AIM EXPERIMENTAL STUDY OF THE HEAT TRANSFER PERFORMANCE OF A RECTANGULAR TWO-PHASE NATURAL CIRCULATION LOOP

A model to predict the steady-state behavior of a rectangular two-phase natural circulation loop has been proposed. The analysis employs a one-dimensional two-fluid model to identify various system parameters, with particular emphasis on the subcooled boiling region. The onset of two-phase region and point of net vapor generation and associated liquid temperatures and vapor qualities have been estimated using a few widely recognized correlations. Predicted results demonstrate that the consideration of subcooled boiling may have significant effect on system behavior, particularly around the transition regions. The interaction of saturated bubbles and subcooled liquid and associated change in heat transfer and frictional forces has been discussed in detail. Fluid stream has been observed to have different combinations of flow stream conditions at boiler exit and condenser inlet. Five probable combinations have been identified and a generalized working-regime map has been proposed on Nsub−NZu plane. Attempts have been made to identify the influence of various control parameters. A favorable sink condition (higher coolant flow rate or lower coolant entry temperature) has been found to be of particular importance to attain a wider operating range of wall heat flux and better heat transfer characteristics. A design map has been proposed to identify favorable operating condition in terms of control parameters to ensure complete condensation.

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Acceleration of Two-Phase Flow by Boiling : 1st Report, Experimental Study of Heat Transfer Performance

Transactions of the Japan Society of Mechanical Engineers ◽

10.1299/kikai1938.41.2691 ◽

1975 ◽

Vol 41 (349) ◽

pp. 2691-2699

Author(s):

Toshitsugu HARA ◽

Akio MITANI ◽

Yasuo MORI ◽

kunio HIJIKATA ◽

Motokazu UCHIDA

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Heat Transfer Performance ◽

Two Phase Flow ◽

Phase Flow ◽

Transfer Performance ◽

Two Phase

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Effect of Loop Tilting on the Heat Transfer and Pressure Drop in Two-Phase CO2 Based Natural Circulation Loop: An Experimental Study

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4047820 ◽

2020 ◽

Vol 13 (2) ◽

Cited By ~ 1

Author(s):

L. R. Thippeswamy ◽

Ajay Kumar Yadav

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Heat Transfer Rate ◽

Transfer Rate ◽

Natural Circulation ◽

Flow Behavior ◽

Experimental Studies ◽

Circulation Loop ◽

Two Phase ◽

Natural Circulation Loop

Abstract The natural circulation loop (NCL) is widely used where the safe and economic heat transfer device is desired. However, the instability associated with the regular change in fluid flow behavior due to the imbalance between friction and buoyant forces is a major disadvantage. One of the erudite solutions to overcome this is to tilt the entire loop by a certain angle, with an inherent penalty in heat transfer and pressure drop. In the present study, experimental studies have been carried out on two-phase carbon dioxide (CO2) based NCL, which has gained popularity because of its compactness and higher heat transfer rate. Pressure drop and heat transfer performance of the loop for various tilt angles (0 deg, 30 deg, and 45 deg) in different planes (XY and YZ planes) have been investigated. Methanol is used as the external fluid in cold and hot heat exchangers in order to maintain low operating temperature in the loop. Results show that the tilting of the loop causes a marginal drop in the heat transfer rate of two-phase CO2 based NCL. Hence, tilting of the loop could be a solution to instability problem without conceding the performance of the loop.

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Experimental study on heat transfer performance of a two-phase single thermosyphon using HFE-7100

Journal of Mechanical Science and Technology ◽

10.1007/s12206-017-0944-0 ◽

2017 ◽

Vol 31 (10) ◽

pp. 4957-4964 ◽

Cited By ~ 4

Author(s):

Sang Hyun Oh ◽

Jong Won Choi ◽

Kye Jung Lee ◽

Won Pyo Jeon ◽

Hyung Hee Cho ◽

...

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Heat Transfer Performance ◽

Transfer Performance ◽

Two Phase

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Investigation of Steady-State Characteristics of Natural Circulation Loop

Volume 4: Thermal Hydraulics ◽

10.1115/icone21-15107 ◽

2013 ◽

Author(s):

Zheng Huang

Keyword(s):

Heat Transfer ◽

Steady State ◽

Two Phase Flow ◽

Flow Instability ◽

Natural Circulation ◽

Circulation Loop ◽

Phase Flow ◽

Two Phase ◽

Natural Circulation Loop ◽

Flow Case

Natural circulation is one of the most important mechanisms of passive safety systems in the advanced NPP design. By using RELAP5, steady-state behaviors of a typical natural circulation loop (NCL) were investigated. The Influences of various system parameters, such as pressure, cooling heat transfer area and loop height were studied. The results show that the heat transfer power of the NCL (i.e. the heat transferred from the heater to the tank by NCL) is linear with respect to the temperatures of boundary heat source and sink, excluding the phase transition region. The NCL operation mode (i.e. two-phase flow or one-phase flow) is mainly determined by the loop pressure. It is found that with the decrease of the pressure, the two-phase flow operation range is widened. The heat transfer power of two-phase flow case is always higher, and varies more substantially with pressure, than that of one-phase flow case under the same boundary temperatures. However, flow instability may occur for two-phase flow case. By increasing the area of heat transfer surface between loop cooling section and tank, the temperature difference between the inlet and the outlet of loop heating section as well as the heat transfer power of the NCL will increase. But the influence is insignificant when the tank temperature is relatively high. It is also observed that for both one-phase flow and two-phase flow, the change of loop height has little effect upon the heat transfer power of the NCL under the given boundary condition in this study.

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