The thermal calculation of air compressor refrigerating dryer is discussed. Jiang Jie ang, Han Biao, Chen Wencai, Tengfei and Wu Hui (Dongfeng Motor Corporation air conditioning and cleaning countermeasures group, Hubei Shiyan 402) are reviewed.
92, the document identification code: B, in recent years, compressor technology magazine published the relationship between the actual amount of refrigerant dryer and the compressed air state (referred to as Article 1) and the heat exchanger process analysis of the precooler in the freeze dryer (referred to as Article 2). At present, as the emerging industry of cold and dry machine industry in an increasingly competitive market situation, the authors can get experts as their core technologies and products are closely related to the calculation formula and the data published, will no doubt improve the cold and dry machine industry design standards, product quality and industry how to face has far-reaching effect of adding WTO.
In 1999, the 1 Dongfeng Motor Corporation under the help of compressed air purification strategy research group according to "piston compressor design", "air conditioning design manual", "attachment" and "refrigeration heat exchanger design manual" and other books of the formula of XLG type cold storage type cold drying machine for thermodynamic calculation, the prototype data calculation the design.
Through field test, found that according to the "cooler design" piston compressor in the book design formula to calculate the heat transfer area of the evaporator and the pre cooler, inlet and outlet of the compressed air thermal parameters and resistance loss value with the measured data of the most close, this is probably the cooling device and cooling compressor dry machine cooling medium it is because of the compressed air. To further illustrate the situation, the formula and calculation data for heat load calculation of the evaporator of cold dry machine in Article 1 are compared with the list of formulas and calculated data according to the design of piston compressor, as shown in Table 1. For the contrast, the parameters of symbols and their physical meaning are consistent with Article 1, and the design parameters are selected: cold and dry compressed air to the rated capacity M /min (volume converted to standard conditions) P rated pressure rated inlet temperature T C =40 converted to the standard air compressor entrance number P section design in the near atmospheric pressure of air thermal calculation formula according to the "piston compressor design" in the design of compressed air cooler thermodynamic calculation formula according to the inlet air temperature of the evaporator t =32 C check wet air saturated vapor pressure gauge P sb evaporator outlet air temperature T evaporator inlet temperature of the compressed air outlet of the evaporator t compressed air temperature T for evaporator inlet and outlet air moisture content for the evaporator inlet and outlet air moisture content in air compressor technology serial section design According to the design pressure near the "cooler" in a piston type compressor for compressed air thermodynamic calculation formula of inlet and outlet of evaporator air enthalpy value for dry release of compressed air through the evaporator cooling heat treatment for 1 m3 / min of the air cold and dry machine evaporator of the air thermal calculation formula (including refrigeration system) hot load bear for cooling water vapor compression and part of the air condenses into water heat energy released by Q take 2 steamed steamed steamed steamed 2 evaporator 1 can be seen from the table two heat load formula of cold dry evaporator, which is to provide a cooling capacity of the refrigeration system for a small heat load to choose refrigeration compressor, and the heat load is closer to the actual needs of the 601? 85 kcal/h, cold and dry machine can achieve the evaporator outlet temperature of the compressed air is better than the original design of the selected The 5 C high 2.22 degrees, plus the separator can not put out the evaporator condensing water particles suspended in the air with 100 separate off, so do the actual cold dew point at the outlet of the compressed air machine will be 7.22 degrees higher than 2 to 3 DEG C or higher, so the cold and dry machine performance is not up to the design requirements and national standards JB/JQ209010 88 requirements. The cause of the two formula to calculate the difference is mainly from the relative humidity in the formula of the moisture content D. In the design of the selected parameters, calculation of air compressor in the moisture content of D should be taken with =1, in the calculation of air conditioning design or intermediate cooler inlet air compressor compressed air humidity, Phi to atmospheric relative humidity relative humidity or air compressor suction environment. It should be explained that the concept of the above value is clear in Article 1. In his article 2 published in 2000, the calculation process of the relevant parameters of the cold dryer at different T temperatures has taken into account this factor.
The article 2 puts forward a very prominent conclusion: theoretically, the final temperature of the cold fluid in the reverse heat transfer can be less than, equal to or greater than the final temperature of the hot fluid. Therefore, in the large and medium cold drying machine, the precooler is mainly reflux heat transfer (for example, figure 3). However, because of the limitation that the cold utilization can not exceed 100, the exhaust temperature of the drying machine can not be raised even in the reverse flow. For example, under the above conditions, the exhaust gas temperature of the drying machine is at the limit of 28.
There is only one cold dry machine in the domestic cold drying machine. The instruction manual says that we should pay attention to whether there is temperature difference between the air and the inlet and outlet. (the normal temperature should be 10~17 degrees C). Foreign companies also have a cold and dry machine "technical manual" mentioned in the standard state of the inlet temperature of air flow, the rated conditions in the cold and dry machine heater (flow side pre cooler cooling) at the outlet of the air temperature than cold dry will not look cold and dry temperature machine import and export it is great or small, or over the range is not normal, this technical performance and equipment of cold and dry machine to judge the user