How is the shell thickness of a water-cooled chiller evaporator determined?

How is the shell thickness of a water-cooled chiller evaporator determined?

• A. Material yield strength
• B. Internal pressure formula (UG-27)
• C. Outer diameter
• D. Heat transfer coefficient

Answer: (B)

Shell thickness is set by the need to safely contain the internal pressure. The ASME code provides a specific internal-pressure thickness formula (UG-27) that determines the minimum wall thickness using the design pressure, the shell diameter, and the material’s allowable stress at the operating temperature, with adjustments for weld efficiency and corrosion allowance. This method directly ties thickness to pressure containment, rather than to the material’s general strength alone, the outer diameter by itself, or thermal design parameters like the heat transfer coefficient. So the thickness is determined from the internal pressure using the code-specified equation, which is why this option is correct.

Shell thickness is set by the need to safely contain the internal pressure. The ASME code provides a specific internal-pressure thickness formula (UG-27) that determines the minimum wall thickness using the design pressure, the shell diameter, and the material’s allowable stress at the operating temperature, with adjustments for weld efficiency and corrosion allowance. This method directly ties thickness to pressure containment, rather than to the material’s general strength alone, the outer diameter by itself, or thermal design parameters like the heat transfer coefficient. So the thickness is determined from the internal pressure using the code-specified equation, which is why this option is correct.