3. Modeling and Numerical Simulation Method Experimental methods have been used to find which design of a radiator or HEX is economic and efficient. However, because of the high cost and the complexity of experiments, a numerical method is adopted in the present work to analyze the performance of HEXs. The physical model of the HEX has to be simplified and certain assumptions have to be set up. Meanwhile the governing equations and corresponding boundary conditions are introduced for the simulation model. On the other hand, the grid independence is carried out to ensure the accuracy and validity of the numerical models. At the end, several important parameters are defined for the analysis of thermal performance and pressure loss in HEXs. 3.1 …show more content…
The finite volume method (FVM) is adopted to convert the governing equations to algebraic equations, so that they can be solved numerically. The Semi-Implicit Method for Pressure Linked Equations (SIMPLE) algorithm is used to couple pressure and velocity. A second-order upwind scheme is used for the space discretization of the momentum, energy and turbulence equations in the simulations. 41 The convergence criterion for continuity, momentum, k and Ɛ equations is below 10-3 .However, for the energy convergence needs to satisfy also the energy balance between the air zone and the water zone under the countercurrent flow condition. Thus, the convergence criterion for energy is below 10-8. The mesh generation is carried out by the preprocessor-software ICEM. There are two major techniques in the mesh generation. One is the blocking technique (mostly for Hexa Meshing, as shown in Fig. 3.4). Another one is the auto meshing technique. The HEX region occupies most of cells (60 ~ 70 % of the whole computational domain). Fig. 3.4. Meshing for the computations: (a) 2-D cross-sectional …show more content…
The results of the grid study for different HEXs are shown in Tables 3.3 and 3.4. It is found that the relative deviation of the pressure drops among the three sets of the grid system is less than 2.2 % in the graphite foam corrugated fin. Furthermore, the relative deviation of the heat transfer coefficients between the three sets of grid system is less than 3 % in the graphite foam corrugated fin. Thus, in order to save computational time and keep the accuracy of the simulation, the Case 2 mesh system is chosen for the graphite foam corrugated fin. The same method was adopted to check the grid independence of other configurations of fins. At the end, the Case 2 grid system is chosen for all the fins. Table 3.4. Grid independence study based on h (frontal velocity is 14 m/s). Case 1 Case 2 Case 3 h Grid H Grid h Grid h deviation (W/m2•K) (W/m2•K) (W/m2•K) (%) Pin-finned (63- 431.24 (93- 400.52 (113- 402.60 0.5 - 7.1 (G) 79-19) 79-19) 79-19) Corrugated (49- 259.26 (75- 263.40 (75- 267.04 1.4 - 3 (G) 81-11) 81-11) 81-19) Stagger (G) (99- 450.10 (99- 454.46 (121- 461.49 1.5 - 2.5 83-11) 83-17) 83-17) Wavy (139- 1077.6 (139- 1088.2 (150- 1100 1.1 - 2 corrugated 100- 100- 100- (G) 15) 21) 21) Wavy
In the first part of the experiment, Part A, the standard solutions were prepared. As a whole, the experiment was conducted by four people, however, for Part A, the group was split in two to prepare the two different solutions. Calibrations curves were created for the standard solutions of both Red 40 and Blue 1. Each solution was treated with a serial 2-fold dilution to gain different concentrations of each solution.
A P A T C G i 0 1 2 3 2. In the next step we move forward by comparing successive characters of pattern P to "parallel" characters of genome String S, moving from one character to the next if they match. 3.
After examining the square table with grids to fit the triangle tiles, my calculation is 20 triangular tiles are used. Here is how I came up with the answer. Inside the table, it consists of four different shapes in triangle, rectangle, square, and a right-angle trapezoid. A square requires four tiles to fill. A rectangle requires two triangle tiles, as it is half of the square.
subsection{Recommending Unexpected Relevant Items} Once the forgotten items have been identified, we need to distinguish relevant ones from the rest. Given user taste shifts, as well as the changes in the system as a whole, not all unexpected items remain relevant, and consequently useful for recommendation. The key concept to identify relevant items is the extbf{relevance score} of the items at each moment. We propose four strategies to define the relevance score of each unexpected item.
In the generations of the immigrant labor of a Slovak family, the Dorejacks demonstrates the tough labor in America. In the novel “Out This Furnace” a captivating, non-fiction story, Thomas Bell suggests that immigrant labor in the early days was tough and factors like labor inequality, the relationship between companies and politics, and essential money shaped immigrants freedom. In the mid-1800’s George Kracha fled his country, Austria, under the ruler of Frank Josef, because of the lack of money and employment, Kracha couldn’t sustain his wife and mother (p.3). Moreover, Kracha’s story began when he arrived in New York to White Hill, he then migrates to several other cities but still in America.
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Observations: 1. The first step had to be repeated due to not following proper instructions. I did not grease the screw, so as I was shaking the mixture, solids were forming around the screwpart of the separatory funnel. 2. When adding 5.0 mL of NaOH to the unknown mixture and shaking it for about 30 seconds, layers had formed.
Web. 2 May 2014. Document URL http://go.galegroup.com/ps/i.do?id=GALE%7CH1420002699&v=2 1&u= cclc_reed&it= r&p=LitRC&sw
80p. Papercutz, $13.99 (9781629917399). 741.5. Gr. 2-5.
The material created replaced the normal material used for previous swimsuits like Nylon, Spandex and the paperlike material. The suits material is extremely thin and foam like and covers the swimmer from the neck to the ankles. The modification of the new material polyurethane has improved performance in various ways. The new material is able to enclose and trap tiny pockets of gas
Heat stress is a condition in which the increase in core body temperature overwhelms the body’s homeostatic thermoregulation abilities, thus producing and absorbing more heat than the body could dissipate [1]. This results in a wide spectrum of heat-related illnesses, ranging from minor conditions such as heat cramps and heat exhaustion to the more severe condition known as heat stroke. Heat stroke is defined as a core body temperature of beyond 40.60C, commonly associated with the dysfunction of the Central Nervous System (CNS) and the failure of multiple organ systems, which may ultimately result in disability or death. [2] Heat stress can be categorized into two different entities: classical and exertional. Classical or environmental heat
Introduction: The objective for the lab was to determine properties of materials by using a tension test. The properties that were determined was Young’s Modulus, ultimate tensile strength, and yield strength. Three aluminum alloys were tested. The first was the AA 2024 , which is high strength used in aerospace applications.