INFLUENCE OF RIBBING ON THE STRESS-STRAIN STATE OF A FLAT ROUND TANK BOTTOM

Options with radial and longitudinal-transverse rib arrangement were considered. The research was carried out by numerical simulation in the ANSYS program. The values of stresses and deformations in the tank bottom were obtained depending on the number and location of stiffeners on it. It is established that the main load is perceived by the Central part of the ribs. Therefore, due to the correct selection of stiffeners, it is possible to reduce the thickness of the head plate. To equalize the stresses on the head surface, the number of edges should be at least six, and the radial placement of the edges is more preferable. With the same deformations, in this case, the stresses in the head are somewhat less. The results obtained make it possible to increase the strength of the flat head and use it in tanks intended for storing liquid and gaseous substances under low pressure.

Pressure Drop and Heat Transfer Performance of Microchannel Heat Exchanger With Circular Reentrant Cavities and Ribs

The rib arrangement has an important influence on the pressure drop and heat transfer performance of a microchannel heat exchanger (MHE) with circular reentrant cavities and ribs. In this study, four kinds of MHEs with circular reentrant cavity and ribs were designed, namely, circular reentrant cavities (circular), circular reentrant cavities and single-sided ribs (circular—single), circular reentrant cavities and odd-symmetric ribs (circular—odd), and circular reentrant cavities and double symmetric ribs (circular—double). The effect of the rib arrangement on the pressure drop and heat transfer performance of MHEs was numerically investigated by ansysfluent 15.0. The experimental platform was then designed and built for the subsequent experimental verification. The results showed that the pressure drop between the inlet and outlet of the MHE with circular reentrant cavities and ribs increased as the inlet flow increased. At the same inlet flowrate, the pressure drop between the inlet and outlet of the MHEs was largest for the circular reentrant cavities and double symmetric ribs, followed by the circular reentrant cavities and odd-symmetric ribs, circular reentrant cavities and single-sided ribs, and the circular reentrant cavities. The presence of the rib structure increased the inlet and outlet pressure drop of the MHE. The MHE with circular reentrant cavities and double symmetric ribs had the largest inlet and outlet pressure drop, followed by that with circular reentrant cavities and odd-symmetric ribs, that with circular reentrant cavities and single-sided ribs, and that with circular reentrant cavities, indicating that the latter exhibited the best pressure drop performance. At the same inlet flowrate, the MHE with circular reentrant cavities had the highest hot water outlet temperature and the MHE with circular reentrant cavities and double symmetric ribs had the lowest temperature, whereas the results were the opposite for the cold-water outlet temperature. This indicates that the heat transfer performance was best for the MHE with circular reentrant cavities and double symmetric ribs, followed by that with circular reentrant cavities and odd-symmetric ribs and that with circular reentrant cavities and single-sided ribs.

Thermo-Hydraulic Performance of a Rectangular Duct With Staggered Inclined Discrete Rib Arrangement

Artificial roughness in the form of ribs is a beneficial strategy to improve the thermal performance of solar air heaters (SAHs). In the present research work, experimental examinations have been conducted on heat transfer and friction characteristics in the rectangular channel, which is roughened through the inclined discrete ribs. The inclined ribs were discretized by creating gaps at the different positions (not inline) on trailing and leading edges in consecutive ribs The rib roughness has relative roughness pitch as 8.0, rib combination of relative gap position is varied from 0.3 & 0.1 to 0.3 & 0.4, and mass flow rate varies between 3000 -14,000 and rib gap width as 1. The higher improvement in the Nusselt number and factor of friction coefficient is obtained to be 2.92 and 3.33 times respectively, as compared with that of the smooth duct. The higher thermo-hydraulic performance parameter (THPP) is obtained for the combination of relative gap position of 0.3 & 0.3. Keywords: Combination of relative gap position, Friction

Developing Secondary Flow and Heat Transfer in the Entrance Region of a Square Channel With 45° Crossed Rib Arrangement

This paper presents developing secondary flow and heat transfer measurements in a ribbed cooling channel. Experiments are carried out for Reynolds number ranging from 25,000–140,000. Regionally averaged local heat transfer measurements are conducted using heated copper segments. Flow measurements are carried out using a miniature five-hole pressure probe and presented for cross sections at intervals of 1.8 hydraulic diameters dh in flow direction. Results are compared to numerical simulations using explicit algebraic Reynolds stress and turbulent heat transfer models. The paper focuses on the entrance region where secondary flow structure has not emerged yet. The findings show that the well-known secondary flow structure of the crossed rib configuration, consisting of one large single rotating secondary flow, is not established until approximately 6–7 dh in main flow direction. Instead two opposed vortices are identified which dominate the flow characteristics and provide an increase in heat transfer of up to 15–20% when compared to the periodically developed flow condition. Thus, for the first time to the author’s knowledge, the paper describes in detail the developing secondary flow in a crossed rib arrangement and links it to the heat transfer distribution observed. In summary, this paper stresses the importance of the developing flow region for the design process in convection cooled gas turbines, especially for short channels of high pressure blades and vanes, as it has a significant effect on cooling channel heat transfer performance.