Matrix compressibility and pore properties (pore size distribution) of a rank range of coals was investigated using mercury intrusion porosimetry (MIP) on coal cores with the pore size distribution also being determined using low temperature at 77 K nitrogen adsorption/desorption isotherms for crushed samples. The coal matrix compressibility is significant when the pressure of MIP is from 0.0074-35 MPa. Mathematical models were developed (based on MIP and nitrogen adsorption/desorption isotherms) to establish the porosity/pore size distribution relationships with matrix compressibility. For coal ranks, the matrix compressibility was between 0.2410-4 to 13.5610-4 MPa-1 , and had a negative exponential relationship with the vitrinite reflectance (R o,m %). Lignites have the maximum matrix compressibility due to their structural open structure having limitied compaction during coalification. In addition to the pore structure relationship the composition, moisture, and ash yields impacts on compressibility were also examined. Inertinite-rich coals however had a low matrix compressibility across the rank range, which may be due to the interinhibitive relationships between the mesopores, macropores and minerals. The wetting action of high moisture (water molecules) weakens the link between the coal particles of the lignites and the subbituminous coals, which causes abnormally high compressibility. Observations here relate to hydrofracturing or CO 2 injection behaviors during enhancing coalbed methane (CBM) recovery.

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The properties of nanoparticles and its aggregation as well as convective heat transfer of nanofluids have received great attentions over the last few decades. It is well certified that nanoparticles and its aggregation can be successfully described by fractal geometry theory and technology. In this review, the fractal properties of nanoparticle and its aggregation are firstly introduced, and then the recent investigations on the fractal models and fractal-based approaches that applied for effective thermal conductivity, convective heat transfer, critical heat flux and subcooled pool boiling of nanofluids, fractal clusters and yield stress property of nanoparticle aggregation are summarized.