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

chapter 4. Then the three modules were incorporated into a main structure which
masters the three modules by calling different ”pdepe” functions to constitute the
simulation model of the PCM-supported HDH system. Figure (6.1) shows the
flow diagram and the control logic of the model.
The solar water heater module receives water mass flow rate and metrological
records as input data. It defines the number of time increments (one-hour time
increments are used here as the meteorological data are recorded hourly) for the
control loops and the inlet water temperature to the thermal buffer. The same
module also entirely solves the governing equations for the thermal buffer (i.e.
equation 4.7 to 4.10 together with equations 4.63 to 4.68 and 4.78 to 4.80) and
defines the outlet water temperature (i.e. the inlet water temperature to the
evaporator).
The evaporator module receives the inlet boundary water temperature from the
solar water heater module, the inlet gas temperature and concentration from the
condenser, and the water mass flow rate as input data. It calculates the hourly
average evaporation rate and outlet brine and gas temperatures (i.e. equation
4.11 to 4.31, equations 4.36 to 4.57, and equations 4.63 to 4.68 ).
The condenser module receives the outlet gas temperature, mass flow rate, and
concentration of the evaporator together with the cooling water mass flow rate
and ambient temperature as input data. It calculates the hourly distilled water,
outlet gas temperature, and concentration, and outlet cooling water temperature
(i.e. equation 4.32 to 4.35 to 4.57, equations 4.17 t0 4.31, and equations 4.63 to
4.68 ).
The energy balance of the heat exchanger downstream of the condenser
(equation 4.81) is performed based on the outlet cooling water temperature from
the condenser, outlet brine temperature from the evaporator, and ambient
temperature of feed seawater (as described in chapter 4) to determine the inlet
water temperature to the solar collector in the next time step. Once the average
hourly values for different parameters have been determined for the time
increment used, the program then goes to an integration mode. The
instantaneously, hourly, and daily values are summed up over the operation
period to determine the total values. The hourly and daily yield, GOR, different
component efficiencies, and the yearly accumulated yield and GOR are
calculated.
6.3 Model validation
The numerical simulation predictions of the HDH unit hourly and accumulated
distillate production were compared with the experimental measurements under
the first two sets of boundary conditions in table (5.2) for the two packing heights
of 78cm and 39cm, respectively (i.e. the first two cases from left hand side in
figures 5.10a and 5.10c respectively). The main indicators used for the model
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