Fan coil units must be reasonably selected for the

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Fan coil units must be reasonably selected for air conditioning systems. Fan coil units are widely used end equipment in centralized air conditioning systems. The reasonable selection of fan coil unit not only directly affects the effect of air conditioning, but also is an important link to ensure the normal operation of the system and reduce the energy consumption of air conditioning. Especially in the occasions with high precision or strict process requirements, it is necessary to reasonably import the air supply parameters with an amount of US $1.566 million in October

air supply and cooling (heating) are the basic functions of fan coil unit. Wind is the medium and carrier of cold, which directly affects the cooling capacity, air supply temperature difference, ventilation times, room temperature gradient and fluctuation range, that is, determines the accuracy and comfort of air conditioning. Therefore, ensuring sufficient air volume is the prerequisite to achieve the expected air conditioning effect. It should be pointed out that the air volume mentioned here is the actual air supply volume of the batch units in normal use

according to the requirements of the room net space volume and the minimum ventilation times, the minimum air supply volume can be calculated. For high-precision process air conditioners, air volume verification is a necessary procedure for the type selection and calculation center. When selecting domestic fan coil units, the model cannot be selected according to the calculation results and the sample parameters, because the nominal air volume listed in the sample of domestic fan coil units is higher than the actual air volume

jb/t, the industrial standard of the former Ministry of machinery industry of China, "fan coil unit", stipulates that the nominal air volume must be measured under the specific working conditions of disc ■ yaw (5) 000j microcomputer controlled electro-hydraulic servo pressure testing machine, which is mainly used to test the mechanical properties of finished highway bridge bearings. The test tube is not water-proof and the static pressure difference between the air inlet and outlet is zero. However, the actual use conditions of fan coil units are obviously different from the test conditions: in actual use, concealed units often should also be equipped with air inlet and return grilles, filters and short air ducts, plus the influence of many factors such as condensate on the surface of the coil, dust accumulation and filter blockage, which will lead to the increase of wind resistance and the decrease of air volume. Surface mounted units also have the problem of air volume decline, but the decline is small, so the actual air volume of domestic fan coil units must be lower than the nominal value. The lack of air volume will cause the cooling capacity to decline, and then form the phenomenon that the actual performance (air and cooling capacity) of the unit is lower than the nominal value, so that the air conditioning system cannot achieve the original design effect. Since the nominal parameters of domestic fan coil units cannot be reproduced under actual service conditions, they cannot be used as the basis for selecting products. The nominal parameters given in China's industry standards and samples of various manufacturers are actually meaningless for concealed units. Because when it is in normal use, the air volume under cold working conditions is 20% - 30% lower than the nominal air volume, and the unit under long-term operation is even 50% lower

in foreign fan coil samples, the air volume and cooling capacity under different external static pressure are generally given for the convenience of users. Although some foreign concise samples only give the nominal air volume, its meaning is different from the provisions of Chinese standards. It generally refers to the air volume value under a certain external static pressure, so the air volume of foreign fan coil units with similar nominal air volume will be 20% - 50% higher than that of domestic units

it should also be emphasized that when using foreign concise samples, it should be noted that foreign companies often implement different standards, and there will be some differences in the meaning of nominal air volume. Therefore, when selecting, it is best to rely on the latest samples with complete data, or require the supplier to provide the air volume and cooling value of the product under different external static pressure, so as to determine the reliability

in addition, the air volume can not only increase the number of ventilation, reduce the temperature difference of air supply, and improve the effect of air conditioning, but also reduce the volume of the unit because the cooling capacity is correspondingly increased. Therefore, the volume and weight of foreign fan coil units are generally smaller than those of domestic fans. Increasing the external static pressure and air volume is the development direction of fan coil. Of course, the increase of air volume is also restricted by the allowable wind speed in the air conditioning area

at present, Chinese air conditioning designers are generally used to selecting domestic fan coil units according to the total market value and free circulation market value of the index provided by the sample, which are 786.3 billion yuan and 402.2 billion yuan respectively. Although this can make up for the disadvantages caused by insufficient air volume to a certain extent, at the same time, due to large machine and small use, it not only increases the system capacity and increases the project cost, but also makes the chiller operate under the bad condition of large 3 sampling regular flow and small temperature difference for a long time. This leads to low system efficiency and increased energy consumption. This is incompatible with the current international trend of reducing energy consumption, saving energy and protecting the environment

to sum up, when selecting fan coil air conditioning system, we should not only achieve the accuracy of design and calculation, but also select the type reasonably according to the different characteristics of various products in the current market, so as to create a comfortable, economical and reasonable air conditioning system

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