Environmental Engineering Reference
In-Depth Information
Subsequently, research operation was begun, actual climatic data were accumulated and
the characteristics of the equipment started to become clear through the winter and summer
component tests and the continuous operation tests. Thus, a new look was taken at the
simulation program. As a result of comparing and examining the calculated values and th
actually measured values, it was concluded that the program must be revised in order that the
operation of the test plant was reproduced as faithfully as possible and more accurate
forecasts were made to cope with different operating conditions and plants of different scales.
The program was revised and manuals were prepared to use the program between October
1985 and January 1986.
9.1.2. Flow Chart of the SOLDES Program
Evacuated glass tube-type of collectors are used and the absorber area can be varied
from 500 m 2 to 20,000 m 2 . The heat collecting system uses a bypass circuit. When the
temperature of the heat collecting system drops below the set value, the bypass operation is
performed, and once the temperature rises above the set value, operation is switched over to
the accumulator side. Solar cell type control is excercised to start and stop the heat
collecting water pump. The accumulator is treated as a thermal stratified type, and the
temperature distribution inside the tank is determined while bearing in mind the inflow and
outflow of the heat collecting water and heating water. The number of collectors used and
the heating water flow rate are varied so that the maximum operating capacity of the
evaporator is not exceeded. However, for the simulation, consideration was given to
maximize the effective use of the collectors and a bypass circuit was installed between the
accumulator and the evaporator. By this means, a system of control was adopted where
some of the heating water returning from the evaporator is bypassed and forwarded to the
evaporator so that the temperature of the heating water entering the evaporator is kept
below the rating. This is particularly useful when the accumulator water temperature is
excessively high.
The evaporator capacity can be varied over the range of 100 to 2,000 m 3 /day, the
maximum brine temperature can be varied from 60 - 80 o C and the number of effects of the
evaporator can be varied fro 13 to 32. The simulation program takes into consideration the
influence of the heating water temperature, heating water flow rate, seawater temperature and
seawater flow rate.
Figure 21 is an abbreviated flow chart of the simulation program. The equipment
specifications, calculation conditions and other data are input to the program and are divided
into two groups: System data No. 1 and System data No. 2. The data input with the System
data No. 1 group serve to output error messages and suspend the execusion of the calculations
in cases where there are errors in the input data or where allowable ranges have been
exceeded. Any calculation period ranging from one day to one year can be designated and a
balance in the system is determined every 30 minutes in relation to the calculation loop. The
calculation results can be output either by the day or by the month. The “SOLDES”
simulation program for the solar desalination plant is composed of 22 subroutine programs,
two sets of system data and four types of climatic data.
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