Begell House Inc.
Heat Transfer Research
HTR
1064-2285
48
3
2017
EXPERIMENTAL AND CFD INVESTIGATION OF LIQUID FLOW OUTSIDE EVAPORATION TUBES AND ITS INFLUENCE ON HEAT TRANSFER
191-209
10.1615/HeatTransRes.2016011566
Chunhua
Qi
Institute of Seawater Desalination & Multipurpose Utilization, SOA, Tianjin 300192, China
Houjun
Feng
Institute of Seawater Desalination & Multipurpose Utilization, SOA, Tianjin 300192, China
Qingchun
Lv
Institute of Seawater Desalination & Multipurpose Utilization, SOA, Tianjin 300192, China
Yulei
Xing
Institute of Seawater Desalination & Multipurpose Utilization, SOA, Tianjin 300192, China
Ming
Zhang
Institute of Seawater Desalination & Multipurpose Utilization, SOA, Tianjin 300192, China
falling-film evaporator
experimental investigation
CFD
VOF
Liquid film flow significantly affects distillation, which directly determines the heat transfer coefficient. This study investigates the effects of flow patterns, as well as of heat and mass transfer on the vapor−liquid interface, on the heat transfer in a horizontal-tube falling-film evaporator. Related data are acquired through simulation and experiment. A volume of fluid model coupled with a user-defined function module was adopted to simulate a liquid−vapor system. In addition, an experimental apparatus and its principal characteristics were introduced. This method was used to test the extended droplets on the tube surface, the flow patterns, and the effect of liquid film state on heat transfer. Simulation results show good agreement with the experimental results, with both having a deviation band within 10%. A computational method suitable for simulating liquid−steam flow is established. Both simulation and experimental results indicate that 0.08 kg/(m·s) of sprinkling density is the breakpoint of liquid outside a tube from columnar flow to sheet flow, and the overall coefficient of heat transfer K under the experimental conditions reaches up to 4.06 kW/m2·K. This value is significant in guiding the design of the spraying density of low-temperature multieffect seawater desalination devices. Thus, this research provides a basis for the further improvement of heat transfer performance.
HEAT TRANSFER IN A CHANNEL WITH INTERMITTENT HEATED ALUMINUM-FOAM HEAT SINKS
211-220
10.1615/HeatTransRes.2016008380
Ayla
Dogan
Department of Mechanical Engineering, Faculty of Engineering, Akdeniz University TR-07058, Antalya, Turkey
Bahadir
Oney
Department of Mechanical Engineering, Faculty of Engineering, Akdeniz University TR-07058, Antalya, Turkey
aluminum-foam heat sink
heat transfer
electronic cooling
channel flow
This work experimentally studied heat transfer associated with three aluminum-foam heat sinks having various porosity size of 10, 20, and 40 PPI (pore per inch). Air was used as the coolant. Aluminum-foam heat sinks have been placed in discrete form on heat sources in a rectangular channel in order to investigate the heat transfer effect on the electronic equipment performance. The lower surface of the channel was equipped with 8 × 2 aluminum-foam heat sinks placed on copper blocks subjected to a uniform heat flux. All the channel surfaces were insulated. The experimental study was made for Reynolds numbers varying from 531 to 2461, while the Grashof number ranged from 4.2 × 107 to 2.7 × 108. The results show that the row-averaged Nusselt number values increase with increasing Grashof number for all pore densities. While the first row of the foam is affected by forced convection flow, with increase in the buoyancy-induced flow and the onset of instability, the row-averaged Nusselt number increases around the middle section of the rows because of the heat transfer enhancement. Comparisons made between the foams having different pore densities show that the 10 PPI aluminum-foam heat sink displays 3% and 18% higher Nusselt number values than those of the 20 PPI and the 40 PPI, respectively, because of its high permeability and low pore density characteristics. The results obtained also represent that the aluminum-foam heat sinks show 2 to 3 times higher thermal performance than those of no aluminum-foam case in the channel.
HEAT TRANSFER IN NANOFLUID MHD FLOW IN A CHANNEL WITH PERMEABLE WALLS
221-238
10.1615/HeatTransRes.2016011839
Mehdi
Fakour
Young Researchers and Elite Club, Sari Branch, Islamic Azad University
Davood
Domiri Ganji
Babol Noshirvani university of technology, Babol
A.
Khalili
Department of Mechanical Engineering, Iran University, Tehran, Iran
A.
Bakhshi
Department of Mechanical Engineering, Babol University of Science and Technology, Babol, Iran
Least Square Method (LSM)
laminar viscous flow
heat transfer
uniform magnetic field
permeale wall channel
In this paper, heat transfer in laminar flow in a channel with permeable walls in the presence of a transverse magnetic field is investigated. The Least Square Method (LSM) is used for solving approximate nonlinear differential equations governing the problem. We have tried to show reliability and performance of the present method compared with the Runge−Kutta numerical method (fourth-rate) to solve this problem. The influence of the four dimensionless numbers: the Hartmann number, Reynolds number, Prandtl number, and the Eckert number on nondimensional velocity and temperature profiles are considered. The results show that the present analytical method is very close to the numerical method. In general, increasing the Reynolds and Hartman numbers reduces the nanofluid flow velocity in the channel and the maximum value of temperature increase and increasing the Prandtl and Eckert number will increase the maximum value of temperature.
ADAPTIVE BOUNDARY INPUT HEAT FLUX AND TEMPERATURE ESTIMATION IN A THREE-DIMENSIONAL DOMAIN
239-261
10.1615/HeatTransRes.2016010870
Nauman
Malik Muhammad
University Brunei Darussalam
adaptive state estimation
Kalman filter
inverse heat conduction
Adaptive state estimator is deployed in this study that works by incorporating the semi-Markovian concept into a Bayesian estimation technique thereby developing an inverse input and state estimator consisting of a bank of parallel adaptively weighted Kalman filters. The problem presented here deals with a three-dimensional system of a cube with one face conducting heat flux and all the other sides being insulated while the temperatures are measured on the accessible faces of the cube. A variety of input heat flux scenarios have been examined to underwrite the robustness of the estimation algorithm and hence insure its usability in practical applications. The analysis and method were not applied previously and the numerical procedure is of great value in predicting input and state in many practical applications where it is not possible to directly measure the input heat flux and temperature distribution in a three-dimensional (3D) domain.
SEEPAGE HEAT TRANSFER BETWEEN CLINKER AND COOLING AIR WITH VARIABLE PROPERTIES OF THE GRATE COOLER
263-281
10.1615/HeatTransRes.2016011341
Meiqi
Wang
School of Mechanical Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, China
Bin
Liu
School of Information Science and Engineering, Yanshan University, Qinhuangdao 066004, China
Yan
Wen
School of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China
Haoran
Liu
School of Information Science and Engineering, Yanshan University, Qinhuangdao 066004, China
porous media
cement clinker
seepage heat transfer
numerical simulation
Heat transfer between a clinker layer and cooling air was studied by using the mechanics of the flow in porous media. Considering local thermal nonequilibrium and thermal dispersion effect, a seepage heat transfer model for compressible fluid flowing through a porous clinker layer was constructed with variable properties of a grate cooler. A solution algorithm for thermally coupled seepage was proposed. The effects of main working parameters, wind pressure, and grate speed on the clinker cooling process were shown. The simulation results showed that there was a large deviation between the variable properties model and constant properties model. The variable properties model can make a more accurate description for the temperature distribution of the clinker layer. With increase in wind pressure, the air temperature and clinker temperature drop while the seepage velocity increases. When raising the grate speed at an invariant feed rate, the seepage velocity increases, the air temperature inside the clinker layer and the clinker temperature at the top of the front clinker layer drop, while the clinker temperature in other regions increases. When raising the grate speed at a certain thickness of the clinker layer, the low velocity area increases while the air temperature and clinker temperature in the clinker layer increase.