Condensation and evaporation heat transfer characteristics in horizontal smooth, herringbone and enhanced surface EHT tubes

Comparison of condensation and evaporation heat transfer on the outside of smooth and enhanced 1EHT tubes

“…This trend was also demonstrated in a bundle study of 1EHT tubes performed by Kukulka and Smith [39]. Performance trends demonstrated for inside condensation in Kukulka et al [7] and Guo et al [5], for the same enhanced structures (inside enhancement) are not found in the present study for the conditions considered. This was unexpected and requires additional investigation.…”

“…Li et al [4] found that rib geometries play only a small role in both average and local heat transfer under forced convection, while for the mixed convection case, rib geometry has a significant effect on heat transfer. Guo et al [5] evaluated convective condensation and evaporation inside a smooth tube, herringbone tube and the 1EHT enhanced surface tube. Overall the 1EHT tube was found to provide increased tubeside enhancement for both condensation and evaporation.…”

“…Kukulka et al [7] performed an experimental investigation in order to determine the evaporation and condensation heat transfer coefficient of R22 and R410A inside the 1EHT tube for low flows. Guo et al [5] performed an experimental investigation to evaluate convective condensation and evaporation of R22, R32 and R410A inside smooth and enhanced tubes. For condensation, they find that the heat transfer coefficient of the 1EHT tube is 1.3-1.95 times that of the smooth tube.…”

Experimental Investigation of the Condensation Heat Transfer Coefficient of R134a inside Horizontal Smooth and Micro-Fin Tubes

“…For smooth tubs, a dimensionless parameter  that characterizes the two-phase flow dynamic viscosity was introduced to the correlations of Dobson In the study of Guo et al [42], the Oliver et al correlation underestimates the heat transfer coefficient when the original value of the variable "s" is set to 0.715, while the predictive ability is improved and most predicted data can be controlled within a 30% error range when this value is set to 0.745, which provides a reference for the correlation modification. Re eq is the equivalent Reynolds number in the correlations of Cavallini That the correlation underestimates the experimental data shows that the forced-convection heat transfer effect has not obtained enough attention for a large mass velocity in the correlation, hence, the modified correlation is intended to enhance the turbulence effect.…”

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

“…They compared the heat transfer for single phase flows and found that the 1EHT surface can produce heat transfer increases of more than 500% when compared to smooth tubes. Guo et al [4] performed an experimental investigation to evaluate convective condensation and evaporation of R22, R32, and R410A inside a smooth tube, a herringbone tube and a newly developed enhanced surface EHT tube at low mass fluxes. The inner surface of the EHT tube was enhanced by dimple/protrusion and secondary petal arrays that it was produced by Vipertex TM too.…”