Nbhtc pure

Thermal Energy Conversion Control Lab. Chonbuk Nat’I Univ.
Nucleate boiling heat transfer coefficients
of
pure halogenated refrigerants
Dongsoo Junga,*, Youngil Kimb, Younghwan Koa, Kilhong Songa
*Department of Mechanical Engineering, Inha University, Incheon 402-751, Republic of Korea
Thermal/Flow Control Research Center, Korea Institute of Science and Technology, Seoul 130-650, Republic of Korea
Sudheer Nandi
(Ph.D.),M.Tech,MBA.
Sustainable Energy . S.korea

Nucleate boiling heat transfer coefficients of pure halogenated
refrigerants
2
• http://www.sciencedirect.com/science/article/pii/S0140700702000403#
http://www.youtube.com/watch?v=s-YmfZNKnlU

Thermal Energy Conversion Control Lab. Chonbuk Nat’I Univ. 3
Qualitative classification flow regimes
.
MIT Department of Nuclear Science and Engineering

Heat transfer and flow regimes in a vertical heated channel. (Thermal non‐equilibrium effec
ts have been neglected in sketching the bulk temperature)

Abstract
• Nucleate pool boiling heat transfer coefficients (HTCs) of HCFC123, CFC11, HCFC142b, HFC134a, CFC12HCFC22, HFC125
and HFC32 on a horizontal smooth tube of 19.0 mm outside diameter have been measured.
• The experimental apparatus was specially designed to accommodate high vapor pressure refrigerants such as HFC32 and
HFC125 with a sight glass.
• A cartridge heater was used to generate uniform heat flux on the tube. Data were taken in the order of decreasing heat flux from
80 to 10 kW m−2 with an interval of 10 kW m-2 in the pool of 7°C.
• Test results showed that HTCs of HFC125 and HFC32 were 50–70% higher than those of HCFC22 while HTCs of HCFC123 and
• HFC134a were similar to those of CFC11 and CFC12 respectively.
• It was also found that nucleate boiling heat transfer correlations available in the literature were not good for certain alternative
refrigerants such as HFC32 and HCFC142b. Hence, a new correlation was developed by a regression analysis taking into account
the variation of the exponent to the heat flux term as a function of reduced pressure and some other properties.
• The new correlation showed a good agreement with all measured data including those of new refrigerants of significantly varying
vapor pressures with a mean deviation of less than 7%.
Keywords: Heat transfer; Mass transfer; Nucleate Boiling; Refrigerant; Measurement
6

Experimental apparatus
shows a schematic diagram of the experimental apparatus for nucleate boiling heat transfer that
can be used to take measurements up to 2500 Kpa

Manufacture of the tube
9

In this study, a cartridge heater was used to generate uniform heat flux on the surface of the heat transfer tube. The uniformity of the heater
was thoroughly checked before its use and it was inserted into the center hole of 9.5 mm diameter which was machined by a gun
drill as mentioned earlier. And then a paste of high thermal conductivity was applied between the inner surface of the hole and cartridge
heater and the heater was pushed through the hole tightly.
Finally, the left end of the tube was capped with a Bakelite piece and epoxy for insulation and soldered with a copper cap for sealing and
the other end with the heater’s electrical connections was sealed with epoxy and a nylon cap as shown in Fig. 2(b).
10

The experimental procedure for a given refrigerant was as
follows
1. Nitrogen was charged to the refrigerant loop up to 1500 kPa with some halogenated refrigerants to check with a
halogen detector if there was any leak.
2. A vacuum pump was turned on few hours to evacuate the system thoroughly and the refrigerant was charged to the
system up to 30 mm higher than the top of the heat transfer tube.
3. The liquid was heated for 2 h by supplying power to the cartridge heater maintaining the heat flux of 60 kW m2 on
the heat transfer tube and the vapor was vented a few times for degassing which was especially important for low
pressure refrigerants that might have trapped some air within.
4. After 1 h, power to the cartridge heater was initiated and the heat flux was increased to 80 kW m2 gradually. And
data were taken under steady state at 7 C from 80 to 10 kW m2 with an interval of 10 kW m2 in the order of decreasing
heat flux to avoid a hysteresis effect.
5. Refrigerant was changed and the same procedures of (1–4) were repeated after the surface was cleaned as described
earlier.
11

Comparison of the present data with a new
correlation for all pure refrigerants.
17
Heat transfer coefficients vs. heat flux on a logarithmic plot.

Conclusions
In this study, nucleate boiling heat transfer coefficients (HTCs) of eight pure halogenated refrigerants of HCFC123, CFC11, HCFC142b,
HFC134a, CFC12, HC FC22, HFC125, and HFC32 were measured at the liquid temperature of 7 C on a plain tube of 19.0 mm outside diameter
. All data were taken from 80 to 10 kW m2 with an interval of 10 kWm2 in the decreasing order of heat flux. Based upon the test results and cor
relation development, following conclusions can be drawn.
(1) At the same pool temperature, refrigerants with higher vapor pressures showed higher nucleate boiling HTCs consistently. This was due to
the fact that the wall superheat required to activate given size cavities became smaller as pressure increased.
(2) Stephan and Abdelsalam’s correlation under predicted the present data by 17.5% while Cooper’s over predicted them by 15.1%. Stephan
and Abdelsalam’s correlation under predicted the data of HFC32 by 48% while Cooper’s over predicted the data of HCFC142b by 44%.
(3) Some dimensionless groups affecting nucleate boiling heat transfer were identified and they were correlated by a regression analysis to
yield a new correlation valid for all halogenated refrigerants tested. Thus developed correlation predicted the present data within 7% deviation
for all refrigerants including HFC32 and HCFC142b. The new correlation takes into account that the exponent to the heat flux term
varies significantly among fluids and also is a strong function of reduced pressure
18

References
[1] Molina MJ, Rowland FS. Stratospheric sink for chlorofluoromethane: chlorine atom catalyzed destruction of ozone. Nature 1974;2
49:810–2.
[2] United Nations Environment Programme. Montreal protocol on substances that deplete the ozone layer. Final Act, 1989.
[3] Air-conditioning and Refrigeration Institute. R22 and R502 alternative refrigerants evaluation program. Arlington (VA, USA): 1992
–1997.
[4] Cavallini A. Working fluids for mechanical refrigeration.Int J Refrigeration 1996;19(8):485–96.
[5] Jung D, Kim C, Song K, Lee J. Nucleate boiling heat transfer coefficients of pure refrigerants. Proc 11th Int Heat Transfer Conf 199
8;2:443–7.
[6] Thome JR. Boiling of new refrigerants: a state-of-the-artreview. Int J Refrigeration 1996;19(7):435–57.
[7] Gorenflo D. State of the art in pool boiling heat transfer of new refrigerants. Int J Refrigeration 2001;24:6–14.
[8] Jung D, Kim C, Cho S, Song K. Condensation heat transfer coefficients of enhanced tubes with alternative refrigerants for CFC11 a
nd CFC12. Int J Refrigeration 1999;22(7):548–57.
[9] Webb RL. Principles of enhanced heat transfer. New York: John Wiley & Sons; 1994. p. 293–4.
[10] Kline SJ, McClintock FA. Describing uncertainties in single- sample experiments.Mechanical Engineers 1953;75:3–9.
[11] McLinden MO, Klein SA, Lemmon EW, Peskin AP. NIST thermodynamic and transport properties of refrigerants and refrigerant
mixtures—REFPROP version 6.0, 1998.
[12] Webb RL, Pais C. Nucleate pool boiling data for five refrigerants on plain, integral-fin and enhanced tube geometries.
Int J Heat Mass Transfer 1992;35(8):1893–904.
[13] Stephan K, Abdelsalam M. Heat transfer correlations for natural convection boiling. Int J Heat Mass Transfer 1980; 23:73–
87.
[14] Cooper MG. Heat flow rates in saturated nucleate pool boiling—a wide-ranging examination using reduced properties.
In: Advances in Heat Transfer, vol. 16. Academic Press; 1984. p. 157–239.
[15] Rohsenow WM, Hartnett JP, Ganic EN. Handbook of heat transfer fundamentals. 2nd ed. McGraw-Hill; 1985. p. 12–22.
[16] Incropera FP, DeWitt DP. Fundamentals of heat and mass transfer. 4th ed. New York: John Wiley & Sons; 1994 p. 536–7.
[17] Cooper MG. Correlations for nucleate boiling—formulation using reduced properties. Physico Chemical Hydrodynamics
1982;3(2):89–111.
19

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