Author

Yasir Rashid

Date of Award

4-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Abdel-Hamid Ismail Mourad

Second Advisor

Dr. Fadi AL Naimat

Third Advisor

Prof. Philip Eames

Abstract

High-energy consumption in buildings is a research issue of great importance today, with solid-liquid phase change materials (PCMs) proving an excellent candidate for passive means to reduce energy consumption. In the current research, a novel protective coating was developed from geopolymer to encapsulate a PCM to prevent leakage in the liquidous phase. The PCM was characterized using a customized temperature history method (THM) and standard differential scanning calorimetry (DSC). Two different porous materials, polyurethane foam and lightweight expanded clay aggregate (LECA), were selected to hold the PCM and act as a matrix in which to develop PCM capsules. Ingredients of the coating were characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Initially, liquid PCM was absorbed into foam and LECA by direct immersion and vacuum impregnation, respectively, until maximal absorption was achieved. A geopolymer coating was developed and applied to spherical foam and LECA matrices containing PCM at low temperatures to produce leak-proof PCM capsules, thus yielding geopolymer coated PCM capsules in matrix of foam (GP-F-PCM) and geopolymer coated PCM capsules in the matrix of LECA (GP-L-PCM). Efficacy of the produced capsules was tested by exposure to harsh outdoor conditions and application of rapid thermal cycles above and below the melting point of the PCM while leak proofing efficiency was examined using diffusion-ooze circle (DOC) test. Alkali-activated geopolymer concrete (GPC) cubes were developed to test thermal performance and compressive strength. Different compositions were developed for each matrix material (foam or LECA) and compared with a reference sample comprising a cube of GPC (i.e., six experimental samples in total, plus the reference). Samples of GPC were cast with 25%, 50% and 75% volume ratio replacement of their solid contents with either spheres of foam, LECA, or the same ratios of GP-F-PCM and GP-L-PCM capsules. Each composition was tested separately and heated until the achievement of steady-state temperature in a customized indoor set-up. Compression tests were performed after seven days and 28 days of curing. Thermal tests revealed that direct addition of foam into GPC increased the back-surface temperature. Increasing the amount of foam had increased the temperature and for the maximum case of 75% foam addition, this increment was 5.8ºC in comparison to the reference.

Addition of GP-F-PCM, LECA, and GP-L-PCM had a positive effect on the temperature drop on the back surface of the cubes. For the best case, a temperature drop of 12.5 °C was obtained at the back surface of cube with 75% GP-F-PCM, with respect to the reference. In comparing the capsules of LECA and foam as the matrix, GP-F-PCM produced more pronounced results because of higher PCM absorption in foam. Heat transmission effect was validated measuring U-values of all the sample cubes. It was observed that U-value for the reference cube was 2.04 W/m2K, which increased to 2.072 W/m2K for 75% foam. The U-value decreased to the levels of 1.092 W/m2K, 1.6 W/m2K and 0.9 W/m2K for 75% GP-F-PCM, 75% LECA and 75% GPL- PCM respectively. In terms of compression strength, the addition of foam had slightly positive effect (+6.3%) but the addition of GP-F-PCM, LECA, and GP-LPCM reduced strength significantly. Compression strength was 9.9 MPa, 10.1 MPa and 10.9 MPa for 75% GP-F-PCM, 75% LECA and 75% GP-L-PCM, which can be attributed to the fragile PCM and weak LECA structure. However, thermally responsive geopolymer concrete is promising and suitable for the construction of building facades, partitioning walls and roofing membranes.

Share

COinS