Delta is commonly used to refer to a difference between two points. So in this case, a delta of 110 degrees means whatever your target temperature is, the radiator should be 110 degrees away from that temperature. Trying to reach 70° means a temp of 180 at the radiator when heating, or -40° when cooling. OP was pointing out that -40° obviously isn’t a feasible temperature for a water-based radiator, so they simply aren’t great for cooling.
Energy transfer is proportional to the difference in temperature between the 2 things (delta T), their contact surface area (in this case the length of the radiator and the size of the fins), and time. If you want a room to change temperature quickly and with radiators that don’t take up an entire wall then you need the water temperature to be very different from the room temperature.
What does deltas mean in this context?
I know I could search it but eh I’m creating content right!
Delta is commonly used to refer to a difference between two points. So in this case, a delta of 110 degrees means whatever your target temperature is, the radiator should be 110 degrees away from that temperature. Trying to reach 70° means a temp of 180 at the radiator when heating, or -40° when cooling. OP was pointing out that -40° obviously isn’t a feasible temperature for a water-based radiator, so they simply aren’t great for cooling.
Temperature difference between the radiator water and room air.
Energy transfer is proportional to the difference in temperature between the 2 things (delta T), their contact surface area (in this case the length of the radiator and the size of the fins), and time. If you want a room to change temperature quickly and with radiators that don’t take up an entire wall then you need the water temperature to be very different from the room temperature.