Experiments Study On Process In Impinging-Streams Dryer

Impinging streams drying developed recently is a new theory and a new technology in drying region. It can help improving the efficiency of drying greatly. This makes it have an excited future on drying. Now, there are many researchers and scientists who have put their attentions to impinging streams. However, the research is not enough. There are still many problems needed to be studied. The most important is the use of impinging streams on drying.In the thesis, the micro-theory of heat and mass transfer and why impinging streams can improve the efficiency of heat and mass transfer is firstly explained. All these make developing impinging streams is very necessary. The parameter which heat and mass transfer depends on is the relative velocity of air-material. So in the thesis, the flow field is analyzed using theory, is simulated with computer using the soft Fluent and is studied by the author conducting experiment. The flow field consists of the velocity distribution of air and material in the accelerating tubes and the impinging region.In the theory analysis, the mathematic models of air velocity distribution and of single particle velocity distribution have been set up respectively. The mathematic model of air velocity distribution is common; it can be used in many cases. The air velocity distribution is simulated with SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) algorithm by using Fluent soft. This soft is one of the best CFD soft which are used extensively in recent years. SIMPLE algorithm is accepted early as a algorithm which suitable for Pressure-Linked Equations. In experiments, the most advanced equipments PIV and CCD which are used to measure the velocity and the process of particle flowing are adopted. The common point of the two equipments is that they measure the velocity through optics imaging, don't disturb the fluid field. PIV can reflect the instantaneous velocity distribution, CCD can reflect the process of material particle flowing.At the end of the thesis, the velocity distribution is given. The depth of material particle flowing into the accelerating tube and the residence time are made out, too. The parameters can provide the dryer designer.