Do radiator encasings block heat convection?

The shelf will reduce the output, but not much — there's a lot of space around it for airflow. The metal case will block heat more (radiation out the front is kind of foiled — but even there not all that much, provided the top and bottom openings are unobstructed. Once upon a time years ago there was a thread on this, with a bunch of examples…

There are three ways to transfer heat

• Conduction
• Convection
• Radiation

Understanding each way heat is transferred is key to understanding how a radiator or other heat emitters operate.

Conduction is heat passing thru solid items from one end to the other. think of a frying pan on the stove. You heat the bottom of the pan with the burner. the bottom gets hot where the flame is located or electric element is located. But the rest of the pan also gets hot by conduction. because the frying pan is one piece of metal, the entire pan gets hot… even the handle. that is why you need a pot holder the to pick up that pan from the stove. Convection can also happen when two solid items are touching each other. So that is conduction.

Convection is when the heat of one item is moved by a fluid like water or air. Think of the water in the boiler gets hot from the flame. then a pump moves that hot water to the heat emitter (the radiator) where the water can harm up that radiator. That water is convecting heat form one place to another place. A radiator will do the same thing in the room using air as the fluid medium that moves the heat. He hot radiator heats the air next to it. that air becomes lighter because hot air is lighter that cold air. When that heated air moves up out of the way, cold air moves across the floor to replace the air that is rising away from the radiator. that cold air then picks up more heat from the radiator and rises away while more cold air moves across the floor to replace it.

Eventually the convection currents cause a very slow convection current circle around the room from the radiator to the ceiling across the ceiling where is cools off and eventually dropping to the floor and back the the radiator. This is why we place radiators on the outside wall when ever we can.

Radiation is the third way to transfer heat. That heat is transferred by infrared radiation. That radiation will heat objects and people without heating the air or space between them. That heat will actually travel down defying gravity. Think of the sun in the sky. relative to earth, those heat rays are traveling down to earth. Have you ever gone to a warehouse that has infrared heaters in the ceiling? that ware house can be 40° or colder, but if you step under the rays of the infrared heater you are instantly warmer. not because the air around you got warmer… No, the infrared rays are bombarding your body and that makes you feel warmer.

So if you block the rays of infrared heat from reaching you with a radiator cover, the you will not feel that heat on your body

Likewise if you block the convection currents from flowing from the bottom of the radiator to the top of the radiator and out into the room, then you block the amount of heat that is released into the room.

If you have an oversized radiator in a room, then you may want to cover it. If you have a covered radiator in a room that is cold, then remove the cover. If you home is balanced, then stop overthinking this project. 🤣🤔🤣🤔🤣🤔🤣🤔🤣🤔

Read my explanation above

As far as this picture…

once you digest my comment you will see that in this illustration the radiator on the left is almost completely covered. The top and bottom are closed off, blocking the convection current (air) flow. The front grill lets only a small amount of infrared radiation out of the enclosure. Pretty much cutting that radiator to less than half of its capacity.

The center cover has a bottom and top opening which may actually increase the convection currents across that radiator. A well designed cover

The one on the right with no cover has both convection and infrared radiation. This is the way that radiator was intended to be installed. So if it is a room that is getting too hot, then you may want to design a cover to slow down the amount if heat into the room.

Of course covers to control and balance heat from a steam radiator is the last step, after you get the venting balanced, so all the radiators are hot at the same time. (Within Rocket Surgery guideline and time constraints)