Refrigeration Engineering

• Extended Surface (Fin) Geometries in Heat Exchangers:
• Fins expand convective heat transfer surface area ($q = h A \Delta T$):
• (I) Longitudinal fins: Rectangular profiles attached along planar furnace or heat exchanger walls.
• (II) Radial (annular) fins: Concentric circular discs around cylindrical evaporator/condenser pipes.
• (III) Conical pin fins (spines): Protruding tapered rods maximizing heat dissipation with minimum fin weight.
• All three are standard, mathematically valid fin geometries.
• Conclusion: (I), (II) and (III) (Option 1).

Correct option: (1) 0), () and (I!)

Analyzing the statements in relation to Basics of thermodynamics and heat transfer:

The correct option is Option 1: Both Statement (I) and Statement (II) are true..

• Thermoduric Bacteria in Milk Pasteurization:
• Microbacterium lacticum:
• Small, non-spore-forming, Gram-positive coryneform rod that exhibits extreme heat resistance.
• Possesses nearly $100\%$ survival rate through standard HTST ($72^\circ\text{C}$ for $15\text{ s}$) and LTLT ($63^\circ\text{C}$ for $30\text{ min}$) milk pasteurization, frequently surviving exposures up to $80 - 85^\circ\text{C}$ for 10 minutes.
• Serves as a major indicator of uncleaned milking equipment biofilms.
• Conclusion: Microbacterium (Option 1).

Correct option: (1) Microbacterium