Evaporation heat transfer and pressure drop characteristics of R-600a in horizontal smooth and helically dimpled tubes

Shafaee, Maziar; Mashouf, H.; Sarmadian, Alireza; Mohseni, S.G.

doi:10.1016/j.applthermaleng.2016.06.148

Cited by 55 publications

(20 citation statements)

References 22 publications

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“…These literatures indicate that the use of passive methods to enhance two phase flow heat transfer performance based on the application of dimple/protrusion patterns, needs more investigation. In this regard, both shallow and deep dimples/protrusions during evaporation of R-600a inside helically dimpled tube in our previous paper [17] show a proper heat transfer augmentation, however, to the best knowledge of the authors, there is no previously study on:…”

Section: Introductionmentioning

confidence: 80%

Condensation heat transfer and pressure drop characteristics of R-600a in horizontal smooth and helically dimpled tubes

Sarmadian

Shafaee

Mashouf

et al. 2017

Experimental Thermal and Fluid Science

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In the present study, condensation heat transfer and frictional pressure drops of refrigerant R-600a (iso-butane) inside a helically dimpled tube and a plain tube of internal diameter 8.3 mm were measured and analyzed. All tests were performed at different vapor qualities up to 0.82 and average saturation temperatures ranging between 38 and 42℃. Refrigerant mass fluxes varied in the range of 114-368 kg/m 2 s. The inner surface of the helically dimpled tube has been designed and reshaped through three-dimensional material surface modifications consists of both shallow and deep protrusions which are placed evenly in helical directions on the tube wall. The experimental results show that the heat transfer coefficients of the dimpled tube are 1.2-2 times of those in smooth tube with a pressure drop penalty just ranging between 58% and 195%. The highest heat transfer coefficient is occurred at vapor quality of 0.53 and mass flow rate of 368 kg/m 2 s. On the other hand, the maximum increase of pressure drop takes place at vapor quality of 0.55 and mass flow rate of 368 kg/m 2 s. Nomenclature ݉ሶ mass flow rate (kg/s) A C p surface area (m ଶ ) specific heat (kJ/kg k)

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Section: Introductionmentioning

confidence: 80%

Condensation heat transfer and pressure drop characteristics of R-600a in horizontal smooth and helically dimpled tubes

Sarmadian

Shafaee

Mashouf

et al. 2017

Experimental Thermal and Fluid Science

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“…The results showed that inserting the wire coils and augmenting the vapor quality and mass velocity contribute to the increment of the heat transfer coefficients. In another empirical study performed by Shafaee et al [17] on boiling of R-600a in plain and rough pipes, it was demonstrated that heat transfer rate and pressure drops in dimpled pipes are larger than those obtained in smooth pipes. To illustrate the impacts of operational conditions and pipe surface roughness on the magnitude of heat transfer coefficient and pressure loss obtained during condensation of R-600a, Sarmadian et al [18] evaluated a two-phase flow heat-exchanger.…”

Section: Introductionmentioning

confidence: 95%

Pressure loss and performance assessment of horizontal spiral coil inserted pipes during forced convective evaporation of R-600a

Alimardani

Moghaddam

Sarmadian

et al. 2019

International Journal of Refrigeration

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“…Their visualization showed that the dimples could accelerate the transition between annular and stratified flows. Shafaee et al [15] performed a saturated flow boiling experiment and reported that the heat transfer performance was substantially improved because of the enhancement design. Additional enhancement structure design analyses were investigated by Ayub et al [16], and their results show that, under similar operating conditions, the enhanced tube with a rod insert provided a three-fold higher heat transfer coefficient than the plain tube; additionally, the corresponding pressure drop penalty was even lower for low mass fluxes.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the Evaporation and Condensation Heat Transfer Coefficients on the External Surface of Tubes in the Annulus of a Tube-in-Tube Heat Exchanger

Tang

Kukulka

et al. 2020

Energies

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An experimental study was carried out to explore the heat transfer characteristics on the outside of smooth and enhanced tubes, during evaporation and condensation of R134A in the annulus of a tube-in-tube heat exchanger. The three-dimensional enhanced surface tube consisted of primary enhancement patterns and secondary patterns; results were compared to the performance of an equivalent smooth tube. The equivalent external diameter of the inside horizontal copper tubes used in this study was 19.05 mm, while the outer tube varied in size, allowing a comparison of heat transfer for different annulus dimensions. Tests were conducted with a fixed inlet/outlet vapor quality and a constant saturation temperature for varied mass velocities in the range of 30 to 100 kg/(m2∙s). For condensation, the ratio of heat transfer coefficient enhancement (enhanced tube/ smooth tube) was up to 1.78; this can be attributed to the turbulence increase, as well as liquid film re-distribution, produced from the dimples. Furthermore, the condensation heat transfer coefficient increased rapidly with increasing mass flux. For flow boiling in the annulus between the 1EHT tube and outer tube, the heat transfer coefficient during boiling was 11–36% higher when compared to the smooth tube at xave = 0.35, while the performance of the 1EHT tube was not as good as the smooth tube at xave = 0.5. The heat transfer deterioration can be explained by decreased effective nucleate flow boiling heat transfer area and the flow pattern transition between a slug/wavy-stratified flow to wavy-stratified flow.

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Evaporation heat transfer and pressure drop characteristics of R-600a in horizontal smooth and helically dimpled tubes

Cited by 55 publications

References 22 publications

Condensation heat transfer and pressure drop characteristics of R-600a in horizontal smooth and helically dimpled tubes

Condensation heat transfer and pressure drop characteristics of R-600a in horizontal smooth and helically dimpled tubes

Pressure loss and performance assessment of horizontal spiral coil inserted pipes during forced convective evaporation of R-600a

Comparison of the Evaporation and Condensation Heat Transfer Coefficients on the External Surface of Tubes in the Annulus of a Tube-in-Tube Heat Exchanger

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