Search

A different models of Shell-and-tube heat exchangers were designed by Ansys geometry & Solidworks to evaluate the best model for heat transfer and to calculate the difference in heat transfer in each model by investigated with numerically modeling. Each model for heat exchanger has different assumptions for first model one tube & one pass with tube length 3 meter, was made with 2 different cases (each case have the same conditions such as same temperature, same velocity, changing the direction of the flow between parallel and counter flow). The flow and temperature fields inside the shell and tubes are resolved using a Ansys CFD 17.2. A set of CFD simulations is performed for a single shell and tube bundle and is compared with the experimental results. the Realizable K-ε model is known for predicting the flow separation better than Standard K-ε. The temperature of each model is examined in detail. Each design was studied separately on the basis of the findings, the designs need modifications to improve heat transfer. The main goal of designing these models is to obtain highest performance for shell and tube heat exchanger with given conditions. These studies were carried out to find the most suitable conditions of operation in shell and tube heat exchanger so that in the future it can improve the performance of heat exchanger in industries through applying these conditions.

Widely known that, heat exchanger is a device that is being used to transfer thermal energy (enthalpy) between two or more fluids, between a solid surface and a fluid, or between solid particulates and a fluid, at different temperatures and in thermal contact. The most common heat transfer devices are concentric tube (double pipe), shell and tube and, plate heat exchanger. Nowadays, Shell and tube heat exchangers were used extensively in most industries as petrochemicals, oil and refineries. According to previous survey, almost 45% of heat exchangers utilized are shell and tube heat exchangers due to its high-pressure application it is more suitable in the field of oil & petrochemical application. Thus, the following study presented shell and tube type only. Due to complexity of studying heat exchangers experimentally, Computational Fluid Dynamics (CFD) used to simulate the effect of local surface heat transfer coefficients on the surfaces by aid of computer numerical calculation and graphical display. In addition, analysis of the physical phenomena involved in fluid flow and heat conduction would be presented in the following research paper with Comparative designs for shell and tube heat exchangers. The paper considered a review for the design of a shell and tube heat exchanger. A variety of heat exchangers are used in industry and in their products. The objective of this paper is to describe most of these heat exchangers in some detail using classification schemes and the basic design methods for two fluid heat exchangers.

Abstract- Improving the performance of modern combustion systems in many engineering application fields has great favorable impact on the energy conservation and global environmental pollution. This can be done through developing state of the art techniques for this purpose. One of them is the combustion within porous media burners. The two-layer porous inert medium burner (PIM) has significant merits such as high burning ratios, very low emission levels, high levels of the combustion stability, and operation at ultra-lean excess air ratios. The main work is to examine a new PIM design has a square cross-section area with two porous layers namely, aluminum oxide as the subcritical layer (quenching layer) and silicon carbide (SiC) as the supercritical layer each of 130 x 130 mm. The burner performance was estimated by recording the axial temperature profile at the selected operated thermal powers. The extent of the combustion stability limits between the flashback limit to the blow-off limit was improved. The excess air ratios of the stability limits at powers 0.7, 1.5, 2.5 kW were deduced to be (1.9-2.8), (1.8-2.6), and (1.5-2.4), respectively. The exhaust emissions were measured by a gas analyzer. The results revealed low levels of the CO emissions and decreased with increasing the operated thermal power. The CO ppm recorded the order of hundreds at powers 0.7 and 1.5 kW but reached the order of tens at power 2.5 kW. The NOx emission recorded ultra-low levels and increase with increasing the thermal power but not exceed 2 ppm.

Steady CFD simulations, which is based on Reynolds Average Navier-Stokes (RANS) approach, were conducted for a model of Horizontal Axis Wind Turbine (HAWT) and compared with experimental data in order to assess the accuracy of these models in simulating the wake flow of HAWTs. The models can be categorized into two categories: fully developed models (Standard k-ε model, Realizable k-ε model, and SST k-ω model) and transitional models (K-kl-ω transition model and Transition SST Model). In this paper, ANSYS FLUENT 19.2 was being used to execute the simulations of the model turbine standing on a closed-loop wind tunnel at Norwegian University of Sciences and Technology (NTNU). Experiments were operating on a high turbulence intensity uniform inflow. Velocity, turbulence intensity, and turbulent kinetic energy profiles are illustrated at two downstream cross sections. Furthermore, contours of these parameters are set to investigate the developing of wake flow behind the turbine. It is demonstrated that models reasonably predict the velocity profile at the wake region. Transitional models are more accurate in predicting the power of the turbine. Turbulent kinetic energy and turbulence intensity were underestimated for all models.

In this research, a numerical investigation was performed on five solar air heaters with different cross-sectional shape to find the best configuration relevant to thermal performance. The selected tested shapes in this study were (circular, semi-circular, half-circle plus isosceles triangle, half circle-negative isosceles triangle shape and crescent shape) and all tested shapes hade the same absorber surface area. The effect of two parameter (velocity and solar radiation intensity) on thermal performance of solar air heater were studied numerically by ANSYS 14.0. The velocity of air was changed from 0.25 to 2.0 (m.s -1 ). Results indicated that the highest efficiencies were accomplished for the circular configuration and reached to about 51.79% at solar radiation intensity 850 (W.m-2 ). The solar radiation intensity was changed from 400 to 1200 (W.m-2 ). Results indicated that the highest efficiencies were accomplished for the circular configuration and reached to about 35.51% at air velocity 1.0 (m.s-1 ).

Biomass gasification process is considered a promising waste-to-energy conversion technique to eliminate the immense environmental issues accompanied with open field burning. The objective of this study is to experimentally study the dynamic behavior of an Imbert based design manufactured bench scale gasifier using cotton stalks as a feed stock. Air was employed as a gasifying agent with a biomass batch feed of 4 kg. The gasification process characteristics are evaluated in terms of lower heating value, gasification efficiency, and operation time. The applied air flow rates are (60, 100, 150, and 200 l/m) achieving varied equivalence ratios between 0.362 – 0.232. An optimum average lower heating value and cold gas efficiency of 4.34 MJ/m3 and 61.7 % respectively are attained at equivalence ratio, ER of 0.304.

The present experimental work aims to enhance the daily productivity of solar stills. A stepped pyramidal still with three trays was fabricated and tested under Tanta conditions, Egypt in September 2016. The still was tested with the brine feed being uninterrupted in one experiment, and with intermittent brine supply in another experiment. For continuous brine supply, the accumulated distillate was 4.95 L. For intermittent brine supply, the accumulated distillate was 4.6 L. Per unit total area, the average daily distillate water productivity is 5.5 and 5.11 L/m2 for the continuous and the intermittent feed stills, respectively. In the two ways, the still yielded a greater productivity than that of conventional pyramid solar still which is 4.4 L/m2 .