Contact type heat exchanger for cocoa slurry preparation
Cocoa slurry is being prepared in tank. Following steps are followed: a. Pour warm water (at 40 C) in the tank b. Slowly add 15 kg of cocoa powder (kept at 20 C) into water while agitating to disperse powder into water c. Inject steam (with absolute pressure of 2.5 bar) into the tank to bring mixture temperature to 95 с d. Tank is well insulated and has a tight lid on top. Assume no heat loss and no loss of water from tank during entire process Now answer the following questions: 1. If desired concentration of cocoa in final slurry is 20%, what is total weight of slurry? What is the amount of water in final slurry? - 2. Using steam tables, determine the latent heat of evaporation provided by steam as it condenses to water into slurry (after injection), -5 points 3. Amount of steam needed to heat the slurry is significant and must be account for in contribution to final amount of water in the slurry (part 1). Assuming 's' as mass of steam needed for the process and 'W'as mass of initial water, write mass balance equation for this process. - 5 points 4. Assuming specific heat of cocoa powder as 2.4 KJ/Kg deg C), and that of water as 4.18 KJ/(kg dec C), write energy balance equation for the process - a. Enthalpy of initial water + enthalpy of cocoa powder + enthalpy of steam enthalpy of final slurry at 95 C 5. Solve the mass and energy balance equations to find mass of initial water and steam needed - 6. Assuming negligible heat addition due to the mixing action, what is the temperature of the slurry before steam injection? -