The following data were obtained in a drying test of a solid food placed in a laboratory tray dryer. Find the critical moisture content, the critical drying rate, the drying time in the constant-rate period, the time necessary for the moisture to fall from the critical moisture content to 70% (wet basis), and the amount of water that was removed from the product in the drying test. It is given that the initial moisture content is 85% wet basis, the bulk density of the solid is 50 kg dry solids/m³, and the thickness of the solid in the tray is 3 cm. Exercises Time Weight (h) (kg) 3.000 0.5 2.500 2.000 (continued) Time Weight (h) (kg) 2 1.600 3 1.500 1.435 6 1.420 8 1.410 10 1.405 12 1.400 13 1.400 265

Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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Solution
Step 1
Express the moisture content of the given data on a dry basis for each given
point.
Step 2
Calculate the amount of dry solid per unit surface area:
ms = thickness in the tray x
А
..kgd.s./m²
Step 3
Calculate the drying rate R for each given point from:
m, dX
R=-
A dt
Step 4
Plot R vs X.
Step 5
Read the values of X, and R. from the plot.
Step 6
Calculate the drying time in the constant-rate period:
Step 7
Read the drying rate at a moisture content of 80% and 70% from the plot, and
calculate the required drying time using the assumption that the falling rate
period is a linear function of X.
Transcribed Image Text:Solution Step 1 Express the moisture content of the given data on a dry basis for each given point. Step 2 Calculate the amount of dry solid per unit surface area: ms = thickness in the tray x А ..kgd.s./m² Step 3 Calculate the drying rate R for each given point from: m, dX R=- A dt Step 4 Plot R vs X. Step 5 Read the values of X, and R. from the plot. Step 6 Calculate the drying time in the constant-rate period: Step 7 Read the drying rate at a moisture content of 80% and 70% from the plot, and calculate the required drying time using the assumption that the falling rate period is a linear function of X.
The following data were obtained in a drying test of a solid food placed in a
laboratory tray dryer. Find the critical moisture content, the critical drying rate,
the drying time in the constant-rate period, the time necessary for the moisture
to fall from the critical moisture content to 70% (wet basis), and the amount of
water that was removed from the product in the drying test. It is given that the
initial moisture content is 85% wet basis, the bulk density of the solid is 50 kg
dry solids /m², and the thickness of the solid in the tray is 3 cm.
Time
Weight
(kg)
(h)
0
3.000
0.5
2.500
1
2.000
Exercises
265
(continued)
Time
Weight
(kg)
(h)
2
1.600
3
1.500
4
1.435
6
1.420
8
1.410
1.405
1.400
1.400
10
12
13
Transcribed Image Text:The following data were obtained in a drying test of a solid food placed in a laboratory tray dryer. Find the critical moisture content, the critical drying rate, the drying time in the constant-rate period, the time necessary for the moisture to fall from the critical moisture content to 70% (wet basis), and the amount of water that was removed from the product in the drying test. It is given that the initial moisture content is 85% wet basis, the bulk density of the solid is 50 kg dry solids /m², and the thickness of the solid in the tray is 3 cm. Time Weight (kg) (h) 0 3.000 0.5 2.500 1 2.000 Exercises 265 (continued) Time Weight (kg) (h) 2 1.600 3 1.500 4 1.435 6 1.420 8 1.410 1.405 1.400 1.400 10 12 13
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