A Zonal Model for Large Enclosures With Combined Stratification Cooling and Natural Ventilation: Part 1—Model Generation and its Procedure

2005 ◽  
Vol 128 (3) ◽  
pp. 367-375 ◽  
Author(s):  
Jun Gao ◽  
Jia-ning Zhao ◽  
Xiao-dong Li ◽  
Fu-sheng Gao
Keyword(s):  
Heat Transfer ◽  
Air Conditioning ◽  
Natural Ventilation ◽  
Influential Factors ◽  
Temperature Profiles ◽  
Combined System ◽  
Zonal Model ◽  
Flow And Heat Transfer ◽  
Heat Penetration ◽  
Zonal Models

This paper describes a combined system of stratificated air conditioning and natural ventilation for large enclosures, which uses stratificated air conditioning to cool the occupied part of a space and uses natural ventilation to cool the upper part to reduce heat penetration into the lower air-conditioned part. A zonal model is constructed to predict the vertical temperature profiles of large enclosures under such a combined system. This model incorporates airflow and heat transfer throughout the space into the mass and heat balance equations for each horizontally settled zone. It introduces some particular flow dynamics and thermal effects into the predictions of mean airflows and temperature distributions. Different from those pressure-based zonal models applied generally to the predictions for small building rooms, it is termed a temperature-based zonal model, which uses correlations based on temperature differences in combination with submodels for modeling of mass flow and heat transfer in the large enclosures. The present paper provides a calculation procedure for the model. Model performances are then discussed through analyzing the impacts of some influential factors on the space air temperature profiles.

Prediction of the Vertical Temperature Distribution in a Large Enclosure Under Combined Air Conditioning and Natural Ventilation

Solar Energy ◽  
2004 ◽  
Author(s):  
Jun Gao ◽  
Xiao-Dong Li ◽  
Jia-Ning Zhao ◽  
Fu-Sheng Gao
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Air Temperature ◽  
Air Conditioning ◽  
Natural Ventilation ◽  
Vertical Temperature ◽  
Combined System ◽  
Efficient System ◽  
Macro Scale ◽  
Vertical Temperature Distribution

This paper describes a combined system of air conditioning and natural ventilation for large enclosures. A multi-zonal model to simulate the vertical temperature distribution is established. This model describes airflow and heat transfer on a ‘macro’ scale compared to CFD model, but it appears very efficient for engineering application. In this model, air density is considered to change with air temperature. Multiple air jets, buoyancy driven natural ventilation and coupled heat transfer are taken into consideration. It is governed by non-linear equations and is resolved by an iterative solution. A program is compiled to calculate the mass flow and temperature distributions. It shows that the combined system of air conditioning and natural ventilation cut considerably down heat gain in occupied zone. By comparison, the combined system can be expected to give lower temperature both in the enclosure and on interior surfaces. Some cases are calculated, and the results suggest that it depends on many factors such as the height of ventilating opening, the effective opening area, and outdoor air temperature to effectively make use of natural ventilation in the combined system. To sum up, this paper presents an energy efficient system for large spaces and also a theoretical model to design the system and predict the vertical temperature distribution.

scholarly journals Flow and Heat Transfer in a Liquid Film over a Permeable Stretching Sheet

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
R. C. Aziz ◽  
I. Hashim ◽  
A. K. Alomari
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Stretching Sheet ◽  
Temperature Fields ◽  
Temperature Profiles ◽  
Suction Parameter ◽  
Boundary Layer Equations ◽  
Similarity Transformations ◽  
Flow And Heat Transfer ◽  
Homotopy Analysis

An analysis has been carried out to study the flow and heat transfer in a liquid film over a permeable stretching sheet. Using similarity transformations, the time-dependent boundary layer equations are reduced to a set of nonlinear ordinary differential equations. The resulting parameter problem and velocity as well as temperature fields are solved using the homotopy analysis method (HAM). Analytic series solutions are given, and numerical results for velocity and the temperature profiles are presented through graphs of different values for pertinent parameter. The effects of unsteadiness parameter and permeability parameter on the velocity and temperature profiles are explored for different values of blowing or suction parameter.

Vertical Temperature Profiles and Cooling Load in Large Spaces Ventilated by Stratified Air-Conditioning Systems: Scale-Model Experiment and Nodal Modeling

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Yukun Xu ◽  
Xin Wang ◽  
Chenlu Shi ◽  
Xiaoqiang Huai ◽  
Fei Wang
Keyword(s):  
Heat Transfer ◽  
Air Temperature ◽  
Air Conditioning ◽  
Heat Transfer Process ◽  
Scale Model ◽  
Temperature Profiles ◽  
Model Experiments ◽  
Thermal Environments ◽  
Load Calculation ◽  
Nodal Model

Abstract An improved heat balance nodal model is proposed to predict the inner wall temperature profiles and calculate the stratified air-conditioning load in large spaces. The model aims to weaken the correlation between load calculation methods and indoor airflow patterns, and to ensure the synchronization of each heat transfer process, so as to be closer to actual situations. The scale-model experiments were conducted in an enthalpy different laboratory in University of Shanghai for Science and Technology (USST) in Shanghai, China. This paper took the air distribution of nozzle air supply system as an example to calculate the inner wall temperatures and the stratified air-conditioning load by the nodal model and verified by the scale-model experiments. The results showed the maximum deviations of the experimental and theoretical values for the inner wall temperatures, the heat transfer load from the nonair-conditioned (NAC) area and the stratified air-conditioning load were all within 5%. The effects of the air temperature in the NAC area on the heat transfer load from the NAC area and the stratified air-conditioning load were analyzed, and the load nomogram was produced. It was found the heat transfer load from the NAC area accounted for 10–30% of the stratified air-conditioning load. The load nomogram compared two methods for determining the air temperature in the NAC area and gave the recommended one. The findings in this paper can be used to further develop load calculation models for non-uniform thermal environments.

Numerical Computation of Fluid Flow and Heat Transfer in Microchannels

2005 ◽  
Author(s):  
Ningli Liu ◽  
Rene Chevray ◽  
Gerald A. Domoto ◽  
Elias Panides
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Energy Equation ◽  
Stokes Equations ◽  
Numerical Approach ◽  
Time Dependent ◽  
Navier Stokes ◽  
Temperature Profiles ◽  
Navier Stokes Equations ◽  
Flow And Heat Transfer

A finite difference numerical approach for solving slightly compressible, time-dependent, viscous laminar flow is presented in this study. Simplified system of Navier-Stokes equations and energy equation are employed in the study in order to perform more efficient numerical calculations. Fluid flow and heat transfer phenomena in two dimensional microchannels are illustrated numerically in this paper. This numerical approach provides a complete numerical simulation of the development of the fluid flow and the temperature profiles through multi-dimensional microchannels.

scholarly journals SIMILARITY AND NONSIMILARITY SOLUTIONS ON FLOW AND HEAT TRANSFER OVER A WEDGE WITH POWER LAW STREAM CONDITION

2015 ◽  
Vol 1 (1) ◽  
pp. 5
Author(s):  
M. Ismoen ◽  
M. F. Karim ◽  
R. Mohamand ◽  
R. Kandasamy
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Differential Equations ◽  
Power Law ◽  
Wall Temperature ◽  
Buoyancy Force ◽  
Free Stream ◽  
Stream Velocity ◽  
Temperature Profiles ◽  
Flow And Heat Transfer

<p class="TRANSAffiliation"><span>The similarity and non-similarity analysis are presented to investigate the effect of buoyancy force on the steady flow and heat transfer of fluid past a heated wedge. The fluid is assumed to be a Newtonian, viscous and incompressible. The wall of the wedge is an impermeable with power law free stream velocity and a wall temperature. Due to the effect of a buoyancy force, a power law of free stream velocity and wall temperature, then the flow field is similar when <em>n = 2m - 1</em>, otherwise is non-similar when <em>n ≠ 2m - 1</em>. The governing boundary layer equations are written into dimensionless forms of ordinary differential equations by means of Falkner-Skan transformation. The resulting ordinary differential equations are solved by Runge-Kutta Gill with shooting method for finding a skin friction and a rate of heat transfer. The effects of buoyancy force and non-uniform wall temperature parameters on the dimensionless velocity and temperature profiles are shown graphically. Comparisons with previously published works are performed and excellent agreement between the results is obtained. The conclusion is drawn that the flow field and temperature profiles are significantly influenced by these parameters.</span></p>

scholarly journals Impact of Square Fuel Assemblies Arrangement on Fluid Flow and Heat Transfer Enhancement inside Water Filled Enclosures

2016 ◽  
Vol 64 ◽  
pp. 144-158
Author(s):  
Karim Ragui ◽  
Abdelkader Boutra ◽  
Youb Khaled Benkahla
Keyword(s):  
Heat Transfer ◽  
Thermal Characteristics ◽  
Computer Code ◽  
Temperature Profiles ◽  
Transfer Enhancement ◽  
Flow And Heat Transfer ◽  
Simpler Algorithm ◽  
Fuel Assemblies ◽  
Volume Method ◽  
Do So

Through this paper, the hydrodynamic and thermal characteristics of a Newtonian fluid within a square cold enclosure containing four inner heaters, arranged in different manners, are numerically investigated. To do so, a developed computer code based on the finite volume method and the SIMPLER algorithm is used. The validity of the latter was ascertained after the comparison between the obtained results and the experimental and numerical ones already available in the literature. To make clear the effect of pertinent parameters such the Rayleigh number and the distance between these heaters, the phenomenon was reported by means of Streamlines, Isotherm plots, velocity and temperature profiles, with a special attention to the local and average Nusselt number evolution. As shown in the latter, taking into account the heaters’ arrangement into the enclosure leads to a significant improvement of the overall transfer. Consequently, powerful correlations predicting the heat transfer ratio into the cold square as a function of the heaters’ disposition are proposed which predict within ±1% the numerical results.

Influence of Jet-Grid Turbulence on Flat Plate Turbulent Boundary Layer Flow and Heat Transfer

1992 ◽  
Vol 114 (1) ◽  
pp. 65-72 ◽  
Author(s):  
C. D. Young ◽  
J. C. Han ◽  
Y. Huang ◽  
R. B. Rivir
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulence Intensity ◽  
Surface Heat ◽  
Length Scale ◽  
Grid Turbulence ◽  
Temperature Profiles ◽  
Flow And Heat Transfer ◽  
Turbulent Boundary Layer Flow ◽  
Layer Flow

The influence of high mainstream turbulence on turbulent boundary layer flow and heat transfer is experimentally investigated for length Reynolds numbers between 4 × 104 and 1.5 × 106. The high mainstream turbulence is produced by a round tube grid with uniform jet injection. Injected air is blown in either an upwind or downwind direction at a controllable flow rate. A flat plate test section instrumented with foil thermocouples is located downstream from the jet grid. The turbulence intensity decay and length scale growth along the test plate, the mean velocity and temperature profiles across the boundary layer, and surface heat transfer distribution are measured. The results show that the grid with downwind injection produces a slightly higher turbulence intensity and a smaller length scale than the grid with upwind injection. A higher turbulence intensity and a smaller length scale further enhance the surface heat transfer coefficient. The jet-induced high turbulence does not alter the downstream velocity and temperature profiles in their logarithmic regions, but the wake regions are lower than the zero turbulence profiles. The Reynolds analogy factor, the augmented friction factor, and the augmented Stanton number are higher than those from existing correlations when the jet grid turbulence intensity is greater than 6 percent.

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