# Heat-flux enhancement response for novel flow-boiler operations under resonant, sub-harmonic, and superharmonic imposition of vapor pulsation frequencies relative to a liquid flow-rate pulsation frequency

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## Abstract

This paper presents fundamental results from experimental investigations of shear/pressure-driven internal flow boiling of FC-72 in a horizontal test section of total flow channel length 1000 mm, gap height 2 mm, and width 15 mm. It compares effects of the frequencies of vapor and liquid pressure fluctuations (pulsations) on the experimentally measured heat-flux rates and heat transfer coefficients at a representative location within the flow boiler under a flow operation method in which re-circulating vapor maintains an annular flow regime over the entire length of the device. For liquid flow/pressure pulsations at 3.8–3.9 Hz, four externally imposed inlet vapor pressure fluctuation conditions were considered: (1) no externally imposed vapor pulsations and (2)–(4): high-amplitude externally imposed vapor pulsations at (2) the same, (3) half, and (4) double the inlet liquid pulsation frequency. Representative pressure differences within the flow boiler are also examined. Local time-averaged heat-flux and heat transfer coefficient responses of these flows are compared with previously published data at the same liquid pulsation frequency, but at a different inlet liquid flow rate, vapor quality, and pressure. The reported measurements, and the discussions and conclusions in this paper, enable better understanding of an established pulsation-induced heat-flux enhancement phenomenon which may be used in future cooling systems to significantly enhance average heat-flux values over the entire length of an annular flow boiler. The main conclusion is that, for the flow conditions investigated, optimal heat transfer efficiency occurs when vapor and liquid pulsations are imposed at the same frequency on the flow-boiler inlet.

## Keywords

Phase-change flow Novel flow boiling Flow pulsations Pulsatile shear-driven flow boiling Annular boiling flows Imposed flow-rate pulsation Imposed pressure pulsation Heat-flux enhancement Frequency matching## List of symbols

## Labels

- S
Separator plate

- C
_{R} Compressor

- F
_{C} Coriolis flow meter

- FC-72
Working fluid used in experiments: Fluorinert™ electronic liquid (C

_{6}F_{14}) from 3M Corp- DPT
Differential pressure transducer: measures pressure differences directly

- APT
Absolute pressure transducer: used for direct measurement of absolute pressure

- HFM-40
Heat-flux meter: used to measure heat-flux directly at a location 40 cm downstream from the flow-boiler inlet

- P
_{V} Vapor pulsator: used to induce fluctuations in vapor pressure and flow rate

- P
_{1}, P_{2} Pumps: used to circulate liquid working fluid in experimental flow loop

- TEC
Thermoelectric cooler (solid state heat pumps)

- L/V separator
Liquid–vapor separator

- V
Valve

- PID
Proportional-integral-derivative (as in the control method)

- IF
Imposed fluctuation, referring to cases in which the vapor pulsator was used to apply pressure fluctuations to the vapor entering the flow boiler

- N-IF
No-imposed fluctuation, referring to cases in which the vapor pulsator was not used

- H-IF
High-amplitude imposed fluctuation, referring to cases in which the vapor pulsator was operated at its maximum amplitude

## Variables

*h*Gap height of flow channel in test section (mm)

*L*Length of flow channel (m)

- \(a\)
Amplitude value, which is the magnitude of the FFT of a flow variable at a frequency of interest, in units associated with that flow variable

- \(f\)
Frequency (Hz)

- \(f_{\text{P:V}}\)
Primary frequency associated with imposed vapor phase flow pulsations (Hz)

- \(f_{\text{P:L}}\)
Primary frequency associated with imposed liquid phase flow pulsations (Hz)

- \(x\)
Distance from the flow channel inlet in the downstream direction (cm)

- \(\dot{m}\)
Mass flow rate (g/s)

- \(p\)
Pressure (kPa)

- \(\Delta p\)
Representative pressure difference between two locations of interest (kPa)

- \(v\)
Average velocity over a reference area (m/s)

- \(T\)
Temperature (°C)

- \(h\)
Heat transfer coefficient (W/m

^{2}K)- \(p^{{\prime }}\)
Pressure fluctuations for frequencies > 0 Hz, used in FFT graphs of absolute pressures (kPa)

- \(t\)
Time (s)

- \(\Delta T\)
Representative temperature difference between saturation temperature (taken at a pressure of interest within the flow boiler) and a corresponding heat-exchange surface temperature (°C)

- \(q^{{\prime \prime }}\)
Heat-flux (W/cm

^{2})

## Subscripts

- 0
At the \(x = 0\;{\text{cm}}\) location

- 10
At the \(x = 10\;{\text{cm}}\) location

- 40
At the \(x = 40\;{\text{cm}}\) location

- 90
At the \(x = 90\;{\text{cm}}\) location

- 0–40
Between the \(x = 0\;{\text{cm}}\) and \(x = 40\;{\text{cm}}\) locations

- 40–90
Between the \(x = 40\;{\text{cm}}\) and \(x = 90\;{\text{cm}}\) locations

- I
Inlet of the test section

- E
Exit of the test section

- R
Re-circulating vapor flow

- P
Imposed pulsations

- L
Liquid

- V
Vapor

- Sat
Saturation, as of temperature

- Avg
Representative of an average value

## Notes

### Acknowledgements

This work was supported by National Science Foundation Grant CBET-1033591. The Principle Investigator on that grant, Dr. Amitabh Narain of Michigan Technological University, has approved independent study and publication of the reported work.

### Author Contribution

Publication of this document was approved by Dr. Amitabh Narain of Michigan Technological University as stated in the acknowledgment. The experiments were conducted by Dr. Michael Kivisalu as a graduate research assistant for Dr. Narain in 2013. Dr. Aliihsan Koca was responsible for data analysis, graphing, and writing of this document as a visiting research scholar at Michigan Technological University assigned to Dr. Narain.

### Compliance with ethical standards

### Conflict of interest

On behalf of all authors, the corresponding author affirms that the preceding statements completely disclose any potential conflict of interest pertaining to this document.

## References

- 1.Kivisalu MT, Gorgitrattanagul P, Mitra S, Naik R, Narain A (2012) Prediction and control of internal condensing flows in the experimental context of their inlet condition sensitivities. Microgravity Sci Technol 24(3):147–155Google Scholar
- 2.Kivisalu MT, Gorgitrattanagul P, Narain A, Naik R, Hasan M (2013) Sensitivity of shear-driven internal condensing flows to pressure fluctuations and its utilization for heat flux enhancements. Int J Heat Mass Transf 56:758–774Google Scholar
- 3.Kivisalu MT, Gorgitrattanagul P, Narain A (2014) Results for high heat-flux flow realizations in innovative operations of milli-meter scale condensers and boilers. Int J Heat Mass Transf 75:381–398Google Scholar
- 4.Kivisalu MT (2015) Experimental investigation of certain internal condensing and boiling flows: their sensitivity to pressure fluctuations and heat transfer enhancements. Dissertation, Michigan Technological UniversityGoogle Scholar
- 5.Naik RR, Narain A (2016) Steady and unsteady simulations for annular internal condensing flows, part II: instability and flow regime transitions. Numer Heat Transf Part B Fundam 69(6):1–16Google Scholar
- 6.Naik RR, Narain A, Mitra S (2016) Steady and unsteady simulations for annular internal condensing flows, part I: algorithm and its accuracy. Numer Heat Transf Part B Fundam 69(6):1–22Google Scholar
- 7.Narain A, Kivisalu MT, Naik R, Gorgitrattanagul N, Mitra S, Hasan MM (2012) Comparative experimental and computational studies for annular condensing and boiling flows in milli-meter scale horizontal ducts. In: Proceedings of ASME 2012 summer heat transfer conference, Rio Grande, Puerto Rico, USA. ASME, pp 563–574Google Scholar
- 8.Narain A, Naik RR, Ravikumar S, Bhasme SS (2015) Fundamental assessments and new enabling proposals for heat transfer correlations and flow regime maps for shear driven condensers in the annular/stratified regime. J Thermal Eng 1:307–321Google Scholar
- 9.Ranga Prasad H, Narain A, Bhasme SS, Naik RR (2017) Shear driven annular flow-boiling in millimeter-scale channels: direct numerical simulations for convective component of the overall heat transfer coefficient. Int J Transp Phenom 15(1):1–35Google Scholar
- 10.Narain A, Ranga Prasad H, Koca A (2017) Internal annular flow-boiling and flow-condensation: context, results and recommendations. In: Kulacke FA (ed) Handbook of Thermal Science and Engineering. Springer, Berlin
**(in press)**Google Scholar - 11.Kandlikar SG, Narai H, Shoji M, Dhir VK (1999) Handbook of phase change: boiling and condensation. Taylor and Francis, New YorkGoogle Scholar
- 12.Nukiyama S (1966) The maximum and minimum values of the heat Q transmitted from metal to boiling water under atmospheric pressure. Int J Heat Mass Transf 9(12):1419–1433Google Scholar
- 13.Carey VP (2008) Liquid-vapor phase-change phenomena, 2nd edn. Series in chemical and mechanical engineering. Taylor and Francis Group, Washington, DCGoogle Scholar
- 14.Lienhard JHI, Lienhard JHV (2003) A heat transfer textbook. Phlogiston Press, CambridgezbMATHGoogle Scholar
- 15.Lienhard JH, Dhir VK, Riherd DM (1973) Peak pool boiling heat-flux measurements on finite horizontal flat plates. J Heat Transf 95(4):477–482Google Scholar
- 16.Kuo CJ, Peles Y (2009) Flow boiling of coolant (HFE-7000) inside structured and plain wall micro channels. J Heat Transf 131(12):1–9Google Scholar
- 17.Harirchian T, Garimella SV (2009) Effects of channel dimension, heat flux, and mass flux on flow boiling regimes in micro channels. Int J Multiph Flow 35(4):349–362Google Scholar
- 18.Qu W, Mudawar I (2004) Measurement and correlation of critical heat flux in two phase micro-channel heat sinks. Int J Heat Mass Transf 47:2045–2059Google Scholar
- 19.Bergles AE, Kandlikar SG (2005) On the nature of critical heat flux in microchannels. J Heat Transf 127(1):101–107Google Scholar
- 20.Choi SR, Evangelista JW, Avedisian CT, Tsang W (2011) Experimental study of chemical conversion of methanol and ethylene glycol in a film boiling reactor. Int J Heat Mass Transf 54:500–511zbMATHGoogle Scholar
- 21.Carey VP (1992) Liquid-vapor phase-change phenomena. Series in chemical and mechanical engineering. Hemisphere Publishing Corporation, Washington, DCGoogle Scholar
- 22.Collier JG, Thome JR (1994) Convective boiling and condensation, 3rd edn. Oxford University Press, OxfordGoogle Scholar
- 23.Taitel Y, Dukler AE (1976) A model for predicting flow regime transitions in horizontal and near horizontal gas-liquid flow. AIChE J 22(1):47–55Google Scholar
- 24.Chung PMY, Kawaji M (2004) The effect of channel diameter on adiabatic two-phase flow characteristics in microchannels. Int J Multiph Flow 30:735–761zbMATHGoogle Scholar
- 25.Zhang T et al (2009) Ledinegg instability in microchannels. Int J Heat Mass Transf 52:5661–5674zbMATHGoogle Scholar
- 26.Tadrist L (2007) Review on two-phase flow instabilities in narrow spaces. Int J Heat Fluid Flow 28(1):54–62MathSciNetGoogle Scholar
- 27.Brutin D, Tadrist L (2006) Destabilization mechanisms and scaling laws of convective boiling in a minichannel. J Thermophys Heat Transf 20(4):850–855Google Scholar
- 28.Barber J, Sefiane K, Brutin D (2007) Two phase boiling and flow instabilities in a microchannel. In: Proceedings of international conference on nanochannels, microchannels and minichannels, Puebla, MexicoGoogle Scholar
- 29.Harirchian T, Garimella SV (2009) Effects of channel dimension, heat flux, and mass flux on flow boiling regimes in microchannels. Int J Multiph Flow 35(4):349–362Google Scholar
- 30.Bergles AE, Kandlikar SG (2005) On the nature of critical heat flux in microchannels. J Heat Transf 127(1):101–107Google Scholar
- 31.Balasubramanian P, Kandlikar SG (2005) Experimental study of flow patterns, pressure drop, and flow instabilities in parallel rectangular minichannels. Heat Transf Eng 26(3):20–27Google Scholar
- 32.Mandrusiak GD, Carey VP, Xu X (1988) An experimental study of convective boiling in a partially heated horizontal channel with offset strip fins. J Heat Transf 110(1):229–236Google Scholar
- 33.Ma A, Wei J, Yuan M, Fang J (2009) Enhanced flow boiling heat transfer of FC-72 on micro-pin-finned surfaces. Int J Heat Mass Transf 52:2925–2931Google Scholar
- 34.Rainey KN, Li G, You SM (2001) Flow boiling heat transfer from plain and microporous coated surfaces in subcooled FC-72. J Heat Transf 123(5):918–925Google Scholar
- 35.Nakayama W, Daikoku T, Kuwahara H, Nakajima T (1980) Dynamic model of enhanced boiling heat transfer on porous surfaces—part I: experimental investigation. J Heat Transf 102(3):445–450Google Scholar
- 36.Hailei W, Peterson RB (2010) Enhanced boiling heat transfer in parallel microchannels with diffusion brazed wire mesh. IEEE Trans Compon Packag Technol 33(4):784–793Google Scholar
- 37.Holland B, Ozman N, Wirtz RA (2008) Flow boiling of FC-72 from a screen laminate extended surface matrix. Microelectron J 39(7):1001–1007Google Scholar
- 38.Liu D, Garimella SV (2007) Flow boiling heat transfer in microchannels. J Heat Transf 129(10):1321–1332Google Scholar
- 39.Zhang L et al (2002) Enhanced nucleate boiling in microchannels. In: Proceedings of the micro electro mechanical systems, the fifteenth IEEE international conference, pp 89–92Google Scholar
- 40.Chih-Jung K, Kosar A, Peles Y, Virost S, Mishra C, Jensen MK (2006) Bubble dynamics during boiling in enhanced surface microchannels. J Microelectromech Syst 15(6):1514–1527Google Scholar
- 41.Kuo CJ, Peles Y (2008) Flow boiling instabilities in microchannels and means for mitigation by Reentrant Cavities. J Heat Transf 130(7):072402–072410Google Scholar
- 42.Kosar A, Kuo CJ, Peles Y (2005) Reduced pressure boiling heat transfer in rectangular microchannels with interconnected Reentrant Cavities. J Heat Transf 127(10):1106–1114Google Scholar
- 43.Delhaye JM (1974) Jump conditions and entropy sources in two-phase systems local instant formulation. Int J Multiph Flow 1(3):395–409zbMATHGoogle Scholar
- 44.Faghri A (1995) Heat pipe science and technology. Taylor and Francis, Washington, DCGoogle Scholar
- 45.Mukherjee A, Dhir VK (2004) Study of lateral merger of vapor bubbles during nucleate pool boiling. J Heat Transf 126(6):1023–1039Google Scholar
- 46.Mukherjee A, Kandlikar S (2005) Numerical simulation of growth of a vapor bubble during flow boiling of water in a microchannel. Microfluid Nanofluid 1(2):137–145Google Scholar
- 47.Kunkelmann C, Ibrahem K, Schweizer N, Herbert S, Stephan P, Tatiana GR (2012) The effect of three-phase contact line speed on local evaporative heat transfer: experimental and numerical investigations. Int J Heat Mass Transf 55:7–8Google Scholar
- 48.Jaikumar A, Kandlikar SG (2016) Pool boiling enhancement through bubble induced convective liquid flow in feeder microchannels. Appl Phys Lett 108(4):041604Google Scholar