A constrained thin film desorption scheme has been experimentally tested to
determine the desorption rates for water from an aqueous lithium bromide mixture
through a confining membrane. Variable conditions include the inlet
concentration, pressure differential across the membrane, and channel height.
Desorption takes place in a channel created between two parallel plates with one of
the walls being both heated and porous. A hydrophobic porous membrane creates
a liquid-vapor interface and allows for vapor removal from the channel. Inlet
concentrations of 32 wt%, 40 wt%, and 50 wt% lithium bromide were tested at an
inlet sub-atmospheric pressure of 33.5 kPa. Pressure differentials across the
membrane of 6 kPa and 12 kPa were imposed along with two channel heights of
170 μm and 745 μm. All cases were run at an inlet mass flow rate of 3.2 g/min,
corresponding to Reynolds numbers of approximately 2.5 to 4.5. The membrane
surface area for desorption was 16.8 cm². A maximum desorption rate (vapor
mass flow rate) of 0.51 g/min was achieved, for the 32 wt%, 12 kPa pressure
differential, and 170 μm channel. Increasing the pressure differential across the
channel allowed for higher desorption rates at a fixed wall superheat, and delayed
the transition to boiling. As the inlet concentration increased the desorber's
performance decreased as more energy was required to produce a fixed desorption
rate. Results are also presented for the variation in the heat transfer coefficient
with the wall superheat temperature. The increase in the channel height had a
negative influence on the heat transfer coefficient, requiring larger superheat
values to produce a fixed desorption rate. / Graduation date: 2005 / Best scan available for tables and computer code in the appendices. The original is faded.
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29258 |
| Date | 17 February 2005 |
| Creators | Thorud, Johnathan D. |
| Contributors | Liburdy, James A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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