Characteristics of drying medium parameters in tunnel-type drying chamber during noodle drying process

Abstract: Dry processing is a key step for Chinese dried noodle production. It closely related to the energy consumption, production efficient and quality property of the product. Temperature, relative humidity, and air velocity of drying medium are the most important factors that influencing the noodle dry processing, and these factors also have mutual influence. In previous studies the effect of temperature and relative humidity on noodle quality has been investigated. But people know little about the flow of the air in tunnel-type drying chamber, it is very important for noodle drying and energy consumption. No appropriate device that can adapt well the special environment conditions in chamber-high temperature, high relative humidity and easy condensation is the main reason. In order to know the air flow conditions and analyze the effect of air velocity on temperature and relative humidity in actual noodle dry processing, a production line with 5 rows of 60 m in tunnel drying room was chose as the research object. In this study a new experimental instrument-meteorograph (Kestrel NK-4500), was used to research the characteristic of drying medium (air velocity, wind direction, temperature, relative humidity). For the sake of discussion in this paper the drying chamber was divide into four stages by length (equal distance)：Ⅰstage (0-15 m), Ⅱstage (15-30 m), Ⅲstage (30-45 m), Ⅳstage (45-60 m). Results showed that there were significant differences in air velocity, temperature and relative humidity among different stages. The air velocity which influenced by the location and density of the ceiling fan, gradually diminished (Ⅰstage: 0.95 m/s, Ⅱstage: 0.89 m/s, Ⅲstage: 0.79 m/s, Ⅳstage: 0.50 m/s) and all were below at 1m/s.The air velocity in middle row (0.54 m/s) was significantly lower than that in left (0.89 m/s) and right (0.90 m/s). Wind direction is analyzed by the wind rose plot. In the drying chamber the wind direction-distribution was prone to the side where the moisture removal mouth located. The temperature in chamber increased during 0～35 m, then decreased. The trend of the relative humidity is similar to the air velocity, increased rapidly in the beginning and then gradually diminished with a average humidity (76.67％). In 4 drying stages, the relative humidity in left side was significantly higher than that in middle and right side, it was mainly influenced by the position of moisture removal mouth. The air velocity significant impacted the temperature and relative humidity in the drying chamber, but in different drying stages the influences were different. During 15-45 m of drying distance, the air velocity had obvious positive correlation with the temperature; but for 0-15 m and 45-60 m, the air velocity and temperature had significant negative correlation. In 0-45 m of drying distance, the air velocity had significant negative correlation with relative humidity. From this study we also find that the meteorograph can adapt well the special environment conditions in chamber with high temperature, high relative humidity and easy condensation.