Assignment 1 submitted via moodle within 27 Aug 10
Problem 1. 50 kg of food at a moisture content of 400 % dry basis is dried to 25 % wet basis. Calculate the amount of water removed F = 50 kg of raw product (400 % d.b.) Product (25 % w.b.) Water removed Drying process Solution P = 13.33 kg , W = 36.67 kg
Problem 2. A membrane separation system is used to concentrate the liquid food from 12 % to 45 % total solid (TS). The process is accomplished in two stages, in the first stage a low total solid liquid stream is released. For the second stage, there are two streams released. The first stream is final product with 45% TS and the others is coming out with 1.5% TS and recycled to the first stage. Determine the magnitude of the recycle stream, the waste stream from first stage contains 0.25 % TS and the stream between stages 1 and 2 contains 30 % TS . The flow rate of 45 % TS final product stream is at 120 kg/min. first stage Second stage Solution F = 457.02 kg/min , W = 337.02 kg/min and R = 63.16 kg / min Feed 12 % TS B 30 % TS R 1.5 % TS 120 kg/ min of product 45 % TS W , 0.25 % TS
Problem 3. Steam is used for peeling of potatoes in a semi-continuous operation . Steam is supplied at the rate of 5 kg per 80 kg of unpeeled potatoes. The unpeeled potatoes enter the system with a temperature of 22 C and the peeled potatoes leave at 35 C . A waste stream from the system leaves at 65 C . The specific heats of unpeeled potato, waste stream and peeled potatoes are 3.7 , 4.2 and 3.5 kJ/ (kg K ) , respectively. If the heat content of steam is 2800 kJ /kg , determine the quantities of the waste stream and the peeled potatoes from the process Solution P = 17.89 kg and W = 67.11 kg
Problem 4. Potato flakes ( 62 % w.b.) are being dried in a concurrent flow dries. The moisture content of the air entering the drier is 0.05 kg of water per 1 kg of dry air. The moisture content of air leaving the drier is 0.125 kg water per 1 kg of dry air. The air flow rate in the drier is 150 kg dried air per hour. As show in a picture , 80 kg of wet potato flakes enter the drier per hour. At steady state , Calculate the following A. What is the mass flow rate of dried patatoes. B. What is the moisture content , dry basis , of “ dried potatoes ” exiting the drier Solution mass flow rate = 68.75 kg/h and MC = 126 %db Air in Exit Air Feed Product
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