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Testing large samples of PCM in water calorimeter and PCM used in room applications by night-air cooling
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The latent-heat-storage capacity in Phase-Change Materials can be used for storing or releasing energy within a small temperature interval. Upon the phase transition taking place in a narrow temperature span, the material takes up or releases more energy compared to sensible heat storage. For an ideal phase-change material, the transition temperature is a single value, but for the most common phase-change materials on the market, used in building applications, the transition temperature is distributed within a temperature range of several degrees.

Integration of phase-change materials in building applications can be effected in several ways, for example by impregnating phase-change materials into porous building materials like concrete, wallboards, bricks or complements of the building structure. Integrating storages filled with phase-change materials makes other implementations, for instance accumulating tanks or envelopes as presented in this thesis, in an air heat exchanger. An appropriate phasetransition temperature of the supposed application is critical to the functionality of the material. For example, in cooling applications, the transition temperature of the material should be a few degrees lower than the requested comfort temperature in the building, and the opposite for heating applications.

In order to assess the thermal properties and the durability of the material, a watercalorimetric equipment was developed and employed in an accelerated testing programme. The heat capacity of the material and in particular possible change in the heat capacity over time, after thermal cycling of the material, were measured. In the thermal cycling of the material from solid to liquid phase, the temperature rise and required energy supply were recorded. The testing programme was undertaken according to control procedures and documents. In order to be able to utilize the heat-storage capacity in the best way, it is necessary to gain knowledge about thermal properties of the material, especially the long-term behaviour of the material and the deterioration rates of the thermal properties.

A semi-full-scale air heat exchanger based on phase-change material was developed and tested under real temperature conditions during the summer of 2004. The test results were used to compare and verify computer simulations made on a similar plant. The air heat exchanger utilises the ambient diurnal temperature swing to charge and discharge the phasechange material. The material tested in the calorimeter and in the air heat exchanger has an estimated phase-change temperature of about 24 °C.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , viii, 29 p.
Keyword [en]
phase-change material, PCM, water calorimeter, air heat exchanger, durability, thermal properties, heat capacity
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:kth:diva-495ISBN: 91-7178-160-9 (print)OAI: oai:DiVA.org:kth-495DiVA: diva2:14216
Presentation
2005-10-25, Hörsalen BMG/ITB-Brynäs, Södra Sjötullsgatan 3, Gävle, 10:00
Opponent
Supervisors
Note
QC 20101123Available from: 2005-11-22 Created: 2005-11-22 Last updated: 2010-11-23Bibliographically approved
List of papers
1. Service life testing of PCM based components in buildings
Open this publication in new window or tab >>Service life testing of PCM based components in buildings
2005 (English)In: 10DBMC International Conference of Building Materials and Components, 2005, 253-260 p.Conference paper, Published paper (Other academic)
Abstract [en]

In the CRAFT project C-TIDE (Changeable Thermal Inertia Dry Enclosures) the possibility of changing the thermal inertia of lightweight buildings with PCM, Phase Change Material, is explored. The project is performed in collaboration with Italian and Swedish partners representing both the industry and research. Lightweight buildings represent a well-established technology in Sweden. In Italy this technology is entering the market.

A problem is the overheating of the building during the hot season, especially in warm climate but also in Nordic climate during summer. This project deals mainly with this problem.

A crucial issue of the use of these materials is the performance over time data of the phase change material that are used in the building. An extensive program is set up to perform long time testing of the thermal properties of the materials that were used in the project. The long time testing programme of the materials was established to correspond with the governing procedure set up by ISO 15686-2 "Buildings and consructed assets– Service life planning – Part 2: Service life prediction procedures".

This paper describes the framework of the testing procedure, the set-up of the testing equipment and preliminary results of the tests.

Keyword
Service life, phase change materials
National Category
Construction Management
Identifiers
urn:nbn:se:kth:diva-8785 (URN)
Note
QC 20101020Available from: 2005-11-22 Created: 2005-11-22 Last updated: 2010-10-20Bibliographically approved
2. Mathematical modelling of PCM air heat exchanger
Open this publication in new window or tab >>Mathematical modelling of PCM air heat exchanger
2006 (English)In: Energy and Buildings, ISSN 0378-7788, Vol. 38, no 2, 82-89 p.Article in journal (Refereed) Published
Abstract [en]

In order to cool a room with a cold night air phase change material, PCM, is stored in an air heat exchanger. During night the PCM crystallises, energy is released. During daytime air is circulated in the unit, energy is absorbed and the indoor air is cooled. The characteristic of PCM is that there is an increase of the specific heat over a limited temperature span. This is the principle that is used in the design of the PCM air heat exchanger unit.

The action of a PCM storage unit will act differently depending of the thermal properties of the material. In an ideal material the phase transition occurs at a given temperature. On the market, compounds containing PCM are available which, in order to create a suitable melting temperature, are mixtures of different products. In these materials, the transition from liquid to solid takes place over a temperature span, i.e. the specific heat varies with the temperature. This can be represented by a c(p)(T) curve, specific heat as a function of the temperature.

In this paper, the development of a mathematical model of the PCM air heat exchanger is presented. Considerations are taken to different shapes of the cp(T) curve. The mathematical model is verified with measurement on a prototype heat exchanger.

The development of the equipment is part of the CRAFT project Changeable Thermal Inertia Dry Enclosures (C-TIDE) the possibility of use of phase change materials integrated into a building is explored.

Keyword
phase change materials, thermal inertia, simulation model, finite difference method
National Category
Construction Management
Identifiers
urn:nbn:se:kth:diva-8786 (URN)10.1016/j.enbuild.2005.04.002 (DOI)000233525500002 ()2-s2.0-27744587136 (Scopus ID)
Note
QC 20101020. Uppdaterad från accepted till pulished (20101020).Available from: 2005-11-22 Created: 2005-11-22 Last updated: 2010-10-20Bibliographically approved
3. Water-calorimetric measurement on large samples of PCM
Open this publication in new window or tab >>Water-calorimetric measurement on large samples of PCM
2005 (English)In: Energy and Buildings, ISSN 0378-7788Article in journal (Other academic) Submitted
Keyword
Phase-change material, PCM, Water calorimeter, Durability, Thermal storage capacity, TSC
National Category
Construction Management
Identifiers
urn:nbn:se:kth:diva-7483 (URN)
Note
QS 20120316Available from: 2005-10-14 Created: 2005-10-14 Last updated: 2012-03-16Bibliographically approved

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