Study for the Effect of Design Parameters on the Performance of Fin-tube Type Heat Exchangers

• Main Authors: Jiin-Wen Hwang, 黃錦文
• Other Authors: Ruey-Yin Tsia
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/99305935333239488997

博士 === 中原大學 === 機械工程學系 === 89 === There are many effect factors not only the tube row, fin type, and fin pitch, but also the inlet conditions and geometrical structure of FHE on the HTP. A study of the inlet conditions, the space between blower and fins, twin blowers, side wall, the air distribution that is blow-through or draw-through towards the HTP of FHE is proposed. After test and analysis the suitable face velocity of coil is between 2.3~2.8m/s. The high face velocity will cause carry over phenomena, and affect outlet air moisture content and enthalpy, which will be caused HTP decrease. The inlet water temperature (Ti) and temperature difference (Tw) can not be too high that will also reduce heat transfer rate. The Ti is usually taken at about 7.22oC. If the Ti is taken too low, the coefficient of performance of cooling equipment will be affected. The ideal Tw is 4.45~5.56oC. To keep Reynolds numbers not lower than 3,500. To have better dehumidified efficiency, 6~8 rows and 8~10 fins per inch is the best choice and face velocity is also decreased to 2.1~2.3m/s at the same time. The higher inlet air moisture content, while Ti or Tw is also too high, the larger heat duty depression ratio will be, these mean that the heat taken away by condensed water can not be neglected. Thus, 6~8 rows is the best for the temperature drop of air throughout the coil. To achieve better performance for heat transfer rate and pressure, for the blow-through system, the distance between the blower and fins at least has to be larger than half of the longitude length of blower volute (LBV) or inlet wheel diameter (IWD), and lower than once of the LBV. For the draw-through system, those effect factors will be lower. For twin blowers type, the distance between the two blowers is almost large than twice of the IWD, and the distance between the blower and side wall is about equal to once of the IWD, for single blower type is good for low than once of the IWD. The aspect ratio of coil face area has to be maintained between 1：2. Besides, the number of tube row is more, and the face velocity of coil is higher, the pressure drop will also be larger.