《CFDcoursework》由会员分享，可在线阅读，更多相关《CFDcoursework（19页珍藏版）》请在金锄头文库上搜索。
1、Contents1. Introduction21.1The method of solution21.2The relaxation factors22.Tube bundles32.1Geometry32.2 Mesh generation42.3boundary conditions and model42.4result and discussion52.4.1Velocity distribution52.4.2 Comparison of the heat transfer coefficient62.4.3The heat transfer under different vel
2、ocity72.4.4 The temperature and pressure drop of different inlet velocity82.5Conclsuion of the water water heat exchanger103. Introduction of the room radiator103.1geometry and boundary conditions113.2Mesh generation113.3 Result and discussion123.3.1The convection heat transfer rate from radiator123
3、.3.2The room heat loss143.4Conclusion15Reference16Appendix171. IntroductionIn this paper, two different types of heat exchanger will be modelled to get fluid flow and heat transfer, which are forced convection heat transfer across a water to water heat exchanger in a duct for waste heat recovery (Th
4、e tube banks or bundles) and natural convection from a radiator in a room for central heating.1.1The method of solution In the present work, simulations were performed under steady conditions, all the computational work was carried out using the software workbench, which is based on control volume m
5、ethod. For the discretization of the unsteady terms and pressure gradient term, the geometry will be decomposed into a computational mesh and then the each integral equation will be discretised into algebraic equation at a set of nodes. In this case study, flow is assumed to be Newtonian and incompr
6、essible, and the model will be solved by the standard k-epsilon model with enhanced wall treatment. The governing equation(1) for turbulent flow is:()t+u-e=S (1)Where t, and u represent the time ,density, and mean flow velocity, means the vector of direction. e And S are effective diffusion and sour
7、ce respectively. The three dimensionless multipliers, the Reynolds number (2), the Prandtl number (3) and Nusselt number (4) are defined as follows:Re=Ud (2)Pr=Cpk (3)Nu=hDk=qTs-Tdk (4)Where the is the density of the fluid; U is the velocity of the fluid; d is the diameter of the tube; is the dynami
8、c viscosity; Cp is the specific heat of the fluid and k is the thermal conductivity of the fluid. Depending upon the maximum velocity, the Reynolds number (5) for the any arrangement can be defined as:Re=DUmaxWhere D and represent present the tube diameter and kinematic viscosity of fluid. The Umax
9、can use the equationUmax=USTST-d to calculate.1.2The relaxation factorsA sensitivity study was carried out by varying the relaxation parameter with the values of 0.1,0.30.7 and 1.2eshita.in this case study ,the relaxation factors is shown as below: The factors of pressure is 0.3,the density is 1,the
10、 momentum is 0.7 and the turbulent kinetic energy is 0.8,turbulent viscosity is 1;energy is 1. 2. Tube bundlesIn many types of heat exchangers, the tubes are arranged as a bundle or a bank in an in-line or staggered manner. Typically, one fluid flows over the tube banks, while the other fluid which
11、has different temperature passes through the tubes c.k and w.a.Due to the outside fluid flows cross over the tube bundles, the transverse velocity component of fluid is enlarged significantly. A non-uniformity of the flow distribution accompanying the secondary flow comes into been, which enhances t
12、he turbulence and augments the heat transfer on the tube surfaces, and leads to the characteristics is very different from that of fluid flowing parallel to tubes. T,KThere are many different ranges of geometry of tube bundles which have been investigated about the convective heat transfer character
13、istics colburn ,and zu. Many researchers proposed a correlation of the heat transfer coefficient as the fluid Reynolds numbers, Prandtl numbers of fluid and tube surface. In this case study, a staggered tube bundles in a cross-flow duct will be investigated. The characteristics of fluid flow and hea
14、t transfer for tube banks with different velocity were investigated by adopting an idealized flow model in the software workbench, using the water as fluid and aluminium as the tubes materials. Meanwhile, the heat transfer rate of each row also will be compared with the heat transfer rate of whole tube bundles. After the discussion, this paper will show the simplified conclusion that of the cross flowing velocity effects on the character
