Heat transfer coefficient for flow boiling in an annular mini gap

Hożejowska, Sylwia; Musiał, Tomasz; Piasecka, Magdalena

doi:10.1051/epjconf/201611402042

Cited by 3 publications

(7 citation statements)

References 17 publications

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“…Neglecting both the thin thermal conductive filler (~10 −4 m) and the thermocouple size, it was assumed that the surface of the copper pipe surface has direct contact with the heater surface. Furthermore, it was assumed that the heat transfer in the test section and the minigap is axisymmetric; i.e., the temperature distributions in the elements of the module depend on only two variables: r, referring to the thickness of the cartridge heater (r 1 ) and the copper pipe (r 2 − r 1 ) and the width of the minigap (r 3 − r 2 ) and z (along the flow direction) [7,10].…”

Section: Mathematical Modelmentioning

confidence: 99%

“…transfer in the test section and the minigap is axisymmetric; i.e., the temperature distributions in the elements of the module depend on only two variables: r, referring to the thickness of the cartridge heater (r1) and the copper pipe (r2 − r1) and the width of the minigap (r3 − r2) and z (along the flow direction) [7,10].…”

Section: Mathematical Modelmentioning

confidence: 99%

“…Several recent authors' papers have been published to address the issues of heat transfer in flow boiling in annular minigaps of the same dimensions as presented in this work [7][8][9][10] and minichannels of rectangular cross-sections, like in [11][12][13][14][15][16]. The aim of Reference [7] was to present mathematical models of heat transfer in flow boiling in a 1-3-mm-wide minigap. The one-and two-dimensional mathematical models were proposed to describe stationary heat transfer in the gap.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Solution of Axisymmetric Inverse Heat Conduction Problem by the Trefftz Method

Hożejowska

Piasecka

2020

Energies

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In this paper, the issue of flow boiling heat transfer in an annular minigap was discussed. The main aim of the paper was determining the boiling heat transfer coefficient at the HFE-649 fluid–heater contact during flow along an annular minigap. The essential element of the experimental stand was a test section vertically oriented with the minigap 2 mm wide. Thermocouples were used to measure the temperature of the heater and fluid at the inlet and the outlet to the minigap. The mathematical model assumed that the fluid flow was laminar and the steady–state heat transfer process was axisymmetric. The temperatures of the heated surface and of the flowing fluid were assumed to fulfill energy equations with adequate boundary conditions. The problem was solved by the Trefftz method. The local heat transfer coefficients at the fluid–test surface interface were calculated due to the third kind boundary condition at the saturated boiling. Graphs were used to illustrate: the measurement of the heater surface temperature, 2D temperature distributions in the pipe and fluid, and the heat transfer coefficient as a function of the distance from the minigap inlet. The measurement uncertainties and accuracy of the heat transfer coefficient determination were estimated.

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Section: Mathematical Modelmentioning

confidence: 99%

Section: Mathematical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Numerical Solution of Axisymmetric Inverse Heat Conduction Problem by the Trefftz Method

Hożejowska

Piasecka

2020

Energies

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“…Previous authors' studies mostly have been performed to evaluate the flow boiling heat transfer in rectangular minichannels, as [1][2][3][4][5]. This paper shows the results of research on flow boiling heat transfer during refrigerant flow along an annular minigap [6][7][8]. Cylindrical geometry of a minigap in other researchers' works can be find in [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…Application of commercial software for solving an inverse heat conduction problem (IHCP), as contemplated in this paper, is limited, which results from the following facts:  too small set of available experimental data which have to be implemented into the codes,  necessity to solve instantaneously energy equations in the annular minigap and the heated surface with an incomplete set of closure equations (unknown boundary condition on the unheated side of the channel). In this paper, two methods are used for solving the IHCP: the Fourier transform and the Trefftz method [8].…”

Section: Introductionmentioning

confidence: 99%

The application of Fourier transform to the identification of temperature distribution in HFE-7100 flow boiling in an annular minigap

Hożejowska

Piasecka

2018

MATEC Web Conf.

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In the paper the results of investigations into HFE-7100 flow boiling heat transfer in a cylindrical minigap a 1 mm wide created between the external glass pipe and the copper pipe were discussed. A cartridge heater located axially heated fluid flowing along the minigap. The cooling fluid temperature and pressure at the inlet and the outlet to/from the minigap and temperature of the heater in 18 points were measured. Two-dimensional mathematical model for heat transfer coefficient determination was proposed. It was assumed that in the test section the heat transfer process was in steady state and the fluid flow was laminar. The temperature of the metal pipe near the heater was assumed to satisfy Laplace’s equation. The problem formulated in this way was solved by two methods: the Fourier transform and the Trefftz method. The working fluid temperature was calculated depending on the flow type: for single phase flow with boiling incipience and for two-phase flow, respectively. The heat transfer coefficient at the fluid – copper pipe interface was calculated due to the Robin condition. Local heat transfer coefficient values obtained from the Fourier transform and from the Trefftz method were similar. Results were presented and discussed.

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Influences on the drying behavior of a concrete ceiling below a cold attic

Lewis

Sarkany

Heiduk

et al. 2021

J. Phys.: Conf. Ser.

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The article describes the current state of a project examining the influences on the moisture distribution in cold attics above concrete ceilings of residential buildings. Considerable research has been done on moisture damages in cold attics, especially in Scandinavia and North America, focussing on spaces above wooden ceilings. The project (ongoing until Sept 2021) underlying the article deals with cold attics above concrete ceilings resting on masonry walls, a frequent variant in Austria. Research was triggered by a regional Austrian building industry association to shed light onto recent detrimental moisture accumulation in the wooden wall plate (= bearing for the rafters along the eaves) and in the two EPS insulation layers on top of the ceiling. Suspected reasons for the moisture problems and for the local moisture distribution are 1) a too small diffusion resistance of the vapour retarder covering the ceiling, 2) insufficient (natural) attic ventilation and 3) convection, e. g. in the gap between the polystyrene blocks. In order to rank these potential causes by influence and also to find a practical solution a two stage experimental approach was chosen: 1) A handy small scale replica (order of dimension: 1m) of the situation was exposed to the according indoor and outdoor climate in a climate chamber. Different vapour retarders on top of the ceiling were chosen. 2) A larger 1:1 replica has been erected as well but not yet delivered monitoring data. In parallel, a hygrothermic model taking convection into account was established and simulations carried out. The project will deliver a contribution to the Austrian standard on moisture safety 8110-2 on how to judge the moisture safety of joints via simulation.

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Heat transfer coefficient for flow boiling in an annular mini gap

Cited by 3 publications

References 17 publications

Numerical Solution of Axisymmetric Inverse Heat Conduction Problem by the Trefftz Method

Numerical Solution of Axisymmetric Inverse Heat Conduction Problem by the Trefftz Method

The application of Fourier transform to the identification of temperature distribution in HFE-7100 flow boiling in an annular minigap

Influences on the drying behavior of a concrete ceiling below a cold attic

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