Question:
Which of the following will be the highest internal pressure for heat exchanger for UHT processing ?
Which of the following will be the highest internal pressure for heat exchanger for UHT processing ?
Show Hint
Since \( 1\text{ bar} \approx 14.5\text{ psi} \), pressures expressed in bar are much higher than those in psi for the same numerical values.
To prevent milk from boiling at \( 140^\circ\text{C} \), pressures well above atmospheric pressure (\( \ge 4\text{ bar} \)) are required.
To prevent milk from boiling at \( 140^\circ\text{C} \), pressures well above atmospheric pressure (\( \ge 4\text{ bar} \)) are required.
Updated On: Jul 21, 2026
- 6 - 8 psi
- 2 - 4 bar
- 6 - 8 bar
- 2 - 4 psi
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Verified By Collegedunia
The Correct Option is C
Solution and Explanation
Step 1: Understanding the Concept:
Ultra-High Temperature (UHT) processing of milk involves heating milk to temperatures of \( 135^\circ\text{C} \) to \( 150^\circ\text{C} \) for a few seconds to achieve commercial sterility.
At these high temperatures, milk would boil and flash evaporate if kept at atmospheric pressure.
Step 2: Detailed Explanation:
To prevent boiling, fouling, and structural damage to the heat exchanger plates or tubes during UHT processing, the system must be operated under high internal pressure.
The saturation pressure of water at \( 140^\circ\text{C} \) is approximately \( 3.6\text{ bar} \) absolute.
To provide a safety margin and ensure that the milk remains completely in the liquid phase without any boiling, the internal operating pressure inside the UHT heat exchanger is maintained at a higher level, typically in the range of 6 to 8 bar (or \( 90 \) to \( 120\text{ psi} \)).
Therefore, option 3 represents the correct pressure range.
Step 3: Final Answer:
The highest internal pressure required for a UHT heat exchanger is 6 - 8 bar.
Ultra-High Temperature (UHT) processing of milk involves heating milk to temperatures of \( 135^\circ\text{C} \) to \( 150^\circ\text{C} \) for a few seconds to achieve commercial sterility.
At these high temperatures, milk would boil and flash evaporate if kept at atmospheric pressure.
Step 2: Detailed Explanation:
To prevent boiling, fouling, and structural damage to the heat exchanger plates or tubes during UHT processing, the system must be operated under high internal pressure.
The saturation pressure of water at \( 140^\circ\text{C} \) is approximately \( 3.6\text{ bar} \) absolute.
To provide a safety margin and ensure that the milk remains completely in the liquid phase without any boiling, the internal operating pressure inside the UHT heat exchanger is maintained at a higher level, typically in the range of 6 to 8 bar (or \( 90 \) to \( 120\text{ psi} \)).
Therefore, option 3 represents the correct pressure range.
Step 3: Final Answer:
The highest internal pressure required for a UHT heat exchanger is 6 - 8 bar.
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