Selecting tube material purely on thermal conductivity: which material offers the highest conductivity among the following common choices?

Introduction / Context:
Thermal conductivity strongly influences the overall heat-transfer coefficient U when tube-side or wall resistance is significant. Although many other criteria matter (cost, corrosion, fouling, strength), this question isolates conductivity to identify the best heat conduction material among common choices.

Given Data / Assumptions:

• Room-temperature, typical commercial alloys.
• No consideration of corrosion resistance, erosion, or mechanical strength.
• Comparison is qualitative but grounded in well-known conductivity rankings.

Concept / Approach:
Approximate conductivities (W/m·K): copper ≈ 380–400; aluminium ≈ 200–235; carbon steel ≈ 45–60; stainless steels ≈ 14–20; titanium ≈ 17–22. Thus, copper clearly leads, producing a smaller wall resistance R_wall = t / (k * A), which increases U for wall-limited cases.

Step-by-Step Solution:
List relative k values: Cu > Al > carbon steel > stainless ≈ titanium.Select the highest: copper.Acknowledge trade-offs: despite high k, copper may be unsuitable in corrosive chloride or ammonia environments; designers often pick Cu-Ni or titanium for seawater, stainless for corrosives, etc.

Verification / Alternative check:
Material property databases and vendor catalogs confirm this ranking over typical operating temperatures relevant to process heat exchangers.

Why Other Options Are Wrong:
Aluminium is good but below copper; steels and titanium have substantially lower k and are chosen for other attributes.

Common Pitfalls:
Optimizing solely for k without considering corrosion and mechanical design; ignoring fouling resistance which can dominate overall U.

Final Answer:
Copper