We are interested in predicting the time it will take for popcorn kernels to pop in a fluidized bed. the superficial air velocity inside the bed is 3 m/s, which is above the minimum fluidization velocity for popcorn kernels. the air temperature is maintained constant at 520 k (247°c) by heating coils placed around the fluidization vessel. the average diameter of the popcorn kernels is 0.5 cm. when the temperature of a kernel reaches 175°c, it will pop. at 25°c, the thermal conductivity of popcorn is 0: 2 w=m ? k, the specific heat is 2000 j=kg ? k, and the density is 1300 kg=m3. a. what is the convective heat-transfer coefficient for air flow around each popcorn kernel? b. what is the biot number for a popcorn kernel? is a lumpedparameter model valid? c. if we assume that the popcorn kernel pops when its centerline temperature reaches 175°c, how long after entering the bed will it take for the popcorn kern