Automotive radiator heat exchange In a water-cooled automobile engine, how does heat transfer from the hot coolant inside the radiator to the surrounding air? Select the most complete combination of modes.

Introduction / Context:
A radiator is a compact crossflow heat exchanger. Understanding the sequence of heat transfer modes helps diagnose cooling problems and design efficient thermal systems in automobiles.

Given Data / Assumptions:

• Coolant flows inside thin metal tubes with external fins.
• Ambient air moves across fins due to vehicle motion and/or a fan.
• Surfaces are metallic and at temperatures modestly above ambient.

Concept / Approach:
The overall process involves three modes. First, energy moves from the moving coolant to the tube inner wall. Second, it travels through the tube/fin metal. Third, it is released from the outer fin surfaces to the air stream. Radiation always exists between warm fins and surroundings, although it is usually smaller than forced convection in automotive service.

Step-by-Step Solution:
Inside tubes: convection from coolant to inner wall (forced by water pump).Across metal: conduction through tube wall and into fins.From fins: primarily convection to air; plus net thermal radiation to nearby surfaces and sky.Therefore the correct and complete answer includes conduction, convection, and radiation.

Verification / Alternative check:
Heat exchanger analysis uses overall heat transfer coefficient U combining inside convection hi, metal conduction, and outside convection ho, with a small radiation term added when needed. This framework confirms all three modes participate.

Why Other Options Are Wrong:
Radiation only or convection only omit essential steps through the metal wall.

Conduction only ignores the fluid-side heat transfer and airside removal.

Convection and radiation ignores the necessary conduction path through the tube/fins.

Common Pitfalls:
Overlooking fouling inside tubes (reduces inner convection), bent/dirty fins (hurts airside convection), or low coolant flow; all degrade overall U more than radiation ever helps.

Final Answer:
conduction, convection and radiation