A heat recovery scrubber is used to produce hot water for heating needs. The temperature of the
Question:
A heat recovery scrubber is used to produce hot water for heating needs. The temperature of the outgoing water must be 60°C, while the temperature of the return water is (28) °C. The heat is recovered from a moist air stream whose temperature is 80°C and relative humidity 90%. The average flow velocity of the incoming air has been measured to be (13) m/s before the scrubber. At the measuring point, the inner diameter of the pipe is 1200 mm. It is being considered to update the process by installing a bed with plastic fillers. Currently, water is sprayed into an empty tower with nozzles, in the new case the tower is filled with fillers in the hope of getting a scrubber with two theoretical bottoms. (A theoretical bottom is defined as a unit where there is equilibrium between liquid and gas phases, in this case water and water vapor).
1) Draw block diagrams of the two process configurations with names of streams and blocks, incl. the bottling of water to keep the amount of water constant. Then use the same variable and parameter names in your calculations. Feel free to use " ´ " where equilibrium assumptions apply
2) Answer the following sub-questions:
a) What is the moisture content of the incoming air?
b) What is the density of the incoming moist air?
c) What is the specific enthalpy of the incoming air i?
d) What is the mass flow of incoming moist air?
e) What is the mass flow of incoming dry air?
3) Calculate the mass flows, the temperatures and the heat effect (ie the heat flow that is used from the hot water stream) for the case without filler bodies
4) Calculate the mass flows, temperatures and heat output for the case of filler bodies
5) By how many percent does the heat effect decrease in the case without fillers if the moist air stream temperature drops to 75 °C during the coldest months of the year (with relative humidity maintained and mass flow dry air)?
Elementary Principles of Chemical Processes
ISBN: 978-1119498759
4th edition
Authors: Richard M. Felder, ? Ronald W. Rousseau, ? Lisa G. Bullard