This air conditioner has sold extremely well this summer, and the maker has added two production lines.
Tips
usage
Describes a surge happening right now, this season or this quarter. The steadier word is 畅销, for something that keeps selling for years, which is why a bestseller is a 畅销书 and never a 热销书.
grammar
A verb, but it stands in front of a noun just as often, with no 的 in between: 热销产品, 热销车型, 热销榜 (the sales chart).