Pool boiling characteristics of nano-fluids

The growth of a vapor bubble in a superheated liquid is controlled by three factors: the inertia of the liquid, the surface tension, and the vapor pressure. As the bubble grows, evaporation takes place at the bubble boundary, and the temperature and vapor pressure in the bubble are thereby decreased. The heat inflow requirement of evaporation, however, depends on the rate of bubble growth, so that the dynamic problem is linked with a heat diffusion problem. Since the heat diffusion problem has been solved, a quantitative formulation of the dynamic problem can be given. A solution for the radius of the vapor bubble as a function of time is obtained which is valid for sufficiently large radius. This asymptotic solution covers the range of physical interest since the radius at which it becomes valid is near the lower limit of experimental observation. It shows the strong effect of heat diffusion on the rate of bubble growth. Comparison of the predicted radius‐time behavior is made with experimental observations in superheated water, and very good agreement is found.

The growth of vapor bubbles in superheated liquids. report no. 26-6

Review of nanofluids for heat transfer applications

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Principles Of Enhanced Heat Transfer

Experimental study and modeling of an Organic Rankine Cycle using scroll expander

Heat transfer and pressure drop correlations for the rectangular offset strip fin compact heat exchanger

Thermal-hydraulic design correlations are developed to predict isothermal f and Nu for in-tube, turbulent flows with twisted-tape inserts. Experimental data taken for water and ethylene glycol are analyzed, and various mechanisms attributed to twisted tapes are identified. Tube blockage and tape-induced vortex mixing are the dominant phenomena that result in increased heat transfer and pressure drop; for loose- to snug-fitting tapes, the fin effects are insignificant. The limiting case of a straight tape insert correlates with the hydraulic-diameter-based smooth tube equation

Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part II—Transition and Turbulent Flows

Laminar flow correlations for f and Nu m are developed based on experimental data for water and ethylene glycol, with tape inserts of three different twist ratios. The uniform wall temperature condition is considered, which typifies practical heat exchangers in the chemical and process industry. These and other available data are analyzed to devise flow regime maps that characterize twisted-tape effects in terms of the dominant enhancement mechanisms. Depending upon flow rates and tape geometry, the enhancement in heat transfer is due to the tube partitioning and flow flockage, longer flow path, and secondary fluid circulation; fin effects are found to be negligible is snug-to loose-fitting tapes

Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part I—Laminar Flows

Experimental heat transfer and isothermal pressure drop data for single-phase water flows in a plate heat exchanger (PHE) with chevron plates are presented. In a single-pass U-type counterflow PHE, three different chevron plate arrangements are considered: two symmetric plate arrangements with {beta} = 30 deg/30 deg and 60 deg/60 deg, and one mixed-plate arrangement with {beta} = 30 deg/60 deg. For water (2 < Pr < 6) flow rates in the 600 < Re < 10{sup 4} regime, data for Nu and f are presented. The results show significant effects of both the chevron angle {beta} and surface area enlargement factor {phi}. As {beta} increases, and compared to a flat-plate pack, up to two to five times higher Nu are obtained; the concomitant f, however, are 13 to 44 times higher. Increasing {phi} also has a similar, though smaller effect. Based on experimental data for Re {ge} 1000 and 30 deg {le} {beta} {le} 60 deg, predictive correlations of the form Nu = C{sub 1}({beta}) D{sub 1}({phi}) Re{sup p1({beta})} Pr{sup 1/3} ({mu}/{mu}{sub w}){sup 0.14} and f = C{sub 2}({beta}) D{sub 2}({phi}) Re{sup p2({beta})} are devised. Finally, at constant pumping power, and depending upon Re, {beta}, and {phi}, the heat transfermore » is found to be enhanced by up to 2.8 times that in an equivalent flat-plate channel.« less

Raj M. Manglik

Papers

Heat transfer and pressure drop correlations for the rectangular offset strip fin compact heat exchanger

Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part II—Transition and Turbulent Flows

Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part I—Laminar Flows

Experimental Study of Turbulent Flow Heat Transfer and Pressure Drop in a Plate Heat Exchanger With Chevron Plates

Enhanced heat transfer due to curvature-induced lateral vortices in laminar flows in sinusoidal corrugated-plate channels