Dragan Curcija | Lawrence Berkeley National Laboratory (original) (raw)

Papers by Dragan Curcija

Applied Energy, May 1, 2019

• A novel c-Si based semi-transparent BIPV laminate was introduced. • Energy performance of the B... more • A novel c-Si based semi-transparent BIPV laminate was introduced. • Energy performance of the BIPV insulated glass unit (IGU) was investigated. • The BIPV laminate has high energy conversion efficiency and visible transmittance. • The BIPV laminate could reduce discomfort glare compared to clear glass windows. • The shade effect was influenced by the solar cell configurations and shading patterns.

A detailed two-dimensional heat transfer analysis of complete fenestration systems was performed ... more A detailed two-dimensional heat transfer analysis of complete fenestration systems was performed using computer models based on the Galerkin finite-element method. Laminar natural convection, coupled with radiative heat transfer in the cavity of the insulated glazing unit (IGU), was modeled simultaneously with conductive heat transfer in the solid parts (i.e., frame, glass panes, spacer, and sealants). Two prototype windows were developed for the purpose of this initial study-both wood, standard double-glazed windows. The overall dimensions of the prototype windows were 0.61 m by 0.61 m (24 in. by 24 in.) and 0.61 m by 1.22 m (24 in. by 48 in,). The two prototype systems have the same cavity width and gas fill (air), but they have different frame designs. Three different sets of boundary conditions were investigated, of which two incorporated fixed surface heat transfer coefficients on the indoor and outdoor window surfaces, and one incorporated variable coefficients. To validate the convective portion of the model, the glazing cavities from the two prototype models -- subjected to a constant-temperature boundary condition on the vertical sides and zero heat flux on the horizontal sides -- were modeled first and compared with other numerical and experimental results. In addition, a constantmore » surface heat transfer coefficient was applied on the vertical boundaries of the interior glazing cavity, and the effects of radiation modeling inside the cavity were investigated. Component and overall U-factors for both prototype windows were then calculated and compared to the available experimental and conduction-only numerical results. Local heat fluxes and temperatures were plotted for the indoor and outdoor surfaces, and the effects of variable surface heat transfer coefficients were compared.« less

The researchers developed a new generation of high-performance façade systems and supporting desi... more The researchers developed a new generation of high-performance façade systems and supporting design and management tools to support industry in meeting California's greenhouse gas reduction targets, reduce energy consumption, and enable an adaptable response to minimize real-time demands on the electricity grid. The project resulted in five outcomes: (1) The research team developed an R-5, 1-inch thick, triplepane, insulating glass unit with a novel low-conductance aluminum frame. This technology can help significantly reduce residential cooling and heating loads, particularly during the evening. (2) The team developed a prototype of a windowintegrated local ventilation and energy recovery device that provides clean, dry fresh air through the façade with minimal energy requirements. (3) A daylight-redirecting louver system was prototyped to redirect sunlight 15-40 feet from the window. Simulations estimated that lighting energy use could be reduced by 35-54 percent without glare. (4) A control system incorporating physics-based equations and a mathematical solver was prototyped and field tested to demonstrate feasibility. Simulations estimated that total electricity costs could be reduced by 9-28 percent on sunny summer days through adaptive control of operable shading and daylighting components and the thermostat compared to state-of-the-art automatic façade controls in commercial building perimeter zones. (5) Supporting models and tools needed by industry for technology R&D and market transformation activities were validated. Attaining California's clean energy goals require making a fundamental shift from today's ad-hoc assemblages of static components to turnkey, intelligent, responsive, integrated building façade systems. These systems offered significant reductions in energy use, peak demand, and operating cost in California.

Lawrence Berkeley National Laboratory, Apr 15, 2003

Accurately analyzing heat transfer in window frame cavities is essential for developing and chara... more Accurately analyzing heat transfer in window frame cavities is essential for developing and characterizing the performance of highly insulating window products. Window frame thermal performance strongly influences overall product thermal performance because framing materials generally perform much more poorly than glazing materials. This paper uses Computational Fluid Dynamics (CFD) modeling to assess the accuracy of the simplified frame cavity conduction/convection models presented in ISO 15099 and used in software for rating and labeling window products. (We do not address radiation heat-transfer effects.) We examine three representative complex cavity cross-section profiles with varying dimensions and aspect ratios. Our results support the ISO 15099 rule that complex cavities with small throats should be subdivided; however, our data suggest that cavities with throats smaller than seven millimeters (mm) should be subdivided, in contrast to the ISO 15099 rule, which places the break point at five mm. The agreement between CFD modeling results and the results of the simplified models is moderate. The differences in results may be a result of the underlying ISO correlations being based on studies where cavity height/length (H/L) aspect ratios were smaller than 0.5 and greater than five (with linear interpolation assumed in between). The results presented here are for horizontal frame members because convection in vertical jambs involves very different aspect 2 ratios that require three-dimensional CFD simulations. Ongoing work focuses on quantifying the exact effect on window thermal performance indicators of using the ISO 15099 approximations in typical real window frames.

Journal of Building Performance Simulation, 2018

Virtually all residential and commercial windows in the U.S. have some form of window attachment,... more Virtually all residential and commercial windows in the U.S. have some form of window attachment, but few have been designed for energy savings. ISO 15099 presents a simulation framework to determine thermal performance of window attachments, but the model has not been validated for these products. This paper outlines a review and validation of the ISO 15099 centre-of-glass heat transfer correlations for perimeter gaps (top, bottom, and side) in naturally ventilated cavities through measurement and simulation. The thermal transmittance impact due to dimensional variations of these gaps is measured experimentally, simulated using computational fluid dynamics, and simulated utilizing simplified correlations from ISO 15099. Results show that the ISO 15099 correlations produce a mean error between measured and simulated heat flux of 2.5 +/-7 percent. These tolerances are similar to those obtained from sealed cavity comparisons and are deemed acceptable within the ISO 15099 framework.

Two-dimensional laminar forced convection on an outdoor fenestration surface, with the wind perpe... more Two-dimensional laminar forced convection on an outdoor fenestration surface, with the wind perpendicular to the glazing surface, was analyzed using the penalty function approach finite-element method (FEM). The air far from the fenestration surface (free-stream conditions) was assumed to be at ASHRAE standard fenestration conditions of {minus}18 C (0 F) and 6.7 m/s (15 mph). A prototype fenestration configuration of a typical wood casement window, consisting of a double-step frame and an insulating glazing unit (IGU), was used in defining the outdoor fenestration profile. A flat-plate geometry was also considered for purposes of comparison with other available numerical and experimental results and for validation of the results for the actual fenestration profile. The results are reported in the form of velocity vector plots and local convective surface heat transfer coefficients. Recommendations on the local outdoor surface convective heat transfer coefficient for use in two- and ...

Ashrae Transactions, 1984

Revue des differentes recommandations publiees dans la litterature, qui sont seulement des approx... more Revue des differentes recommandations publiees dans la litterature, qui sont seulement des approximations, et description du developpement d'une methode plus precise avec introduction de la notion de charge frigorifique negative, de rayonnement solaire negatif, et de gains thermiques negatifs

Venetian blinds are widely used as shading devices for windows. Methods for simulation of blinds ... more Venetian blinds are widely used as shading devices for windows. Methods for simulation of blinds are needed because measurements of their properties are expensive and quite involved. This paper presents novel method (named “directional diffuse method”) for calculation of bidirectional properties of a venetian blind. The shadowing of blind slat surfaces is taken into account during the calculation of the diffuse portion, resulting in a more realistic, nonuniform distribution of the scattered (diffuse) component. The method is applicable to devices with flat or curved slats. The resulting BTDF/BRDF can be used with the glazing layers BTDF/BRDF and full matrix calculation can be performed to get system performance with full spatial resolution. This methodology has been developed and implemented in the new version 6.0 of WINDOW program and has been successfully validated against limited amount of measurements and ray tracing simulations.

The accuracy and sensitivity of fenestration modeling in EnergyPlus (DOE 2019) is very important ... more The accuracy and sensitivity of fenestration modeling in EnergyPlus (DOE 2019) is very important since fenestration is typically the dominant envelope load. New technologies, such as room-side low-E coatings and vacuum glazing, can challenge models that were developed before these technologies existed. In this report, we examine the sensitivity of EnergyPlus results to six available window models, including two simplified models that utilize known overall U and SHGC of the window (simple bulk properties) and creates layer-bylayer descriptions for fenestration system. One of these simplified methods also takes into account the type of frame and number of glazing layers if available. A range of window performance levels are modeled with the residential prototype buildings developed by Pacific Northwest National Laboratory, based on DOE's Residential Reference Building Models. Building models include highand low thermal mass versions to understand the sensitivity of results to fene...

Measurement science is vital in evaluating environmental impacts to assess sustainability. There ... more Measurement science is vital in evaluating environmental impacts to assess sustainability. There are several types of frameworks, analytical tools and metrics that have been developed to assess the achievement of sustainability. The purpose of such frameworks, tools and metrics is to evaluate impact to the environment at different scales depending on project boundaries. This paper provides a detailed review and in-depth mapping of a variety of sustainability frameworks, analysis tools and metrics currently in use related to building and environment. Such a mapping offers clarity to modelers on the hierarchy of measurement sciences in the yet-to-beformulated “science of sustainability.”

Journal of Building Performance Simulation, 2017

Virtually every home in the U.S. has some form of shades, blinds, drapes or other window attachme... more Virtually every home in the U.S. has some form of shades, blinds, drapes or other window attachment, but few have been designed for energy savings. In order to provide a common basis of comparison for thermal performance it is important to have validated simulation tools. This paper outlines a review and validation of the ISO 15099 center-of-glass thermal transmittance correlations for naturally ventilated cavities through measurement and detailed simulations. The focus is on the impacts of room-side ventilated cavities, such as those found with solar screens and horizontal louvered blinds. The thermal transmittance of these systems is measured experimentally, simulated using CFD analysis, and simulated utilizing simplified correlations from ISO 15099. Correlation coefficients are proposed for the ISO 15099 algorithm that reduce the mean error between measured and simulated heat flux for typical solar screens from 16% to 3.5% and from 13% to 1% for horizontal blinds.

In this work, gas-filled tall rectangular cavities, typically found in insulating glazing units (... more In this work, gas-filled tall rectangular cavities, typically found in insulating glazing units (IGUs) of fenestration systems, with constant temperatures at the side walls and zero heat flux at the top and bottom, were investigated. Critical Rayleigh numbers, Ra{sub c}, at which multicellular flow begins to form were determined for aspect ratios from 10.7 to 80. Using a general-purpose fluid flow and heat transfer finite-element analysis computer program (FDI 1993), numerical calculations were performed over the range of aspect ratios, A, from 10 to 80 with Rayleigh numbers, Ra, varying within the laminar flow regime. The calculations revealed that for aspect ratios between 10.7 and 30, the multicellular flow pattern dies out before the flow enters the turbulent flow regime. In addition, the lowest aspect ratio at which multicellular flow patterns existed was 10.7, which is lower than the lowest limit (A = 12) published by other researchers. The resulting critical Rayleigh numbers are plotted on a graph as a function of the aspect ratio and the Rayleigh numbers. The overall heat transfer results in terms of the average, or integrated, Nusselt numbers, Nu, are compared with available numerical and experimental data on multicellular flow in rectangular cavities, and goodmore » agreement was found. Also, streamline contour plots and temperature profiles are plotted for selected cases.« less

Seven different types of insulated glazing units (IGU) were analyzed to determine their thermal p... more Seven different types of insulated glazing units (IGU) were analyzed to determine their thermal performance and condensation resistance potential. To determine the detailed convective, radiative, and conductive heat transfer and to validate computer models, a general-purpose fluid flow and heat transfer finite-element analysis software package and two public domain fenestration heat transfer analysis programs, THERM and WINDOW 4.1, were used. A standard set of boundary conditions was investigated by imposing fixed surface heat transfer coefficients on the indoor and outdoor glass surfaces. In addition, a newly developed condensation resistance model was used to predict temperature distributions on the indoor surfaces. Results are reported in terms of U-factors and temperature distributions on the indoor glass surfaces.

A number of correlations for predicting convective heat transfer in glazing cavities have been de... more A number of correlations for predicting convective heat transfer in glazing cavities have been developed over the years, but the most popular and most widely used, especially in North America, have been the correlations from EISherbiny et al. (1982), This was one of the firs! correlations to include the Nusselt number dependence on the aspect ratio (cavity height to width). However, this dependence applies only for aspect ratios below 20, which are not representative for typical fenestration systems (windows and doors) that usually have higher aspect ratios. Experimental and analytical studies indicate that the Nusselt number dependence on the aspect ratio extends to much higher aspect ratios, although not as strongly as for aspect ratios less than 20. In this work, two-dimensional laminar natural convection heat tran!Jjer of air-filled, high aspect ratio rectangular cavities, subject to constant temperature boundary conditions on the vertical sides and zero heat flux boundary condi...

Solar Energy, 2020

This paper investigated the energy performance of window attachments and analyzed the impact of w... more This paper investigated the energy performance of window attachments and analyzed the impact of window attachments' parameters on air conditioning energy consumption of residential buildings in a cooling-dominated city (Houston) and a heating-dominated city (Minneapolis). Roller and cellular shades were selected as research objects in this study. Nine parameters related to window attachment energy performance were chosen as the probable important influence factors for the parametric study. Three values, high, medium and low levels, were set for each parameter, resulting in a total of 9520 (roller) and 9072 (cellular) combinations respectively. The optical and thermal properties of each combination were calculated with Berkeley Lab WINDOW program before coupling with an EnergyPlus typical residential building model. Based on simulation results, an annual energy performance (AEP) index was proposed to rate the energy saving potential of window attachments. Key parameters which have significant impacts on air conditioning energy consumption were determined through the parameter sensitivity analysis. The research results indicated that solar transmittance and solar reflectance are the most influential factors to the energy performance of window attachments among the nine selected parameters. The current cellular shade could achieve the AEP h and AEP c of 0.19 and 0.12. Among all combinations, the best AEP h and AEP c of cellular shades are 0.68 and 0.89, respectively. Besides, as for roller shades, the current level of AEP h and AEP c are 0.14 and 0.09, and the optimal AEP h and AEP c are 0.43 and 0.79.

Energy and Buildings, 2015

A design tool to evaluate the heat and mass transfer effectiveness and pressure drop of a membran... more A design tool to evaluate the heat and mass transfer effectiveness and pressure drop of a membrane-based enthalpy exchanger was developed and then used to optimize the configuration of an enthalpy exchanger for minimum pressure drop and maximum heat recovery effectiveness. Simulation was used in a parametric study to investigate the energy saving potential of the enthalpy recovery system. The case without energy recovery and air side economizer was used as a baseline. Two comparison cases for the implementation of enthalpy recovery with and without air side economizer were simulated in EnergyPlus. A case using a desiccant wheel for energy recovery was also investigated for comparison purposes. The simulation results show significant energy saving benefits from applying a low pressure drop, high effectiveness enthalpy exchanger in two US cities representing a range of humid climates. The sensitivity of the energy savings potential to pressure drop and heat and mass transfer effectivenesses is also presented.

Applied Energy, 2019