Abstract
In this article, the BSL k-ω model was chosen as the turbulence model to simulate the heat transfer and flow characteristics of the proposed tubes inserted with internal spiral fins when the Re was set as 3000 to 17,000. The numerical results agreed well with the empirical formula. The average deviations of Nu and f between the simulation results and empirical formula results were 5.11% and 8.45%, respectively. By means of numerical simulation, the impact of three configurational parameters on the thermal performance was studied, namely the pitch P, the height H, and the number N of the internal spiral fins. The results showed that the Nu and f of the internal spiral finned tube were 1.77–3.74 and 3.04–10.62 times higher than those of smooth tube, respectively. PEC was also taken into account, ranging from 1.038 to 1.652. When the Re was set as 3000, the PEC achieved the peak value of 1.652 under the height H of the fins at 5 mm, the number N was 8, and the pitch P was 75 mm. However, with the increase of Re, the effect of pressure drop on the comprehensive performance in the tube was stronger than that of thermal enhancement. However, the PEC gradually decreased as the Re increased from 3000 to 17,000. In addition, the velocity and temperature fields were obtained to investigate the mechanisms of heat transfer enhancement.
Highlights
As heat exchange equipment, the heat exchanger plays an important role in the chemical industry, petroleum, power, food and many other industrial productions [1].The requirements for heat exchange equipment in various fields has become more and more difficult to meet, and the demand for a heat exchanger with smaller, more compact and stronger heat exchange capacity has been put forward to adapt to more severe heat exchange situations
For internal spiral finned tubes, the main settings in the software included were as follows: The velocity–pressure coupling was calculated by coupled algorithm and the second-order upwind scheme was applied to solve the momentum and energy equations, except that the turbulent kinetic energy and specific dissipation rate equations were settled by first order upwind
Nu (Nusselt number), f (f factor) and Re (Reynolds number) [34], as the most important indexes to measure heat transfer and flow characteristics of the internal spiral finned tube, were expressed as: Dh where D was the hydraulic diameter of the working fluid, h denoted the average heat transfer coefficient, ∆P = pin − pout represented the pressure difference between inlet and outlet, L
Summary
The heat exchanger plays an important role in the chemical industry, petroleum, power, food and many other industrial productions [1]. In 2012, Liu et al [10] used the combination of experiment and numerical simulation to study the flow and heat transfer characteristics of finned tubes with inner and outer fins. In order to improve the heat transfer performance, various tube inserts have been proposed, including twisted tape [16,17,18,19], twined coil [20,21], fin [22], baffle [23], winglet [24,25,26] and so on. To optimize the synergistic effect between the heat transfer enhancement and the pressure the fins with better comprehensive performance and more appropriate position still need drop to obtain low resistance and efficient heat transfer performance. All the work was accomplished when the Reynolds number was in the range of 3000 to 17,000 and water was chosen as the working fluid
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