Airbase publication

As a cost-effective alternative to experiments, computational fluid dynamics (CFD) can provide new insight in airflow patterns and the related convective heat transfer (CHT). However, together with the governing equations, the description of the boundary conditions determines for a greater part the reliability and the accuracy of CFD simulations. In this study the sensitivity of the predicted CHT to diffuser modelling is studied. Numerical simulations of a modified version of test case E.2 of the IEA Annex 20-project are performed.

In this article, we will present a new multi-level modelling approach to obtain higher precision in HVAC plant simulation models. For this purpose, two different levels of detail in modelling, the coarse component-based approach of Modelica and the detailed physical-based approach of Computational Fluid Dynamics (CFD) were combined. In a first use case, we analysed the thermal hydraulic network of a simple heating system, both with the CFD-approach (3D-model) and the Modelica approach  (1D-model).

A simplified model was developed by use of thermal-ventilation network with the purpose of studying air environment in void space at the central portion of high-rise apartment houses when gas-fired boilers were installed in the void. First, a one-node model was studied assuming uniform temperature distribution in the void space, resulting mismatching between calculated and measured values for building surface temperature. Then, a two-node model was prepared by separating corridor region from void region.

The performance of hot water space heating systems for mild to warm temperate climates is dominated by the efficiency of boiler operation at low load (i.e. below 25% of nameplate capacity). This efficiency is influenced by a number of effects that are poorly represented in common modelling approaches, including static thermal losses from the boiler and distribution system, changes in burner efficiency at different firing rates, thermal inertia in the boiler loop and the effects of cyclic operation. In this paper, a simple model that includes these loss mechanisms is developed.

For the use in Swiss standards on energy performance of cooled buildings, a chiller model for an hourly time step calculation was needed. Unlike the models found in a literature review, the model aimed at should be based only on the information available from standard performance rating, i.e.

This paper reviews the current situation in M&E (services) engineering in the United Kingdom considering the use of simulation in the building design and engineering process. It maps out the different forces that currently act on the deployment of simulation tools in building services design and optimisation. Surveys and in-depth interviews have been used to investigate the factors (key value drivers) that influence the application of simulation technology.

The renovation of a building in terms of thermal insulation will improve the level of energy consumption in winter. To improve the summer comfort, we have simulated the introduction of a phase-change material (PCM) in both situations: removed or not removed building. The dynamic building simulation software CoDyBa has been adapted to consider these materials in the calculations.

In Denmark, cooling of office buildings during summer contributes significantly to electrical consumption. The use of phase change material (PCM) can help to reduce overtemperatures during summer and even out temperature fluctuations over the day, hereby reducing both heating and cooling demands in buildings. This paper describes a numerical method for calculating the latent storage performance of building components containing PCM in order to evaluate the impact on heating and cooling demands.

Most of commercial buildings are intermittently operated in practice. The use of the Radiant Time Series (RTS) method based on the continuous air-conditioning operation could result in largely underestimated peak cooling loads, and inconsistent design. Hence, a new method is developed based on the RTS. The new method only needs one more step after the current RTS design procedure, using the overall periodic transfer coefficients that have computed in this procedure. The additional cooling loads generated by the new method well agree with the results form EnergyPlus simulations.

A mathematical model is presented to predict the behaviour of condensation and frost formation on heat transfer surfaces by simultaneously considering the condensing and frost layer. The model employs one-dimensional transient formulation based upon a local averaging technique, taking into account the variation of the frost density and thickness. The presented model is validated by comparing to experimental data provided by the dry cooler manufacturer. It is found that the model can predict the heat transfer performance of the dry cooler with an accuracy of within 2.19%.