Environmental Engineering Reference
In-Depth Information
•
Heat supplied to accumulator (kcal/hr)
•
Heat supplied to evaporator (kcal/hr)
•
Heat supplied to evaporator (kcal/hr)
Evaporator feedwater flow rate (m
3
/hr)
•
Preheater #1 outlet temp. (
o
C)
•
First effect temp. (
o
C)
•
18
th
effect temp. (
o
C)
•
Product water flow rate (m
3
/hr)
•
Absorber plate temp. of empty collector (
o
C)
•
Header tube temp. of empty collector (
o
C)
•
4.1. Measuring the Heat Collected in Block F
Measuring the heat loss in the piping system in such a large collector bank is obviously
laborious and will require the accurate measurement of collector fluid temperature at many
locations within the field. This was deemed impractical and was ruled out from the outset.
The solution which was found practical is to isolate a single block of collectors and use it
for test measurements in order to find the piping heat loss in this block, then estimate the
heat loss in the piping system of the whole collector bank based on the results obtained
from the measurements carried out on the selected block. Block F was selected for this
purpose since this block was already provided with resistance temperature detectors at inlet
and outlet of the block, as well as a vortex flowmeter for measuring the water flow rate
through the block.
Figure 9 is a schematic diagram of block F showing the location of the temperature
measuring probes. Two RTDs are attached at block inlet (location E) and block outlet
(location F). The RTDs, which are three-wire sheathed platinum resistance elements, are
model RN33-AMAS and are manufactured by Yokogawa Hokushin Corporation. They are
connected to Thermodac 32 via resistance-to-voltage converters which produce 1-5 volt DC
signal outputs that are fed to temperature recorders.
The two output signals from the resistance-to-voltage converters which are attached to
the RTDs at locations E and F are connected to a programmable computing unit (PCU),
model SPLR-100A manufactured by Yokogawa (see Yokogawa Instruction Manual for
Model YF100 vortex flowmeters (1993)), in which the 4-20 mA signal from the vortex
flow meter is also connected to the PCU. A variety of arithmetical computational functions
can be performed by the PCU. Programs can be developed and written to ROM (Read Only
Memory) using a dedicated programming language connecting the PCU to an SPRG
Programmer. The pulse output signal from the PCU represents the heat collected between
E and F and was measured by subtracting the two input temperature signals,
T
F
-
T
E
,
and
multiplying by the flow rate signal and the specific heat of the heat collecting fluid (water)
at the operating temperature to obtain the heat collected between E and F (block heat
collected).
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