Introduction

Air cooler referred to as air cooler, air as coolant, can be used as a cooler, can also be used as a condenser. The air cooler is mainly composed of tube bundles, supports and fans. Air cooler Hot fluid flows in the tube and air blows through the tube bundle outside. Because the amount of ventilation required for heat exchange is large, and the air pressure is not high, axial flow fans are mostly used (see fluid conveying machinery). The type and material of tube bundle of air cooler have great influence on the performance of air cooler. Because the heat transfer coefficient on the air side is very small, fins are often added to the tube to increase the heat transfer area and fluid turbulence and reduce thermal resistance. Most air coolers use radial fins. The optical tube with the outer diameter of 25mm, the low fin tube with the fin height of 12.5mm and the high fin tube with the fin height of 16mm are usually used in the air cooler. The fins are usually made of a material with high thermal conductivity (most commonly aluminum) and are wound or embedded into a light tube. In order to enhance the heat transfer effect of air cooler, water can be sprayed in the inlet air to humidify. This not only reduces the air temperature, but also increases the heat transfer coefficient. The use of air cooler can save a lot of industrial water, reduce environmental pollution and reduce capital construction costs. Especially in water shortage areas, replacing water cooling with air cooling can alleviate the contradiction of water shortage.

structure

The high quality air cooler is mainly composed of three parts: tube bundle, fan and frame (Figure 1). The tube bundle includes a heat transfer tube, a tube box, a side beam and a beam. It can be arranged in three basic forms: horizontal, vertical and inclined top (herringbone) (Figure 2). Among them, horizontal arrangement heat transfer area is large, air distribution is uniform, heat transfer effect is good; When the inclined top is arranged, the ventilator is installed in the central space of the herringbone, which occupies a small area and has a compact structure. In order to counteract the effect of low heat transfer coefficient on the air side, tubes with fins on the outer wall of light tubes are usually used. Finned tube as heat transfer tube, can expand the heat transfer area. Finned tubes are arranged in layers and their ends are connected to the tube box by welding or expansion. Generally, there are 3 to 8 rows of pipes. Tube bundle series size up to 12 meters. The outer diameter of the light tube is often 25 mm and 38 mm, the fin height is generally 12~15 mm, and the tube bundle width is 100~3000 mm. Finned tube is the core element of air cooler, and its form and material directly affect the performance of equipment. Tubes can be made of carbon steel, copper, aluminum and stainless steel; Fin material according to the use of environment and manufacturing process to determine, mostly with industrial pure aluminum, in the corrosion prevention requirements are very high or in the case of special manufacturing process conditions also use copper or stainless steel. The fins can be arranged horizontally or longitudinally. The basic forms of finned tubes (Figure 3) are: wound type, insert type, rolled type, sleeve type, welded type, elliptical tube type, turbulent flow type (including spoke type, slotted type and corrugated type, etc.). The structure of the pipe box mainly includes flange type, pipe block type and collection pipe type (Figure 4). Generally, the former is used for medium and low pressure, and the latter two are used for high pressure. In order to adapt to the thermal expansion of the tube bundle, one end of the tube box is not fixed, allowing displacement along the length of the tube. The ventilator usually adopts axial flow fan.

Ventilation way

There are two ways of ventilation: blowing and blowing. ① Blast type: the air first flows through the fan and then into the bundle. ② Ventilation type: the air first flows through the tube bundle and then into the fan. The operation cost of the former is more economical, the turbulence generated is beneficial to heat transfer, and it is more used. The latter airflow distribution is uniform, conducive to accurate temperature control, small noise, is the direction of development. The outlet temperature of the thermal fluid is mainly controlled by adjusting the air volume through the tube bundle, that is, adjusting the inclination Angle of the blade, the speed of the fan and the opening degree of the shutter. For the fluid that is easy to condense and freeze in winter, hot air circulation or steam heating can be used to adjust the fluid outlet temperature.

Basic form

The basic FORMS OF FINNED TUBE FOR AIR COOLER ARE: SLEEVE TYPE, WOUND TYPE, ROLLED type, welded type, ELLIPTICAL TUBE type, INSERT type, turbulent flow type, spoke air COOLER type, slotted form corrugated form. The tube box structure of air cooler mainly includes flange type, tube block type and collecting tube type. Flange type is generally used for medium and low pressure, and plug type and collection type are used for high pressure.

application

Air (wind) cooler is mainly used for walking machinery (excavator, loader, forklift, crane, combine harvester, road construction machinery, construction machinery, etc.), with air cooling forced to cool the working medium to the required temperature.

cleaning

Most of the cooling water contains calcium, magnesium ions and acid carbonates. When cooling water flows over the metal surface, carbonate is formed. In addition, the oxygen dissolved in the cooling water will cause metal corrosion, the formation of rust. Due to the production of rust scale, the heat transfer effect of condenser decreases. In serious cases, the cooling water has to be sprayed outside the shell, and the pipe will be blocked when the scaling is serious, so that the heat exchange effect will lose its effect. The research data show that the scale deposits have a great impact on the loss of heat transport, and the increase of the deposits will lead to the increase of energy costs. Even a very thin layer of scale will increase the operation cost of the scale part of the equipment by more than 40%. Keeping the cooling channels free of mineral deposits can improve efficiency, save energy, prolong the service life of equipment, and save production time and cost.

Long traditional cleaning methods such as mechanical method (shave, brush) and high pressure water, chemical cleaning (acid) a lot of problems in the equipment when cleaning, such as: cannot completely remove scale and other sediments, acid corrosion on equipment form loopholes, residual acid to secondary material corrosion or corrosion under the scale, eventually led to the replacement equipment, in addition, washing waste liquid is toxic, A lot of money is needed for wastewater treatment.