Development of a Sensor to Detect Condensation of ...

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When steam is injected into the water. , direct condensation takes place depending upon the design of injection, temperature of surrounding water and inlet ...
Advanced Materials Research Vol. 650 (2013) pp 482-487 © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.650.482

Development of a Sensor to Detect Condensation of Super-Sonic Steam Afrasyab Khan1a, Khairuddin Sanaullah2b, Noaman Ul Haq3c, 1,3

Dept of Chemical Engineering, SCME, NUST, Pakistan

2

Dept. of Chemical Engg. & Energy Sustainability Universiti Malaysia Sarawak (UNIMAS)

a,f

[email protected], [email protected], [email protected]

Keywords: Super-Sonic Steam, Condensation, Micro-Controller, Plume.

Abstract. This paper explains the development and functioning of AC driven electrodes based sensor which is used for the study of condensation phenomena of steam. Time for the AC signals starts form 20 msecond to 1 second. Data acquisition system is employed against each time interval and the output data is fed into EIDORS (a free software algorithm). Images show the clear boundaries between pure steam, its interface and water. Introduction Steam’s importance and it’s usage in the present day industrial age is out of question due to myriad dimensions that it has like its use in the direct contact heat exchanger, chemical mixing equipment, steam jet driven injectors and in food processing industry etc. When steam is injected into the water , direct condensation takes place depending upon the design of injection, temperature of surrounding water and inlet mass flow rates and pressures. Many researchers make their contributions on this frontier of science and technology that includes those which explains; different condensation modes [1], temperature profiles around steam plume and its plume shapes [2], plume penetration length [3,4], hydrodynamics of steam jet [5], condensation regime diagrams that depends upon CFD analysis and temperature profiles [6], Sonic steam jets experimental studies [7] and experimental studies on over expanded steam jets [8]. However, most of the studies are mainly related to the supersonic steam temperature , plume shape and hydrodynamic studies and till now non of the study is being conducted on observing the interface width that in turn may provide the efficiency of our designed injection mechanism. In this regard a sensor is designed and developed, which is capable to observe the condensation in a slice of water within time period of 3 seconds at 50Hz frequency and control over ON/OFF times of the AC signals are delivered to the electrodes for getting an image. Electronic System Electronic system for the sensor used for observing condensation phenomena is designed using AT89C51 micro controller, solid state switches Max 4665, key encoder MM74C922, and Decoders 74HC137. 16 Stainless steel electrodes are mounted circumferentially around a column and such arrangement is located at 3 places with total 48 electrodes being thus consumed for the purpose. The sensor thus developed is to capture the interface boundaries movement with constant and variable temperature around the Super-sonic steam plume in radial, vertical and circumferential directions. The block diagram of the system is shown in the Figure 1 and the arrangement of the electrodes mounted on the rig is shown in Figure 2.

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Figure 1: A schematic layout of the Sensor to observe steam condensation

Figure 2: A photograph of the column showing the circumferential location of the electrodes

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Figure 3: The circuit diagram. The sensor is based on an AC source that is capable to provide the 220 [V] at 50 [Hz] and two batteries; one of the two is 5 [V] dc, used to provide DC supply to micro-controller and the other is ±12 [V] reserved for Max 4665 solid state switches. The current rating of the system is 3 [mA] when it is operated at full load. 8 bit micro controller has 4 ports namely Port 0→3, which are used for derived input and thus implements control logic (Schemes Adjacent, Opposite, Cosine). The circuit diagram is shown in Figure 3 and the multiplexing box is shown in Figure 4 (Adjacent signals are sent to the adjacent electrodes shown by 2 LED’s blink at the same time).

Figure 4: A snap showing multiplexing box. Hex key pad is attached to the port 3 of micro-controller using MM74C922 key encoder which is used to deliver inputs to the system. Along with it HD 47780, 16x4 LCD is used and it is attached to the Port 1 of micro-controller. 74HC137 decoders are attached to port 2 to implement decoding schemes for direct signal switching. Low on resistance (5 [Ω]) CMOS analog switches are used for connecting AC signals to the electrodes through decoder 74HC137. Software for the sensor is written using C language using Keil IDE. The flow chart for the sequence of execution of control program is shown in Figure 5.

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After applying the AC Signals at different electrodes PCI-6033E National Instruments Data Acquisition Card Carrying DAQ system is used, which has 64 channels and the banana switches are used across each electrode to acquire the data at the rate of 1000 samples per second. The Banana switches are connected to the electrodes in adjacent fashion as electrode 1 and 2 carry two banana switches from a single BNC cable and electrode 2 and 3 have the switches for BNC wire no 2 and so on up to 16 electrodes as shown in Figure 6.

Figure 5: A flow chart showing the sequence of control program.

Figure 6: A layout of link between Banana switches & electrodes

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The Data obtained is then filtered in MATLAB using MATLAB built in filter ML-FILTER. We take two sets of data one without steam injection and named it as Reference Data and Other after injecting steam and named it as Steam Data. The plots thus obtained are shown in Figure 7. This figure shows plot for 20 msec and in the similar fashion plots for 40, 60, 80, 100, 200, 400, 600, 800, and 1000 msec are obtained. By processing the data for Vrms we get the values for all the time intervals and temperature changes, which ranges from 30 to 60 o C at the increment rate of 5 oC. Then all the data is feed into EIDORS for image reconstruction. The images thus obtained are presented in the next section.

Voltages [V]

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-7

5500

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6500

Time [m-sec]

Figure 7: A plot of steam data obtained at 20 msec.

Figure 8: Images obtained at 20 msec for (a) 30 oC & (b) 60 oC. Results The images obtained for 30 & 60oC at 20 msec are presented in Figure 8. Images of part (a) of this figure shows a clear light blue interface between the blue water and the white steam. However, increase in temperature (part b of figure 8) results in increase of the steam plume, which in turn expands the width of the interface between water and pure steam.

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Conclusion A sensor is designed and developed to study phenomenon of supersonic steam condensation using micro controller solid state switches and other relating electronic components. Images thus obtained by virtue of the sensor provide a good evidence of major increment in the width of interface between water and steam as with the rise of temperature. References: [1] Liang, K.S., Griffith, P., 1994. Experimental and analytical study of direct contact condensation of steam in water. Nucl. Eng. Des. 147, 425–435. [2] X.-Z. Wu et al. International Journal of Multiphase Flow 33 (2007) 1296–1307 [3] Kerney, P.J., Faeth, G.M., Olscn, D.R., 1972. Penetration characteristics of a submerged steam jet. AICHE J. 18, 548–553. [4] Weimer, J.C., Faeth, G.M., Olscn, D.R., 1973. Penetration of vapor jets submerged in sub cooled liquids. AICHE J. 19, 552–558. [5] Simpson, M.E., Chan, C.K., 1982. Hydrodynamics of a subsonic vapor jet in sub cooled liquid. Trans. ASME J. Heat Transfer 104, 271–278. [6] X.-Z. Wu et al. Journal of Nuclear Engineering and Design 239 (2009) 3142-3150 [7] X.-Z. Wu et al. Journal of Chemical Engineering Science 64 (2009) 5002–5012 [8] X.-Z. Wu et al. / Experimental Thermal and Fluid Science 34 (2010) 10–19