Pool Boiling Heat Transfer Characteristics Research Articles

티타늄 평활관 및 전열촉진관에서 R-l34a의 관외측 풀비등 열전달 특성에 대한 연구

Pool boiling heat transfer characteristics of R-134a were investigated in titanium plain and low finned tubes. The diameter of test tube was 15.88㎜ and the fin density was 33 fpi. Tests were conducted at saturation temperatures of 20℃ and 30℃. Heat fluxes varied from 5000 W/㎡ to 50,000 W/㎡ based on surface area of the plain tube. The pool boiling heat transfer coefficients of the titanium horizontal plain tube are lower than those of the copper plain tube by 8.2%. The boiling heat transfer coefficients of the low finned tube are averagely higher than those of the plain tubes by 34%. The average deviation of the Slipcevic correlation from the present data for the low finned tube is 20%.

加圧下におけるリチウム系塩類水溶液のプール核沸騰熱伝達特性(オーガナイズドセッション7 環境に調和した冷凍空調技術)

Lithium salts solutions are used activate agency at absorption refrigerating machine. However, as an influence factor of the nucleate pool boiling heat transfer characteristic, which governs the performance of absorption refrigerating machine, the extensive knowledge of concentration and pressure is not fully acquired yet. This research experimentally brought out the nucleate pool boiling heat transfer characteristics under pressurization to the high concentration aqueous solutions of lithium chloride and lithium bromide

Pool boiling heat transfer from vertical heater array in liquid nitrogen

The heat transfer from an array of discrete sources is expected to differ from the behavior of a single heat source due to the interaction between the flow induced by individual heat sources. This study details the results from experiments conducted to study the pool boiling heat transfer characteristics from a vertical heater array with flush-mounted heat sources. The lower heaters were found to enhance the heat transfer from upper heaters. The bubble pumped convection due to the lower heaters enhanced the preboiling heat transfer coefficient at the upper heater by as much as 700%. The critical heat flux from the upper heaters was also enhanced up to 15%. Correlations are presented for both these effects. 21 refs.

Pool Boiling Heat Transfer Characteristics of the Surface-Worked Heat Transfer Tubes in Narrow Spaces Under Reduced Pressure Conditions.

This paper presents an experimental study dealing with basic boiling heat transfer research concerning a solar-powered absorption chiller. Two kinds of surface-worked (roll-worked and chromium-electroplated mirror face) heat transfer tubes were tested in bulk liquid or in annual narrow spaces under several reduced-pressure conditions, and the saturated boiling heat transfer characteristics were determined. The data obtained of the two kinds of tubes were compared under the same conditions. The experimental results indicated that the roll-worked tubes in bulk liquid indeed receive much greater boiling heat transfer promotion than that in the case of the mirror-face tube. In the case of narrow spaces, the mirror-face tubes are considerably heat-transfer-enhanced in comparison to the case without narrow space, but the roll-worked tubes with annual narrow spaces are not remarkably enhanced compared to the case without narrow space.

Re-entrant cavity surface enhancements for immersion cooling of silicon multichip packages

The performance of silicon reentrant cavity structures for enhanced heat removal from substrates used in silicon multichip systems is described. The heat sink surface consisted of a large array of pyramidal cavities etched into the silicon using standard microelectronic fabrication techniques. Two different reentrant cavity shapes, simple and complex, were studied. A thin-film resistive heater fabricated on a silicon substrate served as the heat source. Experiments were conducted in a pool of the dielectric liquid, refrigerant-113, which has near-zero contact angles with most materials used in electronics fabrication. Tests were run for both saturated and subcooled conditions. The saturated pool boiling heat transfer characteristics of the cavity-enhanced surfaces were superior to those of a plain surface, resulting in a substantial decrease in both the temperature overshoot and the incipient boiling heat flux, and subcooling generally resulted in an increase in incipient boiling heat flux when compared with the saturated conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Pool boiling heat transfer of liquid 3He

Pool boiling heat transfer characteristics of liquid 3He were measured for the first time using the 3He circulation system under saturated vapour pressure at about 1.5 and 2.0 K. The heat transfer surface was a flat plate of 6 mm diameter made of OFHC and set upward. The results show that the ΔT dependence of q., where ΔT is the temperature difference between heat transfer surface and liquid 3He and q. is heat flux, is in good agreement with Kutateladze's correlation in nucleate boiling region, and in the film boiling region both ΔT dependence and absolute values of q. are in reasonable agreement with Breen and Westwater's correlations.

Saturated pool boiling heat transfer characteristics of a porous polyurethane covered heater under atmospheric and reduced pressure conditions.

This experiment is one of basic boiling heat transfer research concerning a solar-powered absorption-type chiller. A heat transfer tube, which was surrounded by a porous, polyurethane, heat-insulating layer of different porosity-size and different radial thichness, was tested under atmospheric and reduced pressure conditions and the saturated boiling heat transfer characteristics were determined. Obtained experimental data for the porous tubes indicates that the minimum incipient boiling heat flux is reduced to the order of one of twentieth and the boiling heat transfer coefficients are improved to the order of several times (2 to 5 times) that of a conventional submerged heater boiling case under the same experimental conditions.

Effect of surface materials on pure mercury boiling heat transfer

THE WETTABILITY of a heating surface by a liquid metal, especially in the case of pure mercury, is of great importance in determining the boiling heat transfer rate. It is frequently assumed that pure mercury does not wet steel surfaces [l]. Therefore, it is also believed that this causes film boiling of pure mercury at low heat fluxes ( 4000 Btu/hftz) and small temperature differences (AT lo”F), such as those reported by Lyon et al. [2]. However, Bonilla er al. [3] and Lee [4] have reported otherwise. In the absence of adequate information on the interfacial energy conditions in pure mercury boiling, an experimental study was necessary to establish heat transfer performance parameters for different surface materials. The survey of literature concerned with pool boiling heat transfer with mercury and mercury with additives can be found in [4] and [5]. It seems that the surface material affects the pool boiling heat transfer characteristics of pure mercury. However, no systematic study on the problem has been reported. In this note, new data are reported for pool boiling heat transfer of pure mercury from horizontal cylinders made of two different surface materials.

An Experimental Investigation Of Pool Boiling At Atmospheric Pressure

This paper deals with an experimental investigation of pool boiling of water and methanol at atmospheric pressure from small horizontal heat sources. The heat sources are inserted into the copper tube submerged in a laterally-confined, finite pool of liquid. The saturated pool boiling heat transfer characteristics and the critical heat flux (CHF) condition were determined in the experiments. In the experiment, an attempt has been made to estimate the heat flux for pool boiling of Water and Methanol at atmospheric pressure. An indoor experiment was conducted to measure (i) the heat flux of water and methanol, (ii) the temperature of the working fluids, (iii) the wall superheat temperatures, (iv) the temperatures at the bottom and side of the pot, (v) time required to be superheated at definite time intervals for a given heat input. The heat input has been varied by changing the voltage with the help of a voltage regulator. A regression analysis has been performed by using the experimental data in the correlation of Rohsenow for pool boiling. Keywords: Pool Boiling; Heat Flux; Wall Superheat; Correlation. DOI: http://dx.doi.org/10.3329/diujst.v6i1.9337 DIUJST 2011; 6(1): 80-86