Boiling Heat Transfer Data Research Articles

The effect of lubricant concentration, miscibility, and viscosity on R134a pool boiling

This paper presents pool boiling heat transfer data for 12 different R134a/lubricant mixtures and pure R134a on a Turbo-BII™-HP surface. The mixtures were designed to examine the effects of lubricant mass fraction, viscosity, and miscibility on the heat transfer performance of R134a. The magnitude of the effect of each parameter on the heat transfer was quantified with a regression analysis. The mechanistic cause of each effect was given based on new theoretical interpretation and/or one from the literature. The model illustrates that large improvements over pure R134a heat transfer can be obtained for R134a/lubricant mixtures with small lubricant mass fraction, high lubricant viscosity, and a large critical solution temperature (CST). The ratio of the heat flux of the R134a/lubricant mixture to that of the pure R134a for fixed wall superheat was given as a function of pure R134a heat flux for all 12 mixtures. The lubricant that had the largest CST with R134a exhibited the greatest heat transfer: 100%±20% greater than that of pure R134a. By contrast, the heat transfer of the mixture with the lubricant that had the smallest viscosity and the smallest CST with R134a was 55%±9% less than that of pure R134a. High-speed films of the pure and mixture pool boiling were taken to observe the effect of the lubricant on the nucleate boiling.

An Experimental Investigation of the Boiling Heat Transfer on the Vertical Square Surface

An experimental study was carried out to identify the various regimes of natural convective pool boiling and to determine the boiling heat transfer curve and Critical Heat Flux(CHF) on a vertical square surface having a 70mm width and a 70mm height. The heater made of copper block with embedded cartridge heaters is submerged in a water tank at atmospheric pressure. As the heat flux increases from 100kW/㎡ to 1.2MW/㎡, the heat transfer regime migrates from the nucleate boiling to the film boiling. The boiling heat transfer data are fitted by Rohsenow type correlation. An explosive vapor generation on the heated surface, whose size and frequency are characterized by the heat flux, is visualized using a high speed digital imaging system.

Pool Boiling in Binary Mixtures of Ammonia/Water. Effect of Heat of Dilution and Dissolution and Heat Transfer Coefficient.

Nucleate boiling heat transfer coefficients have been measured during pool boiling of non-azeotropic mixtures of ammonia/water on a horizontal heated wire. The experiment was carried out at pressures of 0.4 and 0.7 MPa and at heat fluxes below 2.0×106 W/m2 and in overall range of mass fraction. The heat transfer coefficients in the mixtures are smaller than those in single component substances. No existing correlation is found to predict boiling heat transfer data over the range of mass fraction. In the mixtures of ammonia/water, heat of dilution and dissolution is generated near vapor-liquid interface, when vapor of higher concentration of ammonia is condensed and then is diffused into the bulk liquid, while in the most of mixtures, little heat is generated during any dilution and dissolution. In relation to this heat generated, the effect of the heat of dilution and dissolution on pressure and temperature in a system (pressure vessel) is shown.

Enhancement of R123 pool boiling by the addition of hydrocarbons

This paper presents pool boiling heat transfer data for 10 different R123/hydrocarbon mixtures. The data consisted of pool boiling performance of a GEWA-T ™ surface for pure R123 and for 10 dilute solutions of five different hydrocarbons: (1) pentane, (2) isopentane, (3) hexane, (4) cyclohexane, and (5) heptane with R123. The heat flux and the wall superheat were measured for each fluid at 277.6 K. A maximum (19±3.5)% increase over the pure R123 heat flux was achieved with the addition of 0.5% mass isopentane to R123. Other mixtures of isopentane, pentane, hexane, and cyclohexane with R123 exhibited smaller maximums than that of the R123/isopentane (99.5/0.5) mixture. Presumably, a layer enriched in hydrocarbon at the heat transfer surface caused the heat transfer enhancement. Conversely, an R123/heptane (99.5/0.5) mixture and an R123/cylcohexane (99.5/0.5) mixture exhibited only degradations with respect to the pure component performance for all test conditions. Several characteristics of the hydrocarbons were examined to determine their influence on the boiling heat transfer performance: molecular weight, molecular structure, composition, surface tension, and vapor pressure.

Effect of Heating Boundary Conditions on Pool Boiling Experiments

The two widely used experimental methods for pool boiling experiments are evaluated. Boiling heat transfer data employing either the water heating or the electric heating method obtained by various researchers are compared and discussed. The electric heating method is a constant heat flux process, while the water heating method represents a pseudo-exponential temperature profile for the heating water along the tube. It is concluded that the temperature profile along the tube is the major cause of the difference between results from the two methods. The parameters that shape the temperature profile and cause differences are discussed.

Characteristics of heat transfer coefficient during nucleate pool boiling of binary mixtures

Experimental studies were conducted on heat transfer on a horizontal platinum wire during nucleate pool boiling in nonazeotropic binary mixtures of R12+R113, R134a+R113, R22+R113 and R22+R11, at pressures of 0.25 to 0.7 MPa and at heat fluxes up to critical heat flux. The substances employed were chosen such that the components of a given mixture had a large difference in saturation temperatures. The boiling features of the mixtures and the pure substances were observed by photography. The relationship between the boiling features and the reduction in heat transfer coefficient in binary mixtures is discussed in order to propose a correlation useful for predicting the experimental data measured over a wide range of low and high heat fluxes. It is shown that the correlation is applicable also to alcoholic mixtures. The physical role of k, which was introduced to evaluate the effect of heat flux on the reduction in heat transfer coefficient, is clarified based on the measured nucleate pool boiling heat transfer data and the visual observations of the boiling features.

Flow Boiling in Horizontal Tubes: Part 2—New Heat Transfer Data for Five Refrigerants

A summary of a comprehensive experimental study on flow boiling heat transfer is presented for five refrigerants (R134a, R123, R402A, R404A, and R502) evaporating inside plain, horizontal, copper tube test sections. The test data were obtained for both 12.00 mm and 10.92 mm diameters using hot water as the heating source. Besides confirming known trends in flow boiling heat transfer data as a function of test variables, it was also proven that the heat flux level at the dryout point at the top of the tube in annular flow has a very significant downstream effect on heat transfer coefficients in the annular flow regime with partial dryout.

Characteristics of heat transfer coefficients during nucleate pool boiling of binary mixtures

Experimental studies were made on heat transfer on a horizontal platinum wire during nucleate pool boiling in nonazeotropic refrigerant binary mixtures at pressures of 0.25 to 0.7 MPa and at heat fluxes up to CHF. The boiling features of the mixtures and the single-component substances were observed by photography. The relationship between the boiling behavior and the reduction of heat transfer coefficients in binary mixtures is discussed in order to propose a correlation useful for predicting the present experimental data over a wide range of low to high heat fluxes. It is shown that the correlation is applicable to alcoholic mixtures. The physical meaning of k, which was introduced to evaluate the effect of heat flux on the reduction of a heat transfer coefficient, is clarified based on measured nucleate pool boiling heat transfer data and visual observations of the boiling features. © 1998 Scripta Technica, Heat Trans Jpn Res, 27(7): 535–549, 1998

Pool boiling of R-22, R-124 and R-134a on a plain tube

Pool boiling heat transfer on a plain tube having R-22, R-124 and R-134a as working fluids are reported in the present investigation. Experiments are conducted at saturation temperatures of 4.4°C and 26.7°C and at reduced pressures of 0.1 and 0.2. It is shown that the Cooper correlation can predict the present pool boiling heat transfer data satisfactorily. In addition, a semi-analytical prediction method is proposed in this study; this semi-analytical model can not only predict the present data with success, but also give reasonably good accuracy with the experimental data from other researchers.

Characteristics of Heat Transfer during Nucleate Pool Boiling of Binary Mixtures.

Experimental studies have been made on heat transfer on a horizontal platinum wire during nucleate pool boiling in nonazeotropic refrigerant binary mixtures at pressures of 0.25 to 0.7 MPa and at heat fluxes up to CHF. The boiling feature of the mixtures and the single-component substances was observed by photography. The relationship between the boiling behavior and the reduction of heat transfer coefficient in binary mixtures is discussed in order to propose a correlation useful for predicting the present experimental data over a wide range of low to high heat fluxes. It is shown that the correlation is applicable to alcoholic mixtures. The physical meaning of k, which was introduced to evaluate the effect of heat flux on the reduction of heat transfer coefficient, is clarified based on the measured nucleate pool boiling heat transfer data and the visual observation of the boiling features.

The mismatch between laboratory boiling heat transfer data and industrialrequirements

There is a large mis-match between published boiling heat transferdata and the operation of industrial cryogenic plant. Published data are generally obtained on small laboratory test-rigs at uniform heat flux with vertical channel heights of the order of 50mm. Operation of industrial plant demands a constant wall temperature and vertical channel heights of up to 2000mm (2m). Using a 2.7m long cryostat with forced circulation of liquid nitrogen to promote an isothermal bath temperature, results show that boiling heat transfer at constant wall temperature Tw (as in a reboiler-condenser) is strongly affected by local sub-cooling of the liquid. Indeed, no boiling takes place until Tw exceeds the local boiling temperature determined by the pressure head of the liquid. For high thermodynamic efficiency, boiling heat transfer with smalltemperature difference T w-T 0 (where T 0 is the surface saturation temperature) there is a depth of liquid below which there is no boiling.

A phenomenological model for boiling heat transfer and the critical heat flux in tubes containing twisted tapes

New critical heat flux (CHF) and boiling heat transfer data were obtained in the subcooled and low quality regions using refrigerant 113. These data were obtained in a 0.61 cm round tube containing a twisted tape having a twist ratio of 6.25. The new CHF data, plus water data from the literature, were compared to a modified version of the CHF predictive model based on bubble crowding and coalescence in the bubbly layer [Weisman and Pei, Int. J. Heat Mass Transfer26, 1463–1478 (1983), Weisman and Illeslamlou, Fusion Tech.13, 654—659 (1988)]. Reasonably good predictions were obtained within the range of the model. It was also found that the Yang and Weisman [Int. J. Multiphase Flow17, 77–94 (1991)] extension of the CHF model to boiling heat transfer held for swirling flow.

An improved correlation for subcooled and low quality film boiling heat transfer of water at pressures from 0.1 to 8 MPa

A semi-empirical model for inverted annular flow film boiling heat transfer was previously developed which incorporates the effects of all relevant independent parameters and agrees well with available experimental data in the pressure range from 0.1 to 2 MPa. In the present work, this model has been modified to extend its applicability to elevated pressures up to 8 MPa. New expressions for the interfacial energy transfer to the subcooled liquid jet, and for the heat transfer enhancement term due to oscillatory interfacial disturbances were derived. Steady-state film boiling heat transfer data for forced upflow of water in a vertical tube were used to determine the unknown coefficients in the new relations. The data used were obtained from steady-state experiments applying different versions of the so-called “hot-patch” technique. Finally, an explicit film boiling heat transfer correlation has been obtained which approaches Bromley's solution for zero flow and saturated conditions. This correlation has been compared with steady-state data from five different sources which cover mass fluxes ranging from 100 to 1010 kg/(m 2s) in the pressure range from 0.1 to 8 MPa. Results indicate an rms error of 15.5% and a mean deviation of 12.0% between measured and predicted heat transfer coefficients for 3972 data points.

Experiments on subcooled flow boiling heat transfer in a vertical annular channel

Experiments on subcooled flow boiling heat transfer are carried out in a vertical annular channel the inner wall of which is heated and the outer wall insulated. Refrigerant-113 is the working fluid. Flow boiling heat transfer data are reported at three mass velocities (579, 801, and 1102 kg m −2 s −1), three pressures (312, 277, and 243 kPa), and three inlet subcoolings (20.0, 30.0, and 36.5°C). A multiple-hysteresis phenomenon is identified. The measured wall heat transfer coefficients are compared with predictions by various correlations and an improvement of the Shah correlation for annuli is suggested.

Down‐flow shell‐side forced convective boiling

AbstractOne hundred sets of R‐11 two‐phase pressure drop and boiling heat transfer data are reported for cocurrent down‐flow over an in‐line tube bundle. The pressure drop data agree with predicitions using the Diehl correlation. A new heat transfer correlation is reported, accounting for the observed convective and nucleate mechanisms.

Transient boiling heat transfer from two different heat sources: Small diameter wire and thin film flat surface on a quartz substrate

Transient boiling heat transfer data are reported for two different heater surface geometries submerged in liquid nitrogen. During the early part of the transient heat pulse, the heat transfer coefficient for both geometries generally agrees with values predicted from classical transient pure conduction equations. The agreement persists until the time for onset of convection which varies approximately as 1 q 2 where q is the heat flux to the fluid.

Prediction of Nucleate Pool Boiling Heat Transfer Coefficients of Refrigerant-Oil Mixtures

This paper describes an experimental investigation to determine the mechanism governing nucleate pool boiling heat transfer in refrigerant-oil mixtures, the role diffusion plays in this process, and the influence of the fluid mixture properties. Boiling heat transfer data were taken in mixtures of up to 10 percent oil by weight in R-113. Thermophysical properties of the mixtures (density, viscosity, surface tension, specific heat, and contact angle) were measured. The decrease in heat transfer coefficient with increasing oil concentration is attributed to diffusion in an oil-enriched region surrounding the growing vapor bubbles. A correlation based on the postulated mechanism is presented which shows fair agreement with the experimental data from this study and with data obtained from the literature.

The rate of heat transfer for boiling on porous surfaces

It is shown that the constant, C sf , introduced by Rohsenow 6 for correlating pool boiling heat transfer data, may be used in order to characterize plates which have been made porous.

Low-Pressure Transient Flow Film Boiling in Vertically Oriented Rod Bundles

Flow film boiling heat transfer data from Semiscale Mod-3 gravity feed reflood experiments have been compared to existing film boiling correlations. The existing film boiling correlations were found to be inadequate for calculating Semiscale rod bundle results in the low void fraction region. Therefore, a new correlation for flow film boiling was developed. The new correlation is applicable for boiling water with stainless steel electrically heated vertical rods for a pressure range from 127 to 390 kPa. The new correlation is sensitive to such parameters as the local void fraction, the wall temperature, the bulk vapor temperature, and the total mass flux.

Dispersed-Flow Film Boiling Heat Transfer Data near Spacer Grids in a Rod Bundle

A series of steady-state film boiling experiments have been conducted to show the effect of spacer grids on rod bundle heat transfer. Experiments were performed at the Oak Ridge National Laboratory...