thermionic cell

例句：

1. 1.Thermionic valves are widely used in electronic circuits.
   热电阀在电子电路中广泛使用。
2. 2. Thermionic valves are used to control the flow of electricity.
   热电阀用于控制电流的流动。
3. 3.Thermionic valves are used in various applications, including power generation and heating systems.
   热电阀在各种应用中都有使用，包括发电和供暖系统。