Forced convection heat transfer performance of porous twisted tape insert

Heat transfer performance of porous twisted tape insert in a circular tube was experimentally investigated. Tube wall temperatures and pressure drops along the axial distance of the test section at steady state condition were measured for different flows having Reynolds number ranging from 1.4 x 104 to 5.2 x 104 for both the plain and the tube with porous twisted tape insert. Heat transfer coefficient, friction factor, and pumping power were calculated from the measured data. Heat transfer and fluid flow characteristics of the porous twisted tape inserted tube were explained from the measured and calculated values. Performance of the porous twisted tape inserted tube was also evaluated. The results showed for porous twisted tape inserted tube, the average heat transfer coefficient was 2.60 times higher, the heat flux was 1.55 times higher, the friction factor was 2.25 times higher and the pumping power was 2.0 times higher than those of plain tube values for similar flow conditions

Heat transfer and pressure drop characteristics in turbulent flow through a tube

An experimental investigation has been carried out for turbulent flow through a tube with perforated strip inserts. Strips were of mild steels with circular holes of different diameters. Flow varies, with ranging Reynolds numbers from 15,000 to 47,000. Air velocity, tube wall temperatures, and pressure drops were measured for a plain and strip-inserted tube. The heat transfer coefficient and friction factor were found to be 2.80 times and 1.8 times, respectively, that of the plain tube. The heat transfer performance was evaluated and found to be 2.3 times that of the plain tube based on constant blower power

Heat transfer enhancement and development of correlation for turbulent flow through a tube with triple helical tape inserts

Influence of triple helical tapes inserted for turbulent flow through a tube on heat transfer enhancement was studied experimentally. The triple helical tapes made of mild steel with different helix angles, alpha = 9 degrees, 13 degrees, 17 degrees, and 21 degrees were examined for Reynolds number ranging from 22,000 to 51,000. The experiment showed that the Nusselt number, effectiveness and friction factor for the inserts were found to be up to 4.5, 3.45 and 3.0 times, respectively, over the plain tube. The highest enhancement efficiency achieved was 3.7 for the inserts based on constant blower power. Finally, new correlations for predicting heat transfer and friction factor for turbulent flow through a circular tube fitted with the inserts were proposed

Enhancement of Mixing Performance of Two-Layer Crossing Micromixer through Surrogate-Based Optimization

Optimum configuration of a micromixer with two-layer crossing microstructure was performed using mixing analysis, surrogate modeling, along with an optimization algorithm. Mixing performance was used to determine the optimum designs at Reynolds number 40. A surrogate modeling method based on a radial basis neural network (RBNN) was used to approximate the value of the objective function. The optimization study was carried out with three design variables; viz., the ratio of the main channel thickness to the pitch length (H/PI), the ratio of the thickness of the diagonal channel to the pitch length (W/PI), and the ratio of the depth of the channel to the pitch length (d/PI). Through a primary parametric study, the design space was constrained. The design points surrounded by the design constraints were chosen using a well-known technique called Latin hypercube sampling (LHS). The optimal design confirmed a 32.0% enhancement of the mixing index as compared to the reference design

Energy recovery from biomass by fast pyrolysis

Bioenergy is now accepted as having the potential to provide the major part of the projected renewable energy provisions of the future. It has been ascertained that the biomass is a common form of renewable energy and widely used in the world. The use of biomass to provide energy has been identified as a fundamental to the development of civilization. There are different types of thermo-chemical conversion technologies available for converting biomass into energy which stretches from direct burning to more complex processes including gasification or pyrolysis. Among these processes, pyrolysis has become increasingly popular because it gives products of better quality compared to any other thermo-chemical conversion processes for biomass. A computational fluid dynamics (CFD) model is developed using Advanced System for Process Engineering (ASPEN) PLUS which is a computer assisted energy simulation tool to analyse and optimize the performance of pyrolysis process i.e., to maximize the yields of pyrolysis products such as bio-oil, biochar and syngas as a function of pyrolysis temperature, operating conditions, and physical and chemical properties of biomass. The simulation was done for four types of biomass, namely shredded green waste, pine chips, wood and birch. The results show that the shredded green waste is the best for bio-oil production which possesses high cellulose and low moisture content. The bio-oil of up to 58% can be produced from thismaterial