scholarly journals An Enhanced Vertical Ground Heat Exchanger Model for Whole-Building Energy Simulation

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4058
Author(s):  
Matt S. Mitchell ◽  
Jeffrey D. Spitler
Keyword(s):  
Heat Exchanger ◽  
Temperature Response ◽  
Building Energy ◽  
Energy Simulation ◽  
Building Energy Simulation ◽  
Response Factor ◽  
Fluid Temperature ◽  
Ground Heat Exchanger ◽  
Vertical Ground ◽  
Whole Building Energy Simulation

This paper presents an enhanced vertical ground heat exchanger (GHE) model for whole-building energy simulation (WBES). WBES programs generally have computational constraints that affect the development and implementation of component simulation sub-models. WBES programs require models that execute quickly and efficiently due to how the programs are utilized by design engineers. WBES programs also require models to be formulated so their performance can be determined from boundary conditions set by upstream components and environmental conditions. The GHE model developed during this work utilizes an existing response factor model and extends its capabilities to accurately and robustly simulate at timesteps that are shorter than the GHE transit time. This was accomplished by developing a simplified dynamic borehole model and then exercising that model to generate exiting fluid temperature response factors. This approach blends numerical and analytical modeling methods. The existing response factor models are then extended to incorporate the exiting fluid temperature response factor to provide a better estimate of the GHE exiting fluid temperature at short simulation timesteps.

Three-Dimensional Numerical Evaluation of Thermal Performance of Uninsulated Wall Assemblies

2011 ◽  
Author(s):  
El Hassan Ridouane ◽  
Marcus V. A. Bianchi
Keyword(s):  
Thermal Performance ◽  
Energy Savings ◽  
Three Dimensional ◽  
Building Energy ◽  
Energy Performance ◽  
Energy Simulation ◽  
Cavity Surface ◽  
Building Energy Simulation ◽  
Simulation Tools ◽  
Whole Building Energy Simulation

Uninsulated wall assemblies are typical in older homes, as many were built before building codes required insulation. Building engineers need to understand the thermal performance of these assemblies as they consider home energy upgrades if they are to properly predict pre-upgrade performance and, consequently, prospective energy savings from the upgrade. Most whole-building energy simulation tools currently use simplified, 1D characterizations of building envelopes and assume a fixed thermal resistance that does not vary over a building’s temperature range. This study describes a detailed 3D computational fluid dynamics model that evaluates the thermal performance of uninsulated wall assemblies. It accounts for conduction through framing, convection, and radiation and allows for material property variations with temperature. Parameters that were varied include ambient outdoor temperature and cavity surface emissivity. The results may serve as input for building energy simulation tools that model the temperature-dependent energy performance of homes with uninsulated walls.

A Procedure for Testing the Ability of Whole Building Energy Simulation Programs to Thermally Model the Building Fabric

1995 ◽  
Vol 117 (1) ◽  
pp. 7-15 ◽  
Author(s):  
R. D. Judkoff ◽  
J. S. Neymark
Keyword(s):  
International Energy Agency ◽  
Simulation Models ◽  
Building Energy ◽  
Energy Simulation ◽  
Building Energy Simulation ◽  
Thermal Mass ◽  
Reference Ranges ◽  
Energy Agency ◽  
Hourly Data ◽  
Whole Building Energy Simulation

A procedure was developed for systematically testing whole building energy simulation models and diagnosing the sources of predictive disagreement. Field trials of the method were conducted with a number of detailed state-of-the-art programs by researchers from nations participating in International Energy Agency (IEA) Task 12 and Annex 21. The technique consists of a series of carefully specified test case buildings that progress systematically from extremely simple to relatively realistic. Output values for the cases, such as annual loads, annual maximum and minimum temperatures, peak loads, and some hourly data are compared, and used in conjunction with diagnostic logic to determine the algorithms responsible for prediction differences. The more realistic cases, while geometrically simple, test the ability of the programs to model such combined effects as thermal mass, direct solar gain windows, window shading devices, internally generated heat, infiltration, sunspaces, earth coupling, and deadband and setback thermostat control. The more simplified cases facilitate diagnosis by allowing excitation of particular heat transfer mechanisms. The procedure was very effective at revealing bugs, faulty algorithms, and input errors in a group of building energy simulation programs that may be considered among the world’s best. The output data from the simulation programs can be used as reference ranges for comparing and diagnosing other detailed or simplified design tools.

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