Active thermal mass enhancement using phase change materials

Buildings account for around 40% of energy consumption in the UK. For over twenty years active thermal mass systems have been a feature in low-energy buildings in northern Europe. By passing ventilation air, and utilising night ventilation, through the hollow core structures efficient heating and cooling has been achieved. Despite the success, such systems suffer from space overheating and efficiency losses during extended hot periods. Control strategies have largely mitigated this effect however low cost retrofit solutions that enhance the system are of interest. This research therefore investigates the benefit of using innovative phase change material (PCM) solutions to enhance thermal comfort and reduced energy usage of traditional active thermal mass systems. A prototype PCM enhancement was constructed, with energy saving and comfort benefits investigated under controlled laboratory conditions. In absolute terms the PCM solution offered an additional 12.5% energy storage capacity and a 29% increase in active surface area, coupled with the existing sensible thermal mass. Under laboratory conditions the PCM addition saved an additional 0.1 kWh per day, delayed AC onset by 1.2 h and offered an average 1.0 °C reduction in room temperature during 8 h of fixed internal heat gain, contrasted against the original active thermal mass system

A heat pump incorporating thermochemical energy storage

SIGLEAvailable from British Library Document Supply Centre- DSC:D69051/86 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Interzone air movement and its effect on condensation in houses

The work is concerned with measuring interzone air movement and investigating its effect on condensation in traditionally built houses. Air flows through a doorway between the lower and upper floors of a house were measured using a tracer gas technique. To study the effect of the temperature difference on interzone air flows, the lower floor of a house was heated to various temperatures in the range 18-35°C using thermostatically controlled heaters. The upper floor was unheated. Two portable SF6 systems fitted with electron-capture detectors were used for measurements of interzonal air flow. The doorway coefficient of discharge was found to be a function of the temperature difference between the two floors of the house. In the second part of the paper, the effect of interzone air movement on condensation is considered. A two-zone moisture transfer model was established and the effect of a kitchen extract fan on the air flow patterns in the house is discussed.

Influence of tracer-gases on the accuracy of interzonal airflow measurements

The use of sulphur hexafluoride (SF6), nitrous oxide (N2O) or carbon dioxide (CO2) as tracer-gases is examined for the measurement of airflows between two tightly-sealed chambers. The results are compared with measurements made using a calibrated flowmeter. Tracer-gas measurements made using SF6 were found to be in closer agreement with flowmeter measurements than those made using either N2O or CO2.

Monitoring Hydrofluorocarbon Refrigerant Leakage from Air-Conditioning Systems in Buildings

10.1016/0306-2619(95)00027-5Applied Energy534341-347APEN

Experimental study of interzonal natural convection through an aperture

The work was concerned with measuring natural convection through an aperture between two zones in an environmental chamber. Airflow rates between the two zones were measured using a tracer-gas decay technique, and the temperature at the centre of each zone was measured using thermocouples. Zone 1 was heated to various temperatures in the range 18-38°C using thermostatically controlled heaters. Zone 2 was unheated. A multipoint sampling unit was used to collect a tracer-gas sample from each zone. The concentration of SF6 tracer was measured using an infra-red gas analyzer. The heat and mass flow rates between the two zones were calculated from the tracer-gas concentrations and temperature differences. Results were compared with values predicted by existing algorithms for two-zone enclosures. The mass flow rate through the aperture was found to be a function of the temperature difference between the two zones.