Many specialty chemicals are produced in semibatch reactors where a reac. tant is added gradually into a batch reactor. This problem concerns the gov- eming equations of such operations without considering chemical reactions A well-mixed batch reactor initially contains 200 L of pure water. At time 1= 0, we start feeding a brine stream with a salt concentration of 180 g/L into the tank at a constant rate of 50 L/min. Calculate: a. The time the salt concentration in the tank is 60 g/L b. The volume of the tank at that time c. The time and salt concentration in the tank when the volume of the tank is 600L Assume the density of the brine is the same as the density of the water.

Many specialty chemicals are produced in semibatch reactors where a reac. tant is added gradually into a batch reactor. This problem concerns the gov- eming equations of such operations without considering chemical reactions A well-mixed batch reactor initially contains 200 L of pure water. At time 1= 0, we start feeding a brine stream with a salt concentration of 180 g/L into the tank at a constant rate of 50 L/min. Calculate: a. The time the salt concentration in the tank is 60 g/L b. The volume of the tank at that time c. The time and salt concentration in the tank when the volume of the tank is 600L Assume the density of the brine is the same as the density of the water.

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter5: Analysis Of Convection Heat Transfer

Section: Chapter Questions

Problem 5.20P

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Using the information in Problem 1.22, estimate the ambient air temperature that could cause frostbite on a calm day on the ski slopes. 1.22 In order to prevent frostbite to skiers on chair lifts, the weather report at most ski areas gives both an air temperature and the wind-chill temperature. The air temperature is measured with a thermometer that is not affected by the wind. However, the rate of heat loss from the skier increases with wind velocity, and the wind-chill temperature is the temperature that would result in the same rate of heat loss in still air as occurs at the measured air temperature with the existing wind. Suppose that the inner temperature of a 3-mm-thick layer of skin with a thermal conductivity of 0.35W/mKis35C and the air temperature is 20C. Under calm ambient conditions the heat transfer coefficient at the outer skin surface is about 20W/m2K (see Table 1.4), but in a 40-mph wind it increases to 75W/m2K. If frostbite occurs when the skin temperature drops to about 10C, do you advise the skier to wear a face mask? What is the skin temperature drop due to the wind?
1.22 In order to prevent frostbite to skiers on chair lifts, the weather report at most ski areas gives both an air temperature and the wind-chill temperature. The air temperature is measured with a thermometer that is not affected by the wind. However, the rate of heat loss from the skier increases with wind velocity, and the wind-chill temperature is the temperature that would result in the same rate of heat loss in still air as occurs at the measured air temperature with the existing wind. Suppose that the inner temperature of a 3-mm-thick layer of skin with a thermal conductivity of 0.35 W/m K is and the air temperature is . Under calm ambient conditions the heat transfer coefficient at the outer skin surface is about (see Table 1.4), but in a 40-mph wind it increases to . (a) If frostbite occurs when the skin temperature drops to about , do you advise the skier to wear a face mask? (b) What is the skin temperature drop due to the wind?
1.77 Explain each in your own words. (a) What is the mode of heat transfer through a large steel plate that has its surfaces at specified temperatures? (b) What are the modes when the temperature on one surface of the steel plate is not specified, but the surface is exposed to a fluid at a specified temperature?
The drag on an airplane wing in flight is known to be a function of the density of air (), the viscosity of air(), the free-stream velocity (U), a characteristic dimension of the wing (s), and the shear stress on the surface of the wing (s). Show that the dimensionless drag, sU2, can be expressed as a function of the Reynolds number, Us.
To determine the thermal conductivity of a structural material, a large 15-cm-thick slab of the material is subjected to a uniform heat flux of 2500 W/m2 while thermocouples embedded in the wall at 2.5 cm. intervals are read over a period of time. After the system had reached equilibrium, an operator recorded the thermocouple readings shown below for two different environmental conditions: Distance from the Surface (cm) Temperature (C) Test 1 0 40 5 65 10 97 15 132 Test 2 0 95 5 130 10 168 15 208 From these data, determine an approximate expression for the thermal conductivity as a function of temperature between 40 and 208C.
A manufacturer in the United States wants to sell a refrigeration system to a customer in Germany. The standard measure of refrigeration capacity used in the United States is the ton (T); a 1 T capacity means that the unit is capable of making about 1 T of ice per day or has a heat removal rate of 12,00 Btu/h. The capacity of the American system is to be guaranteed at 3 T. What is this guarantee in SI units?
Saponification is a process wherein soap is added to a certain type of oil to produce grease. One such grease is said to have 75.7 % by volume oil and 24.3% by volume soap, wherein the oil and soap have densities 760 kgm/m3 and 6,250 kgm/m3, respectively. This kind of grease is sold by packs shaped like a sphere with a diameter of 20 cm for convenience. Calculate: a) the mass of oil per pack (kgm), b) the mass of soap per pack (kgm), c) the weight of each pack (kgf), d) the specific weight of grease (N/m3), e) will the grease float if it is placed in water whose density is 1000 kgm/m3? Explain.
In the United States, energy for household heating is generally sold using English units, e.g., therm, gal, and cord. A house in Wisconsin uses 1200 therms of thermal energy during the heating season. Calculate the cost of fuel if the furnace uses (a) natural gas with an efficiency of 70%; (b) No. 2 fuel oil, efficiency 65%; (c) kerosene, efficiency 99.9% (unvented); and (d) wood with l5% moisture with an efficiency of 50%. Use the data in Tables 2.2, 2.7, and 2.13. The efficiencies are based on the HHV. Assume the cost of natural gas is $8/MBtu, the cost of No. 2 fuel oil is $3/gal, the cost of kerosene is $3.50/gal, and the cost of wood is $100/cord. Assume the bulk density of cord wood is 30 lbm/ft3 .
The same engineer decides to look into rates of cooling for liquids toexperiment with different cooling solutions for servers. She finds thatthe rate of cooling for one liquid can be modelled by the equation:y = 48 × 0.99t(0 ≤ t ≤ 80)where y is the temperature of the liquid in degrees Celsius and t is thetime in minutes.(i) State whether the type of reduction for this model is linear orexponential. Describe how reduction rate differs between linear andexponential functions. (ii) Calculate the temperature when t = 20. [3](iii) Write down the scale factor and use this to find the percentagedecrease in the temperature per minute. (iv) Use the method shown in Subsection 5.2 of Unit 13 to find the timeat which the temperature is 30◦(v) Determine the halving time of the temperature.
Suppose we got the following data during a test of a 2- stroke engine in which gas is usedas a fuel:Diameter of the piston = 149 mmStroke length = 179 mmClearance volume = 0.88 literrpm of the engine = 302Indicated mean effective pressure = 6.0 barGas consumption = 6.0 m3/hCalorific value of the gas (fuel) = 16990 kJ/m3Make a clear sketch the geometry of this engine using the data and determine thefollowing:i. Indicated power developed by the engine in watt.ii. Air Standard Efficiencyiii. Indicated thermal efficiency of the engine.
According to the U.S. Geological survey, the volume of water in oceans, seas, and bays is 1.41 ✕ 1018 m3. The average concentration of naturally occurring uranium in seawater is 3.15 ✕ 10−6 kg/m3. If 0.670% of naturally occurring uranium is the fissionable isotope U-235 and each fission reaction yields 200 MeV, estimate the amount of time the uranium in the seawater on the planet could meet the planet's energy needs at an average usage of 1.94 ✕ 1013 J/s.
Assume the following: ●In a light water reactor, approximately 1.0kg of spent nuclear fuel is produced for every50. megawatt-days (MWd) of thermal energy input. ●For the purposes of this analysis, assume the spent nuclear fuel produced is 1.8% Pu-240by mass. Pu-240 has a half-life of 6,430 years. ●The thermal efficiency of the power plant is 38% ●Use equation for radioactive decay: Qt= Q0^e-kt where: ○Qt = quantity of radioactive material at time t ○Q0 = original quantity of radioactive material ○k = the decay constant ○t = time interval in years ○The decay constant k is defined by the relation: Half life = ln(2)/k Diablo Canyon stores 95% of its spent nuclear fuel onsite. ii) How many metric tons of Pu-240 in the spent fuel will still be onsite in that year?