juice to make the paste,

b) how much steam will be required in the heat exchanger in this process.

Notes:

• Assume the juice enters the system preheated to boiling point.
• Take the latent heat of evaporation as 2358 kJ/kg, and the latent heat of steam as 2164 kJ/kg.