Erratum: “Transient Melting of a Solid Heated by a Condensing Saturated Vapor—Case 1: Negligible Interface Curvature” (Journal of Heat Transfer, 1975, 97, pp. 570–575)

A performance study is presented of a Rankine organic cycle powered by a low temperature solar collector. In this work a two-phase collector is considered where the heat transfer fluid is vaporized and its saturated vapor expands in a turbine according to a Rankine cycle. The collector system is divided into a boiling and a nonboiling (subcooled) part: The limit between the two depends upon the value of flow rate and radiation. A modified form of the Bliss equation is used to model the thermal performance of the collector in terms of thermal efficiency versus DTI [DTI= (Absorber average temperature-Ambient temperature)/ Solar Radiation]. The system is analyzed by second-law analysis, and it includes several exergy losses of different types (heat transfer, heat loss, etc.) which determine the overall exergy balance. Different working fluids are considered, and optimization to a certain extent is demonstrated from this point of view. In order to minimize irreversibilities and guarantee the most efficient conversion processes, the most important point is the right selection of the collector operating pressure level, which depends on the instantaneous value of radiation and ambient temperature (as well as on the collector thermal performance). The choice of the optimal pressure level is done by means of second-law arguments; the flow rates across the collector, the turbine, and the condenser are consequently determined. A simulation over a typical sunny day in Florence, Italy allows the calculation of the expected daily performance.

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An Experimental Study of Laminar Film Condensation With Stefan Number Greater Than Unity

Journal of Heat Transfer ◽

10.1115/1.2910585 ◽

1991 ◽

Vol 113 (2) ◽

pp. 472-478 ◽

Cited By ~ 4

Author(s):

R. L. Mahajan ◽

T. Y. Chu ◽

D. A. Dickinson

Keyword(s):

Heat Transfer ◽

Saturated Vapor ◽

Temperature Response ◽

Condensation Heat Transfer ◽

Film Condensation ◽

Stefan Number ◽

Laminar Film Condensation ◽

Reported Study ◽

The Difference ◽

Temperature Dependent Properties

Experimental laminar condensation heat transfer data are reported for fluids with Stefan number up to 3.5. The fluid used is a member of a family of fluorinated fluids, which have been used extensively in the electronics industry for soldering, cooling, and testing applications. Experiments were performed by suddenly immersing cold copper spheres in the saturated vapor of this fluid, and heat transfer rates were calculated using the quasi-steady temperature response of the spheres. In these experiments, the difference between saturation and wall temperature varied from 0.5° C to 190°C. Over this range of temperature difference, the condensate properties vary significantly; viscosity of the condensate varies by a factor of nearly 50. Corrections for the temperature-dependent properties of the condensate therefore were incorporated in calculating the Nusselt number based on the average heat transfer coefficient. The results are discussed in light of past experimental data and theory for Stefan number less than unity. To the knowledge of the authors, this is the first reported study of condensation heat transfer examining the effects of Stefan number greater than unity.

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Transient Melting of a Solid Heated by a Condensing Saturated Vapor—Case I: Negligible Interface Curvature

Journal of Heat Transfer ◽

10.1115/1.3450432 ◽

1975 ◽

Vol 97 (4) ◽

pp. 570-575 ◽

Cited By ~ 4

Author(s):

W. Contreras ◽

R. S. Thorsen

Keyword(s):

Liquid Film ◽

Saturated Vapor ◽

Functional Dependence ◽

Transient Behavior ◽

Suspended Solid ◽

Interface Motion ◽

Classical Boundary ◽

Interface Curvature ◽

Closed Form Analytical Solution ◽

Solid Liquid

A transient analysis has been performed to analytically determine the instantaneous dimensionless thickness of a vertically suspended solid at its melting temperature upon which a saturated vapor is condensing. The spatial variation and transient behavior of the melt-condensate liquid film, which is continuously drained, has also been obtained from the closed form analytical solution of the uncoupled equations for the solid-liquid and liquid-vapor interface motions under the condition of assumed negligible interface curvature. Classical boundary layer assumptions were applied to the convection process in the subcooled liquid film which was analyzed using integral techniques. From the analytic solution to the resultant interface motion equations in terms of characteristic curves, the functional dependence of the melting solid and the liquid layer thicknesses on the time and space variables was established. The liquid mass flux and heat transfer coefficient were then obtained analytically.

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Cavitation Bubble Collapse Near a Heated Wall and Its Effect on the Heat Transfer

Journal of Heat Transfer ◽

10.1115/1.4024071 ◽

2013 ◽

Vol 136 (2) ◽

Cited By ~ 10

Author(s):

Bin Liu ◽

Jun Cai ◽

Xiulan Huai ◽

Fengchao Li

Keyword(s):

Heat Transfer ◽

Cavitation Bubble ◽

Stokes Equations ◽

Saturated Vapor ◽

Bubble Diameter ◽

Bubble Radius ◽

Heated Wall ◽

Bubble Collapse ◽

Flow State ◽

Vof Model

In the present work, a numerical investigation on the mechanism of heat transfer enhancement by a cavitation bubble collapsing near a heated wall has been presented. The Navier–Stokes equations and volume of fluid (VOF) model are employed to predict the flow state and capture the liquid-gas interface. The model was validated by comparing with the experimental data. The results show that the microjet violently impinges on the heated wall after the bubble collapses completely. In the meantime, the thickness of the thermal boundary layer and the wall temperature decrease significantly within the active scope of the microjet. The fresh low-temperature liquid and the impingement brought by the microjet should be responsible for the heat transfer reinforcement between the heated wall and the liquid. In addition, it is found that the impingement width of the microjet on the heated wall always keeps 20% of the bubble diameter. And, the enhancement degree of heat transfer significantly depends on such factors as stand-off distance, saturated vapor pressure, and initial bubble radius.

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Analytical and Experimental Investigation of Simultaneous Melting-Condensation on a Vertical Wall

Journal of Heat Transfer ◽

10.1115/1.3245063 ◽

1982 ◽

Vol 104 (1) ◽

pp. 24-33 ◽

Cited By ~ 6

Author(s):

K. Taghavi-Tafreshi ◽

V. K. Dhir

Keyword(s):

Heat Transfer ◽

Boundary Layer ◽

Saturated Vapor ◽

Vertical Wall ◽

Saturated Steam ◽

Interface Temperature ◽

Boundary Layer Equations ◽

Similarity Transformations ◽

High Prandtl Number ◽

Variable Gravity

Melting of a vertical wall as a result of condensation of saturated vapor is investigated both analytically and experimentally. Employing similarity transformations, full boundary layer equations governing laminar films of melt and condensate are solved numerically for high Prandtl number liquids. Numerical results for the melting and condensation heat transfer and for the melt-condensate interface temperature are obtained. Experiments are conducted by condensing saturated steam on vertical surfaces of slabs made of naphthalene, biphenyl and stearic acid. The data are found to compare well with the predictions. The analysis is extended to condensation on melting surfaces with shapes yielding variable gravity in the direction of flow.

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Boiling and Evaporation From Heat Pipe Wicks With Water and Acetone

Journal of Heat Transfer ◽

10.1115/1.3450201 ◽

1974 ◽

Vol 96 (3) ◽

pp. 331-337 ◽

Cited By ~ 27

Author(s):

A. Abhat ◽

R. A. Seban

Keyword(s):

Heat Transfer ◽

Heat Pipe ◽

Atmospheric Pressure ◽

Saturated Vapor ◽

Pool Boiling ◽

Tube Surface ◽

Evaporation Surface ◽

Nucleation Sites ◽

Boiling And Evaporation ◽

Vertical Tubes

Heat transfer for pool boiling with flaxes in the range of 5 × 102 5 × 104 Btu/(ft2 hr) and the associated excess of wall over saturation temperatures are presented, primarily for atmospheric pressure, for vertical tubes in water, ethanol, and acetone, bare or wrapped with screen or felt metal. For the wrapped tubes, this performance is given also for evaporation into surrounding saturated vapor with the liquid being supplied by the wick: this is the significant mode in respect to heat pipe applications. For this mode maximum evaporation rates are also indicated and it is shown that this maximum can be rationalized either in terms of a partially full wick with conduction transfer to the evaporation surface or in terms of a full wick with vapor holes originating at nucleation sites on the tube surface.

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Entropy Generation of Free Convection Film Condensation From Downward Flowing Vapors onto a Cylinder or Sphere

Journal of Mechanics ◽

10.1017/s1727719100001350 ◽

2007 ◽

Vol 23 (4) ◽

pp. 303-308 ◽

Cited By ~ 1

Author(s):

S. C. Dung ◽

S. H. Tzeng ◽

S. A. Yang

Keyword(s):

Heat Transfer ◽

Entropy Generation ◽

Film Flow ◽

Saturated Vapor ◽

Horizontal Cylinder ◽

Generation Rate ◽

Film Condensation ◽

Entropy Generation Rate ◽

Entropy Generation Number ◽

Flow Friction

AbstractThis study aims at analyzing entropy generation rate of saturated vapor flowing slowly onto and condensed on an isothermal sphere/horizontal cylinder. We derive an expression for entropy generation, which accounts for the resultant action of specified irreversibilities of film-wise condensation outside a cylinder/sphere. The result shows that local entropy generation rate increases with Brinkman group parameters. As Rayleigh group parameters increase, dimensionless heat transfer coefficient is enhanced, but entropy generation number is augmented too. Heat transfer irreversibility dominates over the film flow friction irreversibility in the upper half of a sphere, and vice versa for the lower half of a sphere. As for a cylinder, heat transfer irreversibility dominates over film flow friction irreversibility except around the middle way of streamwise length for the cases of Brinkman group parametersBr/ ψ≥ 0.75.

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Analysis on heat transfer and start-up performance of mercury heat pipe

E3S Web of Conferences ◽

10.1051/e3sconf/202124503012 ◽

2021 ◽

Vol 245 ◽

pp. 03012

Author(s):

Xiuxiang Zhang ◽

Kang He ◽

Quan Yang ◽

Chengcai Xi

Keyword(s):

Heat Transfer ◽

Thermal Resistance ◽

Heat Pipe ◽

Saturated Vapor ◽

Heating Power ◽

Good Thermal Stability ◽

Start Up ◽

Steady State Heat ◽

Steady State Heat Transfer ◽

Transient Thermal

Mercury heat pipe has the advantages of good thermal stability and low saturated vapor pressure, which is the best choice for the transition from water heat pipe to liquid metal heat pipe. The effects of heating power and heat pipe structure on start-up time and steady-state heat transfer performance of mercury heat pipe were studied by using transient thermal network model. The results showed that: 1) Increasing the length of condenser is beneficial to reducing the start-up time and thermal resistance; 2) Increasing the heating power or wall thickness will reduce the thermal resistance, but increase the start-up time, and increasing the porosity of wick is just the opposite; 3) Increasing the thickness of wick can increase both the start-up time and the thermal resistance.

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Effects of Vapor Superheat and Condensate Subcooling on Laminar Film Condensation

Journal of Heat Transfer ◽

10.1115/1.521450 ◽

1999 ◽

Vol 122 (1) ◽

pp. 192-196 ◽

Cited By ~ 12

Author(s):

J. Mitrovic

Keyword(s):

Heat Transfer ◽

Single Phase ◽

Saturated Vapor ◽

Interfacial Shear ◽

Film Condensation ◽

Sensible Heat ◽

Laminar Film ◽

Laminar Film Condensation ◽

Condensation Model ◽

The Heat Transfer Coefficient

Nusselt’s model is employed to illustrate the effects of vapor superheat and condensate subcooling on laminar film condensation occurring under simultaneous actions of gravity and interfacial shear. The vapor superheat affects the condensation kinetics in cooperation with heat transfer in both phases. Under comparable conditions, the condensate film is thinner and the heat transfer coefficient larger for superheated than for saturated vapor. The heat flux on the cooling surface arising from the sensible heat of condensate increases as the critical point of the condensing substance is approached and, at this point, the Nusselt condensation model gives the single-phase boundary layer solutions. [S0022-1481(00)00701-5]

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