At approximately 20 °C and near-atmospheric pressure, the thermal conductivity of liquid water is about how large? Evaluate the truth of the statement: “It is about 0.51 (W/m·K).”

Introduction / Context:Accurate property data for water underpin many HVAC and heat-transfer calculations. Thermal conductivity dictates conductive heat flux through liquids and influences convective heat transfer coefficients through dimensionless groups like Prandtl number.

Given Data / Assumptions:

• Temperature near 20 °C (room temperature).
• Pressure near 1 atm.
• Liquid water with typical purity.

Concept / Approach:Standard property tables report the thermal conductivity of liquid water at 20–25 °C in the range of roughly 0.58 to 0.60 W/m·K (commonly cited ~0.598 W/m·K at 25 °C and ~0.59 W/m·K at 20 °C). Therefore, a value of 0.51 W/m·K is significantly lower than accepted reference values, making the given statement false for typical conditions.

Step-by-Step Reasoning:

Verification / Alternative check:Consult engineering property tables or reliable databases; they consistently list ~0.6 W/m·K for liquid water around room temperature.

Why Other Options Are Wrong:

• (a) True is incorrect because the value is too low.
• (c) Pressure effects at near-ambient conditions do not justify 0.51 W/m·K.
• (d) Ice water (solid–liquid mixture) is a different phase consideration; the liquid’s k remains near published values.
• (e) Salinity changes k slightly but not enough here.

Common Pitfalls:Using an outdated or misprinted table; always check units (W/m·K) and ensure the property is for liquid, not vapor.

Final Answer:False