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CHE 254 — Assignment 3 — 090828 2.21 A variable, Q, is reported to have a value of 2.360⋅10−4
kg⋅m2 / h .
(a) Write a dimensional equation for Q', the equivalent variable value expressed in American engineering units, using seconds as the unit for time. (b) Estimate Q' without using a calculator, following the procedure outlined in section 2.5b. (Show your calculationrs.) Then determine Q' with a calculator, expressing your answer in both scientifgic and decimal notation and making sure it has the correct number of significant figures.
CHE 254
Assignment 2 — due 8/26/09 Tom Bertalan, James Clark, Craig Jackson, Rohit Deshane
Tonya Klein
Page 2 of 3 2.28 A concentration C (mol/L) varies with time (min) accoding to the equation C=3.00 exp −2.00⋅t (a) What are the units of 3.00 and 2.00? (b) Suppose the concentration is measured at t =0 and t=1 min. Use two-point linear interpolation or extrapolation to estimate C t=.06 min and C=0.10 mol / L from the measured values, and compare these re3sults with the true values of these quantities. (c) Sketch a curve of C versus t, and show graphically the points you determined in part (b).
CHE 254
Assignment 2 — due 8/26/09 Tom Bertalan, James Clark, Craig Jackson, Rohit Deshane
Tonya Klein
Page 3 of 3 2.33 The temperature in a process unit is controlled by passing cooling water at a measured rate through a jacket that encloses the unit
The exact relationship between the unit temperature T(*C) and the cooling water flow rate (L/s) is extremely complex, and it is desired to derive a simple emperical formula to approximate this relationship over a range of flow rates and temperatures. Data are taken for T versus . Plots of T versus on rectangular and semilog coordinates are distinctly curved (ruling out T =a b and T =aeb as possible empirical functions), but a log plot appears as follows:
A line drawn through the data goes through the points 1=25,T 1=210 and 2 =40, T 2=120 . (a) What is the empirical relationship between and T? (b) Using your derived equation, estimate the cooling water flow rates needed to maintain the process unit temperature at 85*C, 175*C, and 290*C. (c) In which of the tree estimates in part (b) would you have the most confidence and in which would you have the least confidence? Explain your reasoning.
CHE 254
Assignment 2 — due 8/26/09 Tom Bertalan, James Clark, Craig Jackson, Rohit Deshane
Tonya Klein
CHE 254 — Assignment 3 — 090828 2.21 A variable, Q, is reported to have a value of 2.360⋅10−4
kg⋅m2 / h .
(a) Write a dimensional equation for Q', the equivalent variable value expressed in American engineering units, using seconds as the unit for time. (b) Estimate Q' without using a calculator, following the procedure outlined in section 2.5b. (Show your calculationrs.) Then determine Q' with a calculator, expressing your answer in both scientifgic and decimal notation and making sure it has the correct number of significant figures.
CHE 254
Assignment 2 — due 8/26/09 Tom Bertalan, James Clark, Craig Jackson, Rohit Deshane
Tonya Klein
Page 2 of 3 2.28 A concentration C (mol/L) varies with time (min) accoding to the equation C=3.00 exp −2.00⋅t (a) What are the units of 3.00 and 2.00? (b) Suppose the concentration is measured at t =0 and t=1 min. Use two-point linear interpolation or extrapolation to estimate C t=.06 min and C=0.10 mol / L from the measured values, and compare these re3sults with the true values of these quantities. (c) Sketch a curve of C versus t, and show graphically the points you determined in part (b).
CHE 254
Assignment 2 — due 8/26/09 Tom Bertalan, James Clark, Craig Jackson, Rohit Deshane
Tonya Klein
Page 3 of 3 2.33 The temperature in a process unit is controlled by passing cooling water at a measured rate through a jacket that encloses the unit
The exact relationship between the unit temperature T(*C) and the cooling water flow rate (L/s) is extremely complex, and it is desired to derive a simple emperical formula to approximate this relationship over a range of flow rates and temperatures. Data are taken for T versus . Plots of T versus on rectangular and semilog coordinates are distinctly curved (ruling out T =a b and T =aeb as possible empirical functions), but a log plot appears as follows:
A line drawn through the data goes through the points 1=25,T 1=210 and 2 =40, T 2=120 . (a) What is the empirical relationship between and T? (b) Using your derived equation, estimate the cooling water flow rates needed to maintain the process unit temperature at 85*C, 175*C, and 290*C. (c) In which of the tree estimates in part (b) would you have the most confidence and in which would you have the least confidence? Explain your reasoning.
CHE 254
Assignment 2 — due 8/26/09 Tom Bertalan, James Clark, Craig Jackson, Rohit Deshane
Tonya Klein
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