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(d) Often, a low flow of water can make the concentration of dissolved lead in the pipe flow even higher. "fully-developed laminar flow" exists inside the pipe. What is the new k, under this Assume that condition? (e) Short Answer: i. If the bulk fluid velocity voo is increased, with all other parameters kept constant, k (1) is not affected; (2) increases by v.0.2; (3) increases by v.. 0.83 ii. If the fluid velocity is voo is increased, with all other parameters kept constant, CAL (1) is not affected; (2) increases; (3) decreases

(d) Often, a low flow of water can make the concentration of dissolved lead in the pipe flow even higher. "fully-developed laminar flow" exists inside the pipe. What is the new k, under this Assume that condition? (e) Short Answer: i. If the bulk fluid velocity voo is increased, with all other parameters kept constant, k (1) is not affected; (2) increases by v.0.2; (3) increases by v.. 0.83 ii. If the fluid velocity is voo is increased, with all other parameters kept constant, CAL (1) is not affected; (2) increases; (3) decreases

Introduction to Chemical Engineering Thermodynamics
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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PART D AND E

 

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Problem 30-8E. Lead contamination of water in older buildings often comes from lead pipes used to carry drinking water. Although the water chemistry can get complicated, over time a solid lead carbonate (PbCO3) corrosion layer can build up and line the inner surface these pipes. At a drinking water pH of 8 and above, the lead carbonate corrosion layer is not very soluble in water. However, if the water pH is lowed to pH 7 or below, and if dissolved chorine (Cl₂) is also present in the water, then lead carbonate reacts to form lead chloride (PbCl₂), which is soluble in water. This process renders lead of limited solubility at the interface of the corrosion layer and the water flowing through the pipe. For example, at pH 7 and 20 °C, the solubility of lead is 0.630 mmol/m³. The lead concentration of drinking water which is considered safe by the U.S. EPA is 15 µg/L (0.072 mmol/m³). Drinking water at pH 7 flows through a corroded lead pipe of 2.0 cm inner diameter and 16 m length at volumetric flowrate of 62.8 cm³/sec (1.0 gal/min), as shown in Figure 30-8E. A 12 m section of the inner surface of the pipe is uniformly corroded with lead carbonate at the region shown in Figure 1. (a) Estimate the diffusion coefficient of PbCl₂ dissolved in water at 20 °C. (b) Estimate the mass transfer coefficient (kz) of lead chloride (solute A) in water flowing through the pipe. (c) What is the soluble lead concentration in the drinking water exiting the pipe, CAL? As part of your analysis, develop a material balance model for solute A based on the liquid phase. Is this water safe to drink? (d) Often, a low flow of water can make the concentration of dissolved lead in the pipe flow even higher. Assume that "fully-developed laminar flow" exists inside the pipe. What is the new kỵ under this condition? (e) Short Answer: i. If the bulk fluid velocity vo is increased, with all other parameters kept constant, k₁ (1) is not affected; (2) increases by v.0.2; (3) increases by v.. 0.83 ii. If the fluid velocity is v. is increased, with all other parameters kept constant, CAL (1) is not affected; (2) increases; (3) decreases
Transcribed Image Text:Problem 30-8E. Lead contamination of water in older buildings often comes from lead pipes used to carry drinking water. Although the water chemistry can get complicated, over time a solid lead carbonate (PbCO3) corrosion layer can build up and line the inner surface these pipes. At a drinking water pH of 8 and above, the lead carbonate corrosion layer is not very soluble in water. However, if the water pH is lowed to pH 7 or below, and if dissolved chorine (Cl₂) is also present in the water, then lead carbonate reacts to form lead chloride (PbCl₂), which is soluble in water. This process renders lead of limited solubility at the interface of the corrosion layer and the water flowing through the pipe. For example, at pH 7 and 20 °C, the solubility of lead is 0.630 mmol/m³. The lead concentration of drinking water which is considered safe by the U.S. EPA is 15 µg/L (0.072 mmol/m³). Drinking water at pH 7 flows through a corroded lead pipe of 2.0 cm inner diameter and 16 m length at volumetric flowrate of 62.8 cm³/sec (1.0 gal/min), as shown in Figure 30-8E. A 12 m section of the inner surface of the pipe is uniformly corroded with lead carbonate at the region shown in Figure 1. (a) Estimate the diffusion coefficient of PbCl₂ dissolved in water at 20 °C. (b) Estimate the mass transfer coefficient (kz) of lead chloride (solute A) in water flowing through the pipe. (c) What is the soluble lead concentration in the drinking water exiting the pipe, CAL? As part of your analysis, develop a material balance model for solute A based on the liquid phase. Is this water safe to drink? (d) Often, a low flow of water can make the concentration of dissolved lead in the pipe flow even higher. Assume that "fully-developed laminar flow" exists inside the pipe. What is the new kỵ under this condition? (e) Short Answer: i. If the bulk fluid velocity vo is increased, with all other parameters kept constant, k₁ (1) is not affected; (2) increases by v.0.2; (3) increases by v.. 0.83 ii. If the fluid velocity is v. is increased, with all other parameters kept constant, CAL (1) is not affected; (2) increases; (3) decreases
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