Many Beijing apartments, including mine, are heated partially by steam provided by municipal authorities. The way this works is that steam comes into the apartment and is used to heat radiators, and then the cold steam (water) goes back to the city. This kind of scheme is called “district heating.” I don’t know the design details of Beijing’s district heating system, but, if done well, district heating can be very energy efficient.
My apartment has one radiator in each room. The radiators consist of hollow vertical metal tubes, which each are about one inch in diameter and six feet tall, arranged in a grid. The steam (water) flows inside the tubes. This is a pretty common design for many kinds of steam-to-air heat transfer devices.
It turns out that the radiators used for apartment heating are a lot like heat recovery steam generators. In an HRSG, air is used to heat water (to make steam), while in these radiators steam is used to heat air. Below are some photos of the radiator in my living room:
Here’s a schematic of an HRSG from Appendix A of my thesis (highly interested readers should look for Figure A.6):
Aside from not having fins, the radiators in my apartment look pretty similar to HRSGs. Armed with this knowledge, I have several minutes of bland conversation ready for any cocktail party! Spending two years of my life working on HRSG modeling is finally paying off.