Heat transfer under conditions of nucleate boiling

New physical concepts are developed in connection with the two fundamental processes resulting in the transfer of heat from a heater to a liquid under conditions of nucleate boiling.     

Heat transfer in hydrocarbon fuel boiling under conditions of natural convection

Data on the heat-transfer coefficient in boiling of five jet fuels, two automotive gasolines, and a diesel fuel are presented over a wide range of regime parameters. The obtained results are described by a unified similarity equation.Notation heat-transfer coefficient, W/(m²·K) - P _s pressure, MPa - q heat flux density, W/m² - V volume, m³ - T _s temperature, K - ₁ and ₂ density of the liquid and vapor phases, kg/m³ - thermal conductivity, W/(m·K) - viscosity of the liquid, m²/sec - surface tension, N/m - C _p heat capacity, J/(kg·K) - r vaporization heat, J/kg - Nu Nusselt number - P Pecklet number.l=C _p T _{s 1}/(r₂)² serves as a governing dimension Kazan' State Techological University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 438–443, May–June, 1995.     

Heat transfer in nucleate boiling of different low boiling substances

Heat transfer coefficients for nucleate boiling of methane, ethane, ethylene, argon and carbon dioxide were determined using an apparatus for the precise investigation of pool boiling heat transfer in the low temperature range. The apparatus used a horizontal cylinder as the heating element. The influence of the thermophysical properties of the boiling liquid was established by comparing the absolute values of the heat transfer coefficients in a normalized boiling state, i.e. a saturation pressure equal to 10% of the critical pressure and a heat flux density equal to 2 × 10⁴ W m⁻². By including the results for a number of higher boiling liquids, which were investigated previously under similar experimental conditions, and using literature data for three very low boiling liquids, an empirical correlation is established which allows an approximate prediction of the absolute value of the heat transfer coefficient at nucleate boiling for substances of different molecular structure.     

Heat transfer and critical heat fluxes in the boiling of aqueous solutions of polyethylene oxide at reduced pressures under natural-convection conditions

Experimental data are presented on heat transfer and critical heat fluxes in the boiling of aqueous solutions of polyethylene oxide of different concentrations under conditions of natural convection at atmospheric and reduced temperatures.Notation q heat flux - q_cr critical heat flux - q_cr.s critical heat flux during boiling under subheating conditions - T overheating of heating surface relative to-saturation temperature - T_S subheating of liquid core to the saturation temperature - heat-transfer coefficient - P pressure - , densities of the liquid and vapor - c_p isobaric specific heat of water - r heat of vaporization Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 1, pp. 24–28, July, 1984.     

Heat transfer under conditions of boiling of emulsion on the thin wire surface

Results are given of an experimental investigation of heat transfer from thin platinum wires to emulsions in which the dispersed phase is low-boiling compared to the dispersion medium. The investigations are performed using horizontally and vertically arranged heaters. Also investigated is the effect made on the delay of the beginning of boiling of emulsion by the addition to the dispersed phase of minor amounts of PEG-400 polyethylene glycol and A-175 Aerosil (silica powder) nano-powder.     

Experimental study of heat transfer in the boiling of liquids at low pressures under conditions of free motion

The results of an experimental investigation into the boiling of water, ethyl alcohol (96% aqueous solution), and 13% NaCl solution under conditions of free motion at pressures of 0.036–1 bar are presented. The experimentally observed characteristics of the boiling mechanism at low pressures are discussed.Translated from Inzhenerno-Fizichenskii Zhurnal, Vol. 18, No. 4, pp. 624–630, April, 1970.     

Heat transfer in nitrogen-methane mixtures under pressure with film boiling

Heat transfer from a horizontal cylinder into nitrogen-methane mixtures (0 to 100 molar per cent) was studied in the film boiling range at 0.2 and 2.8 MPa. At constant heat flux density ΔT decreases with increasing methane content.Heat transfer from a horizontal cylinder into nitrogen under pressure was studied in the bubble boiling region, in addition to the film boiling range, to provide a connexion between our experiments made on the horizontal surface, q_max at cylinder ~ 0.7 q_max at horizontal surface. For the relation $\text{q}\text{?}{}_{\mathrm{<mtext>max</mtext>}}\text{/}\text{q}\text{?}{}_{\mathrm{<mtext>min</mtext>}}$ at cylinder a value of ten was obtained at all pressures     

Heat transfer during film boiling of a subcooled liquid under conditions of forced flow through channels

An experimental study of heat transfer during the film boiling of subcooled liquid nitrogen in pipes with the Reynolds number Re=80,000-1,500,000 and=0.20–0.95 is reported.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 22, No. 4, pp. 610–613, April, 1972.     

Heat transfer to turbulent stream in pipes under supercritical pressures

Experimental results are presented on heat transfer to several liquid hydrocarbons under supercritical pressures and pseudoboiling conditions. An empirical relation is proposed which generalizes these results.     

Heat transfer in boiling of liquid in a film moving under gravity

Experimental data on heat transfer in boiling in a film of liquid moving under gravity have been processed in dimensionless coordinates. A comparison between the data on heat transfer during boiling in a film with the data on heat transfer in pool boiling is carried out, which makes it possible to more accurately estimate the influence of the film flow velocity and spray entrainment on heat transfer in film boiling.     

Heat exchange in film boiling of cryogenic liquids under natural convection conditions

Heat exchange is studied in stationary and nonstationary cooling of vertical cylinders by hydrogen and nitrogen. An empirical function generalizing the experimental results is presented.     

Heat transfer in a vertical evaporation circuit at low pressures and in vacuo under conditions of vibrational instability

Data relating to the heat-transfer coefficients associated with the boiling of viscous solutions in tubes and annular channels (covering wide ranges of thermal fluxes and apparent levels) under conditions of natural circulation are presented and generalized.     

Heat and mass transfer under frosting conditions

The effect of frost formation on heat transfer between a test cylinder and its gaseous environment was studied experimentally. The main parameters discussed in the paper are: the total heat flux, the steady-state convective heat transfer coefficient, and the mass of frost adhering to the test cylinder. The emphasis of the paper is on the thermal conducivity of frost. The data indicate that the diffusion mechanisms of moisture transfer within the frost layer causes the frost density and thermal conductivity to increase with time. Frost thermal conductivity is a function of the local temperature and average density. The can be used by designers of low temperature systems with uninsulated surfaces.     

Subcooled liquid boiling heat transfer under conditions of stepwise heat-load release

The results of experimental investigations of the effect of liquid subcooling below the saturation temperature on boiling heat transfer under conditions of an increase in a heating load are presented. Water and TS-1 kerosene were used as heat carriers. The obtained experimental data on subcooled liquid boiling heat transfer has been generalized by an empirical relation. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 1, pp. 136–139, January–February, 2007.     

Review on pool boiling heat transfer of carbon dioxide

Although application of carbon dioxide as working fluid in many fields of refrigeration technology has been recommended very often in the recent past, the data on nucleate boiling heat transfer of carbon dioxide in free convection are very scarce in the open literature and new investigations are almost entirely focussed on forced convective flow boiling. In the interpretation of the respective results, heat transfer to carbon dioxide is often characterized as being superior to other refrigerants due to the outstandingly favourable thermophysical properties of carbon dioxide for boiling heat transfer. Different from this view, the discussion of recent results on pool boiling heat transfer of carbon dioxide in this review demonstrates that the high heat transfer coefficients measured for carbon dioxide in comparison to hydrocarbon or halocarbon refrigerants are mainly due to the fact that application of carbon dioxide is mostly envisaged for conditions where reduced saturation pressure p*=p_s/p_c (p_c, critical pressure) is higher than for common refrigerants.

In the first part of the review, the three main influences—by heat flux, saturation pressure and fluid properties—on pool boiling of carbon dioxide are discussed using recent measurements for CO₂ by Kotthoff et al. [S. Kotthoff, U. Chandra, D. Gorenflo, A. Luke, New measurements of pool boiling heat transfer for carbon dioxide in a wide temperature range, Proceedings of the Sixth IIR-Gustav Lorentzen Conference, Glasgow, 2004 [paper 2/A/3.30]; see also S. Kotthoff, U. Chandra, D. Gorenflo, Neue Messungen zum Behältersieden von Kohlendioxid in einem grösseren Temperaturbereich, DKV-Tagungsbericht 22 (2004) [Bd.II. 1] 233–256 and other organic substances (Gorenflo et al.) [D. Gorenflo, S. Kotthoff, U. Chandra, New measurements of pool boiling heat transfer with hydrocarbons and other organics for update of VDI—Heat Atlas calculation method, Proceedings of the Sixth IIR-Gustav Lorentzen Conference, Glasgow, 2004 [paper 1/C/1.00]; Kotthoff and Gorenflo, [S. Kotthoff, D. Gorenflo, Influence of the fluid on pool boiling heat transfer of refrigerants and other organic substances, Proceedings of the IIR-Commission B1 Conference, Vicenza, 2005 [paper #TP-98]. In the second part, a comparison is given with the few former data available and with new results of Loebl and Kraus [S. Loebl, W.E. Kraus, Pool boiling heat transfer of carbon dioxide on a horizontal tube, Proceedings of the Sixth IIR-Gustav Lorentzen Conference, Glasgow, 2004 [paper 1/A/1.20]; S. Loebl, W.E. Kraus, Zum Wärmeübergang bei der Verdampfung von Kohlendioxid am horizontalen Rohr, DKV-Tagungsbericht 22 (2004) [Bd.II.1] 219–232 on the influence of the heating wall (material and surface roughness). Finally, analogies between nucleate pool boiling and new flow boiling data are shown for those domains of flow boiling in which nucleation provides the dominant contribution to heat transfer and convective effects are of secondary importance.     

Heat transfer to helium-I during different boiling regimes at high centrifugal accelerations

Heat transfer during nucleate and film boiling of helium and also the boiling crises up to relative accelerations of (1 ÷ 2) × 10³ have been investigated. The heat transfer surface was a flat copper heater. The heat transfer during nucleate boiling proved to be independent of the relative accelerations. For film boiling, it was found that $\text{α ～ η}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}$. The dependence of the peak nucleate boiling heat flux and the minimum film boiling flux on the relative acceleration is non-monotonic.     

Heat transfer in boiling neon in vertical capillaries

Values for the burnout heat flux and critical temperature difference are measured in boiling neon on the internal surface area of vertical capillaries. A hysteresis is observed as power increases and decreases, which becomes weaker after several increases of power up to the critical heat flux point. The characteristics of the dependences obtained are discussed.     

Heat transfer in liquid boiling on finned surfaces

Results of an experimental investigation of heat transfer in boiling of water and Freon-113 on cylindrical shells with longitudinal fins are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 22, No. 1, pp. 13–18, January, 1972.     

Heat transfer in nucleate boiling (theory)

From a joint solution of the equations describing the individual elementary processes associated with nucleate boiling a theoretical formula is obtained (in criterial form) for the nucleate-boiling heat transfer coefficient of nonmetallic liquids. This formula is compared with the experimental data on water boiling over a broad range of pressures.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 15, No. 5, pp. 809–817, November, 1968.