M. Cˇ ekon et al.: Cardboard-Based Packaging Materials as Renewable Thermal Insulation of Buildings
DOI: 10.7569/JRM.2017.634135
Sample M1 is a HFB with hexagonal cells 68 mm high and 16 mm wide covered by flat cardboard sheet on both sides. Sample M2 is a combination of ten lay- ers of CFB. Individual layers are 2 or 4 mm thick with alternating sequence: the orientation of CFBs rotates by 90° between layers. Sample M3 is a HFB with hex- agonal cells 29 mm high and 14 mm wide covered by flat cardboard sheet on both sides. Sample M4 is made of two layers of HFBs with hexagonal cells 17 mm high and 14 mm wide covered by flat cardboard sheet on both sides. Sample M5 is a HFB with hexagonal cells 12.5 mm high and 13 mm wide covered by flat card- board sheet on both sides. Sample M6 is a HFB with hexagonal cells 17 mm high and 14 mm wide covered by flat cardboard sheet on both sides. Sample M7 is a combination of 14 mm thick CFB panel placed per- pendicular to two layers of 3 mm thick covering CFB. All evaluated CBM samples were obtained as waste products from the packaging industry. The other three samples serve as a reference and are representative of the common contemporary ther- mal insulations. Sample M8 is made of PIR, which is a high performance thermal insulation in the building industry. Sample M9 is made of EPS and sample M10 is made of MW. Basic parameters of the samples are described in Table 1. Thermal parameters were determined by measurements which are described in Section 3. The thermal conductivity of hydroscopic materials strongly depends on moisture. The moisture content of samples presented in Table 1 is so small that the samples are practically dry. 3 THERMAL ANALYSIS Common homogenous materials have thermal trans- fer mainly caused by thermal conduction. Tested
CBMs combine convection and radiation in closed air cavities. This thermal analysis is focused on measur- ing real thermal properties of the samples presented in Figures 1 and 2. These properties have been deter- mined from measured heat flow under known bound- ary condition. Based on these measurements, the equivalent thermal resistance and thermal conductiv- ity were determined. Thermal resistance of tested samples was measured using guarded hot plate method in accordance with ISO 8302 [12]. A TLP 300 DTX-1 thermal conductiv- ity measuring device from Taurus Instruments was used (Figure 3). This device can determine thermal resistance of samples with thickness from 20 mm to 80 mm. Maximum dimension of the measured sam- ples is 300 mm × 300 mm and protected measured field represents an area of 100 mm × 100 mm. Upper and lower surfaces of the tested sample have a set tem- perature difference which is maintained to activate heat flow within the tested sample. Temperatures are controlled by Peltier elements. The total power of the elements is maintained to achieve one-dimensional steady-state heat transfer. Temperature difference on the sample’s surfaces is measured applying two bat- teries of thermocouples on each side. In terms of the equation (Eq. 1), the thermal resistance is calculated from heating power Q through measured area A and temperature difference between sample surfaces Δ T .
T A Q
Δ ×
[m
2 .K.W –1 ]
(1)
R
=
3.1 Thermal Measurement Procedure Although the TLP 300 DTX-1 device implements the system for estimating the thickness of the sample, the sample thickness could be distorted by applying the contact mat. Therefore, before testing each sample,
Table 1 Table of measured materials.
Thickness [mm]
Bulk density [kg·m –3 ]
Moisture ratio [kg·kg –1 ]
Sample Type
M1 M2 M3 M4 M5 M6 M7 M8 M9
HFB 69.662 CFB 34.007 HFB 30.400 HFB 26.810 HFB 13.268 HFB 18.130 CFB 28.625 PIR 20.084 EPS 19.736
24.50 89.52 37.35 47.93 48.25 38.72
2.60% 2.82% 3.98% 3.48% 1.43% 1.69% 3.89%
129.02
52.33 13.74 99.75
n/a n/a n/a
Figure 3 The TLP 300 DTX-1 thermal conductivity measuring device.
M10 MW 25.808
86
J. Renew. Mater. Supplement June 2017
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