Collisional heat transfer coefficient

In gas-solid suspensions and fluidized beds, the heat transfer between particles and the wall surface or between a particle at one temperature and a group of other particles at another temperature is largely due to particle impacts. Thus, the average rate of heat transfer may be expressed in terms of a collisional heat transfer coefficient hc, which is defined by... 

Example 4.1 Determine the collisional heat transfer coefficients under each of the following conditions (1) collisions of a cloud of hot particles with a cold particle (2) collisions of a cloud of cold particles with a hot wall. Assume the particles are in random motion with the average impact velocity of 0.1 m/s. All the particles are spherical and of the same diameter of 100 fim. The particles and wall are made of steel with v = 0.3, E = 2 x 105 MPa, Pp = 7,000 kg/m3, Kp = 30 W/m K, and c = 500 J/kg K. The particle volume fraction is 0.4. 

Therefore, from Fig. 4.2, the correction factor C is found to be 5. The collisional heat transfer coefficient by interparticle collisions is thus given by Eq. (4.34) as... 

---