An experiment has been conducted in detail to study the turbulent heat transfer in horizontal helically coiled tubes over a wide range of experimental parameters. We found that the enhancement of heat transfer in the coils results from the effects of turbulent and secondary flows. With Reynolds number increasing to a high level, the contribution of the secondary flow becomes less to enhance heat transfer, and the average heat transfer coefficient of the coil is closer to that in straight tubes under the same conditions. The local heat transfer coefficients are not evenly distributed along both the tube axis and the periphery on the cross section. The local heat transfer coefficients on the outside are three or four times those on the inside, which is half of the average heat transfer. A correlation is proposed to describe the distribution of the heat transfer coefficients at a cross section. The average cross-section heat transfer coefficients are distributed along the tube axis. The average value at the outlet section should not be taken as the average heat transfer coefficient.

With the development of supercritical fluids technology, more and more attention is being paid to the study of flow and heat transfer under supercritical conditions. In order to better understand the influence of gravity on the flow and heat transfer of supercritical fluids, with the CFD software FLUENT 6.0, a numerical study has been conducted for the developing laminar flow and heat transfer of water in a smooth vertical tube under supercritical pressure. The flow and heat transfer have been studied with the inlet Reynolds number ranging from 500 to 2000, Grashof number er ranging from1

In the present investigation, both pressure fluctuations and differential pressure signals were measured for oil-gas-water multiphase piping flow in wide ranges of flow parameters in horizontal pipe. The signal features were extracted and analyzed, which included time domain features, frequency domain features and fractal features. Both liquid velocity and oil fraction have tremendous influence on the feature analysis, which all the feature have bad clustering and bad separability for the same flow pattern or different flow pattern respectively. It is proved that the recognition methods, RMS of the pressure, PDF or PSD of differential pressure fluctuation, are not able to be employed widely in the industrial applications. The pressure fluctuations exhibit chaotic characters and are influenced by flow patterns. The regulations to identify the special flow pattern are obtained basing on the joint feature analysis. The online intelligent recognition of flow patterns is proposed which is a fusion method combining the special regulations and the pattern recognition. The proposed method was examined in the oil-gas-water loop and the results showed that bubble flow, stratified flow, intermittent flow and annular flow could be identified with more than 90% accuracy.

A simple method is developed in this paper to solve two-dimensional nonlinear steady inverse heat conduction problems. The unknown boundary conditions can be numerically obtained by using the iteration and modification method. The effect of measurement errors of the wall temperature on the algorithm is numerically tested. The results prove that this method has the advantages of fast convergence, high precision, and good stability. The method is successfully applied to estimate the convective heat transfer coefficient in the case of a fluid flowing in an electrically heated helically coiled tube

Byu singa ne nsemble-avem gedt wo-fluid model, with validc losurec onditionso fin terfacialtu omenturne xchanged uet ovirtual mass force, visco us shears tressand dragf orce, amodelfo rp ressurew avep ropagation in a horizontal gas-liquid bubbly flow is proposed. Accordingt ot hes mallp erturbationt heorya nds olvablec onditiono fo eorderlinearu niform equations, ad spersione quationo fpressurew aveis in duced. The pressue wave speedc alculatedf rom the modelis compare danding oods greem entwithe xistingdata. According to the dispersion equation, the propagation and attenuation of pressure wave are investigated systemicaly. The factors affecting pressure wave, sucha sv oidf raction, pressure, wallsh ears tress, perturbationf requency, virtualm ass for ceandd ragforce, are analyzed. The result shows that the decrease in system pmmare, the increase in void fraction and the existence of wall shear stress, will cause a decre inp ressurew avesp eeda nda nIn eressein the a tenuationc oefficientin the horizontalga s-liquidb ubblyflow. Thee ffectso fp erturbstion frequency, virtual mess and drag force on pressure wave in the horizontal gas-liquid bubbly flow at low perturbation frequency are different from that at high perturbation frequency.