• Air-conditioned
• Became distant
• Became less ardent
• Calmed (down)
• Chilled
• Iced down
• Lost enthusiasm
• Lost heat
• Lost intensity
• Lost interest
• Lost passion
• Put in the fridge
• Sat on a sill, as a pie
• Sat on a sill, maybe
• Simmered down
finned cooled cylinder — цилиндр с охлаждающими ребрами