The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Fariborz Haghighat - One of the best experts on this subject based on the ideXlab platform.
-
development of artificial neural network based Heat Convection algorithm for thermal simulation of large rectangular cross sectional area earth to air Heat exchangers
Energy and Buildings, 2010Co-Authors: Jian Zhang, Fariborz HaghighatAbstract:An Earth-to-Air Heat Exchanger (ETAHE) is a low energy cooling and Heating building component. It uses the ground's thermal storage to dampen ambient air temperature oscillations by delivering the air through a horizontally buried duct. To reduce airflow resistance, some hybrid ventilated buildings have recently adopted large cross-sectional area ducts. This paper describes the development of an Artificial Neural Network based Heat Convection (ANN-HC) algorithm to predict local average Nusselt Numbers along the duct surfaces. Furthermore, the ANN-HC algorithm is integrated with a transient three-dimensional Heat transfer model based on finite element analysis of Heat conduction in the ground domain surrounding the ETAHE to establish a new thermal modeling method for ETAHEs. A case study is presented to demonstrate the working principle of the new method. It is shown that the method can very well simulate the interactions between an ETAHE and its environment.
-
convective Heat transfer prediction in large rectangular cross sectional area earth to air Heat exchangers
Building and Environment, 2009Co-Authors: Jian Zhang, Fariborz HaghighatAbstract:An Earth-to-Air Heat Exchanger (ETAHE) uses the ground's thermal storage capacity to dampen ambient air temperature oscillations by delivering the outdoor air to the indoors through a horizontally buried duct. With their lower airflow resistance, large cross-sectional area ETAHEs have been found to be more energy efficient than the conventional small ones, especially when integrated in hybrid ventilation systems. However, the lack of available methods for determining the Heat Convection at the duct surfaces has made accurate energy simulation and proper system design overly difficult. In this study, numerical experiments using computational fluid dynamics (CFD) were conducted to investigate the airflow and thermal behavior in the large ducts. A two-layer turbulence model was used to ensure accuracy in resolving the flow information in the near-wall region, which is critical for predicting accurate Heat Convection. The modeling method was verified by comparing its results with measurements from literature. Parametric studies were conducted to identify the influential design and operation variables for the Heat Convection. Thirty numerical experimental setups designed with the Latin Hypercube Sampling method were simulated to prepare a database with six design parameters as the simulation inputs and average Nusselt numbers over the duct ceiling, wall, and floor as the outputs. Based on the database an artificial neural network (ANN) model was trained to build a mathematical relation between the design variables and the Nusselt numbers. The developed ANN model showed very accurate prediction when compared with test data.
Jian Zhang - One of the best experts on this subject based on the ideXlab platform.
-
development of artificial neural network based Heat Convection algorithm for thermal simulation of large rectangular cross sectional area earth to air Heat exchangers
Energy and Buildings, 2010Co-Authors: Jian Zhang, Fariborz HaghighatAbstract:An Earth-to-Air Heat Exchanger (ETAHE) is a low energy cooling and Heating building component. It uses the ground's thermal storage to dampen ambient air temperature oscillations by delivering the air through a horizontally buried duct. To reduce airflow resistance, some hybrid ventilated buildings have recently adopted large cross-sectional area ducts. This paper describes the development of an Artificial Neural Network based Heat Convection (ANN-HC) algorithm to predict local average Nusselt Numbers along the duct surfaces. Furthermore, the ANN-HC algorithm is integrated with a transient three-dimensional Heat transfer model based on finite element analysis of Heat conduction in the ground domain surrounding the ETAHE to establish a new thermal modeling method for ETAHEs. A case study is presented to demonstrate the working principle of the new method. It is shown that the method can very well simulate the interactions between an ETAHE and its environment.
-
convective Heat transfer prediction in large rectangular cross sectional area earth to air Heat exchangers
Building and Environment, 2009Co-Authors: Jian Zhang, Fariborz HaghighatAbstract:An Earth-to-Air Heat Exchanger (ETAHE) uses the ground's thermal storage capacity to dampen ambient air temperature oscillations by delivering the outdoor air to the indoors through a horizontally buried duct. With their lower airflow resistance, large cross-sectional area ETAHEs have been found to be more energy efficient than the conventional small ones, especially when integrated in hybrid ventilation systems. However, the lack of available methods for determining the Heat Convection at the duct surfaces has made accurate energy simulation and proper system design overly difficult. In this study, numerical experiments using computational fluid dynamics (CFD) were conducted to investigate the airflow and thermal behavior in the large ducts. A two-layer turbulence model was used to ensure accuracy in resolving the flow information in the near-wall region, which is critical for predicting accurate Heat Convection. The modeling method was verified by comparing its results with measurements from literature. Parametric studies were conducted to identify the influential design and operation variables for the Heat Convection. Thirty numerical experimental setups designed with the Latin Hypercube Sampling method were simulated to prepare a database with six design parameters as the simulation inputs and average Nusselt numbers over the duct ceiling, wall, and floor as the outputs. Based on the database an artificial neural network (ANN) model was trained to build a mathematical relation between the design variables and the Nusselt numbers. The developed ANN model showed very accurate prediction when compared with test data.
Kenneth E Goodson - One of the best experts on this subject based on the ideXlab platform.
-
investigation of the natural Convection boundary condition in microfabricated structures
International Journal of Thermal Sciences, 2008Co-Authors: Jack X Hu, Ankur Jain, Kenneth E GoodsonAbstract:Heat loss through surrounding air has an important thermal effect on microfabricated structures. This effect is generally modeled as a natural Convection boundary condition. However, the correct procedure for the determination of the convective coefficient (h) at microscales continues to be debated. In this paper, a microHeater is fabricated on a suspended thin film membrane. The natural Convection on the microHeater is investigated using 3-omega measurements and complex analytical modeling. It is found that the value of h that fits experimental data should have an apparently larger value than that at larger scales; however, it is also shown that the increased h is actually contributed by Heat conduction instead of Heat Convection. A method of determining the correct h that can be used for microfabricated structures is proposed by using the Heat conduction shape factor.
-
investigation of the natural Convection boundary condition in microfabricated structures
ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging o, 2005Co-Authors: Ankur Jain, Kenneth E GoodsonAbstract:Heat loss through surrounding air has important thermal effect on microfabricated structures. This effect is generally modeled as a natural Convection boundary condition. However, how to determine the convective coefficient (h) at microscales is a debate. In this paper, a micro Heater is fabricated on a suspended thin film membrane. The natural Convection is investigated using the 3-omega measurements and complex analytical modeling. It is found that h seems larger than that at larger scales; however, it is also proved that the increased h is actually contributed by Heat conduction instead of Heat Convection. A method of determining the phenomenal h that can be used for microfabricated structures is proposed by using the Heat conduction shape factor.Copyright © 2005 by ASME
Chong Wang - One of the best experts on this subject based on the ideXlab platform.
-
collocation methods for uncertain Heat Convection diffusion problem with interval input parameters
International Journal of Thermal Sciences, 2016Co-Authors: Chong Wang, Zhiping Qiu, Yaowen YangAbstract:Abstract This paper proposes a full grid interval collocation method (FGICM) and a sparse grid interval collocation method (SGICM) to solve the uncertain Heat Convection-diffusion problem with interval input parameters in material properties, applied loads and boundary conditions. The Legendre polynomial series is adopted to approximate the functional dependency of temperature response with respect to the interval parameters. In the process of calculating the expansion coefficients, FGICM evaluates the deterministic solutions directly on the full tensor product grids, while the Smolyak sparse grids are reconstructed in SGICM to avoid the curse of dimensionality. The eventual lower and upper bounds of temperature responses are easily predicted based on the continuously-differentiable property of the approximate function. Comparing results with traditional Monte Carlo simulations and perturbation method, the numerical example evidences the remarkable accuracy and effectiveness of the proposed methods for interval temperature field prediction in engineering.
-
interval analysis of steady state Heat Convection diffusion problem with uncertain but bounded parameters
International Journal of Heat and Mass Transfer, 2015Co-Authors: Chong Wang, Zhiping QiuAbstract:Abstract In this paper, a sensitivity-based interval analysis method (SIAM) and an interval parameter perturbation method (IPPM) are proposed to estimate temperature intervals for the steady-state Heat Convection–diffusion problem with uncertainties in material properties, external loads and boundary conditions. Interval variables are used to characterize the uncertain parameters in the face of limited information. The first-order Taylor expansions are employed in SIAM, while IPPM introduces the surface rail generation method to approximate interval matrices and vectors. Some high-order terms of the Neumann series are retained to calculate the interval matrix inverse in IPPM. By comparing the results with traditional Monte Carlo simulations, two numerical examples are given to demonstrate the feasibility and effectiveness of the proposed approaches at predicting the uncertain temperature field.
-
uncertainty analysis for Heat Convection diffusion problem with large uncertain but bounded parameters
Acta Mechanica, 2015Co-Authors: Chong Wang, Zhiping Qiu, Xianjia ChenAbstract:To extend the restricted applicability of the traditional perturbation method with small uncertainty level, this paper presents a first-order subinterval parameter perturbation method (FSPPM) and a modified subinterval parameter perturbation method (MSPPM) to solve the Heat Convection-diffusion problem with large interval parameters in material properties, external loads and boundary conditions. Based on the subinterval theory, the original uncertain-but-bounded parameters with limited information are divided into several small subintervals. The eventual response interval is assembled by the interval union operation. In both methods, the Taylor series is used to approximate the interval matrix and vector. The inversion of interval matrix in FSPPM is evaluated by the first-order Neumann series, while the modified Neumann series with higher-order terms is proposed to calculate the interval matrix inverse in MSPPM. By comparing the results with the traditional Monte Carlo simulation, two numerical examples evidence the remarkable accuracy and effectiveness of the proposed methods at predicting an uncertain temperature field in engineering.
Raed Abed Mahdi - One of the best experts on this subject based on the ideXlab platform.
-
review of Convection Heat transfer and fluid flow in porous media with nanofluid
Renewable & Sustainable Energy Reviews, 2015Co-Authors: Raed Abed Mahdi, Kannan M. Munisamy, H A Mohammed, Nawaf H. SaeidAbstract:There are two advantages of using porous media. First, its dissipation area is greater than the conventional fins that enhances the Heat Convection. Second is the irregular motion of the fluid flow around the individual beads which mixes the fluid more effectively. Nanofluids result from the mixtures of base fluid with nanoparticles having dimensions of (1–100) nm, with very high thermal conductivities; as a result, it would be the best Convection Heat transfer by using two applications together: porous media and nanofluids. This article aims to summarize the published articles in respect to porosity, permeability (K) and inertia coefficient (Cf) and effective thermal conductivity (keff) for porous media, also on the thermophysical properties of nanofluid and the studies on Convection Heat transfer in porous media with nanofluid.
