A Note on Combined Boiling and Evaporation of Liquid Films on Horizontal Tubes

Lorenz, J.J.; Yung, D.

doi:10.1115/1.3450914

Cited by 58 publications

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“…Lorenz and Yung created a mathematical model published at [1] in 1979 for prediction of a heat transfer coefficient at the surface of a single sprinkled horizontal tube using a simplified geometry. The results of for instance [2, 3, 4] were compared with this model.…”

Section: Mathematical Model Of Heat Transfer Of Boiling Liquidmentioning

confidence: 99%

“…According to [1] higher heat transfers with boiling temperature are achieved in thin liquid films than in steam environment and a conservative approach is the application of a relation defined by Rohsenow …”

Section: Mathematical Model Of Heat Transfer Of Boiling Liquidmentioning

confidence: 99%

“…For a fully developed region at a vertical smooth tube the following two equations are recommended by [1] for a calculation of a heat transfer coefficient at laminar (and also pseudo laminar) and at turbulent flow according to Chun and Seban [9]…”

Section: Mathematical Model Of Heat Transfer Of Boiling Liquidmentioning

confidence: 99%

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Development boiling to sprinkled tube bundle

Kracík

Pospíšil

2016

EPJ Web of Conferences

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Abstract. This paper presents results of a studied heat transfer coefficient at the surface of a sprinkled tube bundle where boiling occurs. Research in the area of sprinkled exchangers can be divided into two major parts. The first part is research on heat transfer and determination of the heat transfer coefficient at sprinkled tube bundles for various liquids, whether boiling or not. The second part is testing of sprinkle modes for various tube diameters, tube pitches and tube materials and determination of individual modes' interface. All results published so far for water as the falling film liquid apply to one to three tubes for which the mentioned relations studied are determined in rigid laboratory conditions defined strictly in advance. The sprinkled tubes were not viewed from the operational perspective where there are more tubes and various modes may occur in different parts with various heat transfer values. The article focuses on these processes. The tube is located in a low-pressure chamber where vacuum is generated using an exhauster via ejector. The tube consists of smooth copper tubes of 12 mm diameter placed horizontally one above another.

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Section: Mathematical Model Of Heat Transfer Of Boiling Liquidmentioning

confidence: 99%

Section: Mathematical Model Of Heat Transfer Of Boiling Liquidmentioning

confidence: 99%

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Development boiling to sprinkled tube bundle

Kracík

Pospíšil

2016

EPJ Web of Conferences

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“…The first part is research on heat transfer and determination of the heat transfer coefficient at sprinkled tube bundles for various liquids, whether boiling or not. For water as the falling film liquid they were for example [6,7,8,9,11]. The second part is testing of sprinkle modes for various tube diameters, tube pitches and tube materials and determination of individual modes' interface.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Effect of Tube Pitch and Surface Alterations on Temperature Field at Sprinkled Tube Bundle

Kracík

Copek

Zachar

et al. 2015

EPJ Web of Conferences

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Abstract. Water flowing on a sprinkled tube bundle forms three basic modes: It is the Droplet mode (liquid drips from one tube to another), the Jet mode (with an increasing flow rate droplets merge into a column) and the Membrane (Sheet) mode (with further increasing of falling film liquid flow rate columns merge and create sheets between the tubes. With sufficient flow rate sheets merge at this state and the tube bundle is completely covered by a thin liquid film). There are several factors influencing the individual mode types as well as heat transfer. Beside the above mentioned falling film liquid flow rate they are for instance tube diameters, tube pitches in a tube bundle or a physical condition of a falling film liquid. This paper presents a summary of data measured at atmospheric pressure at a tube bundle consisting of copper tubes of 12 milimeters diameter and of the studied tube length one meter. The tubes are positioned horizontally one above another with the tested pitches of 15, 20, 25 and 30 mm and there is a distribution tube placed above them with water flowing out. The thermal gradient of 15-40 has been tested with all pitches where the falling film liquid's temperature at the inlet of the distribution tube was 15 °C. The liquid was heated during the flow through the exchanger and the temperature of the sprinkled (heater) liquid at the inlet of the exchanger with a constant flow rate about 7.2 litres per minute was 40 °C. The tested flow of the falling film liquid ranged from 1.0 to 13.0 litres per minute. Sequences of 180 exposures have been recorded in partial flow rate stages by thermographic camera with record frequency of 30 Hz which were consequently assessed using the Matlab programme. This paper presents results achieved at the above mentioned pitches and at three types of tube bundle surfaces.

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“…The first part is research on heat transfer and a determination of the heat-transfer coefficient with respect to sprinkled tube bundles for various liquids, whether boiling or not. For water as the falling film liquid, they were, for example [3][4][5][6][7] . The second part is testing of the sprinkle modes for various tube diameters, tube pitches and tube materials and a determination of individual modes' interface.…”

Section: Introductionmentioning

confidence: 99%

The size effect of heat-transfer surfaces on boiling

Kracík¹,

Baláš²,

Lisý³

et al. 2016

Mater. Tehnol.

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A sprinkled tube bundle is frequently used in technology processes where an increase or decrease of a liquid temperature in a very low-pressure environment is required. Phase transitions of the liquid very often occur at low temperatures at pressures ranging in the thousands of pascals, which enhances the heat transfer. This paper focuses on the issue of a heat-transfer coefficient that is experimentally examined at the surface of a tube bundle. The tube is located in a low-pressure chamber where the vacuum is generated using an exhauster via an ejector. The tube consists of smooth copper tubes of 12 mm diameter placed horizontally one above another. Heating water flows in the bundle from the bottom towards the top at an average input temperature of approximately 40°C and an average flow rate of approximately 7.2 L min -1 . A falling film liquid at an initial temperature of approximately 15°C at an initial tested pressure of approximately 97 kPa (atmospheric pressure) is sprinkled onto the tubes' surface. Afterwards, the pressure in the chamber is gradually decreased. When reaching the minimum pressure of approximately 3 kPa (abs) the water partially evaporates at the lower part of the bundle. Consequently, the influence of the falling film liquid temperature increase is tested. This gradually leads to the boiling of water in a significant part of the bundle and the residual cooling liquid that drops back to the bottom of the vessel is almost not heated anymore. In this paper we present the influences of the size of the heat-transfer surfaces. Keywords: sprinkled tube bundle, water, under pressure, heat transfer Pr{enje po snopu cevi se pogosto uporablja v tehnolo{kih procesih, kjer se zahteva povi{anje ali zmanj{anje temperature teko~ine v okolju z nizkim tlakom. Fazni prehod teko~ine se pogosto pojavi pri nizkih temperaturah in tlakih v obmo~ju nekaj tiso~paskalov, kar vpliva na prenos toplote.^lanek se nana{a na koeficient prenosa toplote, ki je eksperimentalno dolo~en na povr{ini snopa cevi. Cev je name{~ena v nizkotla~ni komori, kjer se vakuum ustvarja s pomo~jo aspiratorja preko ejektorja. Snop cevi sestavljajo gladke bakrene cevi, premera 12 mm, ki so name{~ene horizontalno ena nad drugo. Voda za ogrevanje te~e v snop od spodaj proti vrhu s povpre~no temperaturo okrog 40°C in povpre~no hitrostjo pretoka okrog 7,2 L min -1 . Padajoṽ odni film z za~etno temperaturo okrog 15°C in z za~etnim tlakom okrog 97 kPa (atmosferski tlak) pr{i po povr{ini cevi. Tlak se v komori postopno zni`uje. Ko dose`e minimalni tlak okrog 3 kPa (absolutni tlak) voda delno izhlapi na spodnjem delu snopa. Posledi~no je preizku{en vpliv nara{~anja temperature padajo~e vode. To postopno privede do vrenja vode na ve~jem delu povr{ine snopa in preostala hladilna teko~ina, ki kaplja na dno posode, se skoraj ne segreje ve~.^lanek predstavlja vpliv velikosti povr{ine kjer se prena{a toplota. Klju~ne besede: pr{enje po snopu cevi, podtlak, prenos toplote

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A Note on Combined Boiling and Evaporation of Liquid Films on Horizontal Tubes

Cited by 58 publications

References 0 publications

Development boiling to sprinkled tube bundle

Development boiling to sprinkled tube bundle

Evaluation of the Effect of Tube Pitch and Surface Alterations on Temperature Field at Sprinkled Tube Bundle

The size effect of heat-transfer surfaces on boiling

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