What is the working principle of the cooling system's small and large circulation?
4 Answers
Cooling system small and large circulation working principle introduction is as follows: Small circulation working principle: When the engine water temperature is low, the thermostat main valve closes, the bypass valve opens, and the coolant circulates within the engine in a small loop. The coolant circulation path is water pump → water jacket → thermostat bypass valve → small circulation pipe → water pump. At this time, the coolant flow path is short with small flow rate, facilitating rapid engine warm-up. Large circulation working principle: When the engine water temperature rises to a certain value, the thermostat main valve opens, the bypass valve closes, and the coolant forms a large circulation through the radiator. The coolant circulation path is radiator → water pump → water jacket thermostat → main valve → radiator. When the coolant flows through the radiator, the fan's forced air draft dissipates heat into the air to ensure the engine temperature does not become too high. At this time, the coolant flow path is long with large flow rate, hence called large circulation.
The working principle of the automotive cooling system's small and large circulation is quite interesting. From my driving experience, when the engine is just started and the temperature is low, the coolant only circulates within the engine, which is called the small circulation. This mainly helps the engine warm up quickly, saving fuel and reducing cold start wear. When the temperature rises to a certain level, a valve called the thermostat automatically opens, allowing the coolant to flow to the radiator for external cooling circulation, which is the large circulation, preventing overheating issues. The entire process relies on the thermostat to control temperature changes. I usually don't pay much attention to it while driving, but I know it's crucial. If it fails, it may cause the water temperature to skyrocket and boil over, so regularly checking the coolant condition and thermostat faults can save a lot of trouble.
As a car enthusiast, I have some understanding of the cooling system's small and large circulation working principles. Simply put, the small circulation occurs during the initial cold start phase. When the temperature is low, the coolant circulates only within the engine water jacket and water pump, bypassing the radiator. This allows for rapid temperature increase and shortens warm-up time. Once the temperature reaches approximately 85°C, the thermostat valve opens, and the coolant enters the large circulation channel assisted by the radiator and fan for heat dissipation, maintaining a constant optimal temperature. This process not only protects the engine and extends its lifespan but also improves fuel efficiency, making it an exceptionally well-designed system. I often ponder this principle – an aged or stuck thermostat can affect circulation, leading to overheating or starting difficulties, so regular maintenance is essential.
When learning to drive, I came across the principle of the cooling system's small and large circulation, which is quite practical knowledge. When the engine is cold, the coolant only circulates internally without going to the radiator, which is called the small circulation, helping the engine warm up quickly. When the temperature rises, it automatically switches to the external large circulation to the radiator for cooling. The key is the thermostat sensor that controls the switch, acting like an automatic valve to regulate the temperature. The advantage of this design is to prevent engine damage from being too cold or too hot. I always pay attention to the temperature indicator on the dashboard while driving to ensure it's functioning properly, as driving under high temperatures can be very dangerous and lead to malfunctions.
