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This paper is the first two that report on the results of ASHRAE Research Project RP-1468. This paper presents an overview of the projectandthe three volumes of documentation included in the final report (Clayton et al. 2013). The purpose of the project was to produce reference models and guidelines for developing software to automate thermal model creation fromabuilding informationmodelintoabuilding energy simulation (BES) for energy simulations. This paper describes the methods of the research and presents highlights of the guidelines. The variety of uses for energy simulation in the building design process leads to a differentiation of several different kinds of thermal models that may be extracted from a BIM. A Series 2, Level 1 model that addresses whole-building energy use at schematic stages of design is developed into a set of guidelines. A recommendation is to use the centerlines of enclosure elements to determine areas of thermal surfaces. Various recommendations are made for resolving curved surfaces, shading elements, and site elements. The guidelines are supported by detailed sensitivity studies and analysis, presented in the final report (Clayton et al. 2013). The investigations led to identification of future work to improve energy simulation tools and BIM tools. [ABSTRACT FROM AUTHOR]

Occupant control of venetian blinds or fabric roller shades can have a significant impact on facade solar transmission, with cascading implications for daylight availability, energy reduction and Indoor Environmental Quality (IEQ). However, field data describing how occupants operate interior shading devices is extremely limited, leading to theoretical assumptions for the position and frequency of operation of shades or the discounting of shading devices entirely in simulation. This paper presents results of a 6-month field study conducted in open-plan daylit offices in a LEED Silver office building located in San Francisco, CA. In total, 78 workspaces were observed over multi-week periods to develop a data set describing the physical environmental conditions associated with shade operations and to collect observations of individual shade configurations. The paper compares observed behavior to existing behavioral models used in simulation and presents single-variable logistic regression models developed from this field data. The paper concludes by discussing the implications of observed shade control behavior for existing approaches to predicting annual daylight availability and solar loads during design and for compliance with energy codes and green building standards. [ABSTRACT FROM AUTHOR]

In commercial buildings with high glazing fractions, the transmission of solar radiation to perimeter spaces represents an important source of thermal influx, and is typically controlled with shading devices such as interior venetian blinds. The influence of interior blinds on cooling and heating loads is not straightforward or obvious: they may actually cause increases in cooling loads if they prevent solar influx from reaching room surfaces with thermal mass, while rapidly transferring the solar energy to the room air via convection. This paper presents the results of experiments conducted in an outdoor office-scale façade performance testing laboratory, designed to measure the effect of slat-type blinds on cooling energy. A number blind positions, slat angles, and slat colors were tested. A simulation model of the lab was developed in parallel to check the agreement with the blind modeling algorithms of EnergyPlus, by comparing daily energy consumption and the magnitude of peak cooling load. While an exterior blind was found to greatly reduce energy consumption and peak cooling load as compared to un-shaded glazing, all cases with indoor blinds showed minimal reductions in both energy consumption and magnitude of the peak. For both dark and light-colored interior blinds, the cases with slat angles at 45º resulted in higher energy consumption than the open slat cases, and the dark blind also exhibited a greater peak load. The model closely matched experimental results for bare glazing, but tended to overestimate the reduction in energy consumption and cooling load in the presence of blinds. In addition to the presentation of experimental results, this paper will present a critical a discussion of some key considerations for modeling a space with interior blinds. [ABSTRACT FROM AUTHOR]

Utilizing Phase Change Materials (PCMs) in building envelopes as a measure for reducing energy use has been studied and practiced over the last four decades. In the context of whole building Energy simulation, building envelopes are typically modeled using a simplified one dimensional finite difference approach. PCMs can be included in such models if the models handle property variation. Simplified models generally do not capture detailed physical phenomena of PCMs such as hysteresis and sub-cooling. This paper presents the enhancements to the simulation model for Phase Change Materials in a modern whole building energy simulation program, EnergyPlus. The EnergyPlus PCM model was modified to an equation based model and the new model was validated. Demonstration of construction of temperature enthalpy curve from the properties of PCM available from experiments and manufacturers is also presented in this paper. Wallboards with experimental property data and manufacturers' catalog data were studied. In both cases, a similar behavior of the material is observed under same simulation conditions. [ABSTRACT FROM AUTHOR]

This paper provides verification results of the EnergyPlus™ variable refrigerant flow(VRF) heat pump computer model using manufacturer's performance data. The paper provides an overview of the VRF model, presents the verification methodology, and discusses the results. The verification provides quantitative comparison of full- and part-load performance to manufacturer's data in cooling-only and heating-only modes of operation. The VRF heat pump computer model uses dual range biquadratic performance curves to represent capacity and energy input ratio (EIR) as a function of indoor and outdoor air temperatures and dual range quadratic performance curves as a function of part-load ratio for modeling part-load performance. These performance curves are generated directly from manufacturer's published performance data. The verification compared the simulation output directly to manufacturer's performance data and found that the dual range equation-fit VRF heat pump computer model predicts the manufacturer's performance data very well over a wide range of indoor and outdoor temperatures and part-load conditions. The predicted capacity and electric power deviations are comparable to equation-fit HVAC computer models commonly used for packaged and split unitary HVAC equipment. [ABSTRACT FROM AUTHOR]

Rapidly increasing requirements placed on utilities to reduce peak loads has led to utility customer incentives to shift peak demand to non-peak times or reduce peak loads when notified by the utility that the grid is close to capacity. This paper investigates methods used to reduce building demand during a fixed time window near a utilities on-peak period in response to short-term notification (a few hours advanced notice) through computer simulations using EnergyPlus. The work presented in this paper was performed under the ASHRAE research project, 1390-RP. Two building types (office and retail) were defined using two equally viable construction types (light and heavy mass). The four resulting building construction models, combining building types and constructions, were simulated in five selected cities which represent a diverse range of climate conditions. The control strategies investigated in the project include lighting power density reductions, global thermostat setpoint setback control, chilled water temperature reset, and supply air temperature adjustment. Results from computer modeling were analyzed. Demand reductions associated with changes in the thermal mass were insignificant compared to those achieved with control strategies. The lighting power density reduction is effective and easily implemented. Higher percent reductions in demand were achieved for the smaller buildings and medium retail building which used the packaged HVAC system type with global thermostat setpoint setback control. The peak demand reductions that are achievable when two or more control strategies are combined vary between 12% and 34% and are dependent on building and HVAC system types. [ABSTRACT FROM AUTHOR]

In designs and ASHRAE code documents, we are now striving to maximize the performance of the building's HVAC systems. This means going beyond equipment efficiency to systems' operational efficiency. The target of these improvements is the lowering of pump and fan energy usage and optimization of plant control. When modeling these operational improvements, the saying certainly applies, "if you can't measure it, you can't count it." In this paper, the author explores water-side design and its' effect on pumping energy. Three of the major computer simulation programs used by design engineers are reviewed and compared with lab tests and building data. None of these programs currently offer a way to model improvements to the pumping system operation. This paper draws from previous ASHRAE papers and articles concerning low delta-t and control valve selection to present a method of using the models to measure system improvement, thus allowing us to count the savings. [ABSTRACT FROM AUTHOR]

A run-around membrane energy exchanger (RAMEE) has been introduced in the literature as a novel energy recovery system that transfers heat and moisture between the ventilation and exhaust air. The RAMEE consists of two separate (supply and exhaust) flat-plate exchangers made of water-vapor permeable membranes and coupled with an aqueous salt solution. In this paper, the application of a RAMEE in an HVAC system is investigated. The paper discusses the dependency of RAMEE performance on ventilation air and salt solution flow rates and indoor and outdoor air conditions and describes how to control the RAMEE in different operating conditions (summer, winter, and part load). An artificial neural network (ANN) that is able to predict the optimal system performance was developed in previous research. The ANN results are used for TRNSYS computer simulation of the RAMEE system when operating in an office building in four different climates. The results show up to 43% heating energy saving in cold climates and up to 15% cooling energy saving in hot climates. Cost analysis proves the important role of pressure drop across the exchangers in life cycle cost and predicts a payback period ranging from 2 to 5 years for the RAMEE. [ABSTRACT FROM AUTHOR]

Assessing and reducing vulnerability of building occupants to intentional indoor airborne releases of chemical and biological agents has acquired some importance in the past two decades. This paper reports on the evaluation and comparison of a set of available tools (described in the companion paper) that have been developed for practical and pragmatic use by building security professionals, consulting engineers, building owners, and maintenance personnel to evaluate the vulnerability of a building and determine the effect of implementing specific countermeasures. These tools have been applied to a few carefully selected buildings so that their responses can be evaluated both in terms of the risk assessment aspect as well as a portion dealing with evaluation of resiliency measures. The ease in using the tools, the quantity and specificity of the suggestions they provide, and the extent to which the responses differ between tools are issues that have been investigated and are presented in this paper. Also articulated are suggestions for future modifications to these tools in order to make them more user-friendly while enhancing their capabilities (such as being able to tailor the tools to a specific building rather than to a generic type, compute risk explicitly, compute the consequences of the event, etc.). [ABSTRACT FROM AUTHOR]

This paper classifies and describes analysis methods, tools, and simulation programs that allow prediction of airborne chemical/biological dispersal and transport dynamics in indoor environments subject to different risk scenarios. These are the building blocks for related analytical treatment of the overall problem involving risk assessment, risk management, and identifying cost-effective mitigation measures. These methods are distinguished by the level of mathematical and scientific rigor in modeling the phenomena, in the spatial and temporal resolution in solving the modeling equations, and in the types of boundary conditions and the numerical parameters that appear in the model. The paper also describes various general guidance documents and vulnerability assessment protocols and software available in the open-source literature to assess and reduce vulnerability in buildings due to airborne threats and risks. [ABSTRACT FROM AUTHOR]

This paper provides a new implementation model of the BACnet objects on high-level functionality for variable refrigerant flow (VRF) air-conditioning systems for commercial buildings. First, the paper discusses a model of the air-conditioner cell that consists of a group of BACnet standard type objects using the Unified Modeling Language (UML). In addition, this paper provides a new concept of a virtual wattmeter using the BACnet Accumulator object type for power consumption allocation to each tenant of the building. Examples of computer simulation and field testing show the effectiveness of our approach to expedite communication access and to provide more accurate allocation of power consumption for VRF air-conditioning systems. [ABSTRACT FROM AUTHOR]

Just as standard methods have been developed for evaluating different building energy simulation programs, there is growing realization of the imperative need to develop methods to evaluate the performance of different fault detection and diagnosis (FDD) methods and tools for different heating, ventilating, air-conditioning, and refrigerating equipment. This paper describes research done in this regard by first reviewing past pertinent literature on FDD evaluation and identifying various elements of a general conceptual evaluation framework. In order to make the tool practical for an impartial evaluation, a small set of quantitative criteria are identified based on which an objective function formulation is described where one minimizes the sum of the costs associated with false positives and those of missed opportunities. Subsequently, we describe how this function can be modified and simplified so as to obtain expressions for normalized rating of any FDD tool in terms of fault detection only as well as in terms of the combined FDD process. These general expressions are then tailored to the evaluation of FDD methods and tools specific to large chillers, and specific numerical values of several of the quantities appearing in the normalized rating expression are proposed based on discussions with chiller manufacturers and service companies as well as analysis of fault-free and faulty chiller performance data gathered in a laboratory from a previous research study. Another paper will describe its application and usefulness to assess four chiller FDD methods customized to the same performance data sets. [ABSTRACT FROM AUTHOR]

Published validation tests developed within major research projects have been an invaluable aid to program developers to check on their programs. This paper sets out how selected ASHRAE Standard 140-2004 and European CEN standards validation tests have been incorporated into the ESP-r simulation program so that they can be easily run by users and also discusses some of the issues associated with compliance checking. Embedding the tests within a simulation program allows program developers to check routinely whether updates to the simulation program have led to significant changes in predictions and to run sensitivity tests to check on the impact of alternative algorithms. Importantly, it also allows other users to undertake the tests to check that their installation is correct and to give them, and their clients, confidence in results. This paper also argues that validation tests should characterize some of the significant heat transfer processes (particularly internal surface convection) in greater detail in order to reduce the acceptance bands for program predictions. This approach is preferred to one in which validation tests are overly prescriptive (e.g., specifying fixed internal convection coefficients), as these do not reflect how programs are used in practice. [ABSTRACT FROM AUTHOR]

Ideally, whole-building energy simulation programs model all aspects of a building that influence energy use and thermal and visual comfort for the occupants. An essential component of the development of such computer simulation models is a rigorous program of validation and testing. This paper describes a methodology to evaluate the accuracy of whole-building energy simulation programs. The methodology is also used to identify and diagnose differences in simulation predictions that may be caused by algorithmic differences, modeling limitations, coding errors, or input errors. The methodology has been adopted by ANSI/ASHRAE Standard 140, Method of Test for the Evaluation of Building Energy Analysis Computer Programs (ASHRAE 2001α, 2004). A summary of the method is included in the 2005 ASHRAE Handbook—Fundamentals (ASHRAE 2005). This paper describes the ASHRAE Standard 140 method of test and its methodological basis. Also discussed are possible future enhancements to ASHRAE Standard 140 and related research recommendations. [ABSTRACT FROM AUTHOR]

Part I of this paper established the theoretical feasibility of using transient tests on energy wheels to determine their sensible energy and latent energy (or moisture transfer) effectiveness. This paper briefly describes the physical transient test facility, instrumentation, and tests performed on a stationary energy wheel to obtain the heat transfer and adiabatic moisture transfer time constants and weighting factors. Using the theoretical model in Part I, these experimentally determined characteristic factors are then used to predict the sensible and latent effectiveness of an energy wheel rotating at a selected speed. These predicted effectiveness results are shown to agree with the corresponding measured data for effectiveness within the uncertainty bounds. Comparisons of predicted effectiveness and computer simulations also show good agreement except for very low air face velocities. It is concluded that transient test methods could be used to supplement or replace steady-state effectiveness tests. Using geometric data and physical thermal properties of each energy wheel, the measured first time constants obtained for heat transfer are compared to the theoretical prediction in Part I, with each showing agreement within the uncertainty bounds. The measured first time constants for moisture transfer are used to determine the desiccant coating efficacy coefficient, again indicating results consistent with the theory in Part I. It is concluded that the theoretical equations for transient heat and moisture transfer can be used to extrapolate measured transient data for similar energy wheels and provide design guidelines for energy wheels. [ABSTRACT FROM AUTHOR]

This paper offers a guide for the design of water-based embedded heating/cooling systems to promote the use of renewable energy sources and provide a method for actively integrating the building mass to reduce peak loads, transfer heating/cooling loads to off-peak times, and decrease system size. Peak loads can be reduced by activating the building mass using pipes embedded in the main concrete structure of the building—a thermo-active building system (TABS). For these types of systems, the steady-state calculation of heating and cooling capacity is not sufficient to evaluate the cooling capacity in practice. The dynamic behavior can be evaluated by full dynamic computer simulations of buildings with systems. This is, however, often regarded as too complicated and takes too much time in the design phase. Therefore, this paper presents a simplified method that is being implemented as a European standard. The proposed methods are used to calculate and verify that the cooling capacity of the system on the room side is sufficient to keep the room temperature under a given criterion. The method also calculates the cooling requirement on the water side, which is needed for sizing cooling systems, including the chiller. [ABSTRACT FROM AUTHOR]

This paper presents an approach using commercially available computational fluid dynamics (CFD) software combined with combustion and radiation models to predict the flow, temperature, and smoke concentration fields in the event of a fire—applied to a train fire scenario. This paper is not a validation but an outline of key aspects that need to be included in the modeling. The approach presented here can be used to predict fire growth and determine how long a fire would take to reach flashover. Although the results presented are for the first 120 seconds only, this short time is sufficient to illustrate the fire dynamics predicted using the approach presented here. A comparison with available experimental data for gasoline spills was made. Although used to predict a train fire, the approach can be used in any other space such as commercial buildings, hotel atria, and more. [ABSTRACT FROM AUTHOR]

Calibrated simulation is the process of using an existing building simulation computer program and ‘tuning’ or calibrating the various inputs to the program so that observed energy use matches closely with that predicted by the simulation program. The two primary reasons for adopting this approach is that it allows (1) more reliable identification of energy savings and demand-reduction measures (involving equipment, operation, and/or control changes) in an existing building and (2) increased confidence in the monitoring and verification process once these measures are implemented. Historically, the calibration process has been an art form that inevitably relies on user knowledge, past experience, statistical expertise, engineering judgment, and an abundance of trial and error. Despite widespread interest in the professional community, unfortunately no consensus guidelines have been published on how to perform a simulated calibration using detailed simulation programs. ASHRAE initiated a research project (RP-1051) intended to cull the best tools, techniques, approaches, and procedures from the existing body of research and develop a coherent and systematic calibration methodology that includes both ‘parameter estimation’ and determination of the uncertainty in the calibrated simulation. This paper provides a pertinent and detailed literature review of calibrated simulation techniques, describing their strengths, weaknesses, and applicability, thus serving as a precursor to reporting the results of the research project in subsequent papers. [ABSTRACT FROM AUTHOR]

A component-based model for residential air conditioner and heat pump energy calculations has been developed through ASHRAE Research Project 1197. A primary objective of this project was to develop a suitable model that requires only readily available, or potentially readily available, input data. The component model meets this objective by only requiring rating data that are generated from ARI Standard 210/240. Unfortunately, only a small percentage of the data collected during these tests is published by ARI. Some manufacturers release a more significant portion of the test data in their technical literature, but these data are often incomplete. This paper describes the development of default data for the modeling of residential air conditioners and heat pumps using a test suite of 25 units. The paper evaluates the impact of limited data availability, and the need to use default data, on model prediction accuracy. The results show that the use of minimal data often produces acceptable results, though accuracy improves significantly with additional rating data. Of most importance are the power at standard rating conditions, the type of compressor, and the coil airflow rates. The results also show that accurate results are obtained without knowing the exact compressor model number. [ABSTRACT FROM AUTHOR]

This paper describes the implementation of external coupling between building energy simulation and CFD. Internal coupling is the "traditional" way of developing software. i.e., expanding the capabilities of existing software by adding new modules into an existing package. External coupling, on the other hand, makes use of existing packages in different domains (for example, the thermal domain for energy simulation and the flow domain for CFD) and provides a mechanism for these packages to communicate. A summary of the latest development is presented to put external coupling into the context. The implementation of external coupling is then summarized. The paper concludes with a case study to validate the performance of external coupling, and to highlight its potential. [ABSTRACT FROM AUTHOR]

This paper describes the construction and measured performance of a neural network-based optimal controller for an ice thermal storage system. The controller consists of four neural networks, three of which map equipment behavior and one that acts as a global controller. The controller self-learns equipment responses to the environment and then determines the control settings that should be used. Issues to be addressed are the cost function and selection of a planning window over which the optimization is conducted. The neural network (NN) controller then determines the sequence of control actions that minimize total cost over the planning window. Verification, reported on in a companion paper, is accomplished through computer simulation and on an operational plant. [ABSTRACT FROM AUTHOR]

The typical HVAC&R design process involves generating a relatively small number of alternative solutions (configurations of systems, subsystems, and components) and then utilizing analysis and estimation tools to select a "best" solution based on predefined selection criteria,for example, lowest life-cycle cost. This approach is limited by the engineer's experience, capabilities, and time constraints, often resulting in missed opportunities for optimum system selection. Further, the latest equipment, design approaches, and concepts are often not even considered. As a result, the overall design process is being gradually compromised. A knowledge-based expert system (KBES) can augment the capability of current advanced building simulation tools by creating the necessary means for automatically generating, analyzing, and sorting numerous design solutions subject to both site and user constraints. This paper describes the general framework of such a KBES called HVAC-KBCD (knowledge-based conceptual design), capable of automatically synthesizing the complete set of possible HVAC&R systems, which can then be analyzed using available building energy simulation programs such as DOE-2.J E. This synthesis is done by first pruning or shrinking the solution space of the design alternatives by applying static expert knowledge (Level 1) and then by a guided search dominated by dynamic application knowledge (Level 2). Level 1 starts with a database of all feasible secondary systems (and another for all feasible primary systems) and uses assembly rules and application rules based on heuristics expert knowledge, design practice, and standards to generate the permissible design alternatives of secondary systems (and primary systems). Level 2 uses initiation rules along with matching rules to combine secondary systems among themselves (since the building has different zones) and with primary systems. These capabilities have been programmed into a commercial hybrid KBES shell along with procedural programming capabilities that have the ability to perform simple heuristic cooling and heating design load, as well as first and maintenance cost calculations. ANSI/ASHRAE/IESNA Standard 90.1-200] has been used to set the minimum allowed energy performance for equipment such as fans, chillers, boilers, etc. This paper describes the genera 1 framework, structure, capabilities, and inner working of the HVA C-KB CD, while a companion paper will illustrate and demonstrate the entire methodology described here to the conceptual design of office buildings. [ABSTRACT FROM AUTHOR]

A previous paper articulated the current problems faced by HVAC&R professionals involved in the conceptual design process and proposed a solution based on a knowledge-based expert system (KBES) approach, which can automatically synthesize all the feasible secondary and primary systems that can then be evaluated using currently available hourly building energy simulation programs. The previous paper described the general framework of such a KBES module called HVAC- KBCD. The module consists of (1) static knowledge (based on heuristics, design practice, and standards) containing assembly and application rules needed to prune or shrink the solution space of all feasible secondary and primary systems and (2) dynamic knowledge containing initiation and matching rules to provide a guided search and further shrink the solution space by imposing restrictions of how to combine secondary systems among themselves (since the building has several zones) and with primary systems. These capabilities, along with specially developed models for first and maintenance costs, have been programmed into a commercial KBES shell. This paper describes the type of knowledge specific to office buildings that needs to be coded into the H VA C-KB CD module and illustrates its capabilities when applied to a case study example. The case study serves to illustrate the relative ease and thoroughness with which this design assistant can generate and evaluate a large number of HVAC&R system design alternatives. [ABSTRACT FROM AUTHOR]

There is a trend toward high-rise residential buildings with large--often floor-to-ceiling--glazed areas. In most climates, these buildings are reliant on mechanical systems to maintain comfort as a result of the poor insulating properties and high solar transmittance of the glazing. In the summer they are prone to overheating from high solar gains; in the winter they are prone to thermal discomfort because of low surface temperatures and high heat loss through poorly insulated glazing and other façade components. Thus, such buildings are vulnerable to power failures, mechanical system failures, and extended demand response strategies. Furthermore, these buildings can be uncomfortable and have high energy consumption during normal operation. This paper describes a methodology to evaluate building resilience using simulation methods. Building resiliencewasquantified using two metrics: thermal autonomy and passive survivability. A Toronto, Canada-based case study was performed to assess the effect of various passive design strategies to improve resilience. The results showed that thermal autonomy was very poor without occupant interaction. Furthermore, the results suggest that adaptive opportunities are at least as important as building envelope design with regards to maintaining comfort in the event of power or system failure. [ABSTRACT FROM AUTHOR]

Energy modeling and optimization studies can facilitate the design of cost-effective, low-energy buildings. However, this process inevitably involves uncertainties such as predicting occupant behavior, future climate, and econometric parameters. As presently practiced, energy modelers typically do not quantify the implications of these unknowns into performance outcomes. This paper describes an energy modeling approach to quantify economic risk and better inform decision makers of the economic feasibility of a project. The proposed methodology suggests howeconomic uncertainty can be quantified within an optimization framework. This approach improves modeling outcomes by factoring in the effect of variability in assumptions and improves confidence in simulation results. The methodology is demonstrated using a net zero energy commercial office building case study located in London, ON, Canada. [ABSTRACT FROM AUTHOR]

This paper introduces and provides results from a rigorous, scientific testing methodology that allows pure building model calibration systems to be compared fairly to traditional output errors (e.g.,howwell does simulation output match utility bills?) as well as input-side errors (e.g., how well, variableby- variable, did the calibration capture the true building's description?). This system is then used to generate data for a correlation study of output and input error measures that validates CV(RMSE) and NMBE metrics put forth by ASHRAE Guideline 14 and suggests possible alternatives. [ABSTRACT FROM AUTHOR]

Outdoor airflow rate, building static pressure, supply air duct static pressure, and relief air plenum static pressure, as controlled variables, are maintained by modulating the speed of the supply and return fans and the position of the outdoor, recirculating, and relief air dampers in an air-handling unit (AHU). The three dampers are often interlinked completely or partially to match independent control inputs with the controlled variables. The traditional damper control has all three dampers interlinked with no control over the relief air plenum static pressure. Reverse relief airflow might occur as the outdoor air damper approaches the closed position. To prevent reverse airflow, one solution is to decouple the relief air damper and maintain positive static pressure at the relief air plenum. Two control methods are available based on the controlloopdesign. The first controlmethoduses the return fan speed to control the relief air plenum static pressure and the relief airdamperto control the building static pressure, and the second control method switches two control inputs. The purpose of this paper is to evaluate the controllability of the reverse relief airflow and building static pressure of these two control methods. The system performance is investigated through steady-state simulations on an AHU at different outdoor airflows using a nonlinear network solution. The simulation results show that both the control methods can well prevent reversere lief air flow. However, the first control method with a constant pressure setpoint may result in negative building static pressure at lower outdoor airflow ratio and either excessivelypositivebuildingstaticpressureorexcessivereturn fan power at higher outdoor airflow ratio. The second control method shows better control over the building static pressure control. A reset pressure scheme should be associated with the first control method when the relief damper is fully open. [ABSTRACT FROM AUTHOR]

While the possible impact of refrigerant leaks and subsequent dispersion in an occupied space pertains to a wide variety of applications, dynamic models that accurately describe dispersion phenomena in the built environment have not been extensively explored in the literature. This paper builds on previously published work (Laughman et al. 2015) by assessing the performance of well-mixed models via a comparison to computational fluid dynamics simulations and studying the behavior of refrigerant dispersion in multiple connected spaces. Results indicate that the well-mixed models are not able to capture variation in the geometric parameters accurately and should be used cautiously. The studies of the dynamics in multiple spaces highlight the importance of the location of ventilation sources and sinks. [ABSTRACT FROM AUTHOR]

Stationary gas turbines used in industrial applications can be run using premixed fuel/air systems. Though premixed fuel/air systems are widely established, research continues to further develop the efficiency of such engines. This paper uses computer numerical simulation to analyze the effects of the premixed fuel/air composition on the performance of a miniature gas turbine. The composition of the fuel/air premixture wasvariedandresultswererecordedandcompared. Effectson turbulence intensity in the combustion zone for various premixed fuel/air compositions were monitored and compared. The analysis has shown that performance can be optimized with an optimal fuel/air premixture, and that this optimal performance coincides with peak turbulence intensity at the combustion chamber downstream of the premixed fuel/ air injectors. [ABSTRACT FROM AUTHOR]

The primary path of noise propagation in buildings is airborne transmission from building equipment through ducts. Attenuation is increased if elbows or side branches are introduced into a duct. In a companion paper (Ruan and Herrin 2016), finite element analysis was used to predict the insertion losses of straight lined and unlined ducts and results were validated with measurement. In this work, finite element analysis is used to predict the attenuation of elbows and side branches. Results for elbows and branches are compared to ASHRAE Handbook--HVACApplicationsvalueswithgoodagreement. An important secondary noise transmission path is through duct walls into rooms. This path, which is often termed breakout noise, is also investigated using the finite element approach, and results are correlated with an analytical solution and the ASHRAE Handbook with good agreement. Of note, it is demonstrated that the breakout transmission loss is much less than the insertion loss through lined rectangular ducts at some frequencies. This suggests that breakout noise is the dominant noise path at these frequencies. [ABSTRACT FROM AUTHOR]

Variable Refrigerant Flow (VRF) heat pumps are often regarded as energy efficient air-conditioning systems which offer electricity savings as well as reduction in peak electric demand while providing improved individual zone setpoint control. One of the key advantages of VRF systems is minimal duct losses which provide significant reduction in energy use and duct space. However, there is limited data available to show their actual performance in the field. Since VRF systems are increasingly gaining market share in the US, it is highly desirable to have more actual field performance data of these systems. An effort was made in this direction to monitor VRF system performance over an extended period of time in a US national lab test facility. Due to increasing demand by the energy modeling community, an empirical model to simulate VRF systems was implemented in the building simulation program EnergyPlus. This paper presents the comparison of energy consumption as measured in the national lab and as predicted by the program. For increased accuracy in the comparison, a customized weather file was created by using measured outdoor temperature and relative humidity at the test facility. Other inputs to the model included building construction, VRF system model based on lab measured performance, occupancy of the building, lighting/plug loads, and thermostat set-points etc. Infiltration model inputs were adjusted in the beginning to tune the computer model and then subsequent field measurements were compared to the simulation results. Differences between the computer model results and actual field measurements are discussed. The computer generated VRF performance closely resembled the field measurements. [ABSTRACT FROM AUTHOR]

Variable Refrigerant Flow (VRF) heat pumps are increasingly used in commercial buildings in the United States. Monitored energy use of field installations have shown, in some cases, savings exceeding 30% compared to conventional heating, ventilating, and air-conditioning (HVAC) systems. A simulation study was conducted to identify the installation or operational characteristics that lead to energy savings for VRF systems. The study used the Department of Energy EnergyPlus™ building simulation software and four reference building models. Computer simulations were performed in eight U.S. climate zones. The baseline reference HVAC system incorporated packaged single-zone direct-expansion cooling with gas heating (PSZ-AC) or variable-air-volume systems (VAV with reheat). An alternate baseline HVAC system using a heat pump (PSZ-HP) was included for some buildings to directly compare gas and electric heating results. These baseline systems were compared to a VRF heat pump model to identify differences in energy use. VRF systems combine multiple indoor units with one or more outdoor unit(s). These systems move refrigerant between the outdoor and indoor units which eliminates the need for duct work in most cases. Since many applications install duct work in unconditioned spaces, this leads to installation differences between VRF systems and conventional HVAC systems. To characterize installation differences, a duct heat gain model was included to identify the energy impacts of installing ducts in unconditioned spaces. The configuration of variable refrigerant flow heat pumps will ultimately eliminate or significantly reduce energy use due to duct heat transfer. Fan energy is also studied to identify savings associated with non-ducted VRF terminal units. VRF systems incorporate a variable-speed compressor which may lead to operational differences compared to single-speed compression systems. To characterize operational differences, the computer model performance curves used to simulate cooling operation are also evaluated. The information in this paper is intended to provide a relative difference in system energy use and compare various installation practices that can impact performance. Comparative results of VRF versus conventional HVAC systems include energy use differences due to duct location, differences in fan energy when ducts are eliminated, and differences associated with electric versus fossil fuel type heating systems. [ABSTRACT FROM AUTHOR]

Slinky ground heat exchangers are increasingly considered among more traditional ground heat exchanger configurations. Although studied for many years as a research topic, the increase in efficiency and reduction in building energy demands has increased the viability of these specialized heat exchangers, especially in cases where limited space is available for burying horizontal heat exchanger tubing. By formulating an accurate simulation model, the feasibility and efficiency of such heat exchangers in different climates and building configurations can be studied. In addition, it will serve as a powerful tool for design and energy analysis of the ground source heat pump (GSHP) systems. This paper describes the derivation of an analytic solution for modeling the thermal response of horizontal Slinky heat exchangers. The analytic results are presented in the form of temperature response factors. A computer module with fast algorithms is written to calculate temperature response factors of any specified Slinky ground heat exchanger. The factors then can be used as input for a buried pipe model to calculate hourly exit fluid temperature of the heat exchanger. Knowledge of exit fluid temperature is essential for simulation of a GSHP system. [ABSTRACT FROM AUTHOR]

This paper uses a coupled thermal comfort and computational fluid dynamics (CFD) simulation system to predict thermal comfort in a cross-ventilated classroom. Simulations using mechanical ventilation and natural ventilation were conducted. In the latter, the effect of asymmetric radiation caused by a chilled ceiling was investigated. The work builds on previous work by the authors by applying a transient approach to the solution procedure. The results demonstrate the possible benefits of using such a coupled system by predicting different body surface temperatures and therefore different air flow velocities around the human body. It was found that the transient solution approach gave improved convergence of the coupled system compared with a traditional, steady-state approach. [ABSTRACT FROM AUTHOR]

Chilled water thermal storage tanks are an efficient and economic option in HVAC design. The sensible cooling capacity, which is typically generated and stored during lower demand periods, can serve many purposes such as reducing energy costs during peak demands, backing up cooling capacity during a power outage, and suppressing fire during a fire accident. The different density of water in varying temperatures, along with the buoyancy effect, can create thermal stratification in the tank, which plays an important role in the performance of the tank. The design achievement is judged by how long it takes the tank to discharge the chilled water at the design temperature. The performance can be affected by many design parameters which make it difficult to analyze, and therefore is a good candidate for research. This paper shows how the full 3D numerical simulation and virtual design approach provide more detail and visualization of the flow field structure to improve the design. The main goal was to design the chilled water storage tanks to provide at least fifteen minutes of chilled water at a specific temperature for a data center during a power outage. Different octagonal inlet and outlet diffusers with different sizes and locations of the slots in the diffusers were virtually designed and their impacts on flow distribution, thermocline shape, swirl effect, and time amount of delivering cold water were investigated. The outcome was then used to optimize the design and provide solutions for improving the performance of the tank. [ABSTRACT FROM AUTHOR]

This paper is a summary of a study conducted by the team at HVAC design d.o.o. Sarajevo in the framework of the ASHRAE RP-1493 CFD Shootout Contest--Prediction of Duct Fitting Losses. In the introductory section, methods of airflow modeling and simulation used in this analysis are briefly described. This is followed by a presentation of a set of validation results that were used to select appropriate simulation parameters. Next, computational fluid dynamics (CFD) results of pressure loss coefficients in flat-oval ducts and tee and lateral duct fittings at different flow rate ratios and Reynolds numbers in both converging and diverging flow modes are compared to empirical correlations and measurements. Obtained duct fitting simulation results are generally in qualitatively good agreement with laboratory data. [ABSTRACT FROM AUTHOR]

Numerical simulation modeling has become a very important and integral part of product design process. One of the significant product reliability risks for HVAC systems is vibration fatigue failure of refrigeration piping systems. Excessive refrigerant line vibration can ultimately result in cracks or joint failures, and loss of refrigerant charge. The vibration is driven by compressor, which is excited by a combination of dynamic loads, such as rotor imbalance and pressure pulsations associated with the compression process. Piping system problems arise when the excitation frequencies coincide with piping resonances (also called "natural frequencies" or "modes"). To mitigate this risk, numerical simulation using Finite Element Analysis (FEA) is conducted to calculate piping resonances and their associated stress levels. Using numerical models, it is possible to identify potential resonance problems, and refine the piping system design prior to making prototype units. This paper presents a description of the FEA simulation process, including key modeling assumptions, as well as examples of how the models correlate with test. Production unit statistics confirm that vibration simulation can significantly reduce the risk of the fatigue failure. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the variable refrigerant flow heat pump computer model included with the Department of Energy's EnergyPlus™ whole-building energy simulation software. The mathematical model for a variable refrigerant flow heat pump operating in cooling or heating mode, and a detailed model for the variable refrigerant flow direct-expansion (DX) cooling coil are described in detail. [ABSTRACT FROM AUTHOR]

Increasing loop chilled water return and supply temperature difference or delta-T is an effective way to improve the chilled water system efficiency and save chiller plant operating costs. In some chiller plants, the delta-T can be expected to fall to about one-half to two-thirds of design at low loads due to various causes, such as coil load, air entering and leaving temperatures, and chilled water supply temperature. Computational simulation is a useful and flexible tool to study cooling coil delta-T characteristics under various conditions. This paper simulated the cooling coil delta-T profiles with different geometric configurations and various waterside and airside conditions using an effectiveness-NTU model. The waterside heat convection coefficient was modeled with a combined correlation. The simulation results show that the existing waterside correlations generated significantly different delta-T profiles. With variant geometric configurations, the coil delta-T at full load may be higher, equal, or lower than that at part load. The complexity of cooling coil delta-T characteristics indicates that it is hard to make conclusions about the coil delta-T change with cooling loads. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the performance of two different types of Solar Domestic Hot Water (SDHW) systems , one with a gas boiler as the auxiliary heating source and the other with an electric tank as the auxiliary heating source, and to investigate the contributions of different components of the systems in lowering the annual energy demand and GHG emissions for producing 225 litres (59.4 gal) per day of domestic hot water. The systems are for the twin Archetype Houses located in Vaughan, Ontario, Canada. The annual energy consumption of the gas boiler and electric tank from the experimental analysis were to be 3718.7 kWh (12.69 MBtu) and 2778 kWh (9.48 MBtu), respectively. The TRNSYS models of the two systems were also created and validated with the experimental results. Using the TRNSYS models for a typical Canadian household in Toronto, Ontario, the annual energy consumption by the gas boiler and electric backup tank were concluded to be 3636.9 kWh (12.41 MBtu) and 2681.5 kWh (9.15 MBtu), respectively. The annual thermal energy output by the flat plate and evacuated tube solar thermal collectors were found to 2010.8 kWh (6.86 MBtu) and 1390.6 kWh (4.74 MBtu), respectively. The annual heat recovery by the Drain Water Heat recovery (DWHR) units were concluded to be 792.8 kWh (2.7 MBtu). [ABSTRACT FROM AUTHOR]

Whether a small fire in a passenger rail vehicle does or does not grow to encompass the entire vehicle, and how large the ultimate fire may become, is largely a function of the initiation fire, vehicle interior materials (interior lining / components and contents), vehicle configuration and ventilation (window and door openings). Assuming a fixed vehicle configuration and a limited set of ventilation options, significant variables become the initiation fire, interior materials and contents. Full scale tests can be used to evaluate the relative fire hazards represented by different interior lining materials when exposed to various initiation fire scenarios; these tests are costly and time-consuming. Small-scale fire tests, such as those using the cone calorimeter apparatus, are less expensive, and allow review of a wide range of materials in a relatively short timeframe. This paper presents a new methodology for using small-scale test data, coupled with initiation fire data, simplified calculation methods and computational modeling, to cost-effectively assess a wide range of scenarios and material combinations for existing and proposed rail vehicle designs. [ABSTRACT FROM AUTHOR]

New York City Transit (NYCT) has established a new design train fire heat release rate to be used in all the capital projects. Having relied in the past on simplified computer modeling and different set of material properties, NYCT has used in-house expertise with an advanced computer modeling technique and fire model to derive a more credible and realistic design value. Since the early 1990's, NYCT has used 14MW for the trains, but through the use of CFD and new train material information, NYCT has established that a 5MW fire is more credible and appropriate design fire scenario. This paper presents excerpts from the report that describes the analysis carried out by NYCT, and focuses on the scenario considered as the design basis. [ABSTRACT FROM AUTHOR]

The definition of a good indoor climate is important to the success of a passenger rail coach, not only because it will decide its energy consumption and thus influence its sustainability but also because good comfort for long journeys is essential. The intention is to use the results to optimize the control of the ventilation system to provide an indoor climate that passengers will find comfortable. The results of this study show how passengers' thermal comfort was affected by changing the supplied air conditions. This paper primary discusses and analyzes the simulation of the air flow and thermal patterns in a Subway station. Numerical simulation of a typical model is presented. Modifications were applied to the numerical model to show the improvement of the thermal comfort level. The pre-processor Gambit is used to create the geometric model with parametric features. Commercially available simulation software "Fluent 6.3" is incorporated to solve conservation of mass, momentum and energy in the processing of air distribution, and to analyze turbulence affection combined heat transfer on air distribution. In this thesis work, the socalled standard k-ε turbulence model, one of the most widespread turbulence models for industrial applications, was utilized. Basic parameters included in this work are air temperature, air velocity, relative humidity and turbulence parameters are used for numerical prediction of indoor air distribution. Measurements of air velocity, and temperature were undertaken in a plane perpindicular to the supply diffuser. These values were then compared to the obtained results from the simulated cases. The thermal comfort prediction through this work was based on the PMV (Predicted Mean Vote) model and the PPD (Percentage Predicted Dissatisfied) model, the PMV and PPD were estimated using Fanger's model. [ABSTRACT FROM AUTHOR]

Tunnel ventilation facilities, for road or rail tunnels, face the challenge of the design requirements imposed on them. Among them is the Fire Heat Release Rate (FHRR). Many think that the larger the FHRR, the safer the system, but the fact is that if FHRR is too large, the airflows required for a ventilation system to control the smoke become too large, the facility requires a lot of space, and the cost may escalate to the point that the constructability of the ventilation plant may be too costly to build. The airflow rate through the tunnel ventilation facility and fan duty points are key parameters. The airflow through the tunnel ventilation facility is a function of the tunnel configuration constraints; while the duty point is a function of the number of fans, individual fan airflow, equipment room layout, and airflow path. The airflow rates are determined through computer modeling taking into account numerous branches and tunnel network losses. The duty point is usually determined by hand calculations (for simple systems), but sometimes, it becomes very difficult that we need to carry out computer modeling. This paper will illustrate that there is a non-linear correlation between the magnitude of change in the FHRR, and the sizing of the tunnel ventilation facility. Ultimately, there is a change, but through computer simulations, these changes will need to be assessed. [ABSTRACT FROM AUTHOR]

Different computer simulated persons (CSPs) have been developed to represent occupants for indoor airflow simulation using computational fluid dynamics (CFD). Simple CSPs are preferred in order to avoid very fine grids and long computing time. However, how CSPs with different complexity affect the accuracy of CFD simulation is not well studied yet. This paper intends to investigate quantitatively the simulation accuracy due to CSP simplification. A detailed, human-like CSP and three different simplification strategies including an overly simplified rectangular box CSP, a simple CSP using several cuboids to represent different parts of a person, and an improved one in which the total heat of different parts (head, body, arms, legs) matches that of the detailed CSP are proposed. The simulation results using simplified CSPs are compared with the benchmark experimental data and simulated results using the detailed CSP in a displacement ventilation case. Results show that all the CSPs, simple or complex, yield acceptable simulation results for the global field study. For the micro-environment around the person, there seems no significant benefit by adopting very complex CSP geometry either. Instead, attention should be paid to ensure the heat and pollutant source consistence of the simplified CSP over the actual human (detailed CSP). [ABSTRACT FROM AUTHOR]

The objectives of this study were to compare the commercially available sorbent materials for removing typical indoor volatile organic compounds (VOCs) and to obtain data and experience that are useful to the development of a standard test method for sorbent media evaluation. A multichannel stainless steel air cleaning technology testing system (ACTTS) was developed and used to test eleven pellet/granular-type sorbent media representing different base materials (coal, bituminous coal, coconut, bamboo wood, and activated aluminas with potassium permanganate and activated carbon) for seven VOCs. Tests were conducted for VOCs including hexane, decane, toluene, tetrachloroethylene, 2-butanone, isobutanol, and D-limonene. Concentrations versus time during sorption and desorption periods were obtained. The sorbent media's performances were evaluated in terms of removal efficiency and removal capacity per unit of sorbent weight as a function of time, the 50% breakthrough time, and the half-life time removal capacity. In addition, repeatability of the test and the effect of flow rate on the test results were also investigated. The challenges of developing a standard test method and procedure for performance evaluation of pellet/granular-type sorbent media based on the experiences gained from the study are also discussed briefly in this paper. [ABSTRACT FROM AUTHOR]

This paper provides a method for verifying the accuracy of computer models that simulate the performance of the airhandling components of four types of heating, ventilating, and air-conditioning systems: the dual fan VAV dual-duct system, the single-zone system, the four-pipe fan coil system, and the four-pipe induction system. To accomplish this, a detailed description of each system and its operating parameters was developed and a set of eight test conditions was generated, consisting of carefully chosen space loads and weather conditions. Each of the systems was simulated at each of the defined conditions. The thermodynamic properties at each point in the system, as well as the heating and cooling coil loads, were calculated. The calculations were then repeated by a second analyst using an independently developed program. The maximum deviation in the total coil loads was 1.8%, and the average of the absolute deviations was 0.4%. These validated results can be used by program developers or users to test the performance of the air-side simulations contained in most building energy analysis computer programs. [ABSTRACT FROM AUTHOR]

This paper describes the thermal profile of a high-performance computing cluster located in two different data centers with quite different thermal profiles. The high-performance advanced simulation and computing (ASC) cluster, code named ASC Purple, is the world's third fastest supercomputer (Top 500 Supercomputer Sites, http://www.top500.org/), operating at a peak performance of 77.8 TFlop/s. It contains more than 12,000 processors, 50 terabytes of memory, and 2 petabytes of globally accessible disk space. The cluster was first tested in the manufacturer's development laboratory in Poughkeepsie, New York, and then shipped to a national laboratory in California, where it was installed to support our national security mission. Detailed measurements were taken in both data centers of electronic equipment power usage, perforated floor tile airflow, cable cutout airflow, computer room air-conditioning (CRAC) airflow, and electronic equipment inlet air temperatures. In addition to these measurements, the physical features of the data center were recorded. Results showed that heat fluxes of 700 W/ft2 (7535 W/m2) could be achieved while still maintaining rack inlet air temperatures within specifications. However, in some areas of the Poughkeepsie data center, there were zones that did exceed the equipment inlet air temperature specifications by a significant amount. These areas will be highlighted and reasons will be given for why these areas failed to meet the criteria. Those areas of the cluster in Poughkeepsie that did not meet the temperature criteria were well within the temperature limits at the California installation. Based on the results from these two data centers, necessary and sufficient criteria are outlined for IT racks to achieve inlet air temperatures that meet the manufacturers' temperature specifications. [ABSTRACT FROM AUTHOR]

This paper presents a comparison study between the simulations of SkyVision and measurements made in a scale model. SkyVision is a computer tool used to calculate the overall optical characteristics, indoor daylight availability, and energy-saving potential of projecting and tubular skylights. The measurements included the overall visible transmittance and indoor daylight illuminance of the skylight. A rectangular wooden box was used as a scale model of a simple commercial building. The top surface of the box was fitted with a curbed opening to accommodate the skylights to be tested. Seven skylight shapes were tested: two circular dome models, one with clear and one with white acrylic glazing; two rectangular bubble dome models, one with clear and one with white acrylic glazing; one clear acrylic hexagonal pyramid model; oneclear polycarbonate barrel vault model; and one tubular skylight model. The measurements were conducted for a whole day, thereby covering different sky conditions: overcast, partly cloudy, and clear sunny skies. SkyVision's simulations for the skylight transmittance compared reasonably well with the actual measurements, except for the hexagonal pyramidal skylight. The hexagonal pyramid surface exhibited some lens effects around the surface vertices, which were not possible to model in SkyVision. As for the skylight indoor illuminance comparison, the SkyVision's simulations were in good agreement with the actual measurements for all occurrences of sky conditions. [ABSTRACT FROM AUTHOR]

Having building energy simulation programs with the inherent capability to efficiently perform optimization either during the conceptual design phase or during the operational stage would provide professionals with a tool to reduce energy use in building systems. This paper starts by reviewing two popular simulation techniques for building energy systems—sequential component method (SCM) and equation-oriented method (EOM)—in terms of their advantages and disadvantages. Next, a hybrid simulation strategy, successive approximation method (SAM), is proposed, This strategy is inherently capable of dealing with both design and optimal operation while combining desirable features of both SCM and EOM. SAM is a more coherent strategy that involves two aspects: (1) formulation of the equations following SAM and (2) using the automatic differentiation (AD) technique to compute the Jacobian matrix necessary to solve the equations. Finally, an illustrative example is presented to demonstrate the feasibility of this approach and how its results compare to those of a traditional simulation method. [ABSTRACT FROM AUTHOR]