Hello, I would like to ask a question. Someone else has applied for a patent for the invention of a heat exchange pipe. Can I use his invention to apply it to a specific piece of equipment?

Theoretically, you can apply for a utility model patent, which is equivalent to your invention and creation based on his patent, and his is equivalent to a basic patent. But when you are manufacturing your device, you should be aware that it may be covered by its patent, which means it may infringe its patent rights. But if there is no problem only when applying for a patent, you can apply.