文火

wénhuǒ
small flame (when cooking, simmering etc)

CEDICT

slow fire; gentle heat

Wiktionary

火力较小且缓的火。

重編國語辭典

（烹饪或煎药时）较弱的火力

維基詞典

Entry Composition

1 文 wén
  1. language
  2. culture
  3. writing
  4. formal
  5. literary
  6. gentle
  7. (old) classifier for coins
  8. Kangxi radical 67
2 火 huǒ
  1. fire
  2. urgent
  3. ammunition
  4. fiery or flaming
  5. internal heat (Chinese medicine)
  6. hot (popular)
  7. classifier for military units (old)
  8. Kangxi radical 86