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An aneroid-type thermostat, also known as a bellows thermostat, is an older style of thermostat used in engine coolant systems to regulate the flow of coolant.

Working Principle:

  1. Construction:
  • The thermostat consists of a metal capsule or bellows that contains a volatile liquid, such as acetone or alcohol, and is sealed with a vacuum inside.
  • This bellows is typically made from materials that expand and contract with temperature changes.
  1. Valve Operation:
  • When the engine is cold, the volatile liquid inside the bellows is in a condensed state, causing the bellows to contract.
  • In this contracted state, the thermostat opens a valve, allowing coolant to flow from the engine through the radiator to maintain an optimal operating temperature.
  1. Temperature Activation:
  • As the engine heats up and reaches the desired operating temperature, the coolant temperature increases.
  • The heat causes the volatile liquid inside the bellows to boil and vaporize, expanding the bellows.
  • This expansion closes the valve, restricting coolant flow to the radiator and allowing the engine to retain heat for efficient combustion and internal lubrication.

Features and Applications:

  • Durability: Aneroid-type thermostats are robust and reliable due to their simple mechanical design.
  • Performance: They provide effective temperature regulation in engine coolant systems, ensuring engines operate within their optimal temperature range.
  • Usage: Found in older vehicles and some industrial applications where mechanical reliability and simplicity are preferred over electronic thermostats.

Advantages:

  • No External Power Required: Operates solely based on temperature changes within the coolant system, without needing electrical or electronic control.
  • Cost-Effectiveness: Generally more affordable compared to newer electronic thermostat systems.

An aneroid-type thermostat is a mechanical device used in engine coolant systems to regulate coolant flow based on temperature changes. Its operation relies on the expansion and contraction of a metal bellows containing a volatile liquid, ensuring engines maintain optimal operating temperatures for efficiency and longevity. Although older, these thermostats remain effective in certain applications where mechanical reliability and simplicity are prioritized.

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