THERMAL CHARACTERIZATION OF GYPSUM COMPOSITES BY USING DIFFERENTIAL SCANNING CALORIMETRY

Transcription

1 THERMAL CHARACTERIZATION OF GYPSUM COMPOSITES BY USING DIFFERENTIAL SCANNING CALORIMETRY ANA M. BORREGUERO, IGNACIO GARRIDO, JOSE L. VALVERDE, JUAN F. RODRÍGUEZ AND MANUEL CARMONA

2 INTRODUCTION THERMAL ENERGY STORAGE MATERIALS WORLD ENERGY DEMAND Energy sources RENEWABLE Uranium reactors 1000 years Solar Energy 5000 millions of years Nuclear Fission 1 Million of years Development of new systems for saving energy Use of renewable energy sources CLEAN SOLAR ENERGY UNIVERSAL Carbon 330 years Petroleum 50 years IT NEEDS TO BE STORED! ABSORB STORE RELEASE A PCM is a substance with a high heat of fusion which, melting and solidifying, is able to absorb and store or release large amounts of energy.

3 INTRODUCTION WHY USE PCMS IN BUILDINGS? EU directives 2002/91/EC and 2010/31/UE: Directives on the Energy Performance of Buildings - Buildings are responsible for 40% of energy consumption and 36% of CO 2 emissions in the Europe Community - Energy performance of buildings is key to achieve the EU Climate and Energy objectives. Development of buildings with a more efficient use of energy PCMs application in buildings: Thermal energy storage Reduction of Energy consumption in heaters and air conditioners Environmental pollution Money spent in energy

4 INTRODUCTION HOW DO THE PCMS WORK? HOT OUTSIDE COLD OUTSIDE BUILDING INSIDE Heat stored Heat Released BUILDING INSIDE External T > Melting T PCM becomes liquid (Heat stored) External T < Freezing T PCM solidifies (Heat released) INSIDE THE BUILDING TEMPERATURE REMAINS CLOSE TO THE MELTING POINT

5 INTRODUCTION PCMS INCORPORATION IN BUILDINGS Properties of proper PCMs for applications in buildings - Melting temperature about 25ºC - High latent heat of fusion - Low cost - Good availability - Non-toxic - Non-corrosive Building systems to incorporate PCMs: - Wallboards, ceilings and floors - Shutter of windows - Cooling and heating systems Ways of incorporating PCMs into building materials: - Direct incorporation - PCMs microencapsulation and further incorporation

6 INTRODUCTION PCMS INCORPORATION IN BUILDINGS PCMs microencapsulation and further incorporation MAIN REASONS FOR PCMS MICROENCAPSULATION: - To avoid PCM interaction with the rest of building materials. - To avoid the PCM leakage when they remain liquid. - To give a high area of heat transfer. - Easy handling. - Microcapsules properties modification SHELL: POLYMERS -Low cost -Chemically inert respecting the building materials -Low density

7 INTRODUCTION PCMS INCORPORATION IN BUILDINGS Gypsum Avaliability Widely used in buildings Low cost Easy incorporation of additives In situ or precast slabs gypsum Buildings

8 GLOBAL AIM Gypsum PCM Gypsum composites WITH THERMOREGULATING PROPERTIES Thermal properties improvement Mechanical properties preservation Good durability No gas emissions

9 PARTIAL AIMS Thermal properties improvement Microscale analyses (MDSC) Sample size <10 mg APPARENT HEAT CAPACITY (Cp ap ) EVALUATION Macroscale analyses (Thermal Experimental set up) Blocks 6x10x3 cm 3 EXPERIMENTAL CHECKING THE TES CAPACITY IMPROVEMENT (sensible and latent heat) PREDICTION OF THE THERMAL BEHAVIOR

10 MATERIALS, METHODOLOGY AND SET UP PROPERTIES OF THE MICROENCAPSULATED PCMS Product Shell Core Synthesis technique msd-(ldpe EVA-RT27) LDPE-EVA Rubitherm RT27 Spray drying msp-(ps-rt27) Polystyrene Rubitherm RT27 Suspension polymerization Micronal DS 5001X PMMA Paraffin wax msd-cnfs LDPE-EVA Rubitherm RT27 and CNFs Spray drying (Commercial product) Spray drying Product dpn 0.5 (mm) dpv 0.5 (mm) T f (ºC) DH f (J/g) Paraffin content (wt%) msd-(ldpe EVA-RT27) msp-(ps-rt27) Micronal DS 5001X Unkown msd-cnfs

11 MATERIALS, METHODOLOGY AND SET UP GYPSUM COMPOSITE MANUFACTURING Microcapsules/ Hemihydrate (wt%) Component Water (g) Hemihydrate (g) Microcapsules (g) Block dimensions: 3x6x10 cm 3 Powder material

12 MATERIALS, METHODOLOGY AND SET UP MODULATED DIFFERNCIAL SCANING COLORIMETRY (MDSC) Sample Inert reference Basis of operation: Measurement of the difference in heat flow between both of them as a function of time and temperature

13 MATERIALS, METHODOLOGY AND SET UP MODULATED DIFFERNCIAL SCANING COLORIMETRY (MDSC) Conventional DSC Linear heating rate for scanning MDSC A sinusoidal modulation is overlaid on the conventional linear heating ramp

14 MATERIALS, METHODOLOGY AND SET UP MODULATED DIFFERNCIAL SCANING COLORIMETRY (MDSC) APPARENT HEAT CAPACITY EVALUATION Conventional DSC or macroscale equipment MDSC Direct apparent heat capacity-temperature curve Applied method - heating rate of 0.5ºC/min - amplitude of ±0.5 ºC - period of 100 seconds - temperature change from 10 to 40 ºC

15 MATERIALS, METHODOLOGY AND SET UP THERMAL BEHAVIOR EXPEROMENTAL SET UP 1. CHECK THE FEASIBILITY OF USING THE MDSC FOR TES CAPACITY EVALUATION OF THE COMPOSITE MATERIALS 2. EXPERIMENTAL DATA REQUIRED, IN ADDITION TO THE APPARENT HEAT CAPACITY, TO PREDICT THE THERMAL BEHAVIOR 1.Rotameter 2.Signal transmitter and converter 3.Computer 4.Peristaltic pump 5. Thermostatic bath 6.Thermocouples 7.Isothermal chamber 8.Insulating structure

16 MATERIALS, METHODOLOGY AND SET UP THERMAL BEHAVIOR EXPERIMENTAL SET UP Thermal treatment: Cell temperature change from 18 to 40ºC Measurements: - gypsum blocks temperatures in six positions - incoming and outgoing heat fluxes Surface (2) Surface (1) Middle (2) Plate (2) Middle (1) Plate (1) q outgoing Composite block Hollow cell Liquid flow direction q outgoing q outgoing q incoming Liquid flow direction

17 RESULTS MICROSCALE

18 C p ap (J/kgºC) (J/kgºC) RESULTS APPARENT HEAT CAPACITIES BY MDSC (<10 mg) C p ap (J/kgºC) C p ap msd-(ldpe EVA-RT27)/Hemihydrate (wt%) msd-cnfs msp-(ps-rt27)/hemihydrate (wt%) Temperature (ºC) Temperature (ºC) Micronal DS 5001X/Hemihydrate (wt%) Microcapsules / hemihydrate Heat capacity Narrower peak when CNFs addition Temperature (ºC)

19 RESULTS APPARENT HEAT CAPACITIES BY MDSC (J/kgºC) Gypsum msd-(ldpe EVA-RT27) msp-(ps-rt27) Micronal DS 5001X C p ap ap c p msd-(ldpe-eva-rt27) > Temperature (ºC) ap c p Micronal DS 5001X > Material ap c p msp-(ps-rt27) > Cp LDPE 1800 PMMA 1466 PS 1300 Gypsum 1090 ap c p Cp ap depends on the shell material and on the DH f of PCM gypsum

20 RESULTS TES CAPACITIES BY MDSC DH (J/kg) H = q acc = Te Cp ap Ti dt For a temperature change from 18 to 36 ºC Microcapsules type msd-(ldpe EVA-RT27) msp-(ps-rt27) Micronal DS 5001X DH = 47% Microcapsules/Hemihydrate (wt%)

21 RESULTS MACROSCALE

22 RESULTS TES CAPACITIES BY THE THERMAL BEHAVIOR SET UP q acc (W) msd- (LDPE EVA-RT27)/Hemihydrate (wt%) Accumulated heat when the composite materials are subjected to a temperature change from 18 to 36 ºC q acc MDSC (J/kg) 0.0 THE MDSC SEEMS TO BE SUITABLE Time (s) FOR HEAT CAPACITY EVALUATION OF msd-(ldpe EVA-RT27) msp-(ps-rt27) Micronal DS 5001X Gypsum COMPOSITE MATERIALS WITH PCMS q acc Macroescale set up (J/Kg) Deviation (%)

23 RESULTS TES CAPACITIES IMPROVEMENT BUILDING APPLICATION 1m 3 of gypsum boards with a 15% of msd-(ldpe EVA-RT27) TES = q acc ρ b Due to the microcapsules: Savings of 4.5 kwh/operating cycle 0.35 kg CO 2 / kwh (CNE, 2010) Reduction of 1.6kg CO 2 emissions/operating cycle

24 RESULTS THERMAL BEHAVIOR PREDICTION

25 RESULTS THERMAL BEHAVIOR PREDICTION PROBLEM: Boundary conditions movement with the solid-liquid interface SOLUTION: Apparent heat-capacity as a temperature function

26 Temperature (ºC) Temperature (ºC) Temperature (ºC) RESULTS THERMAL BEHAVIOR PREDICTION msd-(ldpe EVA-RT27) (wt%) Experimental Theoretical msp-(ps-rt27) (wt% ) Experimental Theoretical Time (s) THE MDSC HEAT CAPACITY-TEMPERATURE Time (s) CURVES ARE SUITABLE FOR THERMAL BEHAVIOR PREDICTION Micronal DS 5001X (wt%) Experimental Theoretical Good agreement between experimental and predicted data Time (s)

27 CONCLUSIONS THE MDSC SEEMS TO BE SUITABLE FOR HEAT CAPACITY EVALUATION OF COMPOSITE MATERIALS WITH PCMS The higher the microcapsules content, the higher the heat capacity The addition of CNFs promotes faster heat absorption the Cp ap depends on the shell type and the PCM latent heat of fusion The addition of PCMs allows to obtain composite materials with improved TES capacity which allow to save 4.5 kwh and reduce the CO 2 emissions in 1.6kg per operating cycle THE MDSC HEAT CAPACITY-TEMPERATURE CURVES ARE SUITABLE FOR THERMAL BEHAVIOR PREDICTION

28 THERMAL CHARACTERIZATION OF GYPSUM COMPOSITES BY USING DIFFERENTIAL SCANNING CALORIMETRY Thank you for your attention Acknowledgments Acciona Infraestructuras S.A. Spanish Ministry of Science and Innovation

29 RESULTS INFLUENCE OF THE HEATING RATE Heat Flow (W/g) C 93.96J/g C u u u u u u u C 94.93J/g u u u u -3 u u C 94.90J/g C -5 heating rate 0.5ºC/min u hetaing rate 5ºC/min heating rate 10ºC/min Exo Up C Temperature ( C) Universal V4.2E TA Instruments

30 Pared Aislante PCM Ciclo durante el día Ciclo durante la noche

31 C p ap (J/kgºC) Gypsum 7.5 msd-(ldpe EVA-RT27) 15.0 msd-(ldpe EVA-RT27) 7.5 msp-(ps-rt27) 15.0 msp-(ps-rt27) 7.5 Micronal DS 5001X 15.0 Micronal DS 5001X 7.5 msd-cnfs Temperature (ºC)

32 Intensity (u.a.) Intensidad (u.a.) MATERIALS, METHODOLOGY AND SET UP PROPERTIES OF THE MICROENCAPSULATED PCMS Scanning Electron Microscopy (SEM) Low Angle Laser Light Scattering (LALLS) 0 Differential Scanning Calorimetry (DSC) DH f =96,7 J/g -2 DH f J/g -3 DH f J/g Microcapsule Pure paraffin -2 DH f =96,2 J/g Material Original After thermal treatment Temperatura (ºC) Temperature (ºC)

33 MATERIALS, METHODOLOGY AND SET UP MICROENCAPSULATION OF PCMS Spray drying technique Feed Gas for solvent evaporation Gas + solvent Product Suspension polymerization

34 Temperature (ºC) Cp average =f(t) Time (s)

35 THERMAL BEHAVIOUR OF BUILDING MATERIALS CONTAINING MICROCAPSULES Mathematical Model Fourier heat conduction equation for one dimension - Enthalpy dependence with temperature h c ap p T T R h t c - and k dependence with temperature liq w w l 1.0 l - L f is the melted PCM fraction T T 0 ; l f = 0 i1 T k x x i i PCM f PCM f c i1 T 0 < T T f ; l T >T f ; l f = 1 liq i wi wpcm l f PCM 1.0 l f Taking into account the temperature dependences, equation 1 becomes: f T0 Tf T T 0 c c ap p ap p dt dt [5] [6] [7] sol PCM sol PCM [1] [2] [3] [4] T t c ap p T k x x ap c p c p T T ap T T R [8]

36 THERMAL BEHAVIOUR OF BUILDING MATERIALS CONTAINING MICROCAPSULES Mathematical Model Boundary conditions: dt. x 0; k Q dx t 0; T x0 T ini [9] [10] dt dt x ; k kcorcho dx dx x x [11] For the insulating material zone: T t k x corcho c corcho corcho p T x x corcho T x [12] Boundary conditions x corcho; t 0; T k corcho T ini corcho dt dx x corcho h T T c [13] [14] Model Solution By finite differences Rosenbrock method for numerically integration Unknown k and h c as fitting parameters Visual Basic application minimizing the sum of the square of offsets by a nonlinear least square fitting