Submitted by Maria.Kapsalaki on Thu, 10/31/2013 - 10:25
Rotary heat recovery exchangers are widely used in ventilation systems, and the units are known for their high efficiency and almost maintenance-free operation. Temperature efficiencies above 80% are not uncommon. Performing dynamical analyses of rotary heat exchangers are in many situations advantageous, especially in connection to installation of such equipment in VAV systems. Efficiencies and flows are varying parameters that are crucial for energy calculations, but also for control. The dynamical analysis can effectively be carried out by addressing a dynamical model.
We describe a novel modeling technique, based on Duhamel's theorem, to study the effects of time-varying winds on radon transport in soil near buildings. The technique, implemented in the model RapidSTART, reduces computational times for transient, three-dimensional, wind-induced soil-gas and radon transport by three to four orders of magnitude compared with conventional finite-dierence models.
Explicit algebraic equations for calculation of wind and stack driven ventilation were developed by parametrically matching exact solutions to the flow equations for building envelopes. These separate wind and stack effect flow calculation procedures were incorporated in a simple natural ventilation model, AIM- 2, with empirical functions for superposition of wind and stack effect and for estimating wind shelter.
Infiltration has traditionally been assumed to contribute to the energy load of a building by an amount equal to the product of the infiltration flow rate and the enthalpy difference between inside and outside. Application of such a simple formula may produce an unreasonably high contribution because of heat recovery within the building envelope. Previous laboratory and simulation research has indicated that such heat transfer between the infiltrating air and walls may be substantial.
This study describes an approach for measuring and modeling diffusive and advective transport of radon through building materials. Goal of these measurements and model calculations is to improve our understanding concerning the factors influencing the transport of radon through building materials. To reach this goal, a number of experiments has to be conducted. These experiments, including measurements in a large cylinder for creating diffusive and advective transport of radon under controlled, dwelling-like conditions, are described here and the initial results are presented.
In buildings growing conditions for mould fungi can occur and cause fungus infestation. Therefore,consequent measures have to be taken to avoid health dangers that come from mould fungi inbuildings. In order to avoid the mould fungus formation, a strategy has to be set up that focuses on thegrowth conditions for mould fungi. While in Germany only relative humidity is used as an assessmentcriterion for mould growth risk, more and more measured isopleths are used abroad.
The present paper deals with modeling of various low-exergy system components and their integrationinto the energy system for buildings and small communities. The exergy content of a certain amount ofenergy is defined as the part of this energy that can be used to produce mechanical energy. The qualityof a certain amount of energy is defined as the relative exergy content of this energy. Most of ourbuildings with their heating and cooling systems today are built for conversion of high quality energysources to low quality use with a huge destruction of the available exergy as a result.
Recently most houses in northern Japan are highly insulated and air-tight, which can lead to seriousproblems such as indoor air pollution. It is important to evaluate the performance of an air-tight housefrom the viewpoint of ventilation. However, in general, houses consist of multiple rooms and each roomhas airflows in different directions which mix with each other. Therefore it is not easy to measure realventilation rates.The purpose of this paper is to evaluate a simplified method for measuring airflow rates in houseswhich have a basement with outer insulation.
The objective of the paper is to present a new educational concept for improving the accessibility towhole building Heat, Air & Moisture (HAM) simulation models developed in the simulation environmentHAMLab. We provided a library of buildings, including the default performances of the buildingsthemselves, on a website. Students can select the most appropriate building, adapt the inputparameters, simulate and evaluate the results. In case a higher resolution is required, two stepsexplain how to implement respectively advanced controllers and HAM details.