Heat transfer characteristics of a two-phase thermosyphon heat exchanger

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An approach -relaying on application of nanofluid as a working fluid, to improve performance of the two-phase thermosyphon heat exchanger (TPTHEx) has been proposed. The prototype heat exchanger consists of two horizontal cylindrical vessels connected by two risers and a downcomer. Tube bundles placed in the lower and upper cylinders work as an evaporator and a condenser, respectively. Distilled water and nanofluid water-Al2O3 solution were used as working fluids. Nanoparticles were tested at the concentration of 0.01% and 0.1% by weight. A modified Peclet equation and Wilson method were used to estimate the overall heat transfer coefficient of the tested TPTHEx. The obtained results indicate better performance of the TPTHEx with nanofluids as working fluid compared to distilled water, independent of nanoparticle concentration tested. However, increase in nanoparticle concentration results in overall heat transfer coefficient decrease of the TPTHEx examined. It has been observed that, independent of nanoparticle concentration tested, decrease in operating pressure results in evaporation heat transfer coefficient increase.

“…All data readings have been performed during steady-states. More details concerning experimental setup and procedure are presented in [24]. …”

Section: Methodsmentioning

confidence: 99%

Section: Prototype Two-phase Thermosyphon Heat Exchangermentioning

confidence: 99%

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Effect of nanofluid concentration on two-phase thermosyphon heat exchanger performance

Cieśliński

2016

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“…It is important to note that numerous theoretical and empirical studies of boiling in minichannels have been conducted in the research centers of Poland [10][11][12][13][14]. The state of the art presented above as well as the literature review shows unequivocally the need for further regular, theoretical and experimental, research of flow boiling heat transfer in minichannels since the effect of thermodynamic parameters on the boiling activity in minichannels with different geometries and spatial orientation has not been clearly determined yet.…”

Section: Introductionmentioning

confidence: 99%

Measurements of two-phase flow patterns and local void fraction in vertical rectangular minichannel

Kaniowski¹,

Poniewski²

2013

Technology advancements entail a necessity to remove huge amounts of heat produced by today's electronic devices based on highly integrated circuits, major generators of heat. Heat transfer to boiling liquid flowing through narrow minichannels is a modern solution to the problem of heat transfer enhancement. The study was conducted for FC-72 boiling in a rectangular, vertical and asymmetrically heated minichannel that had depths of 0.5-1.

“…Their study shows potential use of the two-phase flow in the domain of electronic cooling and high-efficiency heat transfer from a source to a final cooling media. Cieśliński and Fiuk [24] studied experimentally the two-phase thermosyphon loop with horizontal evaporator and horizontal condenser using water, methanol and refrigerant R-141b as working fluids. Cieśliński [25] measured also the effect of concentration of the water-based Al 2 O 3 -nanofluid on thermal performance of the two-phase thermosyphon heat exchanger.…”

Section: Introductionmentioning

confidence: 99%

Validation of the generalized model of two-phase thermosyphon loop based on experimental measurements of volumetric flow rate

Bieliński

2016

The current paper presents the experimental validation of the generalized model of the two-phase thermosyphon loop. The generalized model is based on mass, momentum, and energy balances in the evaporators, rising tube, condensers and the falling tube. The theoretical analysis and the experimental data have been obtained for a new designed variant. The variant refers to a thermosyphon loop with both minichannels and conventional tubes. The thermosyphon loop consists of an evaporator on the lower vertical section and a condenser on the upper vertical section. The one-dimensional homogeneous and separated two-phase flow models were used in calculations. The latest minichannel heat transfer correlations available in literature were applied. A numerical analysis of the volumetric flow rate in the steady-state has been done. The experiment was conducted on a specially designed test apparatus. Ultrapure water was used as a working fluid. The results show that the theoretical predictions are in good agreement with the measured volumetric flow rate at steady-state.