scholarly journals THE INFLUENCE OF THERMAL RESISTANCE AND THERMAL MASS ON THE SEASONAL PERFORMANCE OF WALLING SYSTEMS IN AUSTRALIA

2015 ◽  
Vol 10 (4) ◽  
pp. 107-126 ◽  
Author(s):  
Dariusz Alterman ◽  
Adrian W. Page ◽  
Behdad Moghtaderi ◽  
Congcong Zhang ◽  
Trevor Moffiet
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Thermal Mass ◽  
New Approach ◽  
Comfort Levels ◽  
Building Enclosures ◽  
Seasonal Performance ◽  
Brick Veneer ◽  
R Value ◽  
Time Required

This paper describes an experimental investigation of the thermal performance of four Australian domestic walling systems (cavity brick, insulated cavity brick, insulated brick veneer and insulated reverse brick veneer) having various combinations of thermal insulation and of thermal mass location within the wall. This experimental analysis extends further the previous studies of the benefits of thermal mass on the overall thermal performance of building enclosures (Gregory et al. 2008, Luo at al. 2008, Alashaary et al. 2009). The comparison is based on the time required to maintain thermal comfort for free-floating internal conditions. The results clearly show that internal comfort levels are influenced by both the thermal resistance of the walls as well as the extent and location of the thermal mass, with neither parameter being the sole predictor. The best thermal performance is therefore obtained by an appropriate combination of thermal mass and resistance, rather than focussing on the overall wall thermal resistance (R-value) alone. A new approach of density temperature plots for comparison of temperature variation is also used in the assessment of module thermal performance.

scholarly journals Use of Dissimilar Walling Systems on Residential Building Envelopes for Improving Their Thermal Performance

2009 ◽  
Vol 4 (2) ◽  
pp. 107-125
Author(s):  
Katherine Gregory ◽  
Behdad Moghtaderi ◽  
Adrian Page
Keyword(s):  
Energy Consumption ◽  
Thermal Performance ◽  
Residential Building ◽  
Climatic Conditions ◽  
Building Envelope ◽  
Thermal Mass ◽  
Building Envelopes ◽  
Numerical Predictions ◽  
Brick Veneer ◽  
East And West

This paper summarises the results of a combined numerical, statistical and experimental study concerned with the use of dissimilar walling systems on the external parts of a given building envelope. The rational behind this “hybrid wall” concept, as opposed to conventional approaches where identical walls are used in a building envelope, is to achieve a more effective distribution of thermal mass across the envelope and, hence, improve the overall thermal performance of the building. The effectiveness of the “hybrid wall” concept was investigated using a series of hypothetical building modules of common Australian residential constructions, namely Light Weight (LW), Brick Veneer (BV), Reverse Brick Veneer (RBV) and Cavity Brick (CB). These designs were examined numerically using a commercial energy rating tool known as “AccuRate”, statistically using JMP software and experimentally using a novel bench-scale setup developed as part of this study. The performance of each design was evaluated by its energy consumption. The numerical predictions and experimental data highlighted that the east and west walls have the most impact on the energy consumption under Australian climatic conditions. It was found that considerable reductions in the energy consumption could be achieved in cases where the hybrid wall concept was implemented through the use of high thermal mass insulated walls on the east and west sides of the building envelope.

scholarly journals The Significance of Temperature Based Approach Over the Energy Based Approaches in the Buildings Thermal Assessment

2017 ◽  
Vol 19 (1) ◽  
pp. 39-50 ◽  
Author(s):  
Aiman Albatayneh ◽  
Dariusz Alterman ◽  
Adrian Page ◽  
Behdad Moghtaderi
Keyword(s):  
Energy Consumption ◽  
Thermal Comfort ◽  
Thermal Performance ◽  
Low Energy ◽  
Heating And Cooling ◽  
Adaptive Thermal Comfort ◽  
Brick Veneer ◽  
Time Required ◽  
Cooling Loads ◽  
Thermal Comfort Model

Abstract The design of low energy buildings requires accurate thermal simulation software to assess the heating and cooling loads. Such designs should sustain thermal comfort for occupants and promote less energy usage over the life time of any building. One of the house energy rating used in Australia is AccuRate, star rating tool to assess and compare the thermal performance of various buildings where the heating and cooling loads are calculated based on fixed operational temperatures between 20 °C to 25 °C to sustain thermal comfort for the occupants. However, these fixed settings for the time and temperatures considerably increase the heating and cooling loads. On the other hand the adaptive thermal model applies a broader range of weather conditions, interacts with the occupants and promotes low energy solutions to maintain thermal comfort. This can be achieved by natural ventilation (opening window/doors), suitable clothes, shading and low energy heating/cooling solutions for the occupied spaces (rooms). These activities will save significant amount of operating energy what can to be taken into account to predict energy consumption for a building. Most of the buildings thermal assessment tools depend on energy-based approaches to predict the thermal performance of any building e.g. AccuRate in Australia. This approach encourages the use of energy to maintain thermal comfort. This paper describes the advantages of a temperature-based approach to assess the building’s thermal performance (using an adaptive thermal comfort model) over energy based approach (AccuRate Software used in Australia). The temperature-based approach was validated and compared with the energy-based approach using four full scale housing test modules located in Newcastle, Australia (Cavity Brick (CB), Insulated Cavity Brick (InsCB), Insulated Brick Veneer (InsBV) and Insulated Reverse Brick Veneer (InsRBV)) subjected to a range of seasonal conditions in a moderate climate. The time required for heating and/or cooling using the adaptive thermal comfort approach and AccuRate predictions were estimated. Significant savings (of about 50 %) in energy consumption in minimising the time required for heating and cooling were achieved by using the adaptive thermal comfort model.

Transient Thermal Analysis for the Automotive Underhood and Underbody Components

2013 ◽  
Author(s):  
Yu Hsien Wu ◽  
Kumar Srinivasan ◽  
Steven Patterson ◽  
Emmanuel Bot
Keyword(s):  
Thermal Analysis ◽  
Thermal Management ◽  
Dissimilar Materials ◽  
Thermal Mass ◽  
New Approach ◽  
The Past ◽  
Full Vehicle ◽  
Development Cycle ◽  
Transient Thermal ◽  
Steady State Solutions

The transient thermal simulation is an important part of thermal management development for new vehicle architectures. Different techniques have been studied in the past to address this coupled conduction/convection/radiation problem. In order to fully capture the transient thermal behavior of various underhood and underbody components, it is also necessary to accurately model the thermal mass of each part and the thermal links between dissimilar materials. The paper will outline a new, efficient methodology for this type of thermal analysis that shows acceptable results for complex full vehicle thermal analysis without sacrificing accuracy. The methodology is based on approximating the transient convective field with intermittent steady state solutions. The paper will present results from this new approach and compare them with fully transient simulation results as well as experimental data. The new methodology can be optimized to significantly reduce simulation run times without sacrificing accuracy and to be more practical for application in the vehicle development cycle.

Characterizing Bulk Thermal Conductivity and Interface Contact Resistance Effects of Thermal Interface Materials in Electronic Cooling Applications

2003 ◽  
Author(s):  
Vadim Gektin ◽  
Sai Ankireddi ◽  
Jim Jones ◽  
Stan Pecavar ◽  
Paul Hundt
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Contact Resistance ◽  
Thermal Performance ◽  
Electronic Cooling ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Interface Contact ◽  
Interface Materials ◽  
Bulk Thermal Conductivity

Thermal Interface Materials (TIMs) are used as thermally conducting media to carry away the heat dissipated by an energy source (e.g. active circuitry on a silicon die). Thermal properties of these interface materials, specified on vendor datasheets, are obtained under conditions that rarely, if at all, represent real life environment. As such, they do not accurately portray the material thermal performance during a field operation. Furthermore, a thermal engineer has no a priori knowledge of how large, in addition to the bulk thermal resistance, the interface contact resistances are, and, hence, how much each influences the cooling strategy. In view of these issues, there exists a need for these materials/interfaces to be characterized experimentally through a series of controlled tests before starting on a thermal design. In this study we present one such characterization for a candidate thermal interface material used in an electronic cooling application. In a controlled test environment, package junction-to-case, Rjc, resistance measurements were obtained for various bondline thicknesses (BLTs) of an interface material over a range of die sizes. These measurements were then curve-fitted to obtain numerical models for the measured thermal resistance for a given die size. Based on the BLT and the associated thermal resistance, the bulk thermal conductivity of the TIM and the interface contact resistance were determined, using the approach described in the paper. The results of this study permit sensitivity analyses of BLT and its effect on thermal performance for future applications, and provide the ability to extrapolate the results obtained for the given die size to a different die size. The suggested methodology presents a readily adaptable approach for the characterization of TIMs and interface/contact resistances in the industry.

Spreadsheet Tool for Quick-Turn 3D Numerical Modeling of Package Thermal Performance With Non-Uniform Die Heating

2001 ◽  
Author(s):  
Abhay A. Watwe ◽  
Ravi S. Prasher
Keyword(s):  
Finite Element ◽  
Numerical Modeling ◽  
Finite Volume ◽  
Thermal Performance ◽  
Three Dimensional ◽  
3D Numerical Modeling ◽  
Conventional Analysis ◽  
Time Required ◽  
The Impact ◽  
Fourier Equation

Abstract Traditional methods of estimating package thermal performance employ numerical modeling using commercially available finite-volume or finite-element tools. Use of these tools requires training and experience in thermal modeling. This methodology restricts the ability of die designers to quickly evaluate the thermal impact of their die architecture due to the added throughput time required to enlist the services of a thermal analyst. This paper describes the development of an easy to use spreadsheet tool, which performs quick-turn numerical evaluations of the impact of non-uniform die heating. The tool employs well-established finite-volume numerical techniques to solve the steady-state, three-dimensional Fourier equation of conduction in the package geometry. Minimal input data is required and the inputs are customized using visual basic pull-down menus to assist die designers who may not be thermal experts. Data showing comparison of the estimates from the spreadsheet tool with that obtained from a conventional analysis using the commercially available finite element code ANSYS™ is also presented.

Experimental Investigation of Heat Transfer in Impingement Air Cooled Plate Fin Heat Sinks

2005 ◽  
Vol 128 (4) ◽  
pp. 412-418 ◽  
Author(s):  
Zhipeng Duan ◽  
Y. S. Muzychka
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Transfer Model ◽  
Heat Sinks ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Developing Flow ◽  
Rectangular Channels

Impingement cooling of plate fin heat sinks is examined. Experimental measurements of thermal performance were performed with four heat sinks of various impingement inlet widths, fin spacings, fin heights, and airflow velocities. The percent uncertainty in the measured thermal resistance was a maximum of 2.6% in the validation tests. Using a simple thermal resistance model based on developing laminar flow in rectangular channels, the actual mean heat transfer coefficients are obtained in order to develop a simple heat transfer model for the impingement plate fin heat sink system. The experimental results are combined into a dimensionless correlation for channel average Nusselt number Nu∼f(L*,Pr). We use a dimensionless thermal developing flow length, L*=(L∕2)∕(DhRePr), as the independent parameter. Results show that Nu∼1∕L*, similar to developing flow in parallel channels. The heat transfer model covers the practical operating range of most heat sinks, 0.01<L*<0.18. The accuracy of the heat transfer model was found to be within 11% of the experimental data taken on four heat sinks and other experimental data from the published literature at channel Reynolds numbers less than 1200. The proposed heat transfer model may be used to predict the thermal performance of impingement air cooled plate fin heat sinks for design purposes.

Thermal Performance of Micro-Jet Impingement Device With Parallel Flow, Jet-Adjacent Fluid Removal

2018 ◽  
Author(s):  
Todd M. Bandhauer ◽  
David R. Hobby ◽  
Chris Jacobsen ◽  
Dave Sherrer
Keyword(s):  
Reynolds Number ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heated Surface ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Thermal Interface Material ◽  
Cooling Device ◽  
Impingement Cooling ◽  
Jet Array

In a variety of electronic systems, cooling of various components imposes a significant challenge. A major aspect that inhibits the performance of many cooling solutions is the thermal resistance between the chip package and the cooling structure. Due to its low thermal conductivity, the thermal interface material (TIM) layer imposes a significant thermal resistance on the chip to cooling fluid thermal path. Advanced cooling methods that bypass the TIM have shown great potential in research and some specialty applications, yet have not been adopted widely by industry due to challenges associated with practical implementation and economic constraints. One advanced cooling method that can bypass the TIM is jet impingement. The impingement cooling device investigated in the current study is external to the integrated circuit (IC) package and could be easily retrofitted onto any existing microchip, similar to a standard heatsink. Jet impingement cooling has proven effective in previous studies. However, it has been shown that jet-to-jet interference severely degrades thermal performance of an impinging jet array. The present research addresses this challenge by utilizing a flow path geometry that allows for withdrawal of the impinging fluid immediately adjacent to each jet in the array. In this study, a jet impingement cooling solution for high-performance ICs was developed and tested. The cooling device was fabricated using modern advanced manufacturing techniques and consisted of an array of micro-scale impinging jets. A second array of fluid return paths was overlain across the jet array to allow for direct fluid extraction in the immediate vicinity of each jet, and fluid return passages were oriented in parallel to the impinging jets. The following key geometric parameters were utilized in the device: jet diameter (D = 300μm), distance from jet to impinging surface (H/D = 2.5), spacing between jets (S/D = 8), spacing between fluid returns (Sr/D = 8), diameter of fluid returns (Dr/D = 5). The device was mounted to a 2cm × 2cm uniformly heated surface which produced up to 165W and the resulting fluid-to-surface temperature difference was measured at a variety of flow rates. For this study, the device was tested using single-phase water. Jet Reynolds number ranged from 300–1500 and an average heat transfer coefficient of 13,100 W m−2 K−1 was achieved at a Reynolds number of only Red = 305.

Understanding the Impact of Flow Bypass on the Thermal Performance of Air Cooled Heat Sinks

2014 ◽  
Author(s):  
Krishna Kota ◽  
Mohamed M. Awad
Keyword(s):  
Energy Conservation ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Sinks ◽  
Laminar Regime ◽  
Flow Energy ◽  
Factor Α ◽  
The Impact ◽  
Fundamental Mass

In this effort, theoretical modeling was employed to understand the impact of flow bypass on the thermal performance of air cooled heat sinks. Fundamental mass and flow energy conservation equations across a longitudinal fin heat sink configuration and the bypass region were applied and a generic parameter, referred as the Flow Bypass Factor (α), was identified from the theoretical solution that mathematically captures the effect of flow bypass as a quantifiable parameter on the junction-to-ambient thermal resistance of the heat sink. From the results obtained, it was found that, at least in the laminar regime, the impact of flow bypass on performance can be neglected for cases when the bypass gap is typically less than 5% of the fin height, and is almost linear at high relative bypass gaps (i.e., usually for bypass gaps that are more than 10–15% of the fin height). It was also found that the heat sink thermal resistance is more sensitive to small bypass gaps and the effect of flow bypass decreases with increasing bypass gap.

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