1. The heat medium of the air heater system should be hot water, steam or heat transfer oil;

2. The heat medium parameters (pressure and temperature) of the air heating system should be stable, and the heater using steam as the heat medium must keep the pressure stable at 50-100kpa according to the steam pressure.

 3. When the air heater is designed in a closed drying room or drying workshop or workshop heating, when the enthalpy of the outdoor air or the mixed indoor and outdoor air is less than 10.5kj/kg, it is advisable to design a fresh air preheater. When the heat medium is hot water at +5°C, antifreeze measures should be taken.

4. The air heater can be installed horizontally or vertically. When installed horizontally, it should have a slope of >1/100 to remove condensed water.

5. When the temperature rise of the heated air is large, it should be installed in series; when the amount of passing air is large, it should be installed in parallel.

When the heat medium is steam, the steam pipeline and the heater should be connected in parallel; when the heat medium is hot water, the hot water pipeline and the heater can be connected in parallel and in series.

6. On the steam pipeline at the inlet of the air heater, a pressure gauge and a regulating valve should be installed, and a steam trap should be installed on the condensate pipeline.

A shut-off valve must be installed before and after the steam trap, and an inspection pipe must be installed after the steam trap. A regulating valve and a thermometer should be installed on the heat return line of the hot water system of the air heater, and an air release valve should also be installed on the heater.

7. Considering factors such as scaling and dust accumulation of the air heater, the heat transfer area should be added by 10%-20%;

8. The air mass flow rate V passing through the air heater should adopt the economic mass flow rate that minimizes the sum of operating costs and initial investment, usually around v=8kg/㎡.s.

9. When the heat medium of the air heater is hot water, its heat transfer coefficient K value is affected by the flow rate of hot water. Increasing the flow rate of hot water can increase the K value.

The resistance is extremely increased. Therefore, in general low-temperature hot water <100°C heating systems, the flow rate of hot water is generally 0.6-1.8m/s, which is more economical. For high-temperature hot water, the flow velocity is about 0.2m/s.

10. When calculating the pressure loss of the air heater, a safety factor of 1.1 is considered for the air side; a safety factor of 1.2 is considered for the water side. For the steam coefficient, the steam pressure before the heater should be kept not less than 30kpa;

11. The temperature difference between the inner and outer media of the air heater is large, and steel pipe steel sheets and copper pipe aluminum sheets can be selected according to different conditions.

12. For the air heater with both cold and hot functions, the heat medium should be hot water, the temperature of the hot water should be lower than 65 ℃, and it should be softened.