A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Use of phase-change materials to enhance the thermal performance of building insulations
Materials that undergo a phase change at temperatures encountered in the building envelope alter the rate heat gain or loss from conditioned spaces by absorbing and releasing heat in response to changing thermal boundary conditions. One type of phase change involves transition from solid to liquid (absorbing heat) or liquid to solid (releasing heat) of a compound like n-octadecane (C18H38), which has a melting point of about 83 deg F (28 deg C) and a heat of fusion of 65 Btu/lbm (151 kJ/kg). Inorganic salt hydrates and other types of mixtures exhibit heat effects as hydration levels or dilution occurs. The selection of a material to use as a phase change material (PCM) in conjunction with conventional thermal insulation is guided by the phase change temperature, the magnitude of the heat effect, cost, and issues such as flammability and corrosiveness. A review of recent work in the area of cellulosic building insulation is given by Kosny et al. The performance of paraffinic PCMs like n- octadecane has been discussed by Zhang, Kissock, and Stovall for wall applications. Petrie has reported performance data for an inorganic PCM in an attic application. The location of PCM in the building envelope is the second consideration. PCM mixed with building thermal insulation before application is attractive from a manufacturing and installation point of view. This type of application, however, typically results in an incomplete participation of the PCM in the heat transfer process since some fraction of the PCM may not pass through the phase-change temperature during outdoor temperature swings. The PCM must be located in a region that undergoes sufficient temperature variation to cycle across the phase-change temperature. PCM in packets, for example, can be positioned to provide optimum performance which occurs when all of the PCM participates in the phase change process. This paper deals with localized PCM applications. A companion paper in the Conference deals with distributed systems. The use of localized PCM in the building envelope reduces the heat flow in and out of conditioned space resulting in reduced utility load. Two methods of measuring the magnitude of the savings due to PCM have been discussed. A heat-flow meter apparatus can be used to measure the effect of PCM on heat flux resulting from a step-change in a boundary temperature. A two-compartment test chamber can be used to observe the performance of insulation systems with a cyclic boundary temperature. A heating load reduction of 69% and a cooling load reduction of 83% due to the presence of PCM between insulation layers was calculated for an example configuration.
Use of phase-change materials to enhance the thermal performance of building insulations
Materials that undergo a phase change at temperatures encountered in the building envelope alter the rate heat gain or loss from conditioned spaces by absorbing and releasing heat in response to changing thermal boundary conditions. One type of phase change involves transition from solid to liquid (absorbing heat) or liquid to solid (releasing heat) of a compound like n-octadecane (C18H38), which has a melting point of about 83 deg F (28 deg C) and a heat of fusion of 65 Btu/lbm (151 kJ/kg). Inorganic salt hydrates and other types of mixtures exhibit heat effects as hydration levels or dilution occurs. The selection of a material to use as a phase change material (PCM) in conjunction with conventional thermal insulation is guided by the phase change temperature, the magnitude of the heat effect, cost, and issues such as flammability and corrosiveness. A review of recent work in the area of cellulosic building insulation is given by Kosny et al. The performance of paraffinic PCMs like n- octadecane has been discussed by Zhang, Kissock, and Stovall for wall applications. Petrie has reported performance data for an inorganic PCM in an attic application. The location of PCM in the building envelope is the second consideration. PCM mixed with building thermal insulation before application is attractive from a manufacturing and installation point of view. This type of application, however, typically results in an incomplete participation of the PCM in the heat transfer process since some fraction of the PCM may not pass through the phase-change temperature during outdoor temperature swings. The PCM must be located in a region that undergoes sufficient temperature variation to cycle across the phase-change temperature. PCM in packets, for example, can be positioned to provide optimum performance which occurs when all of the PCM participates in the phase change process. This paper deals with localized PCM applications. A companion paper in the Conference deals with distributed systems. The use of localized PCM in the building envelope reduces the heat flow in and out of conditioned space resulting in reduced utility load. Two methods of measuring the magnitude of the savings due to PCM have been discussed. A heat-flow meter apparatus can be used to measure the effect of PCM on heat flux resulting from a step-change in a boundary temperature. A two-compartment test chamber can be used to observe the performance of insulation systems with a cyclic boundary temperature. A heating load reduction of 69% and a cooling load reduction of 83% due to the presence of PCM between insulation layers was calculated for an example configuration.
Use of phase-change materials to enhance the thermal performance of building insulations
Verwendung von Phasenübergangswerkstoffen zur Steigerung der Wärmeleistung von Gebäudeisolierungen
Alderman, R.J. (author) / arbrough, D.W. (author)
2007
8 Seiten, 8 Bilder, 7 Quellen
Conference paper
English
Conductivities and conductances of building materials and insulations
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