What hot air circulation methods can be used for air cooled heat exchangers (air coolers) in low-temperature environments?

Answer: Using a hot air circulating air cooler in a low-temperature environment is an effective measure of anti freezing and anti condensation. The following hot air circulation methods can be used in low-temperature environments:

1) Blast type internal hot air circulation: This design requires one of the two combined fans in each span of the air cooler to be able to operate at an adjustable angle. When the ambient temperature drops to a dangerous point, adjust the inclination angle of one fan blade to drive air to flow downwards and enter another fan for circulation. In order to prevent the influence of wind direction and speed on the downward airflow, a wind screen is installed at the inlet of the fan, which is generally 1.2-2.4m high. There should be a buffer interval of about 3 ℃ in the design between blowing downwards during reversing and blowing upwards during resetting, otherwise the fan will repeatedly change when blowing upwards or downwards. In addition, in some cases, when the fan blows downwards, consideration should be given to whether the equipment below the fan can withstand higher air temperatures. The disadvantage of this hot air circulation method is that the cold and hot air cannot achieve good circulation and sufficient mixing, and there is still a phenomenon of stratified flow of cold and hot air. If not handled properly, it may still cause freezing. This design is used for fluid outlet temperature without strict control requirements, but it also aims to maintain the superiority of the original design of the fan, which can save the investment of blinds.

(2) The internal hot air circulation method with top louvers: Due to the use of louver structures, the hot air circulation performance can be significantly improved. There are two operating modes available: summer and winter. In summer operation, both fans supply air upwards and use self regulating fans and top louvers to regulate the outlet temperature of the fluid. When the temperature drops to a dangerous level, it changes to winter operation mode, allowing one of the fans to supply air upwards. Adjust the angle of the fan blades based on the change in fluid outlet temperature, and adjust the opening of the louvers based on the temperature of the circulating air entering the pipe bundle.

(3) The suction type internal hot air circulation method: The basic situation and application are similar to the blowing type internal hot air circulation method.

Although the above three internal hot air circulation methods have the advantages of simple design and low investment, they cannot truly circulate and mix air well. Despite the use of wind screens, cold and hot air still undergoes stratified flow, which can cause freezing or changes in fluid outlet temperature, and cannot fully meet the selection requirements in severe cold weather conditions. Therefore, the external hot air circulation method is highly valued. Although it requires more investment and complex design, precise control of the fluid outlet temperature can be achieved. External hot air circulation is only used for blast type structural types.

4) Blast type external hot air circulation method: This hot air circulation method generally arranges the hot air circulation channel and louvers on both sides of the air cooler with downward air flow, and the running fan always blows upwards. When the ambient temperature drops to the specified value, open the bypass louver

Window, close the top louver to ensure that the temperature of the mixed air reaching the tube bundle is at the specified value. This design does not necessarily use a self regulating fan. If a regular fan is used, the outlet temperature can be controlled by adjusting the louvers, but this control is not precise. This hot air circulation design scheme can operate at any temperature and can close all inlet and outlet louvers,

The air is circulated through hot air. The regulation of external hot air circulation is to maintain the temperature of the air entering the tube bundle as a constant value, change the air flow rate passing through the tube bundle, and achieve the purpose of controlling the outlet temperature of the process fluid. The temperature of the air entering the bundle is maintained by adjusting the intake, exhaust, and short circuit louvers with the help of an air temperature regulator. The adjustment of air flow is achieved by controlling the adjustable fan with the help of a fluid outlet temperature regulator. Pressure balance must be calculated for air inlet, outlet, side louvers, steam coils, and bends

Pressure loss. In the external hot air circulation mode, the maximum output of the fan is not in summer, but in winter. The necessary amount of circulating air should be calculated based on the required mixed air temperature, and for safety reasons, an additional amount must be left. The external hot air circulation can be designed as a single-sided hot air circulation, which has the advantage of saving materials. The non circulating side can be connected to other air coolers to reduce footprint and facilitate layout. The external hot air circulation method can also be used for the technical renovation of old factories.

The above several hot air recirculation methods each have their own characteristics, and some methods are more systematic

Complex, involving multiple components, and the failure of one component can affect the operation of the entire equipment, so the reliability of the components is relatively high. Generally, blinds are prone to malfunctions in severe cold areas, so the materials for the bearings, pins, and connecting rods of blinds need to be strengthened compared to the standard. The fan, motor, and transmission mechanism must be of high quality and have a certain safety factor.