Niels Christian Bergsøe

Humidity as a Control Parameter for Ventilation

The objective of this study was to develop energy efficient ventilation strategies that will provide both a healthy and comfortable indoor climate and reduce energy consumption compared to present ventilation standards. Humidity was used as a control parameter for the ventilation. Four different ventilation strategies were tested in a test apartment. The results of the experiments indicated that humidity can be used as a control parameter for ventilation and that energy can be saved without compromising indoor air quality.

Evaluation of air cleaning technologies existing in the Danish market: Experiments in a duct and in a test room

Five portable air cleaning technologies including one new technology were evaluated to find their effectiveness in removing ultrafine particles. Measurements were carried out both in a duct and in a test room. The results showed that the technologies that use/create ozone to clean air can increase the ozone level significantly in the room. Moreover, they can cause generation of ultrafine particles and consequently increase ultrafine particle concentration in the room. The study suggests using a mechanical filter with low pressure drop as a recommended air cleaning technology in order to remove ultrafine particles efficiently from the indoor environment.

Performance and Effectiveness of Portable Air Cleaners in an Office Room: An Experimental Study

Nowadays, many people work in an office environment. Air pollutants, including particles and gases, are generated by humans and by different devices that are used in offices. Pollutants can also enter an office room with the air supplied from outdoors. It has been established that air pollutants have adverse health effects on human body. Air cleaning devices are commonly marketed as being beneficial for the health by removing air pollutants and consequently improving indoor air quality. The performance of five air cleaning technologies was tested in order to determine the generation of ozone and particles in an office room. The particle removal effectiveness of the technologies was also determined in order to clarify their ability to remove UFPs (ultrafine particles) in the office room. The tested five air cleaning technologies are non-thermal plasma, corona discharge ionizer, portable air purifier, electrostatic fibrous filter and three-dimensional fibrous filter. The interior surfaces of the office room emit low levels of volatile organic compounds, since the office room has not been refurbished for about two decades. The results showed that the particle removal effectiveness of the technologies was ranged between 0.2 and 0.45 for the office room. The three technologies using/generating ozone significantly increased the ozone level in the office room. However, no increase of the UFP concentration was detected.

Combining active chilled beams and air-cleaning technologies to improve the indoor climate in offices: Testing of a low pressure mechanical filter in a laboratory environment

This project is part of a long-term research program to study the possibilities of using efficient air-cleaning technologies to improve indoor air quality in buildings. The purpose of this part of the project was to study the energy-saving potential of combining the cooling and cleaning of air in offices. For this purpose, a mechanical filter with low-pressure drop was selected for testing in a laboratory environment. The measurements included tests of the filter in ductwork to study the efficiency of the filter. Moreover, the combined system of the filter and a chilled beam was tested in a room. The efficiency of the mechanical filter to remove ultrafine particles was examined using pure wax candles and salt as sources of emission particles. The measurements in the duct showed that the efficiency of the filter ranged between 54% and 78% and that the pressure loss was less than 5 Pa (0.104 Ibf/ft2). Furthermore, the measurement results of the combined system showed that adding the filter accelerated the removal rate of the particles by 2 h−1. However, the efficiency of the chilled beam in exchanging heat was reduced by 38%.

Analysis of control strategies for a novel HVAC system equipped with a room-temperature water loop

This article presents a simulation-based study that investigated four control strategies to regulate a novel two-pipe system for office buildings. The main characteristic of the system is its ability to provide simultaneous heating and cooling by operating a single water circuit with supply temperature of about 22◦C. The study was conducted by considering a typical office building model in two different climates, Chicago (US) and Copenhagen (Denmark). Simulations were performed in Dymola, a commercial simulation environment for Modelica models. The four control strategies ranged from linear SISO (single input, single output) to PI (proportionalintegral) feedback controllers with detailed information about the indoor climate in the building. Results showed that all the four strategies were able to maintain comfortable levels of indoor air temperatures in the zones. With regard to the annual energy use, savings of about 7-10% were achieved when comparing PI feedback controllers with SISO strategies.

Procedure for Balancing an Air Distribution System with Decentralised Fans

AbstractThis paper presents results from an on-going project concerning new design procedures for mechanical ventilation systems with low energy use. Conventional constant air volume (CAV) systems are usually balanced using flat plate dampers. The purpose of using balancing dampers is to intentionally introduce pressure drops in the duct system thus nominal airflows are achieved throughout the ductwork within specified tolerances. However, introduction of pressure drops will increase energy requirement for the ventilation system and in addition, balancing a duct system is a time consuming task and often flawed. This paper presents a new procedure for balancing of C AV systems in combination with decentralised fans. The new system was based on replacing the balancing dampers with decentralised fans. By replacing the balancing dampers with decentralised fans, airflows can be balanced by adjusting the speed of the fans. In conventional air distribution systems the fan provides the necessary pressure to overc...

Transfer of Ultrafine Particles and Air in Multi-storey Buildings

An emerging issue in Denmark is passive smoking in residential buildings where non-smokers are exposed to smoke from their neighbours. There are various ways that smoke is transferred from one flat to another. The air transfer rate between two flats in a multi-storey building depends on its construction, tightness and age. This paper presents results of a study on the transfer of ultrafine particles and tracer gas in an older multi-storey building in Copenhagen. The aim of the study was to quantify the transfer of ultrafine particles and gases from one flat to another flat before and after sealing the floor. A new floor-sealing method was applied to seal the floor between the two flats. The sealing method was developed by a firm specialising in sealing. Indoor ultrafine particle concentrations and tracer gas were measured continuously in the two flats during the measuring periods. In the unoccupied flat, the gas source was N2O and the particle source was burning cigarettes. Reduction of the concentration of ultrafine particles and tracer gas by sealing the floor with polyethylene and joint filler made of bitumen was studied. It was evaluated how the sealing performed with regard to decreasing the amount of ultrafine particles and a tracer gas transferred between two flats separated by a floor. When the floor between the flats was not sealed, the results showed that about 4% of the ultrafine particles and 14% of the tracer gas were transferred. After sealing, the amount transferred was reduced to 1.6% and 5%, respectively.