PCM Habitat

8/2/2019 PCM Habitat

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Classification of PCM

PCM

organic

non-paraffin

hydrate salts

inorganicmetallics

organic-organic

eutectic organic-inorganic

norgan c- norgan c


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Commercial PCM

PCM name Type of product Melting point [C] Heat of fusion [kJ/kg] Source

RT 20 Paraffin 22 172 Rubitherm GmBH

Climsel C23 Salt hydrate 23 148 Climator

ClimselC24 Salt hydrate 24 216 Climator



STL 27 Salt hydrate 27 213 Mitsubishi chemical

S27 Salt hydrate 27 207 CristopiaRT 30 Paraffin 28 206 Rubitherm GmBH


TH 29 Salt hydrate 29 188 TEAP

Climsel C32 Salt hydrate 32 212 Climator

RT32 Paraffin 31 130 Rubitherm GmBH


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Characteristics of PCM

Advantages DisadvantagesFrom Phase change materials: overview Centrefor sustainable engineering

Organic Simple to use

Non-corrosive

No or low su ercoolin

Generally more expensive

Lower latent heat density

Often uite broad meltin ran e

No nucleating agentrecyclable

High volume changes during phasechanges

Can be combustible

ome reac w concre e on

Salt-based Generally cheap

Good latent heat density

Need careful preparation

Need additives to stablise for long term use

Well defined PC temperature

Non-flammable

Biodegradable and recyclable

Can be corrosive to some metals


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Buildin a lications

UNDERFLOOR

AIR EXCHANGER

WALL


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A lications

polymers

Encapsuled in plastic or metallic packaging

steelaluminium


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A lications

Impregnation porous materials as panelboard and concrete

Macrocapsule PCMsMicroencapsulated PCMs

15 mm thick board = 9 cm thick concrete wall


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Schematic view of a li htwei ht wall

8 m

Images from P. Schossig et al article

SEM (Scanning Electron Microscope) image

of PCM micro-capsules in gypsum plaster


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Pro erties of PCMs

Thermophysical properties

- melting temperature in the desired operating temperature range

- high latent heat of fusion per unit of volume

-

- small volume change on phase transformation

- small vapour pressure at operating temperature

- congruen me ng o e pcm or a cons an s orage capac y


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Pro erties of PCMs

high nucleation rate to avoid supercooling of the liquid phase

high rate of crystal growth

Chemical properties

- complete reversible freeze/melt cycle

-- no corrosiveness to the construction materials

- non-toxic- -


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Stabilit of PCM

Stability of the proprieties of PCM after many cycles of.

The major problem in using salt hydrates as PCM is thatmost of them melt incongruently.

The thermal ca acit of ure salt declines uickl from aninitial value of 238 kJ/kg to 63 kJ/kg after 40 cycles.


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Stabilit of PCM

Several technique to become stable the PCM has studied :

Calorimeter analysis allow to measure the thermalproprieties of Phase Change Material

, ,behavior of the PCM after many cycles of fusion andsolidification


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Measurement techni ue

DSC (Differential Scanning Calorimetry)

Measure the tem oral variation of the thermal enerexchanged with the sample of PCM.

The output of the measurement is the energy time diagram(thermogram)

Use a very small quantities of sample (1-10 mg)

TA (Thermal Analysis)

Measure the tem oral variation of tem erature in the sam leof PCM.

The out ut of the measurement is the tem erature - timediagram

Use small or big quantities of sample (10 g 10 kg)


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Calorimeter analysis


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Wall A lication

A PCM layer can be placed within wall constructions to increase

The room air temperature results more comfortable and less varied

The energy consumption for both air conditioning and heating will decrease


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Wall A lication 1

A PCM layer can be placed within the wall close to the external

DAYdeal of the energy that flows throughthe wall

NIGHTThe PCM layer release energy stored in theday outside and inside the building


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Wall A lication 2

A PCM layer can be placed within the wall close to the externallayer with a ventilated air chamber

DAYThe PCM layer in warm days store agreat deal of the energy that flows

roug e wa ue n par cu ar o e

solar radiation

The PCM layer release outside theenergy stored in the day

evacuates part of the energy stored


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Wall A lication 3

A PCM layer can be placed behind a glass and a air chamber

The PCM layer is directlyirradiated to solar radiation and

NIGHTThe PCM release the energy store

If the energy want to be evacuateoutside, the air chamber will be


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Wall A lication 4

A PCM layer can be placed within wall constructions to increase

The PCM is contained to theinternal finish

The PCM exchange energy with

the internal room

Store energy when the airtemperature is higher than thetemperature of fusion

e ease energy store w en t e a rtemperature is lower than thetemperature of fusion


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Wall - confrontationGlauber salts

melting temperature 32C, density 1450 kg/m3, latent heat offusion 1.9105 J/kg, specific heat in the liquid and solid statee ual to 3.6103 J/ k K .

Na2SO410H2O

Paolo Principi

Dipartimento di Energetica Universit Politecnica delle MarcheAncona (Italia)


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Air tem erature surface interne


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Thermal flow Wm-2 throu h south wall


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Underfloor a lications

Two PCM layer and


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Underfloor a lications

air temperature

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25

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[C] BOX 3

10

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0

5

Time

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Underfloor a licationssurface temperature

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[C] R1 Box3

R1 Box4

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Underfloor a licationssurface temperature

50

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25

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[C] R2 Box3

R2 Box4

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time


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Trans arent PCM fa ade anel


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Ceilin air exchan er


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storing outside coolingreleasing stored cooling

Ni ht behaviourDay behaviour


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Heat exchanging

absorption

LIQUIDSOLID

release

Daily cycle

The efficiency of PCM is associate with the heat exchanging


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Heat exchanging

Climate condition with high oscillation of

temperature day - night

Natural Ventilation

The exchanging is facilitate with the natural air flow


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Heat exchanging

Artificial ventilation

The changing and discharging is improved withmechanical system of ventilation

Hydraulic system

e energy s carr e roug an sys em w wa eror other liquid

PCM Habitat

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