This set of Automobile Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Heat Rejection and Cooling”.
1. Why is radiator provided?
a) To cool the jacket water
b) To pressurize the cooling water
c) To provide additional water flow
d) To cool the external surface of the engine
Explanation: Radiator is provided to cool the jacket water. The heat from the combustion gases is transferred to the various parts of the engine like cylinder head and walls, piston and valves.
2. Why is thermostat used?
a) To control the velocity of water
b) To control the distribution of water to various cylinders
c) To control the water temperature
d) To control the pressure of water
Explanation: Thermostat is used to control the water temperature. Whenever the engine is started from cold, the coolant temperature has to be brought to the desired level so that the warmup time is less.
3. What is the advantage of the liquid cooling system?
a) Dependent only on water supply
b) Power absorbed by the pump is considerable
c) Even cooling
d) Very cheap
Explanation: The advantage of the liquid cooling system is even cooling. In this system, water is used as a coolant and made to circulate through the jackets provided around the cylinder, cylinder head, valve ports and seats.
4. What is the material of the radiator cooling tube?
Explanation: Radiator cooling tubes are made of copper. Radiator cores are classified as tubular or cellular. The main disadvantage is repairing any of the damaged tubes.
5. What is a direct system of cooling the air?
a) Cooling water flows by gravity
b) Hot water is continuously cooled and circulated
c) Hot water is simply discharged
d) Water is allowed to evaporate in the cylinder jacket
Explanation: In direct system of cooling air, hot water is simply discharged. In air-cooled system, a current of air is made to flow past the outside of the cylinder barrel.
6. Which pump is used in a forced cooling system?
a) Piston pump
b) Gear pump
c) Vane pump
d) Centrifugal pump
Explanation: Centrifugal pump is used in a forced cooling system. The pump is used to maintain the circulation of the water through the system. The power is transmitted to the pump spindle.
7. What is the purpose of the thermostat in an engine cooling system?
a) To allow the engine to warm-up quickly
b) To prevent the coolant from boiling
c) To pressurize the system
d) To indicate to the driver the coolant temperature
Explanation: The thermostat is used to allow the engine to warm-up quickly. The thermostat unit consists of closed bellows with a volatile liquid.
8. Why does the engine overheating happen?
a) Due to a broken fan belt
b) Due to excess coolant
c) Due to an open thermostat
d) Due to the stuck radiator pressure cap
Explanation: The engine overheating happens due to a broken fan belt. When a fan is broke, it cannot cool the hot water. It should be capable of removing about 30% of the heat from the combustion chamber.
9. What is the purpose of a fan in a liquid cooling system?
a) To disperse engine fumes
b) To pump cold air over the hot water
c) To cool the external surface of the engine
d) To drive airflow when the vehicle speed is low
Explanation: A fan in a liquid cooling system is used to pump cold air over the hot water. The fan is mounted on the impeller spindle which is driven by a suitable belt pulley arrangement.
10. How does the water circulation happen in a thermosyphon cooling system?
a) Due to conduction currents
b) Due to a gear drove water pump
c) Due to change in the density of water
d) Due to a belt-driven water impeller
Explanation: The water circulation happens in a thermosyphon cooling system due to conduction currents. This system is simple and automatic.
Sanfoundry Global Education & Learning Series – Automobile Engineering.
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