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Transient temperature measurement of noisy film boiling and silent film boiling in He II
Cryogenics 40 (2000) 241±244
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Transient temperature measurement of noisy ®lm boiling and silent ®lm boiling in He II P. Zhang a,*, M. Murakami b, R.Z. Wang a a
Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200030, People's Republic of China b Institute of Engineering Mechanics and Systems, University of Tsukuba, Tsukuba-city 305-8573, Japan Received 15 December 1999; accepted 17 April 2000
Abstract Previous studies showed that there is a sharp dierence of pressure oscillation between noisy ®lm boiling and silent ®lm boiling in He II. In this study, transient temperature measurement was carried out to add supplementary information of noisy ®lm boiling and silent ®lm boiling. Ó 2000 Elsevier Science Ltd. All rights reserved. Keywords: He II; Temperature measurement; Noisy ®lm boiling; Silent ®lm boiling
1. Introduction There are two basic ®lm boiling modes in saturated He II: noisy ®lm boiling and silent ®lm boiling. It can be understood from previous studies that the two ®lm boiling modes are dierent from each other. Noisy ®lm boiling is characterized by a very loud noise and severe mechanical vibration, while neither noise nor vibration can be detected during silent ®lm boiling [1,2]. Pressure oscillation of noisy ®lm boiling is rather regular and the amplitude of it is quite large, while pressure oscillation of silent ®lm boiling almost cannot be detected. Boiling boundary maps for a thin wire heater and a planar heater have been constructed by Leonard [1] and Zhang [3], respectively. Pressure oscillations of noisy ®lm boiling and silent ®lm boiling have been studied in detail by Yamaguchi [4] and Zhang [5]. However, little is known about the discrepancy of temperature oscillation of two basic ®lm boiling modes. In this study, transient temperature measurement was carried out to identify the dierence between two ®lm boiling modes. 2. Methods and results A specially designed glass cryostat was used in the experiments, and a planar heater was used to cause *
Corresponding author. Fax: +86-21-62933250. E-mail address: [email protected] (P. Zhang).
boiling in He II bath [3], which was excited by a dc stepwise electric current for a time period of th . The immersion depth of the heater, h, could be read from a steel ruler along the cryostat. Two superconductor temperature sensors [3,6] were mounted in line at a distance dT right above the heater, as shown in Fig. 1. and The sensing element consisted of gold (about 200 A) thin ®lms which were vacuum detin (about 1000 A) posited on outer surface of a ®ne quartz ®ber of 40 lm in diameter and 1.5 mm in length. Constant electrical bias current was applied to the sensor element. The transition temperature of it can be shifted to around super¯uid temperature by trimming the thickness ratio of two ®lms and by adjusting the bias electric current. The sensitivity of it is very high and the response time is very short [6]. The superconductor temperature sensor was calibrated before and after experiment to ensure its stability. The experiments were conducted under saturated vapor pressure conditions. The bath temperature was controlled by regulating the vapor pressure in liquid helium bath with the pressure regulating system. The signal of temperature oscillation measured by the superconductor temperature sensor was 100 times ampli®ed by a low noise pre-ampli®er. All data were recorded by a storage oscilloscope and then stored on a computer for further data analysis. Noisy ®lm boiling happens at lower bath temperature and deeper immersion depth of the heater. It is shown by the video camera in the experiments that a big vapor
0011-2275/00/$ - see front matter Ó 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 1 1 - 2 2 7 5 ( 0 0 ) 0 0 0 2 3 - 0
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P. Zhang et al. / Cryogenics 40 (2000) 241±244
Fig. 1. Schematic set-up of the measurement section.
bubble as big as the heater size is expanding and crushing repeatedly on the heater surface accompanied by a loud noise. Fig. 2 shows the experimental results of noisy ®lm boiling. It is seen from Fig. 2(a) that there are many temperature peaks due to very severe expanding and crushing of the vapor bubble. It is rather dicult to calibrate the superconductor temperature sensor when the temperature is above the k-temperature as in this case. Accordingly the calibration is limited only up to the k-temperature, so that the output signal is directly plotted in the ®gure when it is larger than the correspondence of the k-temperature. The temperature is higher than that needed to make the thermodynamic state of helium cross the saturated vapor pressure line, the temperature peaks in Fig. 2(b) result from the expansion of the vapor bubble to the location of the superconductor temperature sensors. The enlarged parts from 0 to 500 ms are shown in Fig. 2(b). Some indicators corresponding to the k-temperature and the vapor temperature for two sensors are also shown in the ®gure, which are got from calibration lines and calculated by the Clapeyron equation, respectively. Taking the curve of the superconductor temperature sensor at dT 4 mm as an example, the temperature oscillation wave indicates that it is composed of: (1) initial temperature rise due to the arrival of the propagating thermal boundary layer [3,6] and (2) subsequent rapid and large temperature rise due to the arrival of the vapor bubble. Both of them are combined into a temperature spike. The propagating of thermal boundary layers corresponds to the movement of the vapor bubble. It can be seen from Fig. 2(a) that the temperature peaks indicate that the superconductor temperature sensors are included in vapor bubbles when they become large enough. Silent ®lm boiling state appears as the immersion depth of the heater is very small. The experimental results are shown in Fig. 3. The liquid±vapor interface around a thin wire heater during silent ®lm boiling is very smooth, and its shape does not change as time
Fig. 2. Simultaneous temperature measurement results of noisy ®lm boiling in He II by two in lined superconductor temperature sensors for the whole process (a), the former stage (b) and the later stage (c). (A) Indicator of the k-temperature for the sensor at 15 mm; (B) indicator of the k-temperature for the sensor at 4 mm; (C) indicator of the vapor temperature for the sensor at 15 mm; (D) indicator of the vapor temperature for the sensor at 4 mm. (1), (2) See the text for details.
elapses [7]. However, the liquid±vapor interface on the planar heater is not so smooth as that around the thin wire heater because the liquid±vapor interface is much larger in the planar heaterÕs case, as shown by the visualization picture of silent ®lm boiling in Fig. 4. Since some small-scale unstable ¯utters can also be seen on the
P. Zhang et al. / Cryogenics 40 (2000) 241±244
Fig. 3. Temperature rise near the heater surface in He II (a) and the instability of the liquid±vapor interface at the initial moment of the heating (b) during silent ®lm boiling.
243
liquid±vapor interface, there is still some instability at the initial moment of the heating, which can be detected by the superconductor temperature sensor. Those enlarged parts are shown in Fig. 3(b). It can also be seen from Fig. 3 that temperature near the heater surface keeps rising even after the heating is shut o, because the heat is still transferred into He II from the higher temperature heater surface. The temperature rise near the heater surface is about 100 mK at t 5 s under the condition in Fig. 3, and the temperature rise speeds are the same at dierent locations above the heater, which means the heat transfer process during silent ®lm boiling is uniform in He II. Another interesting phenomenon is that average temperature rise of He II bath is only about 75 mK at t 5 s under the condition in Fig. 2. Further more, the temperature rise processes are not uniform at dierent locations above the heater, as shown in Fig. 2(c), due to the unstable motion of He II near the heater surface caused by the violent expansion and crushing of the vapor bubble. The higher temperature rise near the heater surface indicates that more heat is transferred into He II in silent ®lm boiling. It can be concluded that heat transfer rate of silent ®lm boiling is higher than that of noisy case based on temperature rise measurement near the heater surface, which coincides with the results got from the heater surface temperature measurement [8].
Fig. 4. Side view of silent ®lm boiling on the planar heater by Schileren method.
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P. Zhang et al. / Cryogenics 40 (2000) 241±244
3. Conclusions Temperature oscillations during noisy ®lm boiling and silent ®lm boiling in He II were measured by the superconductor temperature sensors. Noisy ®lm boiling happens when the immersion depth of the heater is large. A vapor bubble as big as the heater size expands and crushes repeatedly on the heater surface, and temperature spikes during noisy ®lm boiling are due to the expansion of a vapor bubble to the location of the superconductor temperature sensor. Silent ®lm boiling happens when the immersion depth of the heater is small. The vapor ®lm is rather smooth during silent ®lm boiling, and not many temperature spikes are detected except some instability in the initial moment of the heating. It can also be concluded from the experimental results that heat transfer rate of silent ®lm boiling is higher than that of noisy case, which agrees with former results got from a dierent approach. Acknowledgements This research is partially supported by Chinese National Nature Science Foundation, Science and Tech-
nology Foundation of Shanghai Jiao Tong University and ®nancial support from Shanghai and National Education Committee.
References [1] Leonard AC. Helium-2 noisy ®lm boiling and silent ®lm boiling heat transfer coecient values. Proceedings of the ICEC 1970;3:109. [2] Bussieres P, Leonard AC. Noise associated with heat transfer to liquid helium II. Bull IIR Annexe 1966;5:61. [3] Zhang P, Murakami M, Wang RZ, Inaba H. Study of ®lm boiling in He II by pressure and temperature oscillation measurements. Cryogenics 1999;39:609. [4] Yamaguchi M, Murakami M. Study of pressure oscillation during noisy ®lm boiling in He II. Cryogenics 1997;37:523. [5] Zhang P, Murakami M, Wang RZ, Inaba H. In¯uence of bath temperature on noisy ®lm boiling in He II. In: Proceedings of the ICCR'98. International Academic Publishers, p. 341. [6] Shimazaki T, Murakami M, Iida T. Second sound wave heat transfer, thermal boundary layer formation and boiling: highly transient heat transport phenomena in He II. Cryogenics 1995;35:645. [7] Katsuki Y. Visualization study of transient boiling phenomena in He II. MS Thesis. University of Tsukuba, 1995. [8] Frost W. Heat transfer at low temperatures, 1st ed. New York: Plenum Press; 1975.
www.elsevier.com/locate/cryogenics
Transient temperature measurement of noisy ®lm boiling and silent ®lm boiling in He II P. Zhang a,*, M. Murakami b, R.Z. Wang a a
Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200030, People's Republic of China b Institute of Engineering Mechanics and Systems, University of Tsukuba, Tsukuba-city 305-8573, Japan Received 15 December 1999; accepted 17 April 2000
Abstract Previous studies showed that there is a sharp dierence of pressure oscillation between noisy ®lm boiling and silent ®lm boiling in He II. In this study, transient temperature measurement was carried out to add supplementary information of noisy ®lm boiling and silent ®lm boiling. Ó 2000 Elsevier Science Ltd. All rights reserved. Keywords: He II; Temperature measurement; Noisy ®lm boiling; Silent ®lm boiling
1. Introduction There are two basic ®lm boiling modes in saturated He II: noisy ®lm boiling and silent ®lm boiling. It can be understood from previous studies that the two ®lm boiling modes are dierent from each other. Noisy ®lm boiling is characterized by a very loud noise and severe mechanical vibration, while neither noise nor vibration can be detected during silent ®lm boiling [1,2]. Pressure oscillation of noisy ®lm boiling is rather regular and the amplitude of it is quite large, while pressure oscillation of silent ®lm boiling almost cannot be detected. Boiling boundary maps for a thin wire heater and a planar heater have been constructed by Leonard [1] and Zhang [3], respectively. Pressure oscillations of noisy ®lm boiling and silent ®lm boiling have been studied in detail by Yamaguchi [4] and Zhang [5]. However, little is known about the discrepancy of temperature oscillation of two basic ®lm boiling modes. In this study, transient temperature measurement was carried out to identify the dierence between two ®lm boiling modes. 2. Methods and results A specially designed glass cryostat was used in the experiments, and a planar heater was used to cause *
Corresponding author. Fax: +86-21-62933250. E-mail address: [email protected] (P. Zhang).
boiling in He II bath [3], which was excited by a dc stepwise electric current for a time period of th . The immersion depth of the heater, h, could be read from a steel ruler along the cryostat. Two superconductor temperature sensors [3,6] were mounted in line at a distance dT right above the heater, as shown in Fig. 1. and The sensing element consisted of gold (about 200 A) thin ®lms which were vacuum detin (about 1000 A) posited on outer surface of a ®ne quartz ®ber of 40 lm in diameter and 1.5 mm in length. Constant electrical bias current was applied to the sensor element. The transition temperature of it can be shifted to around super¯uid temperature by trimming the thickness ratio of two ®lms and by adjusting the bias electric current. The sensitivity of it is very high and the response time is very short [6]. The superconductor temperature sensor was calibrated before and after experiment to ensure its stability. The experiments were conducted under saturated vapor pressure conditions. The bath temperature was controlled by regulating the vapor pressure in liquid helium bath with the pressure regulating system. The signal of temperature oscillation measured by the superconductor temperature sensor was 100 times ampli®ed by a low noise pre-ampli®er. All data were recorded by a storage oscilloscope and then stored on a computer for further data analysis. Noisy ®lm boiling happens at lower bath temperature and deeper immersion depth of the heater. It is shown by the video camera in the experiments that a big vapor
0011-2275/00/$ - see front matter Ó 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 1 1 - 2 2 7 5 ( 0 0 ) 0 0 0 2 3 - 0
242
P. Zhang et al. / Cryogenics 40 (2000) 241±244
Fig. 1. Schematic set-up of the measurement section.
bubble as big as the heater size is expanding and crushing repeatedly on the heater surface accompanied by a loud noise. Fig. 2 shows the experimental results of noisy ®lm boiling. It is seen from Fig. 2(a) that there are many temperature peaks due to very severe expanding and crushing of the vapor bubble. It is rather dicult to calibrate the superconductor temperature sensor when the temperature is above the k-temperature as in this case. Accordingly the calibration is limited only up to the k-temperature, so that the output signal is directly plotted in the ®gure when it is larger than the correspondence of the k-temperature. The temperature is higher than that needed to make the thermodynamic state of helium cross the saturated vapor pressure line, the temperature peaks in Fig. 2(b) result from the expansion of the vapor bubble to the location of the superconductor temperature sensors. The enlarged parts from 0 to 500 ms are shown in Fig. 2(b). Some indicators corresponding to the k-temperature and the vapor temperature for two sensors are also shown in the ®gure, which are got from calibration lines and calculated by the Clapeyron equation, respectively. Taking the curve of the superconductor temperature sensor at dT 4 mm as an example, the temperature oscillation wave indicates that it is composed of: (1) initial temperature rise due to the arrival of the propagating thermal boundary layer [3,6] and (2) subsequent rapid and large temperature rise due to the arrival of the vapor bubble. Both of them are combined into a temperature spike. The propagating of thermal boundary layers corresponds to the movement of the vapor bubble. It can be seen from Fig. 2(a) that the temperature peaks indicate that the superconductor temperature sensors are included in vapor bubbles when they become large enough. Silent ®lm boiling state appears as the immersion depth of the heater is very small. The experimental results are shown in Fig. 3. The liquid±vapor interface around a thin wire heater during silent ®lm boiling is very smooth, and its shape does not change as time
Fig. 2. Simultaneous temperature measurement results of noisy ®lm boiling in He II by two in lined superconductor temperature sensors for the whole process (a), the former stage (b) and the later stage (c). (A) Indicator of the k-temperature for the sensor at 15 mm; (B) indicator of the k-temperature for the sensor at 4 mm; (C) indicator of the vapor temperature for the sensor at 15 mm; (D) indicator of the vapor temperature for the sensor at 4 mm. (1), (2) See the text for details.
elapses [7]. However, the liquid±vapor interface on the planar heater is not so smooth as that around the thin wire heater because the liquid±vapor interface is much larger in the planar heaterÕs case, as shown by the visualization picture of silent ®lm boiling in Fig. 4. Since some small-scale unstable ¯utters can also be seen on the
P. Zhang et al. / Cryogenics 40 (2000) 241±244
Fig. 3. Temperature rise near the heater surface in He II (a) and the instability of the liquid±vapor interface at the initial moment of the heating (b) during silent ®lm boiling.
243
liquid±vapor interface, there is still some instability at the initial moment of the heating, which can be detected by the superconductor temperature sensor. Those enlarged parts are shown in Fig. 3(b). It can also be seen from Fig. 3 that temperature near the heater surface keeps rising even after the heating is shut o, because the heat is still transferred into He II from the higher temperature heater surface. The temperature rise near the heater surface is about 100 mK at t 5 s under the condition in Fig. 3, and the temperature rise speeds are the same at dierent locations above the heater, which means the heat transfer process during silent ®lm boiling is uniform in He II. Another interesting phenomenon is that average temperature rise of He II bath is only about 75 mK at t 5 s under the condition in Fig. 2. Further more, the temperature rise processes are not uniform at dierent locations above the heater, as shown in Fig. 2(c), due to the unstable motion of He II near the heater surface caused by the violent expansion and crushing of the vapor bubble. The higher temperature rise near the heater surface indicates that more heat is transferred into He II in silent ®lm boiling. It can be concluded that heat transfer rate of silent ®lm boiling is higher than that of noisy case based on temperature rise measurement near the heater surface, which coincides with the results got from the heater surface temperature measurement [8].
Fig. 4. Side view of silent ®lm boiling on the planar heater by Schileren method.
244
P. Zhang et al. / Cryogenics 40 (2000) 241±244
3. Conclusions Temperature oscillations during noisy ®lm boiling and silent ®lm boiling in He II were measured by the superconductor temperature sensors. Noisy ®lm boiling happens when the immersion depth of the heater is large. A vapor bubble as big as the heater size expands and crushes repeatedly on the heater surface, and temperature spikes during noisy ®lm boiling are due to the expansion of a vapor bubble to the location of the superconductor temperature sensor. Silent ®lm boiling happens when the immersion depth of the heater is small. The vapor ®lm is rather smooth during silent ®lm boiling, and not many temperature spikes are detected except some instability in the initial moment of the heating. It can also be concluded from the experimental results that heat transfer rate of silent ®lm boiling is higher than that of noisy case, which agrees with former results got from a dierent approach. Acknowledgements This research is partially supported by Chinese National Nature Science Foundation, Science and Tech-
nology Foundation of Shanghai Jiao Tong University and ®nancial support from Shanghai and National Education Committee.
References [1] Leonard AC. Helium-2 noisy ®lm boiling and silent ®lm boiling heat transfer coecient values. Proceedings of the ICEC 1970;3:109. [2] Bussieres P, Leonard AC. Noise associated with heat transfer to liquid helium II. Bull IIR Annexe 1966;5:61. [3] Zhang P, Murakami M, Wang RZ, Inaba H. Study of ®lm boiling in He II by pressure and temperature oscillation measurements. Cryogenics 1999;39:609. [4] Yamaguchi M, Murakami M. Study of pressure oscillation during noisy ®lm boiling in He II. Cryogenics 1997;37:523. [5] Zhang P, Murakami M, Wang RZ, Inaba H. In¯uence of bath temperature on noisy ®lm boiling in He II. In: Proceedings of the ICCR'98. International Academic Publishers, p. 341. [6] Shimazaki T, Murakami M, Iida T. Second sound wave heat transfer, thermal boundary layer formation and boiling: highly transient heat transport phenomena in He II. Cryogenics 1995;35:645. [7] Katsuki Y. Visualization study of transient boiling phenomena in He II. MS Thesis. University of Tsukuba, 1995. [8] Frost W. Heat transfer at low temperatures, 1st ed. New York: Plenum Press; 1975.