Air conditioning unit filter and heat exchange equipment dusting and scaling treatment method

After the dusting phenomenon occurs in the filter of the HC air conditioning and refrigeration network air conditioning unit (also known as the air conditioning box), the air resistance will increase and the fan efficiency will deteriorate. However, if the heat exchanger is dusted or fouled, it will lead to transmission. The increase in thermal resistance. And the corrosion of dirt for a long time is easy to cause the pressure resistance of the pipeline to deteriorate, and even the phenomenon of system leakage; after the scaling of the water spray system, the nozzle is often blocked, which seriously affects the heat exchange efficiency of the spray chamber. In order to improve the efficiency of the air conditioning system and extend the service life of the equipment, it is entirely possible and necessary to design a simple and easy maintenance device to regularly and easily maintain the air conditioning equipment. With the addition of this unit, we only need to add an additional solution tank or replace the ordinary spray pump with an acid-resistant pump, so it is extremely economical during the actual maintenance process.

First, the filter form commonly used in air conditioners

1, initial effect filter

The primary filter generally uses a metal mesh, a porcelain ring, a glass filament, a coarse-pored polyurethane foam or various rayon as a filter layer, and a network and a fixed frame constitute a filter. In recent years, non-woven fabrics are being developed and utilized. The above filters need to be manually cleaned and replaced. In order to reduce the workload of the cleaning filter and improve the operating efficiency, a transmission wound filter can be used. This filter is mainly composed of a metal mesh (fiber cloth) filter material and a filter material roll. The filter is slowly rotated by the transmission mechanism, and the dust is cleaned by itself in the oil tank, and continuously works.

2, medium efficiency filter

This filter is generally used with a diameter of about lOp. A glass fiber of about m, a medium-porous polyethylene foam or a filter made of acrylic, polypropylene, polyester or the like as a filter material. Different filtration effects will be obtained at different filter layer thicknesses and filtration rates. In order to improve the filtration efficiency and increase the processing air volume, it is often made into a drawer type or bag type filter element. At present, the medium-efficiency filter has gradually adopted a chemical fiber filter, and the filter material is made into a felt shape, and the fiber is dense and dense along the thickness direction of the filter material, from coarse to fine. Under the same conditions, chemical fiber filters are more efficient and less resistant than foam or glass fiber filters. The advantages of large dust holding capacity.

3, high efficiency filter

High-efficiency filters are mainly used in ultra-clean air conditioning systems. For final filtration, pre- and intermediate-stage pre-filters should be installed. The filter material of such a filter is ultrafine cotton fiber, ultrafine glass wool or the like. These filter media are generally less than 1 m in diameter and the filter material is in the form of a sheet of paper. In order to reduce the flow resistance and increase the diffusion effect on the fine dust, a low filtration rate (for example, 2.0 to 2.5 cm/s) is employed. To do this, fold the paper multiple times. The filtration area is 50 to 60 times the ventilation area. After the filter paper is folded, the middle passage is separated by a corrugated separator. High-efficiency filters can be used in non-toxic biological cleanrooms to achieve efficient capture of bacteria in airborne dust particles.

Second, the cause and harm of dusting and scaling

In addition to the ultra-clean air conditioning system, the general comfort air conditioning unit often uses a coarse filter. During use, the dust particles in the air are adsorbed on the filter screen, which inevitably causes the filter to become clogged, increasing the resistance of the airflow and affecting the efficiency of the fan. In severe cases, the fan head is insufficient and the air supply requirement cannot be met. The filter should be cleaned regularly to meet the operating conditions of the air conditioning unit.

But in actual use. Some construction units neglect the problem of convenient maintenance, and the operators only consider how to facilitate and extend the single running time of the air conditioning unit when maintaining and managing the air conditioning unit. Sometimes even the coarse filter is removed. After the unit is operated for a certain period of time, the dust is adsorbed between the fins of the heat exchanger of the air conditioning unit, thereby causing a decrease in heat exchange efficiency and a sharp decrease in the amount of air supplied. In addition, since the dust adheres to the fins, the condensation water cannot be condensed toward the beads during operation and cannot be smoothly dropped onto the water tray, which increases the heat transfer resistance.

Surface heat exchanger for both hot and cold. The use of hot water or steam in the heat medium inevitably causes scaling (mainly scale) inside the pipe. Since the thermal conductivity λ of the heat exchanger steel wall is large (λ≌50w/m·k), the thermal conductivity λ of the scale is small (λ=1.2～1.4W/m·k), only the former 2 .4 to 2.8%. As a result, the heat transfer resistance of the heat exchanger is increased, and the effect of the air conditioning unit is significantly reduced. For the spray chamber, dusting and fouling also have a serious impact. We can analyze the following factors that affect the heat exchange efficiency of the spray chamber:

(1) Mass flow rate of air up (u is air flow rate, m/s; p is air density, kg/m). When the fins of the filter or heat exchanger are blocked, the air mass flow rate through the air conditioning unit is reduced, and the air flow rate is decreased. Experiments have shown that the heat exchange efficiency of the spray chamber is deteriorated due to the decrease in air mass flow rate and the decrease in air flow rate.

(2) Water spray coefficient μ. The water spray coefficient refers to the amount of water used to process each kg of air. If the air volume passing through the spray chamber is G (kg/la) and the total spray volume is W (kg/h), the spray coefficient μ is expressed as:

When the system piping becomes fine, the nozzle is clogged, causing the water spray to decrease and the water spray coefficient to decrease. Practice has proved that a reduction in the water spray coefficient within a certain range will result in a decrease in the heat exchange efficiency of the spray chamber.

(3) Structural characteristics of the water spray chamber. The structural characteristics of the spray chamber mainly refer to the form of the nozzle, the aperture, the nozzle arrangement density, the number of rows, the spacing of the pipes, the direction of the water spray, and the section size of the spray chamber. Experiments have shown that when the other conditions are the same, the nozzle aperture is small, the water droplets are small, and the contact area with air is increased, so the heat exchange efficiency is good. However, the smaller the aperture of the nozzle, the more likely the nozzle is blocked, and once the nozzle is blocked due to fouling, the design requirements cannot be guaranteed, and the advantage cannot be reflected.

Third, the treatment of dust and scaling

1, the processing of the filter

Since the filter of the air conditioning unit is basically detachable, it is convenient to clean or replace it. Under normal circumstances, it can be washed with water. However, if there is oily dust in the environment, it is not effective to wash with water. In this case, it is treated with polyester dust (a washing liquid). The specific method is: after removing the dusty filter, it is drenched with water and dried to dry. Then, apply a proper amount of the liquid to the filter evenly, and let the liquid permeate for 3 to 5 minutes. Finally, rinse with water until the dust is completely removed, and normal operation can be resumed.

2. Treatment of water spray pipes and nozzles

We can set a water inlet valve and a drain valve at the highest and lowest points of the sprinkler system (see Figure 1). A solution tank is placed on top of the air conditioning unit. In operation, first close the water outlet valve before the spray pump, open the drain valve to drain the water in the spray pipe, and then close the nozzle. Fill the tubing with the prepared scale remover (eg gram) from the solution tank through the inlet valve. When the predetermined time (usually 3 to 4 hours) is reached, the drain valve is opened to remove the liquid, and finally rinsed with water for 2 to 3 times. If the spray pump used is an acid-resistant pump (an acid-resistant pump can also be added), we can set up a pipe in the inlet pipe of the pump and a solution tank (see Figure 2) to form a cycle. When using, first remove the water in the water tray through the drain valve, then pour the prepared scale remover into the circulating water tank, start the pump to force the circulation for 1 to 2 hours, and finally use the clean water to cycle 2 to 3 times.

3. Heat exchanger treatment

In order to make the surface fins of the heat exchanger fully contact with the liquid medicine, it is preferable to use a circular spray on the surface of the heat exchanger, and a forced circulation is adopted for the inside. Both can be cycled in the same tank and the flow can be adjusted via the respective valves (see Figure 3). The number of nozzles of the liquid medicine can be determined according to the size of the windward area of ​​the heat exchanger and the spray area of ​​a single nozzle. Other parameters such as pump head, flow rate, nozzle water spray pressure, pipe diameter, etc. can be easily checked from the nozzle water spray performance chart. Got it. In the specific operation, first spray the surface fins of the heat exchanger with clean water. After the dust on the surface of the fins is sufficiently wet and there is no dripping, the liquid medicine is sprayed, and the liquid and the fins are fully contacted for 10 to 15 minutes, and then the water is cleaned. Thoroughly washed away.

Fourth, matters needing attention

1. Equipment and piping used for descaling and cleaning should be pre-considered when the equipment is installed. If it is not considered during installation, it can be temporarily installed during the specific operation. After the operation, the equipment and piping can be removed without waiting for the next operation. Use it again.

2. After the descaling and cleaning operations are finished, be sure to rinse the liquid to prevent the residual liquid from corroding the equipment.

3, the maintenance of air conditioning units generally choose spring and autumn. Through the above-mentioned methods to carry out economic and effective maintenance on a regular basis, the heat and humidity exchange efficiency of the unit and the fan head and purification requirements can be ensured, and the service life of the unit is prolonged and the economic benefit of the enterprise is improved.

HVAC tour is a large investment and technical training activities by the air conditioning and refrigeration networks HC, HC heat pump network, HC heating heating network, HC fresh air network, 51 batches of network co-host plant, designed to help companies develop new markets, development of channels and seek Potential business opportunities, at the same time, for the engineering and dealers to organize the most cutting-edge technical training, build a bridge of communication between industry, enterprises and businesses. Fill in the form below and register for registration↓↓↓

Editor in charge: Fu Shuifang