Chapter 7, Problem 7.10E

H.W 1. A feed of 4535 kg/h of a 2.0 wt % salt solution at 311 K enters continuously a single-effect evaporator and is being concentrated to 3.0%. The evaporation is at atmospheric pressure and the area of the evaporator is 69.7m². Saturated steam at 383.2 K is supplied for heating. Since the solution is dilute, it can be assumed to have the same boiling point as water. The heat capacity of the feed can be taken as cp = 4.10 kJ/kg K. Calculate the amounts of vapor and liquid product, and the overall heat-transfer coefficient U?

The switch in Fig.1 has been closed for a long time. It opens at t = Find i(t) for t > 0. 50 www 1.5 H m t=0 10 Ω 9A 0.

e a) 1) Indicate whether each statement below is True or False: Precipitates have a more regular structure than crystals. b) A protein will be more likely to precipitate when the surrounding pH is at its pl. c) Larger proteins are more likely to precipitate than smaller proteins. d) Precipitation nucleation typically follows a secondary nucleation mechanism. e) Precipitates in a CSTR are usually uniform in size. f) Crystallization nucleation usually follows a secondary nucleation mechanism. g) The most common scale-up method for precipitation and crystallization is constant P/V h) Evaporation is commonly carried out above atmospheric pressure. i) The boiling point of a solvent typically rises as the concentration of solute increases. j) Scale-up of evaporation units is usually carried out by increasing evaporator height. k) Unbound water is more difficult to remove than bound water when drying. 1) The most common convection dryer is a freeze dryer. m) Vacuum shelf dryers typically heat…

5) Wet insulin crystals containing 32 g water per 100 g of dry insulin need to be dried in air to a moisture level of 5 g water per 100 g of dry insulin. For your convenience, a graph of water content of insulin vs. relative humidity and a psychrometric chart are provided below. a) Determine the percentage of bound and unbound water in the wet crystals before drying. b) Determine the relative humidity of the air to accomplish the drying to 5 g water/100 g dry solids. c) For drying with air at 20°C, what should be the moisture content of the air (g moisture/g dry air)? Water content (g/100 g dry solids) 40 30 20 10 Cefazolin sodium tPA 20 40 Insulin 60 Relative humidity (%) 80 100

A power plant needs to evaporate 1500.0 lbm/h of water at 40.0 °F at 1 atm. Utility superheated steam at 1200 °F and 40 bar is available, but the steam cannot drop below 20 bar and 700 °F. Use the steam tables to determine the specific enthalpies of the four streams. The reference for the enthalpies should be water at the triple point. You may interpolate in Tables B6. and B7, and can also use external, automated sources. Determine the amount of superheated steam required to accomplish the evaporation for a superheated steam outlet of 700 °F and 20 bar. Assume no heat losses and use the steam tables to determine enthalpies.

Recitation 11 Problem 1 400 kg/min of steam enters a steam turbine at 300 °C and 80 bar through a 8.5-cm diameter line and exits at 100 °C and 10.0 bar through a 5.5-cm line. The exiting stream may be vapor, liquid, or "wet steam", a mist composed of saturated water vapor and entrained liquid droplets. Find how much power W (kW) is transferred from the turbine to the steam? The answer can be positive or negative. Neglect AE, but not AEK. What percentage (%) of the total power is due to kinetic energy changes?

A 30.0-g block of iron at 200.0°C is dropped into a liter of water in an insulated flask at 25.0°C and 1 atm. The specific enthalpy of iron is given by the expression Ĥ(J/g) = 17.3 T(°C).

Recitation 11 Problem 2 Eight fluid ounces (1 qt = fl 32 oz) of a beverage in a glass at 23.0 °C is to be cooled by adding ice and stirring. The properties of the beverage may be taken to be those of liquid water. The enthalpy of the ice relative to liquid water at the triple point is -348 kJ/kg. Estimate the mass of ice (g) that must melt to bring the liquid temperature to 4.0 °C, neglecting energy losses to the surroundings. (Note: For this isobaric batch process, the energy balance reduces to Q = AH)

A  solid slab    of    5.15    wt%    agar    gel    at    278    K    is    6.00    mm    thick and contains  a  uniform    concentration    of    urea    of    0.2    kmol/m3. Diffusion    is only     in     the     direction     through     two     parallel  flat  surfaces   6.00     mm     apart.    The     slab     is     suddenly     immersed     in     pure     turbulent     water     so     that     the surface     resistance     can     be     assumed     to     be     negligible;  i.e,     the     convective coefficient    hm is    very    large.    The    diffusivity    of    urea    in    the    agar    is    4.72e-10    m2/s.    a)    Calculate     the    concentration    at     the    midpoint    of     the    slab    and     (b) 1.50     mm     from     the     surface     after     19     h.     c) if   the     thickness     of     the     slab     is    halved,    what    would    be    the    midpoint    concentration    in    19    h.