Experimental and Numerical Analysis of a PCM-Supported ...

The product condensed water was measured hourly in calibrated plastic jars. Before
fully operating the rig, the water level inside the cold storage tanks was adjusted to a
certain level beyond which water overflows to the calibrated plastic jars through 12
mm diameter pipes. The quantity of condensate accumulated in the measuring jars
was noted every hour. From this, the mass flow rate of the output condensate
produced by the plant was easily measured within uncertainty range of ± 5 %. This
range of uncertainty results from the fact that water surface in the condensate tank is
concaved due to surface tension, while the small diameter of the overflow pipe
causes a hydraulic resistance resulting in partly accumulation of 5% of the
condensate from one hour to the next. However, comparing the accumulated
condensate over 4 operation hours under constant boundary conditions between
different experiments guarantees fair assessment of different setups and boundary
conditions.
An error analysis was performed to clearly define the uncertainty margins for the
measured parameters and how measuring errors propagate and how (quantitatively)
they impact the calculated variables. Relevant error bars that are useful for
quantitative qualification of the results will always appear on the comparative graphs
throughout the present analysis.
The thermocouples were inserted into the rig through small diameter pipes which
were welded in the tubes and lower elbows. Small umbrellas were used for
protecting the tips of thermocouples, used for measuring the gas temperatures
against falling water droplets to ensure right reference of the measured data. On the
other hand, the thermocouple tips for measuring outlet cold and hot water
temperatures at the lower elbows were immersed in a small sponge supported by a
little water collection plate to ensure measuring water temperatures. Gas
temperature sensors are also protected by small umbrellas at the top of the
evaporator and condenser while water temperature sensors are inserted into the
water mains directly upstream the shower heads.
5.3 Functional description
The test rig configuration comprises three closed loops as shown in figure (5.1); the
air loop, the hot water loop, and the cooling water loop. The plant works on a similar
operation cycle which has been described by figure (4.1). The test runs were
performed over a time span of 4 hours under steady boundary conditions. The
condensate is discarded and measured using calibrated jars. During the plant
operation, mass flow meters were checked regularly and the output distillate was
measured every one hour.
The start-up procedures for the experimental apparatus are described as follows:
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