Question

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: The cylinder wall temperature of air-cooled engine is generally higher than that of water cooled engine
Reason R: The control of cylinder temperature is more difficult in air cooled engines
In light of the above statements, choose the correct answer from the options given below

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true but R is NOT the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Hint:

Liquid-cooled engines maintain a much more stable temperature because water's high specific heat capacity acts as a thermal buffer.
Air-cooled systems are simpler and lighter but operate at higher, more variable temperatures.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Internal combustion engines generate significant heat during the combustion cycle.
To keep the engine within safe operating temperatures, this heat must be dissipated using either an air-cooling or a liquid-cooling system.
Detailed Explanation:
Let us analyze Assertion A:
Air-cooled engines rely on heat transferring from the cylinder walls to cooling fins, which is then dissipated by the surrounding air.
Because air has a much lower thermal conductivity and specific heat capacity than water, heat transfer is less efficient.
This results in higher normal operating cylinder wall temperatures (typically 150\(^\circ\)C to 200\(^\circ\)C) compared to water-cooled engines (typically 80\(^\circ\)C to 110\(^\circ\)C).
Thus, Assertion A is true.
Let us analyze Reason R:
In water-cooled engines, a thermostat regulates the flow of coolant to maintain a stable, optimal operating temperature regardless of external conditions.
In contrast, air-cooled engines rely on ambient air temperature and air velocity.
This makes it much more difficult to maintain a precise, uniform temperature across different load conditions and climates.
Thus, Reason R is true.
Since the difficulty in controlling heat dissipation (R) is the direct cause of the higher cylinder wall temperatures (A) in air-cooled engines, the reason is the correct explanation of the assertion.

Step 2: Final Answer:
Both Assertion A and Reason R are true, and Reason R is the correct explanation of Assertion A.