Detail publikace

The Size Effect of Heat-Transfer Surfaces on Boiling

Originální název

The Size Effect of Heat-Transfer Surfaces on Boiling

Anglický název

The Size Effect of Heat-Transfer Surfaces on Boiling

Jazyk

en

Originální abstrakt

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. 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.

Anglický abstrakt

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. 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.

Dokumenty

BibTex


@article{BUT119543,
  author="Petr {Kracík} and Martin {Lisý} and Marek {Baláš} and Jiří {Pospíšil}",
  title="The Size Effect of Heat-Transfer Surfaces on Boiling",
  annote="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. 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.
",
  address="Inštitut za kovinske materiale in technologije Ljubljana",
  chapter="119543",
  doi="10.17222/mit.2015.245",
  howpublished="print",
  institution="Inštitut za kovinske materiale in technologije Ljubljana",
  number="6",
  volume="50",
  year="2016",
  month="december",
  pages="939--944",
  publisher="Inštitut za kovinske materiale in technologije Ljubljana",
  type="journal article in Web of Science"
}